--- /dev/null
+/*
+ * linux/mm/vmscan.c
+ *
+ * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
+ *
+ * Swap reorganised 29.12.95, Stephen Tweedie.
+ * kswapd added: 7.1.96 sct
+ * Removed kswapd_ctl limits, and swap out as many pages as needed
+ * to bring the system back to freepages.high: 2.4.97, Rik van Riel.
+ * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
+ * Multiqueue VM started 5.8.00, Rik van Riel.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/gfp.h>
+#include <linux/kernel_stat.h>
+#include <linux/swap.h>
+#include <linux/pagemap.h>
+#include <linux/init.h>
+#include <linux/highmem.h>
+#include <linux/vmpressure.h>
+#include <linux/vmstat.h>
+#include <linux/file.h>
+#include <linux/writeback.h>
+#include <linux/blkdev.h>
+#include <linux/buffer_head.h> /* for try_to_release_page(),
+ buffer_heads_over_limit */
+#include <linux/mm_inline.h>
+#include <linux/backing-dev.h>
+#include <linux/rmap.h>
+#include <linux/topology.h>
+#include <linux/cpu.h>
+#include <linux/cpuset.h>
+#include <linux/compaction.h>
+#include <linux/notifier.h>
+#include <linux/rwsem.h>
+#include <linux/delay.h>
+#include <linux/kthread.h>
+#include <linux/freezer.h>
+#include <linux/memcontrol.h>
+#include <linux/delayacct.h>
+#include <linux/sysctl.h>
+#include <linux/oom.h>
+#include <linux/prefetch.h>
+#include <linux/printk.h>
+
+#include <asm/tlbflush.h>
+#include <asm/div64.h>
+
+#include <linux/swapops.h>
+#include <linux/balloon_compaction.h>
+
+#include "internal.h"
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/vmscan.h>
+
+struct scan_control {
+ /* How many pages shrink_list() should reclaim */
+ unsigned long nr_to_reclaim;
+
+ /* This context's GFP mask */
+ gfp_t gfp_mask;
+
+ /* Allocation order */
+ int order;
+
+ /*
+ * Nodemask of nodes allowed by the caller. If NULL, all nodes
+ * are scanned.
+ */
+ nodemask_t *nodemask;
+
+ /*
+ * The memory cgroup that hit its limit and as a result is the
+ * primary target of this reclaim invocation.
+ */
+ struct mem_cgroup *target_mem_cgroup;
+
+ /* Scan (total_size >> priority) pages at once */
+ int priority;
+
+ unsigned int may_writepage:1;
+
+ /* Can mapped pages be reclaimed? */
+ unsigned int may_unmap:1;
+
+ /* Can pages be swapped as part of reclaim? */
+ unsigned int may_swap:1;
+
+ /* Can cgroups be reclaimed below their normal consumption range? */
+ unsigned int may_thrash:1;
+
+ unsigned int hibernation_mode:1;
+
+ /* One of the zones is ready for compaction */
+ unsigned int compaction_ready:1;
+
+ /* Incremented by the number of inactive pages that were scanned */
+ unsigned long nr_scanned;
+
+ /* Number of pages freed so far during a call to shrink_zones() */
+ unsigned long nr_reclaimed;
+};
+
+#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
+
+#ifdef ARCH_HAS_PREFETCH
+#define prefetch_prev_lru_page(_page, _base, _field) \
+ do { \
+ if ((_page)->lru.prev != _base) { \
+ struct page *prev; \
+ \
+ prev = lru_to_page(&(_page->lru)); \
+ prefetch(&prev->_field); \
+ } \
+ } while (0)
+#else
+#define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
+#endif
+
+#ifdef ARCH_HAS_PREFETCHW
+#define prefetchw_prev_lru_page(_page, _base, _field) \
+ do { \
+ if ((_page)->lru.prev != _base) { \
+ struct page *prev; \
+ \
+ prev = lru_to_page(&(_page->lru)); \
+ prefetchw(&prev->_field); \
+ } \
+ } while (0)
+#else
+#define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
+#endif
+
+/*
+ * From 0 .. 100. Higher means more swappy.
+ */
+int vm_swappiness = 60;
+/*
+ * The total number of pages which are beyond the high watermark within all
+ * zones.
+ */
+unsigned long vm_total_pages;
+
+static LIST_HEAD(shrinker_list);
+static DECLARE_RWSEM(shrinker_rwsem);
+
+#ifdef CONFIG_MEMCG
+static bool global_reclaim(struct scan_control *sc)
+{
+ return !sc->target_mem_cgroup;
+}
+#else
+static bool global_reclaim(struct scan_control *sc)
+{
+ return true;
+}
+#endif
+
+static unsigned long zone_reclaimable_pages(struct zone *zone)
+{
+ int nr;
+
+ nr = zone_page_state(zone, NR_ACTIVE_FILE) +
+ zone_page_state(zone, NR_INACTIVE_FILE);
+
+ if (get_nr_swap_pages() > 0)
+ nr += zone_page_state(zone, NR_ACTIVE_ANON) +
+ zone_page_state(zone, NR_INACTIVE_ANON);
+
+ return nr;
+}
+
+bool zone_reclaimable(struct zone *zone)
+{
+ return zone_page_state(zone, NR_PAGES_SCANNED) <
+ zone_reclaimable_pages(zone) * 6;
+}
+
+static unsigned long get_lru_size(struct lruvec *lruvec, enum lru_list lru)
+{
+ if (!mem_cgroup_disabled())
+ return mem_cgroup_get_lru_size(lruvec, lru);
+
+ return zone_page_state(lruvec_zone(lruvec), NR_LRU_BASE + lru);
+}
+
+/*
+ * Add a shrinker callback to be called from the vm.
+ */
+int register_shrinker(struct shrinker *shrinker)
+{
+ size_t size = sizeof(*shrinker->nr_deferred);
+
+ /*
+ * If we only have one possible node in the system anyway, save
+ * ourselves the trouble and disable NUMA aware behavior. This way we
+ * will save memory and some small loop time later.
+ */
+ if (nr_node_ids == 1)
+ shrinker->flags &= ~SHRINKER_NUMA_AWARE;
+
+ if (shrinker->flags & SHRINKER_NUMA_AWARE)
+ size *= nr_node_ids;
+
+ shrinker->nr_deferred = kzalloc(size, GFP_KERNEL);
+ if (!shrinker->nr_deferred)
+ return -ENOMEM;
+
+ down_write(&shrinker_rwsem);
+ list_add_tail(&shrinker->list, &shrinker_list);
+ up_write(&shrinker_rwsem);
+ return 0;
+}
+EXPORT_SYMBOL(register_shrinker);
+
+/*
+ * Remove one
+ */
+void unregister_shrinker(struct shrinker *shrinker)
+{
+ down_write(&shrinker_rwsem);
+ list_del(&shrinker->list);
+ up_write(&shrinker_rwsem);
+ kfree(shrinker->nr_deferred);
+}
+EXPORT_SYMBOL(unregister_shrinker);
+
+#define SHRINK_BATCH 128
+
+static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
+ struct shrinker *shrinker,
+ unsigned long nr_scanned,
+ unsigned long nr_eligible)
+{
+ unsigned long freed = 0;
+ unsigned long long delta;
+ long total_scan;
+ long freeable;
+ long nr;
+ long new_nr;
+ int nid = shrinkctl->nid;
+ long batch_size = shrinker->batch ? shrinker->batch
+ : SHRINK_BATCH;
+
+ freeable = shrinker->count_objects(shrinker, shrinkctl);
+ if (freeable == 0)
+ return 0;
+
+ /*
+ * copy the current shrinker scan count into a local variable
+ * and zero it so that other concurrent shrinker invocations
+ * don't also do this scanning work.
+ */
+ nr = atomic_long_xchg(&shrinker->nr_deferred[nid], 0);
+
+ total_scan = nr;
+ delta = (4 * nr_scanned) / shrinker->seeks;
+ delta *= freeable;
+ do_div(delta, nr_eligible + 1);
+ total_scan += delta;
+ if (total_scan < 0) {
+ pr_err("shrink_slab: %pF negative objects to delete nr=%ld\n",
+ shrinker->scan_objects, total_scan);
+ total_scan = freeable;
+ }
+
+ /*
+ * We need to avoid excessive windup on filesystem shrinkers
+ * due to large numbers of GFP_NOFS allocations causing the
+ * shrinkers to return -1 all the time. This results in a large
+ * nr being built up so when a shrink that can do some work
+ * comes along it empties the entire cache due to nr >>>
+ * freeable. This is bad for sustaining a working set in
+ * memory.
+ *
+ * Hence only allow the shrinker to scan the entire cache when
+ * a large delta change is calculated directly.
+ */
+ if (delta < freeable / 4)
+ total_scan = min(total_scan, freeable / 2);
+
+ /*
+ * Avoid risking looping forever due to too large nr value:
+ * never try to free more than twice the estimate number of
+ * freeable entries.
+ */
+ if (total_scan > freeable * 2)
+ total_scan = freeable * 2;
+
+ trace_mm_shrink_slab_start(shrinker, shrinkctl, nr,
+ nr_scanned, nr_eligible,
+ freeable, delta, total_scan);
+
+ /*
+ * Normally, we should not scan less than batch_size objects in one
+ * pass to avoid too frequent shrinker calls, but if the slab has less
+ * than batch_size objects in total and we are really tight on memory,
+ * we will try to reclaim all available objects, otherwise we can end
+ * up failing allocations although there are plenty of reclaimable
+ * objects spread over several slabs with usage less than the
+ * batch_size.
+ *
+ * We detect the "tight on memory" situations by looking at the total
+ * number of objects we want to scan (total_scan). If it is greater
+ * than the total number of objects on slab (freeable), we must be
+ * scanning at high prio and therefore should try to reclaim as much as
+ * possible.
+ */
+ while (total_scan >= batch_size ||
+ total_scan >= freeable) {
+ unsigned long ret;
+ unsigned long nr_to_scan = min(batch_size, total_scan);
+
+ shrinkctl->nr_to_scan = nr_to_scan;
+ ret = shrinker->scan_objects(shrinker, shrinkctl);
+ if (ret == SHRINK_STOP)
+ break;
+ freed += ret;
+
+ count_vm_events(SLABS_SCANNED, nr_to_scan);
+ total_scan -= nr_to_scan;
+
+ cond_resched();
+ }
+
+ /*
+ * move the unused scan count back into the shrinker in a
+ * manner that handles concurrent updates. If we exhausted the
+ * scan, there is no need to do an update.
+ */
+ if (total_scan > 0)
+ new_nr = atomic_long_add_return(total_scan,
+ &shrinker->nr_deferred[nid]);
+ else
+ new_nr = atomic_long_read(&shrinker->nr_deferred[nid]);
+
+ trace_mm_shrink_slab_end(shrinker, nid, freed, nr, new_nr, total_scan);
+ return freed;
+}
+
+/**
+ * shrink_slab - shrink slab caches
+ * @gfp_mask: allocation context
+ * @nid: node whose slab caches to target
+ * @memcg: memory cgroup whose slab caches to target
+ * @nr_scanned: pressure numerator
+ * @nr_eligible: pressure denominator
+ *
+ * Call the shrink functions to age shrinkable caches.
+ *
+ * @nid is passed along to shrinkers with SHRINKER_NUMA_AWARE set,
+ * unaware shrinkers will receive a node id of 0 instead.
+ *
+ * @memcg specifies the memory cgroup to target. If it is not NULL,
+ * only shrinkers with SHRINKER_MEMCG_AWARE set will be called to scan
+ * objects from the memory cgroup specified. Otherwise all shrinkers
+ * are called, and memcg aware shrinkers are supposed to scan the
+ * global list then.
+ *
+ * @nr_scanned and @nr_eligible form a ratio that indicate how much of
+ * the available objects should be scanned. Page reclaim for example
+ * passes the number of pages scanned and the number of pages on the
+ * LRU lists that it considered on @nid, plus a bias in @nr_scanned
+ * when it encountered mapped pages. The ratio is further biased by
+ * the ->seeks setting of the shrink function, which indicates the
+ * cost to recreate an object relative to that of an LRU page.
+ *
+ * Returns the number of reclaimed slab objects.
+ */
+static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
+ struct mem_cgroup *memcg,
+ unsigned long nr_scanned,
+ unsigned long nr_eligible)
+{
+ struct shrinker *shrinker;
+ unsigned long freed = 0;
+
+ if (memcg && !memcg_kmem_is_active(memcg))
+ return 0;
+
+ if (nr_scanned == 0)
+ nr_scanned = SWAP_CLUSTER_MAX;
+
+ if (!down_read_trylock(&shrinker_rwsem)) {
+ /*
+ * If we would return 0, our callers would understand that we
+ * have nothing else to shrink and give up trying. By returning
+ * 1 we keep it going and assume we'll be able to shrink next
+ * time.
+ */
+ freed = 1;
+ goto out;
+ }
+
+ list_for_each_entry(shrinker, &shrinker_list, list) {
+ struct shrink_control sc = {
+ .gfp_mask = gfp_mask,
+ .nid = nid,
+ .memcg = memcg,
+ };
+
+ if (memcg && !(shrinker->flags & SHRINKER_MEMCG_AWARE))
+ continue;
+
+ if (!(shrinker->flags & SHRINKER_NUMA_AWARE))
+ sc.nid = 0;
+
+ freed += do_shrink_slab(&sc, shrinker, nr_scanned, nr_eligible);
+ }
+
+ up_read(&shrinker_rwsem);
+out:
+ cond_resched();
+ return freed;
+}
+
+void drop_slab_node(int nid)
+{
+ unsigned long freed;
+
+ do {
+ struct mem_cgroup *memcg = NULL;
+
+ freed = 0;
+ do {
+ freed += shrink_slab(GFP_KERNEL, nid, memcg,
+ 1000, 1000);
+ } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
+ } while (freed > 10);
+}
+
+void drop_slab(void)
+{
+ int nid;
+
+ for_each_online_node(nid)
+ drop_slab_node(nid);
+}
+
+static inline int is_page_cache_freeable(struct page *page)
+{
+ /*
+ * A freeable page cache page is referenced only by the caller
+ * that isolated the page, the page cache radix tree and
+ * optional buffer heads at page->private.
+ */
+ return page_count(page) - page_has_private(page) == 2;
+}
+
+static int may_write_to_queue(struct backing_dev_info *bdi,
+ struct scan_control *sc)
+{
+ if (current->flags & PF_SWAPWRITE)
+ return 1;
+ if (!bdi_write_congested(bdi))
+ return 1;
+ if (bdi == current->backing_dev_info)
+ return 1;
+ return 0;
+}
+
+/*
+ * We detected a synchronous write error writing a page out. Probably
+ * -ENOSPC. We need to propagate that into the address_space for a subsequent
+ * fsync(), msync() or close().
+ *
+ * The tricky part is that after writepage we cannot touch the mapping: nothing
+ * prevents it from being freed up. But we have a ref on the page and once
+ * that page is locked, the mapping is pinned.
+ *
+ * We're allowed to run sleeping lock_page() here because we know the caller has
+ * __GFP_FS.
+ */
+static void handle_write_error(struct address_space *mapping,
+ struct page *page, int error)
+{
+ lock_page(page);
+ if (page_mapping(page) == mapping)
+ mapping_set_error(mapping, error);
+ unlock_page(page);
+}
+
+/* possible outcome of pageout() */
+typedef enum {
+ /* failed to write page out, page is locked */
+ PAGE_KEEP,
+ /* move page to the active list, page is locked */
+ PAGE_ACTIVATE,
+ /* page has been sent to the disk successfully, page is unlocked */
+ PAGE_SUCCESS,
+ /* page is clean and locked */
+ PAGE_CLEAN,
+} pageout_t;
+
+/*
+ * pageout is called by shrink_page_list() for each dirty page.
+ * Calls ->writepage().
+ */
+static pageout_t pageout(struct page *page, struct address_space *mapping,
+ struct scan_control *sc)
+{
+ /*
+ * If the page is dirty, only perform writeback if that write
+ * will be non-blocking. To prevent this allocation from being
+ * stalled by pagecache activity. But note that there may be
+ * stalls if we need to run get_block(). We could test
+ * PagePrivate for that.
+ *
+ * If this process is currently in __generic_file_write_iter() against
+ * this page's queue, we can perform writeback even if that
+ * will block.
+ *
+ * If the page is swapcache, write it back even if that would
+ * block, for some throttling. This happens by accident, because
+ * swap_backing_dev_info is bust: it doesn't reflect the
+ * congestion state of the swapdevs. Easy to fix, if needed.
+ */
+ if (!is_page_cache_freeable(page))
+ return PAGE_KEEP;
+ if (!mapping) {
+ /*
+ * Some data journaling orphaned pages can have
+ * page->mapping == NULL while being dirty with clean buffers.
+ */
+ if (page_has_private(page)) {
+ if (try_to_free_buffers(page)) {
+ ClearPageDirty(page);
+ pr_info("%s: orphaned page\n", __func__);
+ return PAGE_CLEAN;
+ }
+ }
+ return PAGE_KEEP;
+ }
+ if (mapping->a_ops->writepage == NULL)
+ return PAGE_ACTIVATE;
+ if (!may_write_to_queue(inode_to_bdi(mapping->host), sc))
+ return PAGE_KEEP;
+
+ if (clear_page_dirty_for_io(page)) {
+ int res;
+ struct writeback_control wbc = {
+ .sync_mode = WB_SYNC_NONE,
+ .nr_to_write = SWAP_CLUSTER_MAX,
+ .range_start = 0,
+ .range_end = LLONG_MAX,
+ .for_reclaim = 1,
+ };
+
+ SetPageReclaim(page);
+ res = mapping->a_ops->writepage(page, &wbc);
+ if (res < 0)
+ handle_write_error(mapping, page, res);
+ if (res == AOP_WRITEPAGE_ACTIVATE) {
+ ClearPageReclaim(page);
+ return PAGE_ACTIVATE;
+ }
+
+ if (!PageWriteback(page)) {
+ /* synchronous write or broken a_ops? */
+ ClearPageReclaim(page);
+ }
+ trace_mm_vmscan_writepage(page, trace_reclaim_flags(page));
+ inc_zone_page_state(page, NR_VMSCAN_WRITE);
+ return PAGE_SUCCESS;
+ }
+
+ return PAGE_CLEAN;
+}
+
+/*
+ * Same as remove_mapping, but if the page is removed from the mapping, it
+ * gets returned with a refcount of 0.
+ */
+static int __remove_mapping(struct address_space *mapping, struct page *page,
+ bool reclaimed)
+{
+ BUG_ON(!PageLocked(page));
+ BUG_ON(mapping != page_mapping(page));
+
+ spin_lock_irq(&mapping->tree_lock);
+ /*
+ * The non racy check for a busy page.
+ *
+ * Must be careful with the order of the tests. When someone has
+ * a ref to the page, it may be possible that they dirty it then
+ * drop the reference. So if PageDirty is tested before page_count
+ * here, then the following race may occur:
+ *
+ * get_user_pages(&page);
+ * [user mapping goes away]
+ * write_to(page);
+ * !PageDirty(page) [good]
+ * SetPageDirty(page);
+ * put_page(page);
+ * !page_count(page) [good, discard it]
+ *
+ * [oops, our write_to data is lost]
+ *
+ * Reversing the order of the tests ensures such a situation cannot
+ * escape unnoticed. The smp_rmb is needed to ensure the page->flags
+ * load is not satisfied before that of page->_count.
+ *
+ * Note that if SetPageDirty is always performed via set_page_dirty,
+ * and thus under tree_lock, then this ordering is not required.
+ */
+ if (!page_freeze_refs(page, 2))
+ goto cannot_free;
+ /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
+ if (unlikely(PageDirty(page))) {
+ page_unfreeze_refs(page, 2);
+ goto cannot_free;
+ }
+
+ if (PageSwapCache(page)) {
+ swp_entry_t swap = { .val = page_private(page) };
+ mem_cgroup_swapout(page, swap);
+ __delete_from_swap_cache(page);
+ spin_unlock_irq(&mapping->tree_lock);
+ swapcache_free(swap);
+ } else {
+ void (*freepage)(struct page *);
+ void *shadow = NULL;
+
+ freepage = mapping->a_ops->freepage;
+ /*
+ * Remember a shadow entry for reclaimed file cache in
+ * order to detect refaults, thus thrashing, later on.
+ *
+ * But don't store shadows in an address space that is
+ * already exiting. This is not just an optizimation,
+ * inode reclaim needs to empty out the radix tree or
+ * the nodes are lost. Don't plant shadows behind its
+ * back.
+ */
+ if (reclaimed && page_is_file_cache(page) &&
+ !mapping_exiting(mapping))
+ shadow = workingset_eviction(mapping, page);
+ __delete_from_page_cache(page, shadow);
+ spin_unlock_irq(&mapping->tree_lock);
+
+ if (freepage != NULL)
+ freepage(page);
+ }
+
+ return 1;
+
+cannot_free:
+ spin_unlock_irq(&mapping->tree_lock);
+ return 0;
+}
+
+/*
+ * Attempt to detach a locked page from its ->mapping. If it is dirty or if
+ * someone else has a ref on the page, abort and return 0. If it was
+ * successfully detached, return 1. Assumes the caller has a single ref on
+ * this page.
+ */
+int remove_mapping(struct address_space *mapping, struct page *page)
+{
+ if (__remove_mapping(mapping, page, false)) {
+ /*
+ * Unfreezing the refcount with 1 rather than 2 effectively
+ * drops the pagecache ref for us without requiring another
+ * atomic operation.
+ */
+ page_unfreeze_refs(page, 1);
+ return 1;
+ }
+ return 0;
+}
+
+/**
+ * putback_lru_page - put previously isolated page onto appropriate LRU list
+ * @page: page to be put back to appropriate lru list
+ *
+ * Add previously isolated @page to appropriate LRU list.
+ * Page may still be unevictable for other reasons.
+ *
+ * lru_lock must not be held, interrupts must be enabled.
+ */
+void putback_lru_page(struct page *page)
+{
+ bool is_unevictable;
+ int was_unevictable = PageUnevictable(page);
+
+ VM_BUG_ON_PAGE(PageLRU(page), page);
+
+redo:
+ ClearPageUnevictable(page);
+
+ if (page_evictable(page)) {
+ /*
+ * For evictable pages, we can use the cache.
+ * In event of a race, worst case is we end up with an
+ * unevictable page on [in]active list.
+ * We know how to handle that.
+ */
+ is_unevictable = false;
+ lru_cache_add(page);
+ } else {
+ /*
+ * Put unevictable pages directly on zone's unevictable
+ * list.
+ */
+ is_unevictable = true;
+ add_page_to_unevictable_list(page);
+ /*
+ * When racing with an mlock or AS_UNEVICTABLE clearing
+ * (page is unlocked) make sure that if the other thread
+ * does not observe our setting of PG_lru and fails
+ * isolation/check_move_unevictable_pages,
+ * we see PG_mlocked/AS_UNEVICTABLE cleared below and move
+ * the page back to the evictable list.
+ *
+ * The other side is TestClearPageMlocked() or shmem_lock().
+ */
+ smp_mb();
+ }
+
+ /*
+ * page's status can change while we move it among lru. If an evictable
+ * page is on unevictable list, it never be freed. To avoid that,
+ * check after we added it to the list, again.
+ */
+ if (is_unevictable && page_evictable(page)) {
+ if (!isolate_lru_page(page)) {
+ put_page(page);
+ goto redo;
+ }
+ /* This means someone else dropped this page from LRU
+ * So, it will be freed or putback to LRU again. There is
+ * nothing to do here.
+ */
+ }
+
+ if (was_unevictable && !is_unevictable)
+ count_vm_event(UNEVICTABLE_PGRESCUED);
+ else if (!was_unevictable && is_unevictable)
+ count_vm_event(UNEVICTABLE_PGCULLED);
+
+ put_page(page); /* drop ref from isolate */
+}
+
+enum page_references {
+ PAGEREF_RECLAIM,
+ PAGEREF_RECLAIM_CLEAN,
+ PAGEREF_KEEP,
+ PAGEREF_ACTIVATE,
+};
+
+static enum page_references page_check_references(struct page *page,
+ struct scan_control *sc)
+{
+ int referenced_ptes, referenced_page;
+ unsigned long vm_flags;
+
+ referenced_ptes = page_referenced(page, 1, sc->target_mem_cgroup,
+ &vm_flags);
+ referenced_page = TestClearPageReferenced(page);
+
+ /*
+ * Mlock lost the isolation race with us. Let try_to_unmap()
+ * move the page to the unevictable list.
+ */
+ if (vm_flags & VM_LOCKED)
+ return PAGEREF_RECLAIM;
+
+ if (referenced_ptes) {
+ if (PageSwapBacked(page))
+ return PAGEREF_ACTIVATE;
+ /*
+ * All mapped pages start out with page table
+ * references from the instantiating fault, so we need
+ * to look twice if a mapped file page is used more
+ * than once.
+ *
+ * Mark it and spare it for another trip around the
+ * inactive list. Another page table reference will
+ * lead to its activation.
+ *
+ * Note: the mark is set for activated pages as well
+ * so that recently deactivated but used pages are
+ * quickly recovered.
+ */
+ SetPageReferenced(page);
+
+ if (referenced_page || referenced_ptes > 1)
+ return PAGEREF_ACTIVATE;
+
+ /*
+ * Activate file-backed executable pages after first usage.
+ */
+ if (vm_flags & VM_EXEC)
+ return PAGEREF_ACTIVATE;
+
+ return PAGEREF_KEEP;
+ }
+
+ /* Reclaim if clean, defer dirty pages to writeback */
+ if (referenced_page && !PageSwapBacked(page))
+ return PAGEREF_RECLAIM_CLEAN;
+
+ return PAGEREF_RECLAIM;
+}
+
+/* Check if a page is dirty or under writeback */
+static void page_check_dirty_writeback(struct page *page,
+ bool *dirty, bool *writeback)
+{
+ struct address_space *mapping;
+
+ /*
+ * Anonymous pages are not handled by flushers and must be written
+ * from reclaim context. Do not stall reclaim based on them
+ */
+ if (!page_is_file_cache(page)) {
+ *dirty = false;
+ *writeback = false;
+ return;
+ }
+
+ /* By default assume that the page flags are accurate */
+ *dirty = PageDirty(page);
+ *writeback = PageWriteback(page);
+
+ /* Verify dirty/writeback state if the filesystem supports it */
+ if (!page_has_private(page))
+ return;
+
+ mapping = page_mapping(page);
+ if (mapping && mapping->a_ops->is_dirty_writeback)
+ mapping->a_ops->is_dirty_writeback(page, dirty, writeback);
+}
+
+/*
+ * shrink_page_list() returns the number of reclaimed pages
+ */
+static unsigned long shrink_page_list(struct list_head *page_list,
+ struct zone *zone,
+ struct scan_control *sc,
+ enum ttu_flags ttu_flags,
+ unsigned long *ret_nr_dirty,
+ unsigned long *ret_nr_unqueued_dirty,
+ unsigned long *ret_nr_congested,
+ unsigned long *ret_nr_writeback,
+ unsigned long *ret_nr_immediate,
+ bool force_reclaim)
+{
+ LIST_HEAD(ret_pages);
+ LIST_HEAD(free_pages);
+ int pgactivate = 0;
+ unsigned long nr_unqueued_dirty = 0;
+ unsigned long nr_dirty = 0;
+ unsigned long nr_congested = 0;
+ unsigned long nr_reclaimed = 0;
+ unsigned long nr_writeback = 0;
+ unsigned long nr_immediate = 0;
+
+ cond_resched();
+
+ while (!list_empty(page_list)) {
+ struct address_space *mapping;
+ struct page *page;
+ int may_enter_fs;
+ enum page_references references = PAGEREF_RECLAIM_CLEAN;
+ bool dirty, writeback;
+
+ cond_resched();
+
+ page = lru_to_page(page_list);
+ list_del(&page->lru);
+
+ if (!trylock_page(page))
+ goto keep;
+
+ VM_BUG_ON_PAGE(PageActive(page), page);
+ VM_BUG_ON_PAGE(page_zone(page) != zone, page);
+
+ sc->nr_scanned++;
+
+ if (unlikely(!page_evictable(page)))
+ goto cull_mlocked;
+
+ if (!sc->may_unmap && page_mapped(page))
+ goto keep_locked;
+
+ /* Double the slab pressure for mapped and swapcache pages */
+ if (page_mapped(page) || PageSwapCache(page))
+ sc->nr_scanned++;
+
+ may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
+ (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
+
+ /*
+ * The number of dirty pages determines if a zone is marked
+ * reclaim_congested which affects wait_iff_congested. kswapd
+ * will stall and start writing pages if the tail of the LRU
+ * is all dirty unqueued pages.
+ */
+ page_check_dirty_writeback(page, &dirty, &writeback);
+ if (dirty || writeback)
+ nr_dirty++;
+
+ if (dirty && !writeback)
+ nr_unqueued_dirty++;
+
+ /*
+ * Treat this page as congested if the underlying BDI is or if
+ * pages are cycling through the LRU so quickly that the
+ * pages marked for immediate reclaim are making it to the
+ * end of the LRU a second time.
+ */
+ mapping = page_mapping(page);
+ if (((dirty || writeback) && mapping &&
+ bdi_write_congested(inode_to_bdi(mapping->host))) ||
+ (writeback && PageReclaim(page)))
+ nr_congested++;
+
+ /*
+ * If a page at the tail of the LRU is under writeback, there
+ * are three cases to consider.
+ *
+ * 1) If reclaim is encountering an excessive number of pages
+ * under writeback and this page is both under writeback and
+ * PageReclaim then it indicates that pages are being queued
+ * for IO but are being recycled through the LRU before the
+ * IO can complete. Waiting on the page itself risks an
+ * indefinite stall if it is impossible to writeback the
+ * page due to IO error or disconnected storage so instead
+ * note that the LRU is being scanned too quickly and the
+ * caller can stall after page list has been processed.
+ *
+ * 2) Global reclaim encounters a page, memcg encounters a
+ * page that is not marked for immediate reclaim or
+ * the caller does not have __GFP_IO. In this case mark
+ * the page for immediate reclaim and continue scanning.
+ *
+ * __GFP_IO is checked because a loop driver thread might
+ * enter reclaim, and deadlock if it waits on a page for
+ * which it is needed to do the write (loop masks off
+ * __GFP_IO|__GFP_FS for this reason); but more thought
+ * would probably show more reasons.
+ *
+ * Don't require __GFP_FS, since we're not going into the
+ * FS, just waiting on its writeback completion. Worryingly,
+ * ext4 gfs2 and xfs allocate pages with
+ * grab_cache_page_write_begin(,,AOP_FLAG_NOFS), so testing
+ * may_enter_fs here is liable to OOM on them.
+ *
+ * 3) memcg encounters a page that is not already marked
+ * PageReclaim. memcg does not have any dirty pages
+ * throttling so we could easily OOM just because too many
+ * pages are in writeback and there is nothing else to
+ * reclaim. Wait for the writeback to complete.
+ */
+ if (PageWriteback(page)) {
+ /* Case 1 above */
+ if (current_is_kswapd() &&
+ PageReclaim(page) &&
+ test_bit(ZONE_WRITEBACK, &zone->flags)) {
+ nr_immediate++;
+ goto keep_locked;
+
+ /* Case 2 above */
+ } else if (global_reclaim(sc) ||
+ !PageReclaim(page) || !(sc->gfp_mask & __GFP_IO)) {
+ /*
+ * This is slightly racy - end_page_writeback()
+ * might have just cleared PageReclaim, then
+ * setting PageReclaim here end up interpreted
+ * as PageReadahead - but that does not matter
+ * enough to care. What we do want is for this
+ * page to have PageReclaim set next time memcg
+ * reclaim reaches the tests above, so it will
+ * then wait_on_page_writeback() to avoid OOM;
+ * and it's also appropriate in global reclaim.
+ */
+ SetPageReclaim(page);
+ nr_writeback++;
+
+ goto keep_locked;
+
+ /* Case 3 above */
+ } else {
+ wait_on_page_writeback(page);
+ }
+ }
+
+ if (!force_reclaim)
+ references = page_check_references(page, sc);
+
+ switch (references) {
+ case PAGEREF_ACTIVATE:
+ goto activate_locked;
+ case PAGEREF_KEEP:
+ goto keep_locked;
+ case PAGEREF_RECLAIM:
+ case PAGEREF_RECLAIM_CLEAN:
+ ; /* try to reclaim the page below */
+ }
+
+ /*
+ * Anonymous process memory has backing store?
+ * Try to allocate it some swap space here.
+ */
+ if (PageAnon(page) && !PageSwapCache(page)) {
+ if (!(sc->gfp_mask & __GFP_IO))
+ goto keep_locked;
+ if (!add_to_swap(page, page_list))
+ goto activate_locked;
+ may_enter_fs = 1;
+
+ /* Adding to swap updated mapping */
+ mapping = page_mapping(page);
+ }
+
+ /*
+ * The page is mapped into the page tables of one or more
+ * processes. Try to unmap it here.
+ */
+ if (page_mapped(page) && mapping) {
+ switch (try_to_unmap(page, ttu_flags)) {
+ case SWAP_FAIL:
+ goto activate_locked;
+ case SWAP_AGAIN:
+ goto keep_locked;
+ case SWAP_MLOCK:
+ goto cull_mlocked;
+ case SWAP_SUCCESS:
+ ; /* try to free the page below */
+ }
+ }
+
+ if (PageDirty(page)) {
+ /*
+ * Only kswapd can writeback filesystem pages to
+ * avoid risk of stack overflow but only writeback
+ * if many dirty pages have been encountered.
+ */
+ if (page_is_file_cache(page) &&
+ (!current_is_kswapd() ||
+ !test_bit(ZONE_DIRTY, &zone->flags))) {
+ /*
+ * Immediately reclaim when written back.
+ * Similar in principal to deactivate_page()
+ * except we already have the page isolated
+ * and know it's dirty
+ */
+ inc_zone_page_state(page, NR_VMSCAN_IMMEDIATE);
+ SetPageReclaim(page);
+
+ goto keep_locked;
+ }
+
+ if (references == PAGEREF_RECLAIM_CLEAN)
+ goto keep_locked;
+ if (!may_enter_fs)
+ goto keep_locked;
+ if (!sc->may_writepage)
+ goto keep_locked;
+
+ /* Page is dirty, try to write it out here */
+ switch (pageout(page, mapping, sc)) {
+ case PAGE_KEEP:
+ goto keep_locked;
+ case PAGE_ACTIVATE:
+ goto activate_locked;
+ case PAGE_SUCCESS:
+ if (PageWriteback(page))
+ goto keep;
+ if (PageDirty(page))
+ goto keep;
+
+ /*
+ * A synchronous write - probably a ramdisk. Go
+ * ahead and try to reclaim the page.
+ */
+ if (!trylock_page(page))
+ goto keep;
+ if (PageDirty(page) || PageWriteback(page))
+ goto keep_locked;
+ mapping = page_mapping(page);
+ case PAGE_CLEAN:
+ ; /* try to free the page below */
+ }
+ }
+
+ /*
+ * If the page has buffers, try to free the buffer mappings
+ * associated with this page. If we succeed we try to free
+ * the page as well.
+ *
+ * We do this even if the page is PageDirty().
+ * try_to_release_page() does not perform I/O, but it is
+ * possible for a page to have PageDirty set, but it is actually
+ * clean (all its buffers are clean). This happens if the
+ * buffers were written out directly, with submit_bh(). ext3
+ * will do this, as well as the blockdev mapping.
+ * try_to_release_page() will discover that cleanness and will
+ * drop the buffers and mark the page clean - it can be freed.
+ *
+ * Rarely, pages can have buffers and no ->mapping. These are
+ * the pages which were not successfully invalidated in
+ * truncate_complete_page(). We try to drop those buffers here
+ * and if that worked, and the page is no longer mapped into
+ * process address space (page_count == 1) it can be freed.
+ * Otherwise, leave the page on the LRU so it is swappable.
+ */
+ if (page_has_private(page)) {
+ if (!try_to_release_page(page, sc->gfp_mask))
+ goto activate_locked;
+ if (!mapping && page_count(page) == 1) {
+ unlock_page(page);
+ if (put_page_testzero(page))
+ goto free_it;
+ else {
+ /*
+ * rare race with speculative reference.
+ * the speculative reference will free
+ * this page shortly, so we may
+ * increment nr_reclaimed here (and
+ * leave it off the LRU).
+ */
+ nr_reclaimed++;
+ continue;
+ }
+ }
+ }
+
+ if (!mapping || !__remove_mapping(mapping, page, true))
+ goto keep_locked;
+
+ /*
+ * At this point, we have no other references and there is
+ * no way to pick any more up (removed from LRU, removed
+ * from pagecache). Can use non-atomic bitops now (and
+ * we obviously don't have to worry about waking up a process
+ * waiting on the page lock, because there are no references.
+ */
+ __clear_page_locked(page);
+free_it:
+ nr_reclaimed++;
+
+ /*
+ * Is there need to periodically free_page_list? It would
+ * appear not as the counts should be low
+ */
+ list_add(&page->lru, &free_pages);
+ continue;
+
+cull_mlocked:
+ if (PageSwapCache(page))
+ try_to_free_swap(page);
+ unlock_page(page);
+ putback_lru_page(page);
+ continue;
+
+activate_locked:
+ /* Not a candidate for swapping, so reclaim swap space. */
+ if (PageSwapCache(page) && vm_swap_full())
+ try_to_free_swap(page);
+ VM_BUG_ON_PAGE(PageActive(page), page);
+ SetPageActive(page);
+ pgactivate++;
+keep_locked:
+ unlock_page(page);
+keep:
+ list_add(&page->lru, &ret_pages);
+ VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page), page);
+ }
+
+ mem_cgroup_uncharge_list(&free_pages);
+ free_hot_cold_page_list(&free_pages, true);
+
+ list_splice(&ret_pages, page_list);
+ count_vm_events(PGACTIVATE, pgactivate);
+
+ *ret_nr_dirty += nr_dirty;
+ *ret_nr_congested += nr_congested;
+ *ret_nr_unqueued_dirty += nr_unqueued_dirty;
+ *ret_nr_writeback += nr_writeback;
+ *ret_nr_immediate += nr_immediate;
+ return nr_reclaimed;
+}
+
+unsigned long reclaim_clean_pages_from_list(struct zone *zone,
+ struct list_head *page_list)
+{
+ struct scan_control sc = {
+ .gfp_mask = GFP_KERNEL,
+ .priority = DEF_PRIORITY,
+ .may_unmap = 1,
+ };
+ unsigned long ret, dummy1, dummy2, dummy3, dummy4, dummy5;
+ struct page *page, *next;
+ LIST_HEAD(clean_pages);
+
+ list_for_each_entry_safe(page, next, page_list, lru) {
+ if (page_is_file_cache(page) && !PageDirty(page) &&
+ !isolated_balloon_page(page)) {
+ ClearPageActive(page);
+ list_move(&page->lru, &clean_pages);
+ }
+ }
+
+ ret = shrink_page_list(&clean_pages, zone, &sc,
+ TTU_UNMAP|TTU_IGNORE_ACCESS,
+ &dummy1, &dummy2, &dummy3, &dummy4, &dummy5, true);
+ list_splice(&clean_pages, page_list);
+ mod_zone_page_state(zone, NR_ISOLATED_FILE, -ret);
+ return ret;
+}
+
+/*
+ * Attempt to remove the specified page from its LRU. Only take this page
+ * if it is of the appropriate PageActive status. Pages which are being
+ * freed elsewhere are also ignored.
+ *
+ * page: page to consider
+ * mode: one of the LRU isolation modes defined above
+ *
+ * returns 0 on success, -ve errno on failure.
+ */
+int __isolate_lru_page(struct page *page, isolate_mode_t mode)
+{
+ int ret = -EINVAL;
+
+ /* Only take pages on the LRU. */
+ if (!PageLRU(page))
+ return ret;
+
+ /* Compaction should not handle unevictable pages but CMA can do so */
+ if (PageUnevictable(page) && !(mode & ISOLATE_UNEVICTABLE))
+ return ret;
+
+ ret = -EBUSY;
+
+ /*
+ * To minimise LRU disruption, the caller can indicate that it only
+ * wants to isolate pages it will be able to operate on without
+ * blocking - clean pages for the most part.
+ *
+ * ISOLATE_CLEAN means that only clean pages should be isolated. This
+ * is used by reclaim when it is cannot write to backing storage
+ *
+ * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages
+ * that it is possible to migrate without blocking
+ */
+ if (mode & (ISOLATE_CLEAN|ISOLATE_ASYNC_MIGRATE)) {
+ /* All the caller can do on PageWriteback is block */
+ if (PageWriteback(page))
+ return ret;
+
+ if (PageDirty(page)) {
+ struct address_space *mapping;
+
+ /* ISOLATE_CLEAN means only clean pages */
+ if (mode & ISOLATE_CLEAN)
+ return ret;
+
+ /*
+ * Only pages without mappings or that have a
+ * ->migratepage callback are possible to migrate
+ * without blocking
+ */
+ mapping = page_mapping(page);
+ if (mapping && !mapping->a_ops->migratepage)
+ return ret;
+ }
+ }
+
+ if ((mode & ISOLATE_UNMAPPED) && page_mapped(page))
+ return ret;
+
+ if (likely(get_page_unless_zero(page))) {
+ /*
+ * Be careful not to clear PageLRU until after we're
+ * sure the page is not being freed elsewhere -- the
+ * page release code relies on it.
+ */
+ ClearPageLRU(page);
+ ret = 0;
+ }
+
+ return ret;
+}
+
+/*
+ * zone->lru_lock is heavily contended. Some of the functions that
+ * shrink the lists perform better by taking out a batch of pages
+ * and working on them outside the LRU lock.
+ *
+ * For pagecache intensive workloads, this function is the hottest
+ * spot in the kernel (apart from copy_*_user functions).
+ *
+ * Appropriate locks must be held before calling this function.
+ *
+ * @nr_to_scan: The number of pages to look through on the list.
+ * @lruvec: The LRU vector to pull pages from.
+ * @dst: The temp list to put pages on to.
+ * @nr_scanned: The number of pages that were scanned.
+ * @sc: The scan_control struct for this reclaim session
+ * @mode: One of the LRU isolation modes
+ * @lru: LRU list id for isolating
+ *
+ * returns how many pages were moved onto *@dst.
+ */
+static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
+ struct lruvec *lruvec, struct list_head *dst,
+ unsigned long *nr_scanned, struct scan_control *sc,
+ isolate_mode_t mode, enum lru_list lru)
+{
+ struct list_head *src = &lruvec->lists[lru];
+ unsigned long nr_taken = 0;
+ unsigned long scan;
+
+ for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
+ struct page *page;
+ int nr_pages;
+
+ page = lru_to_page(src);
+ prefetchw_prev_lru_page(page, src, flags);
+
+ VM_BUG_ON_PAGE(!PageLRU(page), page);
+
+ switch (__isolate_lru_page(page, mode)) {
+ case 0:
+ nr_pages = hpage_nr_pages(page);
+ mem_cgroup_update_lru_size(lruvec, lru, -nr_pages);
+ list_move(&page->lru, dst);
+ nr_taken += nr_pages;
+ break;
+
+ case -EBUSY:
+ /* else it is being freed elsewhere */
+ list_move(&page->lru, src);
+ continue;
+
+ default:
+ BUG();
+ }
+ }
+
+ *nr_scanned = scan;
+ trace_mm_vmscan_lru_isolate(sc->order, nr_to_scan, scan,
+ nr_taken, mode, is_file_lru(lru));
+ return nr_taken;
+}
+
+/**
+ * isolate_lru_page - tries to isolate a page from its LRU list
+ * @page: page to isolate from its LRU list
+ *
+ * Isolates a @page from an LRU list, clears PageLRU and adjusts the
+ * vmstat statistic corresponding to whatever LRU list the page was on.
+ *
+ * Returns 0 if the page was removed from an LRU list.
+ * Returns -EBUSY if the page was not on an LRU list.
+ *
+ * The returned page will have PageLRU() cleared. If it was found on
+ * the active list, it will have PageActive set. If it was found on
+ * the unevictable list, it will have the PageUnevictable bit set. That flag
+ * may need to be cleared by the caller before letting the page go.
+ *
+ * The vmstat statistic corresponding to the list on which the page was
+ * found will be decremented.
+ *
+ * Restrictions:
+ * (1) Must be called with an elevated refcount on the page. This is a
+ * fundamentnal difference from isolate_lru_pages (which is called
+ * without a stable reference).
+ * (2) the lru_lock must not be held.
+ * (3) interrupts must be enabled.
+ */
+int isolate_lru_page(struct page *page)
+{
+ int ret = -EBUSY;
+
+ VM_BUG_ON_PAGE(!page_count(page), page);
+
+ if (PageLRU(page)) {
+ struct zone *zone = page_zone(page);
+ struct lruvec *lruvec;
+
+ spin_lock_irq(&zone->lru_lock);
+ lruvec = mem_cgroup_page_lruvec(page, zone);
+ if (PageLRU(page)) {
+ int lru = page_lru(page);
+ get_page(page);
+ ClearPageLRU(page);
+ del_page_from_lru_list(page, lruvec, lru);
+ ret = 0;
+ }
+ spin_unlock_irq(&zone->lru_lock);
+ }
+ return ret;
+}
+
+/*
+ * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and
+ * then get resheduled. When there are massive number of tasks doing page
+ * allocation, such sleeping direct reclaimers may keep piling up on each CPU,
+ * the LRU list will go small and be scanned faster than necessary, leading to
+ * unnecessary swapping, thrashing and OOM.
+ */
+static int too_many_isolated(struct zone *zone, int file,
+ struct scan_control *sc)
+{
+ unsigned long inactive, isolated;
+
+ if (current_is_kswapd())
+ return 0;
+
+ if (!global_reclaim(sc))
+ return 0;
+
+ if (file) {
+ inactive = zone_page_state(zone, NR_INACTIVE_FILE);
+ isolated = zone_page_state(zone, NR_ISOLATED_FILE);
+ } else {
+ inactive = zone_page_state(zone, NR_INACTIVE_ANON);
+ isolated = zone_page_state(zone, NR_ISOLATED_ANON);
+ }
+
+ /*
+ * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they
+ * won't get blocked by normal direct-reclaimers, forming a circular
+ * deadlock.
+ */
+ if ((sc->gfp_mask & GFP_IOFS) == GFP_IOFS)
+ inactive >>= 3;
+
+ return isolated > inactive;
+}
+
+static noinline_for_stack void
+putback_inactive_pages(struct lruvec *lruvec, struct list_head *page_list)
+{
+ struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
+ struct zone *zone = lruvec_zone(lruvec);
+ LIST_HEAD(pages_to_free);
+
+ /*
+ * Put back any unfreeable pages.
+ */
+ while (!list_empty(page_list)) {
+ struct page *page = lru_to_page(page_list);
+ int lru;
+
+ VM_BUG_ON_PAGE(PageLRU(page), page);
+ list_del(&page->lru);
+ if (unlikely(!page_evictable(page))) {
+ spin_unlock_irq(&zone->lru_lock);
+ putback_lru_page(page);
+ spin_lock_irq(&zone->lru_lock);
+ continue;
+ }
+
+ lruvec = mem_cgroup_page_lruvec(page, zone);
+
+ SetPageLRU(page);
+ lru = page_lru(page);
+ add_page_to_lru_list(page, lruvec, lru);
+
+ if (is_active_lru(lru)) {
+ int file = is_file_lru(lru);
+ int numpages = hpage_nr_pages(page);
+ reclaim_stat->recent_rotated[file] += numpages;
+ }
+ if (put_page_testzero(page)) {
+ __ClearPageLRU(page);
+ __ClearPageActive(page);
+ del_page_from_lru_list(page, lruvec, lru);
+
+ if (unlikely(PageCompound(page))) {
+ spin_unlock_irq(&zone->lru_lock);
+ mem_cgroup_uncharge(page);
+ (*get_compound_page_dtor(page))(page);
+ spin_lock_irq(&zone->lru_lock);
+ } else
+ list_add(&page->lru, &pages_to_free);
+ }
+ }
+
+ /*
+ * To save our caller's stack, now use input list for pages to free.
+ */
+ list_splice(&pages_to_free, page_list);
+}
+
+/*
+ * If a kernel thread (such as nfsd for loop-back mounts) services
+ * a backing device by writing to the page cache it sets PF_LESS_THROTTLE.
+ * In that case we should only throttle if the backing device it is
+ * writing to is congested. In other cases it is safe to throttle.
+ */
+static int current_may_throttle(void)
+{
+ return !(current->flags & PF_LESS_THROTTLE) ||
+ current->backing_dev_info == NULL ||
+ bdi_write_congested(current->backing_dev_info);
+}
+
+/*
+ * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
+ * of reclaimed pages
+ */
+static noinline_for_stack unsigned long
+shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
+ struct scan_control *sc, enum lru_list lru)
+{
+ LIST_HEAD(page_list);
+ unsigned long nr_scanned;
+ unsigned long nr_reclaimed = 0;
+ unsigned long nr_taken;
+ unsigned long nr_dirty = 0;
+ unsigned long nr_congested = 0;
+ unsigned long nr_unqueued_dirty = 0;
+ unsigned long nr_writeback = 0;
+ unsigned long nr_immediate = 0;
+ isolate_mode_t isolate_mode = 0;
+ int file = is_file_lru(lru);
+ struct zone *zone = lruvec_zone(lruvec);
+ struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
+
+ while (unlikely(too_many_isolated(zone, file, sc))) {
+ congestion_wait(BLK_RW_ASYNC, HZ/10);
+
+ /* We are about to die and free our memory. Return now. */
+ if (fatal_signal_pending(current))
+ return SWAP_CLUSTER_MAX;
+ }
+
+ lru_add_drain();
+
+ if (!sc->may_unmap)
+ isolate_mode |= ISOLATE_UNMAPPED;
+ if (!sc->may_writepage)
+ isolate_mode |= ISOLATE_CLEAN;
+
+ spin_lock_irq(&zone->lru_lock);
+
+ nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &page_list,
+ &nr_scanned, sc, isolate_mode, lru);
+
+ __mod_zone_page_state(zone, NR_LRU_BASE + lru, -nr_taken);
+ __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
+
+ if (global_reclaim(sc)) {
+ __mod_zone_page_state(zone, NR_PAGES_SCANNED, nr_scanned);
+ if (current_is_kswapd())
+ __count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scanned);
+ else
+ __count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scanned);
+ }
+ spin_unlock_irq(&zone->lru_lock);
+
+ if (nr_taken == 0)
+ return 0;
+
+ nr_reclaimed = shrink_page_list(&page_list, zone, sc, TTU_UNMAP,
+ &nr_dirty, &nr_unqueued_dirty, &nr_congested,
+ &nr_writeback, &nr_immediate,
+ false);
+
+ spin_lock_irq(&zone->lru_lock);
+
+ reclaim_stat->recent_scanned[file] += nr_taken;
+
+ if (global_reclaim(sc)) {
+ if (current_is_kswapd())
+ __count_zone_vm_events(PGSTEAL_KSWAPD, zone,
+ nr_reclaimed);
+ else
+ __count_zone_vm_events(PGSTEAL_DIRECT, zone,
+ nr_reclaimed);
+ }
+
+ putback_inactive_pages(lruvec, &page_list);
+
+ __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
+
+ spin_unlock_irq(&zone->lru_lock);
+
+ mem_cgroup_uncharge_list(&page_list);
+ free_hot_cold_page_list(&page_list, true);
+
+ /*
+ * If reclaim is isolating dirty pages under writeback, it implies
+ * that the long-lived page allocation rate is exceeding the page
+ * laundering rate. Either the global limits are not being effective
+ * at throttling processes due to the page distribution throughout
+ * zones or there is heavy usage of a slow backing device. The
+ * only option is to throttle from reclaim context which is not ideal
+ * as there is no guarantee the dirtying process is throttled in the
+ * same way balance_dirty_pages() manages.
+ *
+ * Once a zone is flagged ZONE_WRITEBACK, kswapd will count the number
+ * of pages under pages flagged for immediate reclaim and stall if any
+ * are encountered in the nr_immediate check below.
+ */
+ if (nr_writeback && nr_writeback == nr_taken)
+ set_bit(ZONE_WRITEBACK, &zone->flags);
+
+ /*
+ * memcg will stall in page writeback so only consider forcibly
+ * stalling for global reclaim
+ */
+ if (global_reclaim(sc)) {
+ /*
+ * Tag a zone as congested if all the dirty pages scanned were
+ * backed by a congested BDI and wait_iff_congested will stall.
+ */
+ if (nr_dirty && nr_dirty == nr_congested)
+ set_bit(ZONE_CONGESTED, &zone->flags);
+
+ /*
+ * If dirty pages are scanned that are not queued for IO, it
+ * implies that flushers are not keeping up. In this case, flag
+ * the zone ZONE_DIRTY and kswapd will start writing pages from
+ * reclaim context.
+ */
+ if (nr_unqueued_dirty == nr_taken)
+ set_bit(ZONE_DIRTY, &zone->flags);
+
+ /*
+ * If kswapd scans pages marked marked for immediate
+ * reclaim and under writeback (nr_immediate), it implies
+ * that pages are cycling through the LRU faster than
+ * they are written so also forcibly stall.
+ */
+ if (nr_immediate && current_may_throttle())
+ congestion_wait(BLK_RW_ASYNC, HZ/10);
+ }
+
+ /*
+ * Stall direct reclaim for IO completions if underlying BDIs or zone
+ * is congested. Allow kswapd to continue until it starts encountering
+ * unqueued dirty pages or cycling through the LRU too quickly.
+ */
+ if (!sc->hibernation_mode && !current_is_kswapd() &&
+ current_may_throttle())
+ wait_iff_congested(zone, BLK_RW_ASYNC, HZ/10);
+
+ trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id,
+ zone_idx(zone),
+ nr_scanned, nr_reclaimed,
+ sc->priority,
+ trace_shrink_flags(file));
+ return nr_reclaimed;
+}
+
+/*
+ * This moves pages from the active list to the inactive list.
+ *
+ * We move them the other way if the page is referenced by one or more
+ * processes, from rmap.
+ *
+ * If the pages are mostly unmapped, the processing is fast and it is
+ * appropriate to hold zone->lru_lock across the whole operation. But if
+ * the pages are mapped, the processing is slow (page_referenced()) so we
+ * should drop zone->lru_lock around each page. It's impossible to balance
+ * this, so instead we remove the pages from the LRU while processing them.
+ * It is safe to rely on PG_active against the non-LRU pages in here because
+ * nobody will play with that bit on a non-LRU page.
+ *
+ * The downside is that we have to touch page->_count against each page.
+ * But we had to alter page->flags anyway.
+ */
+
+static void move_active_pages_to_lru(struct lruvec *lruvec,
+ struct list_head *list,
+ struct list_head *pages_to_free,
+ enum lru_list lru)
+{
+ struct zone *zone = lruvec_zone(lruvec);
+ unsigned long pgmoved = 0;
+ struct page *page;
+ int nr_pages;
+
+ while (!list_empty(list)) {
+ page = lru_to_page(list);
+ lruvec = mem_cgroup_page_lruvec(page, zone);
+
+ VM_BUG_ON_PAGE(PageLRU(page), page);
+ SetPageLRU(page);
+
+ nr_pages = hpage_nr_pages(page);
+ mem_cgroup_update_lru_size(lruvec, lru, nr_pages);
+ list_move(&page->lru, &lruvec->lists[lru]);
+ pgmoved += nr_pages;
+
+ if (put_page_testzero(page)) {
+ __ClearPageLRU(page);
+ __ClearPageActive(page);
+ del_page_from_lru_list(page, lruvec, lru);
+
+ if (unlikely(PageCompound(page))) {
+ spin_unlock_irq(&zone->lru_lock);
+ mem_cgroup_uncharge(page);
+ (*get_compound_page_dtor(page))(page);
+ spin_lock_irq(&zone->lru_lock);
+ } else
+ list_add(&page->lru, pages_to_free);
+ }
+ }
+ __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
+ if (!is_active_lru(lru))
+ __count_vm_events(PGDEACTIVATE, pgmoved);
+}
+
+static void shrink_active_list(unsigned long nr_to_scan,
+ struct lruvec *lruvec,
+ struct scan_control *sc,
+ enum lru_list lru)
+{
+ unsigned long nr_taken;
+ unsigned long nr_scanned;
+ unsigned long vm_flags;
+ LIST_HEAD(l_hold); /* The pages which were snipped off */
+ LIST_HEAD(l_active);
+ LIST_HEAD(l_inactive);
+ struct page *page;
+ struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
+ unsigned long nr_rotated = 0;
+ isolate_mode_t isolate_mode = 0;
+ int file = is_file_lru(lru);
+ struct zone *zone = lruvec_zone(lruvec);
+
+ lru_add_drain();
+
+ if (!sc->may_unmap)
+ isolate_mode |= ISOLATE_UNMAPPED;
+ if (!sc->may_writepage)
+ isolate_mode |= ISOLATE_CLEAN;
+
+ spin_lock_irq(&zone->lru_lock);
+
+ nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &l_hold,
+ &nr_scanned, sc, isolate_mode, lru);
+ if (global_reclaim(sc))
+ __mod_zone_page_state(zone, NR_PAGES_SCANNED, nr_scanned);
+
+ reclaim_stat->recent_scanned[file] += nr_taken;
+
+ __count_zone_vm_events(PGREFILL, zone, nr_scanned);
+ __mod_zone_page_state(zone, NR_LRU_BASE + lru, -nr_taken);
+ __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
+ spin_unlock_irq(&zone->lru_lock);
+
+ while (!list_empty(&l_hold)) {
+ cond_resched();
+ page = lru_to_page(&l_hold);
+ list_del(&page->lru);
+
+ if (unlikely(!page_evictable(page))) {
+ putback_lru_page(page);
+ continue;
+ }
+
+ if (unlikely(buffer_heads_over_limit)) {
+ if (page_has_private(page) && trylock_page(page)) {
+ if (page_has_private(page))
+ try_to_release_page(page, 0);
+ unlock_page(page);
+ }
+ }
+
+ if (page_referenced(page, 0, sc->target_mem_cgroup,
+ &vm_flags)) {
+ nr_rotated += hpage_nr_pages(page);
+ /*
+ * Identify referenced, file-backed active pages and
+ * give them one more trip around the active list. So
+ * that executable code get better chances to stay in
+ * memory under moderate memory pressure. Anon pages
+ * are not likely to be evicted by use-once streaming
+ * IO, plus JVM can create lots of anon VM_EXEC pages,
+ * so we ignore them here.
+ */
+ if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
+ list_add(&page->lru, &l_active);
+ continue;
+ }
+ }
+
+ ClearPageActive(page); /* we are de-activating */
+ list_add(&page->lru, &l_inactive);
+ }
+
+ /*
+ * Move pages back to the lru list.
+ */
+ spin_lock_irq(&zone->lru_lock);
+ /*
+ * Count referenced pages from currently used mappings as rotated,
+ * even though only some of them are actually re-activated. This
+ * helps balance scan pressure between file and anonymous pages in
+ * get_scan_count.
+ */
+ reclaim_stat->recent_rotated[file] += nr_rotated;
+
+ move_active_pages_to_lru(lruvec, &l_active, &l_hold, lru);
+ move_active_pages_to_lru(lruvec, &l_inactive, &l_hold, lru - LRU_ACTIVE);
+ __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
+ spin_unlock_irq(&zone->lru_lock);
+
+ mem_cgroup_uncharge_list(&l_hold);
+ free_hot_cold_page_list(&l_hold, true);
+}
+
+#ifdef CONFIG_SWAP
+static int inactive_anon_is_low_global(struct zone *zone)
+{
+ unsigned long active, inactive;
+
+ active = zone_page_state(zone, NR_ACTIVE_ANON);
+ inactive = zone_page_state(zone, NR_INACTIVE_ANON);
+
+ if (inactive * zone->inactive_ratio < active)
+ return 1;
+
+ return 0;
+}
+
+/**
+ * inactive_anon_is_low - check if anonymous pages need to be deactivated
+ * @lruvec: LRU vector to check
+ *
+ * Returns true if the zone does not have enough inactive anon pages,
+ * meaning some active anon pages need to be deactivated.
+ */
+static int inactive_anon_is_low(struct lruvec *lruvec)
+{
+ /*
+ * If we don't have swap space, anonymous page deactivation
+ * is pointless.
+ */
+ if (!total_swap_pages)
+ return 0;
+
+ if (!mem_cgroup_disabled())
+ return mem_cgroup_inactive_anon_is_low(lruvec);
+
+ return inactive_anon_is_low_global(lruvec_zone(lruvec));
+}
+#else
+static inline int inactive_anon_is_low(struct lruvec *lruvec)
+{
+ return 0;
+}
+#endif
+
+/**
+ * inactive_file_is_low - check if file pages need to be deactivated
+ * @lruvec: LRU vector to check
+ *
+ * When the system is doing streaming IO, memory pressure here
+ * ensures that active file pages get deactivated, until more
+ * than half of the file pages are on the inactive list.
+ *
+ * Once we get to that situation, protect the system's working
+ * set from being evicted by disabling active file page aging.
+ *
+ * This uses a different ratio than the anonymous pages, because
+ * the page cache uses a use-once replacement algorithm.
+ */
+static int inactive_file_is_low(struct lruvec *lruvec)
+{
+ unsigned long inactive;
+ unsigned long active;
+
+ inactive = get_lru_size(lruvec, LRU_INACTIVE_FILE);
+ active = get_lru_size(lruvec, LRU_ACTIVE_FILE);
+
+ return active > inactive;
+}
+
+static int inactive_list_is_low(struct lruvec *lruvec, enum lru_list lru)
+{
+ if (is_file_lru(lru))
+ return inactive_file_is_low(lruvec);
+ else
+ return inactive_anon_is_low(lruvec);
+}
+
+static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
+ struct lruvec *lruvec, struct scan_control *sc)
+{
+ if (is_active_lru(lru)) {
+ if (inactive_list_is_low(lruvec, lru))
+ shrink_active_list(nr_to_scan, lruvec, sc, lru);
+ return 0;
+ }
+
+ return shrink_inactive_list(nr_to_scan, lruvec, sc, lru);
+}
+
+enum scan_balance {
+ SCAN_EQUAL,
+ SCAN_FRACT,
+ SCAN_ANON,
+ SCAN_FILE,
+};
+
+/*
+ * Determine how aggressively the anon and file LRU lists should be
+ * scanned. The relative value of each set of LRU lists is determined
+ * by looking at the fraction of the pages scanned we did rotate back
+ * onto the active list instead of evict.
+ *
+ * nr[0] = anon inactive pages to scan; nr[1] = anon active pages to scan
+ * nr[2] = file inactive pages to scan; nr[3] = file active pages to scan
+ */
+static void get_scan_count(struct lruvec *lruvec, int swappiness,
+ struct scan_control *sc, unsigned long *nr,
+ unsigned long *lru_pages)
+{
+ struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
+ u64 fraction[2];
+ u64 denominator = 0; /* gcc */
+ struct zone *zone = lruvec_zone(lruvec);
+ unsigned long anon_prio, file_prio;
+ enum scan_balance scan_balance;
+ unsigned long anon, file;
+ bool force_scan = false;
+ unsigned long ap, fp;
+ enum lru_list lru;
+ bool some_scanned;
+ int pass;
+
+ /*
+ * If the zone or memcg is small, nr[l] can be 0. This
+ * results in no scanning on this priority and a potential
+ * priority drop. Global direct reclaim can go to the next
+ * zone and tends to have no problems. Global kswapd is for
+ * zone balancing and it needs to scan a minimum amount. When
+ * reclaiming for a memcg, a priority drop can cause high
+ * latencies, so it's better to scan a minimum amount there as
+ * well.
+ */
+ if (current_is_kswapd()) {
+ if (!zone_reclaimable(zone))
+ force_scan = true;
+ if (!mem_cgroup_lruvec_online(lruvec))
+ force_scan = true;
+ }
+ if (!global_reclaim(sc))
+ force_scan = true;
+
+ /* If we have no swap space, do not bother scanning anon pages. */
+ if (!sc->may_swap || (get_nr_swap_pages() <= 0)) {
+ scan_balance = SCAN_FILE;
+ goto out;
+ }
+
+ /*
+ * Global reclaim will swap to prevent OOM even with no
+ * swappiness, but memcg users want to use this knob to
+ * disable swapping for individual groups completely when
+ * using the memory controller's swap limit feature would be
+ * too expensive.
+ */
+ if (!global_reclaim(sc) && !swappiness) {
+ scan_balance = SCAN_FILE;
+ goto out;
+ }
+
+ /*
+ * Do not apply any pressure balancing cleverness when the
+ * system is close to OOM, scan both anon and file equally
+ * (unless the swappiness setting disagrees with swapping).
+ */
+ if (!sc->priority && swappiness) {
+ scan_balance = SCAN_EQUAL;
+ goto out;
+ }
+
+ /*
+ * Prevent the reclaimer from falling into the cache trap: as
+ * cache pages start out inactive, every cache fault will tip
+ * the scan balance towards the file LRU. And as the file LRU
+ * shrinks, so does the window for rotation from references.
+ * This means we have a runaway feedback loop where a tiny
+ * thrashing file LRU becomes infinitely more attractive than
+ * anon pages. Try to detect this based on file LRU size.
+ */
+ if (global_reclaim(sc)) {
+ unsigned long zonefile;
+ unsigned long zonefree;
+
+ zonefree = zone_page_state(zone, NR_FREE_PAGES);
+ zonefile = zone_page_state(zone, NR_ACTIVE_FILE) +
+ zone_page_state(zone, NR_INACTIVE_FILE);
+
+ if (unlikely(zonefile + zonefree <= high_wmark_pages(zone))) {
+ scan_balance = SCAN_ANON;
+ goto out;
+ }
+ }
+
+ /*
+ * There is enough inactive page cache, do not reclaim
+ * anything from the anonymous working set right now.
+ */
+ if (!inactive_file_is_low(lruvec)) {
+ scan_balance = SCAN_FILE;
+ goto out;
+ }
+
+ scan_balance = SCAN_FRACT;
+
+ /*
+ * With swappiness at 100, anonymous and file have the same priority.
+ * This scanning priority is essentially the inverse of IO cost.
+ */
+ anon_prio = swappiness;
+ file_prio = 200 - anon_prio;
+
+ /*
+ * OK, so we have swap space and a fair amount of page cache
+ * pages. We use the recently rotated / recently scanned
+ * ratios to determine how valuable each cache is.
+ *
+ * Because workloads change over time (and to avoid overflow)
+ * we keep these statistics as a floating average, which ends
+ * up weighing recent references more than old ones.
+ *
+ * anon in [0], file in [1]
+ */
+
+ anon = get_lru_size(lruvec, LRU_ACTIVE_ANON) +
+ get_lru_size(lruvec, LRU_INACTIVE_ANON);
+ file = get_lru_size(lruvec, LRU_ACTIVE_FILE) +
+ get_lru_size(lruvec, LRU_INACTIVE_FILE);
+
+ spin_lock_irq(&zone->lru_lock);
+ if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
+ reclaim_stat->recent_scanned[0] /= 2;
+ reclaim_stat->recent_rotated[0] /= 2;
+ }
+
+ if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
+ reclaim_stat->recent_scanned[1] /= 2;
+ reclaim_stat->recent_rotated[1] /= 2;
+ }
+
+ /*
+ * The amount of pressure on anon vs file pages is inversely
+ * proportional to the fraction of recently scanned pages on
+ * each list that were recently referenced and in active use.
+ */
+ ap = anon_prio * (reclaim_stat->recent_scanned[0] + 1);
+ ap /= reclaim_stat->recent_rotated[0] + 1;
+
+ fp = file_prio * (reclaim_stat->recent_scanned[1] + 1);
+ fp /= reclaim_stat->recent_rotated[1] + 1;
+ spin_unlock_irq(&zone->lru_lock);
+
+ fraction[0] = ap;
+ fraction[1] = fp;
+ denominator = ap + fp + 1;
+out:
+ some_scanned = false;
+ /* Only use force_scan on second pass. */
+ for (pass = 0; !some_scanned && pass < 2; pass++) {
+ *lru_pages = 0;
+ for_each_evictable_lru(lru) {
+ int file = is_file_lru(lru);
+ unsigned long size;
+ unsigned long scan;
+
+ size = get_lru_size(lruvec, lru);
+ scan = size >> sc->priority;
+
+ if (!scan && pass && force_scan)
+ scan = min(size, SWAP_CLUSTER_MAX);
+
+ switch (scan_balance) {
+ case SCAN_EQUAL:
+ /* Scan lists relative to size */
+ break;
+ case SCAN_FRACT:
+ /*
+ * Scan types proportional to swappiness and
+ * their relative recent reclaim efficiency.
+ */
+ scan = div64_u64(scan * fraction[file],
+ denominator);
+ break;
+ case SCAN_FILE:
+ case SCAN_ANON:
+ /* Scan one type exclusively */
+ if ((scan_balance == SCAN_FILE) != file) {
+ size = 0;
+ scan = 0;
+ }
+ break;
+ default:
+ /* Look ma, no brain */
+ BUG();
+ }
+
+ *lru_pages += size;
+ nr[lru] = scan;
+
+ /*
+ * Skip the second pass and don't force_scan,
+ * if we found something to scan.
+ */
+ some_scanned |= !!scan;
+ }
+ }
+}
+
+/*
+ * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
+ */
+static void shrink_lruvec(struct lruvec *lruvec, int swappiness,
+ struct scan_control *sc, unsigned long *lru_pages)
+{
+ unsigned long nr[NR_LRU_LISTS];
+ unsigned long targets[NR_LRU_LISTS];
+ unsigned long nr_to_scan;
+ enum lru_list lru;
+ unsigned long nr_reclaimed = 0;
+ unsigned long nr_to_reclaim = sc->nr_to_reclaim;
+ struct blk_plug plug;
+ bool scan_adjusted;
+
+ get_scan_count(lruvec, swappiness, sc, nr, lru_pages);
+
+ /* Record the original scan target for proportional adjustments later */
+ memcpy(targets, nr, sizeof(nr));
+
+ /*
+ * Global reclaiming within direct reclaim at DEF_PRIORITY is a normal
+ * event that can occur when there is little memory pressure e.g.
+ * multiple streaming readers/writers. Hence, we do not abort scanning
+ * when the requested number of pages are reclaimed when scanning at
+ * DEF_PRIORITY on the assumption that the fact we are direct
+ * reclaiming implies that kswapd is not keeping up and it is best to
+ * do a batch of work at once. For memcg reclaim one check is made to
+ * abort proportional reclaim if either the file or anon lru has already
+ * dropped to zero at the first pass.
+ */
+ scan_adjusted = (global_reclaim(sc) && !current_is_kswapd() &&
+ sc->priority == DEF_PRIORITY);
+
+ blk_start_plug(&plug);
+ while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
+ nr[LRU_INACTIVE_FILE]) {
+ unsigned long nr_anon, nr_file, percentage;
+ unsigned long nr_scanned;
+
+ for_each_evictable_lru(lru) {
+ if (nr[lru]) {
+ nr_to_scan = min(nr[lru], SWAP_CLUSTER_MAX);
+ nr[lru] -= nr_to_scan;
+
+ nr_reclaimed += shrink_list(lru, nr_to_scan,
+ lruvec, sc);
+ }
+ }
+
+ if (nr_reclaimed < nr_to_reclaim || scan_adjusted)
+ continue;
+
+ /*
+ * For kswapd and memcg, reclaim at least the number of pages
+ * requested. Ensure that the anon and file LRUs are scanned
+ * proportionally what was requested by get_scan_count(). We
+ * stop reclaiming one LRU and reduce the amount scanning
+ * proportional to the original scan target.
+ */
+ nr_file = nr[LRU_INACTIVE_FILE] + nr[LRU_ACTIVE_FILE];
+ nr_anon = nr[LRU_INACTIVE_ANON] + nr[LRU_ACTIVE_ANON];
+
+ /*
+ * It's just vindictive to attack the larger once the smaller
+ * has gone to zero. And given the way we stop scanning the
+ * smaller below, this makes sure that we only make one nudge
+ * towards proportionality once we've got nr_to_reclaim.
+ */
+ if (!nr_file || !nr_anon)
+ break;
+
+ if (nr_file > nr_anon) {
+ unsigned long scan_target = targets[LRU_INACTIVE_ANON] +
+ targets[LRU_ACTIVE_ANON] + 1;
+ lru = LRU_BASE;
+ percentage = nr_anon * 100 / scan_target;
+ } else {
+ unsigned long scan_target = targets[LRU_INACTIVE_FILE] +
+ targets[LRU_ACTIVE_FILE] + 1;
+ lru = LRU_FILE;
+ percentage = nr_file * 100 / scan_target;
+ }
+
+ /* Stop scanning the smaller of the LRU */
+ nr[lru] = 0;
+ nr[lru + LRU_ACTIVE] = 0;
+
+ /*
+ * Recalculate the other LRU scan count based on its original
+ * scan target and the percentage scanning already complete
+ */
+ lru = (lru == LRU_FILE) ? LRU_BASE : LRU_FILE;
+ nr_scanned = targets[lru] - nr[lru];
+ nr[lru] = targets[lru] * (100 - percentage) / 100;
+ nr[lru] -= min(nr[lru], nr_scanned);
+
+ lru += LRU_ACTIVE;
+ nr_scanned = targets[lru] - nr[lru];
+ nr[lru] = targets[lru] * (100 - percentage) / 100;
+ nr[lru] -= min(nr[lru], nr_scanned);
+
+ scan_adjusted = true;
+ }
+ blk_finish_plug(&plug);
+ sc->nr_reclaimed += nr_reclaimed;
+
+ /*
+ * Even if we did not try to evict anon pages at all, we want to
+ * rebalance the anon lru active/inactive ratio.
+ */
+ if (inactive_anon_is_low(lruvec))
+ shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
+ sc, LRU_ACTIVE_ANON);
+
+ throttle_vm_writeout(sc->gfp_mask);
+}
+
+/* Use reclaim/compaction for costly allocs or under memory pressure */
+static bool in_reclaim_compaction(struct scan_control *sc)
+{
+ if (IS_ENABLED(CONFIG_COMPACTION) && sc->order &&
+ (sc->order > PAGE_ALLOC_COSTLY_ORDER ||
+ sc->priority < DEF_PRIORITY - 2))
+ return true;
+
+ return false;
+}
+
+/*
+ * Reclaim/compaction is used for high-order allocation requests. It reclaims
+ * order-0 pages before compacting the zone. should_continue_reclaim() returns
+ * true if more pages should be reclaimed such that when the page allocator
+ * calls try_to_compact_zone() that it will have enough free pages to succeed.
+ * It will give up earlier than that if there is difficulty reclaiming pages.
+ */
+static inline bool should_continue_reclaim(struct zone *zone,
+ unsigned long nr_reclaimed,
+ unsigned long nr_scanned,
+ struct scan_control *sc)
+{
+ unsigned long pages_for_compaction;
+ unsigned long inactive_lru_pages;
+
+ /* If not in reclaim/compaction mode, stop */
+ if (!in_reclaim_compaction(sc))
+ return false;
+
+ /* Consider stopping depending on scan and reclaim activity */
+ if (sc->gfp_mask & __GFP_REPEAT) {
+ /*
+ * For __GFP_REPEAT allocations, stop reclaiming if the
+ * full LRU list has been scanned and we are still failing
+ * to reclaim pages. This full LRU scan is potentially
+ * expensive but a __GFP_REPEAT caller really wants to succeed
+ */
+ if (!nr_reclaimed && !nr_scanned)
+ return false;
+ } else {
+ /*
+ * For non-__GFP_REPEAT allocations which can presumably
+ * fail without consequence, stop if we failed to reclaim
+ * any pages from the last SWAP_CLUSTER_MAX number of
+ * pages that were scanned. This will return to the
+ * caller faster at the risk reclaim/compaction and
+ * the resulting allocation attempt fails
+ */
+ if (!nr_reclaimed)
+ return false;
+ }
+
+ /*
+ * If we have not reclaimed enough pages for compaction and the
+ * inactive lists are large enough, continue reclaiming
+ */
+ pages_for_compaction = (2UL << sc->order);
+ inactive_lru_pages = zone_page_state(zone, NR_INACTIVE_FILE);
+ if (get_nr_swap_pages() > 0)
+ inactive_lru_pages += zone_page_state(zone, NR_INACTIVE_ANON);
+ if (sc->nr_reclaimed < pages_for_compaction &&
+ inactive_lru_pages > pages_for_compaction)
+ return true;
+
+ /* If compaction would go ahead or the allocation would succeed, stop */
+ switch (compaction_suitable(zone, sc->order, 0, 0)) {
+ case COMPACT_PARTIAL:
+ case COMPACT_CONTINUE:
+ return false;
+ default:
+ return true;
+ }
+}
+
+static bool shrink_zone(struct zone *zone, struct scan_control *sc,
+ bool is_classzone)
+{
+ struct reclaim_state *reclaim_state = current->reclaim_state;
+ unsigned long nr_reclaimed, nr_scanned;
+ bool reclaimable = false;
+
+ do {
+ struct mem_cgroup *root = sc->target_mem_cgroup;
+ struct mem_cgroup_reclaim_cookie reclaim = {
+ .zone = zone,
+ .priority = sc->priority,
+ };
+ unsigned long zone_lru_pages = 0;
+ struct mem_cgroup *memcg;
+
+ nr_reclaimed = sc->nr_reclaimed;
+ nr_scanned = sc->nr_scanned;
+
+ memcg = mem_cgroup_iter(root, NULL, &reclaim);
+ do {
+ unsigned long lru_pages;
+ unsigned long scanned;
+ struct lruvec *lruvec;
+ int swappiness;
+
+ if (mem_cgroup_low(root, memcg)) {
+ if (!sc->may_thrash)
+ continue;
+ mem_cgroup_events(memcg, MEMCG_LOW, 1);
+ }
+
+ lruvec = mem_cgroup_zone_lruvec(zone, memcg);
+ swappiness = mem_cgroup_swappiness(memcg);
+ scanned = sc->nr_scanned;
+
+ shrink_lruvec(lruvec, swappiness, sc, &lru_pages);
+ zone_lru_pages += lru_pages;
+
+ if (memcg && is_classzone)
+ shrink_slab(sc->gfp_mask, zone_to_nid(zone),
+ memcg, sc->nr_scanned - scanned,
+ lru_pages);
+
+ /*
+ * Direct reclaim and kswapd have to scan all memory
+ * cgroups to fulfill the overall scan target for the
+ * zone.
+ *
+ * Limit reclaim, on the other hand, only cares about
+ * nr_to_reclaim pages to be reclaimed and it will
+ * retry with decreasing priority if one round over the
+ * whole hierarchy is not sufficient.
+ */
+ if (!global_reclaim(sc) &&
+ sc->nr_reclaimed >= sc->nr_to_reclaim) {
+ mem_cgroup_iter_break(root, memcg);
+ break;
+ }
+ } while ((memcg = mem_cgroup_iter(root, memcg, &reclaim)));
+
+ /*
+ * Shrink the slab caches in the same proportion that
+ * the eligible LRU pages were scanned.
+ */
+ if (global_reclaim(sc) && is_classzone)
+ shrink_slab(sc->gfp_mask, zone_to_nid(zone), NULL,
+ sc->nr_scanned - nr_scanned,
+ zone_lru_pages);
+
+ if (reclaim_state) {
+ sc->nr_reclaimed += reclaim_state->reclaimed_slab;
+ reclaim_state->reclaimed_slab = 0;
+ }
+
+ vmpressure(sc->gfp_mask, sc->target_mem_cgroup,
+ sc->nr_scanned - nr_scanned,
+ sc->nr_reclaimed - nr_reclaimed);
+
+ if (sc->nr_reclaimed - nr_reclaimed)
+ reclaimable = true;
+
+ } while (should_continue_reclaim(zone, sc->nr_reclaimed - nr_reclaimed,
+ sc->nr_scanned - nr_scanned, sc));
+
+ return reclaimable;
+}
+
+/*
+ * Returns true if compaction should go ahead for a high-order request, or
+ * the high-order allocation would succeed without compaction.
+ */
+static inline bool compaction_ready(struct zone *zone, int order)
+{
+ unsigned long balance_gap, watermark;
+ bool watermark_ok;
+
+ /*
+ * Compaction takes time to run and there are potentially other
+ * callers using the pages just freed. Continue reclaiming until
+ * there is a buffer of free pages available to give compaction
+ * a reasonable chance of completing and allocating the page
+ */
+ balance_gap = min(low_wmark_pages(zone), DIV_ROUND_UP(
+ zone->managed_pages, KSWAPD_ZONE_BALANCE_GAP_RATIO));
+ watermark = high_wmark_pages(zone) + balance_gap + (2UL << order);
+ watermark_ok = zone_watermark_ok_safe(zone, 0, watermark, 0, 0);
+
+ /*
+ * If compaction is deferred, reclaim up to a point where
+ * compaction will have a chance of success when re-enabled
+ */
+ if (compaction_deferred(zone, order))
+ return watermark_ok;
+
+ /*
+ * If compaction is not ready to start and allocation is not likely
+ * to succeed without it, then keep reclaiming.
+ */
+ if (compaction_suitable(zone, order, 0, 0) == COMPACT_SKIPPED)
+ return false;
+
+ return watermark_ok;
+}
+
+/*
+ * This is the direct reclaim path, for page-allocating processes. We only
+ * try to reclaim pages from zones which will satisfy the caller's allocation
+ * request.
+ *
+ * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
+ * Because:
+ * a) The caller may be trying to free *extra* pages to satisfy a higher-order
+ * allocation or
+ * b) The target zone may be at high_wmark_pages(zone) but the lower zones
+ * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
+ * zone defense algorithm.
+ *
+ * If a zone is deemed to be full of pinned pages then just give it a light
+ * scan then give up on it.
+ *
+ * Returns true if a zone was reclaimable.
+ */
+static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
+{
+ struct zoneref *z;
+ struct zone *zone;
+ unsigned long nr_soft_reclaimed;
+ unsigned long nr_soft_scanned;
+ gfp_t orig_mask;
+ enum zone_type requested_highidx = gfp_zone(sc->gfp_mask);
+ bool reclaimable = false;
+
+ /*
+ * If the number of buffer_heads in the machine exceeds the maximum
+ * allowed level, force direct reclaim to scan the highmem zone as
+ * highmem pages could be pinning lowmem pages storing buffer_heads
+ */
+ orig_mask = sc->gfp_mask;
+ if (buffer_heads_over_limit)
+ sc->gfp_mask |= __GFP_HIGHMEM;
+
+ for_each_zone_zonelist_nodemask(zone, z, zonelist,
+ requested_highidx, sc->nodemask) {
+ enum zone_type classzone_idx;
+
+ if (!populated_zone(zone))
+ continue;
+
+ classzone_idx = requested_highidx;
+ while (!populated_zone(zone->zone_pgdat->node_zones +
+ classzone_idx))
+ classzone_idx--;
+
+ /*
+ * Take care memory controller reclaiming has small influence
+ * to global LRU.
+ */
+ if (global_reclaim(sc)) {
+ if (!cpuset_zone_allowed(zone,
+ GFP_KERNEL | __GFP_HARDWALL))
+ continue;
+
+ if (sc->priority != DEF_PRIORITY &&
+ !zone_reclaimable(zone))
+ continue; /* Let kswapd poll it */
+
+ /*
+ * If we already have plenty of memory free for
+ * compaction in this zone, don't free any more.
+ * Even though compaction is invoked for any
+ * non-zero order, only frequent costly order
+ * reclamation is disruptive enough to become a
+ * noticeable problem, like transparent huge
+ * page allocations.
+ */
+ if (IS_ENABLED(CONFIG_COMPACTION) &&
+ sc->order > PAGE_ALLOC_COSTLY_ORDER &&
+ zonelist_zone_idx(z) <= requested_highidx &&
+ compaction_ready(zone, sc->order)) {
+ sc->compaction_ready = true;
+ continue;
+ }
+
+ /*
+ * This steals pages from memory cgroups over softlimit
+ * and returns the number of reclaimed pages and
+ * scanned pages. This works for global memory pressure
+ * and balancing, not for a memcg's limit.
+ */
+ nr_soft_scanned = 0;
+ nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
+ sc->order, sc->gfp_mask,
+ &nr_soft_scanned);
+ sc->nr_reclaimed += nr_soft_reclaimed;
+ sc->nr_scanned += nr_soft_scanned;
+ if (nr_soft_reclaimed)
+ reclaimable = true;
+ /* need some check for avoid more shrink_zone() */
+ }
+
+ if (shrink_zone(zone, sc, zone_idx(zone) == classzone_idx))
+ reclaimable = true;
+
+ if (global_reclaim(sc) &&
+ !reclaimable && zone_reclaimable(zone))
+ reclaimable = true;
+ }
+
+ /*
+ * Restore to original mask to avoid the impact on the caller if we
+ * promoted it to __GFP_HIGHMEM.
+ */
+ sc->gfp_mask = orig_mask;
+
+ return reclaimable;
+}
+
+/*
+ * This is the main entry point to direct page reclaim.
+ *
+ * If a full scan of the inactive list fails to free enough memory then we
+ * are "out of memory" and something needs to be killed.
+ *
+ * If the caller is !__GFP_FS then the probability of a failure is reasonably
+ * high - the zone may be full of dirty or under-writeback pages, which this
+ * caller can't do much about. We kick the writeback threads and take explicit
+ * naps in the hope that some of these pages can be written. But if the
+ * allocating task holds filesystem locks which prevent writeout this might not
+ * work, and the allocation attempt will fail.
+ *
+ * returns: 0, if no pages reclaimed
+ * else, the number of pages reclaimed
+ */
+static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
+ struct scan_control *sc)
+{
+ int initial_priority = sc->priority;
+ unsigned long total_scanned = 0;
+ unsigned long writeback_threshold;
+ bool zones_reclaimable;
+retry:
+ delayacct_freepages_start();
+
+ if (global_reclaim(sc))
+ count_vm_event(ALLOCSTALL);
+
+ do {
+ vmpressure_prio(sc->gfp_mask, sc->target_mem_cgroup,
+ sc->priority);
+ sc->nr_scanned = 0;
+ zones_reclaimable = shrink_zones(zonelist, sc);
+
+ total_scanned += sc->nr_scanned;
+ if (sc->nr_reclaimed >= sc->nr_to_reclaim)
+ break;
+
+ if (sc->compaction_ready)
+ break;
+
+ /*
+ * If we're getting trouble reclaiming, start doing
+ * writepage even in laptop mode.
+ */
+ if (sc->priority < DEF_PRIORITY - 2)
+ sc->may_writepage = 1;
+
+ /*
+ * Try to write back as many pages as we just scanned. This
+ * tends to cause slow streaming writers to write data to the
+ * disk smoothly, at the dirtying rate, which is nice. But
+ * that's undesirable in laptop mode, where we *want* lumpy
+ * writeout. So in laptop mode, write out the whole world.
+ */
+ writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
+ if (total_scanned > writeback_threshold) {
+ wakeup_flusher_threads(laptop_mode ? 0 : total_scanned,
+ WB_REASON_TRY_TO_FREE_PAGES);
+ sc->may_writepage = 1;
+ }
+ } while (--sc->priority >= 0);
+
+ delayacct_freepages_end();
+
+ if (sc->nr_reclaimed)
+ return sc->nr_reclaimed;
+
+ /* Aborted reclaim to try compaction? don't OOM, then */
+ if (sc->compaction_ready)
+ return 1;
+
+ /* Untapped cgroup reserves? Don't OOM, retry. */
+ if (!sc->may_thrash) {
+ sc->priority = initial_priority;
+ sc->may_thrash = 1;
+ goto retry;
+ }
+
+ /* Any of the zones still reclaimable? Don't OOM. */
+ if (zones_reclaimable)
+ return 1;
+
+ return 0;
+}
+
+static bool pfmemalloc_watermark_ok(pg_data_t *pgdat)
+{
+ struct zone *zone;
+ unsigned long pfmemalloc_reserve = 0;
+ unsigned long free_pages = 0;
+ int i;
+ bool wmark_ok;
+
+ for (i = 0; i <= ZONE_NORMAL; i++) {
+ zone = &pgdat->node_zones[i];
+ if (!populated_zone(zone))
+ continue;
+
+ pfmemalloc_reserve += min_wmark_pages(zone);
+ free_pages += zone_page_state(zone, NR_FREE_PAGES);
+ }
+
+ /* If there are no reserves (unexpected config) then do not throttle */
+ if (!pfmemalloc_reserve)
+ return true;
+
+ wmark_ok = free_pages > pfmemalloc_reserve / 2;
+
+ /* kswapd must be awake if processes are being throttled */
+ if (!wmark_ok && waitqueue_active(&pgdat->kswapd_wait)) {
+ pgdat->classzone_idx = min(pgdat->classzone_idx,
+ (enum zone_type)ZONE_NORMAL);
+ wake_up_interruptible(&pgdat->kswapd_wait);
+ }
+
+ return wmark_ok;
+}
+
+/*
+ * Throttle direct reclaimers if backing storage is backed by the network
+ * and the PFMEMALLOC reserve for the preferred node is getting dangerously
+ * depleted. kswapd will continue to make progress and wake the processes
+ * when the low watermark is reached.
+ *
+ * Returns true if a fatal signal was delivered during throttling. If this
+ * happens, the page allocator should not consider triggering the OOM killer.
+ */
+static bool throttle_direct_reclaim(gfp_t gfp_mask, struct zonelist *zonelist,
+ nodemask_t *nodemask)
+{
+ struct zoneref *z;
+ struct zone *zone;
+ pg_data_t *pgdat = NULL;
+
+ /*
+ * Kernel threads should not be throttled as they may be indirectly
+ * responsible for cleaning pages necessary for reclaim to make forward
+ * progress. kjournald for example may enter direct reclaim while
+ * committing a transaction where throttling it could forcing other
+ * processes to block on log_wait_commit().
+ */
+ if (current->flags & PF_KTHREAD)
+ goto out;
+
+ /*
+ * If a fatal signal is pending, this process should not throttle.
+ * It should return quickly so it can exit and free its memory
+ */
+ if (fatal_signal_pending(current))
+ goto out;
+
+ /*
+ * Check if the pfmemalloc reserves are ok by finding the first node
+ * with a usable ZONE_NORMAL or lower zone. The expectation is that
+ * GFP_KERNEL will be required for allocating network buffers when
+ * swapping over the network so ZONE_HIGHMEM is unusable.
+ *
+ * Throttling is based on the first usable node and throttled processes
+ * wait on a queue until kswapd makes progress and wakes them. There
+ * is an affinity then between processes waking up and where reclaim
+ * progress has been made assuming the process wakes on the same node.
+ * More importantly, processes running on remote nodes will not compete
+ * for remote pfmemalloc reserves and processes on different nodes
+ * should make reasonable progress.
+ */
+ for_each_zone_zonelist_nodemask(zone, z, zonelist,
+ gfp_zone(gfp_mask), nodemask) {
+ if (zone_idx(zone) > ZONE_NORMAL)
+ continue;
+
+ /* Throttle based on the first usable node */
+ pgdat = zone->zone_pgdat;
+ if (pfmemalloc_watermark_ok(pgdat))
+ goto out;
+ break;
+ }
+
+ /* If no zone was usable by the allocation flags then do not throttle */
+ if (!pgdat)
+ goto out;
+
+ /* Account for the throttling */
+ count_vm_event(PGSCAN_DIRECT_THROTTLE);
+
+ /*
+ * If the caller cannot enter the filesystem, it's possible that it
+ * is due to the caller holding an FS lock or performing a journal
+ * transaction in the case of a filesystem like ext[3|4]. In this case,
+ * it is not safe to block on pfmemalloc_wait as kswapd could be
+ * blocked waiting on the same lock. Instead, throttle for up to a
+ * second before continuing.
+ */
+ if (!(gfp_mask & __GFP_FS)) {
+ wait_event_interruptible_timeout(pgdat->pfmemalloc_wait,
+ pfmemalloc_watermark_ok(pgdat), HZ);
+
+ goto check_pending;
+ }
+
+ /* Throttle until kswapd wakes the process */
+ wait_event_killable(zone->zone_pgdat->pfmemalloc_wait,
+ pfmemalloc_watermark_ok(pgdat));
+
+check_pending:
+ if (fatal_signal_pending(current))
+ return true;
+
+out:
+ return false;
+}
+
+unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
+ gfp_t gfp_mask, nodemask_t *nodemask)
+{
+ unsigned long nr_reclaimed;
+ struct scan_control sc = {
+ .nr_to_reclaim = SWAP_CLUSTER_MAX,
+ .gfp_mask = (gfp_mask = memalloc_noio_flags(gfp_mask)),
+ .order = order,
+ .nodemask = nodemask,
+ .priority = DEF_PRIORITY,
+ .may_writepage = !laptop_mode,
+ .may_unmap = 1,
+ .may_swap = 1,
+ };
+
+ /*
+ * Do not enter reclaim if fatal signal was delivered while throttled.
+ * 1 is returned so that the page allocator does not OOM kill at this
+ * point.
+ */
+ if (throttle_direct_reclaim(gfp_mask, zonelist, nodemask))
+ return 1;
+
+ trace_mm_vmscan_direct_reclaim_begin(order,
+ sc.may_writepage,
+ gfp_mask);
+
+ nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
+
+ trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
+
+ return nr_reclaimed;
+}
+
+#ifdef CONFIG_MEMCG
+
+unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *memcg,
+ gfp_t gfp_mask, bool noswap,
+ struct zone *zone,
+ unsigned long *nr_scanned)
+{
+ struct scan_control sc = {
+ .nr_to_reclaim = SWAP_CLUSTER_MAX,
+ .target_mem_cgroup = memcg,
+ .may_writepage = !laptop_mode,
+ .may_unmap = 1,
+ .may_swap = !noswap,
+ };
+ struct lruvec *lruvec = mem_cgroup_zone_lruvec(zone, memcg);
+ int swappiness = mem_cgroup_swappiness(memcg);
+ unsigned long lru_pages;
+
+ sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
+ (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
+
+ trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc.order,
+ sc.may_writepage,
+ sc.gfp_mask);
+
+ /*
+ * NOTE: Although we can get the priority field, using it
+ * here is not a good idea, since it limits the pages we can scan.
+ * if we don't reclaim here, the shrink_zone from balance_pgdat
+ * will pick up pages from other mem cgroup's as well. We hack
+ * the priority and make it zero.
+ */
+ shrink_lruvec(lruvec, swappiness, &sc, &lru_pages);
+
+ trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
+
+ *nr_scanned = sc.nr_scanned;
+ return sc.nr_reclaimed;
+}
+
+unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
+ unsigned long nr_pages,
+ gfp_t gfp_mask,
+ bool may_swap)
+{
+ struct zonelist *zonelist;
+ unsigned long nr_reclaimed;
+ int nid;
+ struct scan_control sc = {
+ .nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
+ .gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
+ (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
+ .target_mem_cgroup = memcg,
+ .priority = DEF_PRIORITY,
+ .may_writepage = !laptop_mode,
+ .may_unmap = 1,
+ .may_swap = may_swap,
+ };
+
+ /*
+ * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
+ * take care of from where we get pages. So the node where we start the
+ * scan does not need to be the current node.
+ */
+ nid = mem_cgroup_select_victim_node(memcg);
+
+ zonelist = NODE_DATA(nid)->node_zonelists;
+
+ trace_mm_vmscan_memcg_reclaim_begin(0,
+ sc.may_writepage,
+ sc.gfp_mask);
+
+ nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
+
+ trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
+
+ return nr_reclaimed;
+}
+#endif
+
+static void age_active_anon(struct zone *zone, struct scan_control *sc)
+{
+ struct mem_cgroup *memcg;
+
+ if (!total_swap_pages)
+ return;
+
+ memcg = mem_cgroup_iter(NULL, NULL, NULL);
+ do {
+ struct lruvec *lruvec = mem_cgroup_zone_lruvec(zone, memcg);
+
+ if (inactive_anon_is_low(lruvec))
+ shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
+ sc, LRU_ACTIVE_ANON);
+
+ memcg = mem_cgroup_iter(NULL, memcg, NULL);
+ } while (memcg);
+}
+
+static bool zone_balanced(struct zone *zone, int order,
+ unsigned long balance_gap, int classzone_idx)
+{
+ if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone) +
+ balance_gap, classzone_idx, 0))
+ return false;
+
+ if (IS_ENABLED(CONFIG_COMPACTION) && order && compaction_suitable(zone,
+ order, 0, classzone_idx) == COMPACT_SKIPPED)
+ return false;
+
+ return true;
+}
+
+/*
+ * pgdat_balanced() is used when checking if a node is balanced.
+ *
+ * For order-0, all zones must be balanced!
+ *
+ * For high-order allocations only zones that meet watermarks and are in a
+ * zone allowed by the callers classzone_idx are added to balanced_pages. The
+ * total of balanced pages must be at least 25% of the zones allowed by
+ * classzone_idx for the node to be considered balanced. Forcing all zones to
+ * be balanced for high orders can cause excessive reclaim when there are
+ * imbalanced zones.
+ * The choice of 25% is due to
+ * o a 16M DMA zone that is balanced will not balance a zone on any
+ * reasonable sized machine
+ * o On all other machines, the top zone must be at least a reasonable
+ * percentage of the middle zones. For example, on 32-bit x86, highmem
+ * would need to be at least 256M for it to be balance a whole node.
+ * Similarly, on x86-64 the Normal zone would need to be at least 1G
+ * to balance a node on its own. These seemed like reasonable ratios.
+ */
+static bool pgdat_balanced(pg_data_t *pgdat, int order, int classzone_idx)
+{
+ unsigned long managed_pages = 0;
+ unsigned long balanced_pages = 0;
+ int i;
+
+ /* Check the watermark levels */
+ for (i = 0; i <= classzone_idx; i++) {
+ struct zone *zone = pgdat->node_zones + i;
+
+ if (!populated_zone(zone))
+ continue;
+
+ managed_pages += zone->managed_pages;
+
+ /*
+ * A special case here:
+ *
+ * balance_pgdat() skips over all_unreclaimable after
+ * DEF_PRIORITY. Effectively, it considers them balanced so
+ * they must be considered balanced here as well!
+ */
+ if (!zone_reclaimable(zone)) {
+ balanced_pages += zone->managed_pages;
+ continue;
+ }
+
+ if (zone_balanced(zone, order, 0, i))
+ balanced_pages += zone->managed_pages;
+ else if (!order)
+ return false;
+ }
+
+ if (order)
+ return balanced_pages >= (managed_pages >> 2);
+ else
+ return true;
+}
+
+/*
+ * Prepare kswapd for sleeping. This verifies that there are no processes
+ * waiting in throttle_direct_reclaim() and that watermarks have been met.
+ *
+ * Returns true if kswapd is ready to sleep
+ */
+static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order, long remaining,
+ int classzone_idx)
+{
+ /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
+ if (remaining)
+ return false;
+
+ /*
+ * The throttled processes are normally woken up in balance_pgdat() as
+ * soon as pfmemalloc_watermark_ok() is true. But there is a potential
+ * race between when kswapd checks the watermarks and a process gets
+ * throttled. There is also a potential race if processes get
+ * throttled, kswapd wakes, a large process exits thereby balancing the
+ * zones, which causes kswapd to exit balance_pgdat() before reaching
+ * the wake up checks. If kswapd is going to sleep, no process should
+ * be sleeping on pfmemalloc_wait, so wake them now if necessary. If
+ * the wake up is premature, processes will wake kswapd and get
+ * throttled again. The difference from wake ups in balance_pgdat() is
+ * that here we are under prepare_to_wait().
+ */
+ if (waitqueue_active(&pgdat->pfmemalloc_wait))
+ wake_up_all(&pgdat->pfmemalloc_wait);
+
+ return pgdat_balanced(pgdat, order, classzone_idx);
+}
+
+/*
+ * kswapd shrinks the zone by the number of pages required to reach
+ * the high watermark.
+ *
+ * Returns true if kswapd scanned at least the requested number of pages to
+ * reclaim or if the lack of progress was due to pages under writeback.
+ * This is used to determine if the scanning priority needs to be raised.
+ */
+static bool kswapd_shrink_zone(struct zone *zone,
+ int classzone_idx,
+ struct scan_control *sc,
+ unsigned long *nr_attempted)
+{
+ int testorder = sc->order;
+ unsigned long balance_gap;
+ bool lowmem_pressure;
+
+ /* Reclaim above the high watermark. */
+ sc->nr_to_reclaim = max(SWAP_CLUSTER_MAX, high_wmark_pages(zone));
+
+ /*
+ * Kswapd reclaims only single pages with compaction enabled. Trying
+ * too hard to reclaim until contiguous free pages have become
+ * available can hurt performance by evicting too much useful data
+ * from memory. Do not reclaim more than needed for compaction.
+ */
+ if (IS_ENABLED(CONFIG_COMPACTION) && sc->order &&
+ compaction_suitable(zone, sc->order, 0, classzone_idx)
+ != COMPACT_SKIPPED)
+ testorder = 0;
+
+ /*
+ * We put equal pressure on every zone, unless one zone has way too
+ * many pages free already. The "too many pages" is defined as the
+ * high wmark plus a "gap" where the gap is either the low
+ * watermark or 1% of the zone, whichever is smaller.
+ */
+ balance_gap = min(low_wmark_pages(zone), DIV_ROUND_UP(
+ zone->managed_pages, KSWAPD_ZONE_BALANCE_GAP_RATIO));
+
+ /*
+ * If there is no low memory pressure or the zone is balanced then no
+ * reclaim is necessary
+ */
+ lowmem_pressure = (buffer_heads_over_limit && is_highmem(zone));
+ if (!lowmem_pressure && zone_balanced(zone, testorder,
+ balance_gap, classzone_idx))
+ return true;
+
+ shrink_zone(zone, sc, zone_idx(zone) == classzone_idx);
+
+ /* Account for the number of pages attempted to reclaim */
+ *nr_attempted += sc->nr_to_reclaim;
+
+ clear_bit(ZONE_WRITEBACK, &zone->flags);
+
+ /*
+ * If a zone reaches its high watermark, consider it to be no longer
+ * congested. It's possible there are dirty pages backed by congested
+ * BDIs but as pressure is relieved, speculatively avoid congestion
+ * waits.
+ */
+ if (zone_reclaimable(zone) &&
+ zone_balanced(zone, testorder, 0, classzone_idx)) {
+ clear_bit(ZONE_CONGESTED, &zone->flags);
+ clear_bit(ZONE_DIRTY, &zone->flags);
+ }
+
+ return sc->nr_scanned >= sc->nr_to_reclaim;
+}
+
+/*
+ * For kswapd, balance_pgdat() will work across all this node's zones until
+ * they are all at high_wmark_pages(zone).
+ *
+ * Returns the final order kswapd was reclaiming at
+ *
+ * There is special handling here for zones which are full of pinned pages.
+ * This can happen if the pages are all mlocked, or if they are all used by
+ * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
+ * What we do is to detect the case where all pages in the zone have been
+ * scanned twice and there has been zero successful reclaim. Mark the zone as
+ * dead and from now on, only perform a short scan. Basically we're polling
+ * the zone for when the problem goes away.
+ *
+ * kswapd scans the zones in the highmem->normal->dma direction. It skips
+ * zones which have free_pages > high_wmark_pages(zone), but once a zone is
+ * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
+ * lower zones regardless of the number of free pages in the lower zones. This
+ * interoperates with the page allocator fallback scheme to ensure that aging
+ * of pages is balanced across the zones.
+ */
+static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
+ int *classzone_idx)
+{
+ int i;
+ int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
+ unsigned long nr_soft_reclaimed;
+ unsigned long nr_soft_scanned;
+ struct scan_control sc = {
+ .gfp_mask = GFP_KERNEL,
+ .order = order,
+ .priority = DEF_PRIORITY,
+ .may_writepage = !laptop_mode,
+ .may_unmap = 1,
+ .may_swap = 1,
+ };
+ count_vm_event(PAGEOUTRUN);
+
+ do {
+ unsigned long nr_attempted = 0;
+ bool raise_priority = true;
+ bool pgdat_needs_compaction = (order > 0);
+
+ sc.nr_reclaimed = 0;
+
+ /*
+ * Scan in the highmem->dma direction for the highest
+ * zone which needs scanning
+ */
+ for (i = pgdat->nr_zones - 1; i >= 0; i--) {
+ struct zone *zone = pgdat->node_zones + i;
+
+ if (!populated_zone(zone))
+ continue;
+
+ if (sc.priority != DEF_PRIORITY &&
+ !zone_reclaimable(zone))
+ continue;
+
+ /*
+ * Do some background aging of the anon list, to give
+ * pages a chance to be referenced before reclaiming.
+ */
+ age_active_anon(zone, &sc);
+
+ /*
+ * If the number of buffer_heads in the machine
+ * exceeds the maximum allowed level and this node
+ * has a highmem zone, force kswapd to reclaim from
+ * it to relieve lowmem pressure.
+ */
+ if (buffer_heads_over_limit && is_highmem_idx(i)) {
+ end_zone = i;
+ break;
+ }
+
+ if (!zone_balanced(zone, order, 0, 0)) {
+ end_zone = i;
+ break;
+ } else {
+ /*
+ * If balanced, clear the dirty and congested
+ * flags
+ */
+ clear_bit(ZONE_CONGESTED, &zone->flags);
+ clear_bit(ZONE_DIRTY, &zone->flags);
+ }
+ }
+
+ if (i < 0)
+ goto out;
+
+ for (i = 0; i <= end_zone; i++) {
+ struct zone *zone = pgdat->node_zones + i;
+
+ if (!populated_zone(zone))
+ continue;
+
+ /*
+ * If any zone is currently balanced then kswapd will
+ * not call compaction as it is expected that the
+ * necessary pages are already available.
+ */
+ if (pgdat_needs_compaction &&
+ zone_watermark_ok(zone, order,
+ low_wmark_pages(zone),
+ *classzone_idx, 0))
+ pgdat_needs_compaction = false;
+ }
+
+ /*
+ * If we're getting trouble reclaiming, start doing writepage
+ * even in laptop mode.
+ */
+ if (sc.priority < DEF_PRIORITY - 2)
+ sc.may_writepage = 1;
+
+ /*
+ * Now scan the zone in the dma->highmem direction, stopping
+ * at the last zone which needs scanning.
+ *
+ * We do this because the page allocator works in the opposite
+ * direction. This prevents the page allocator from allocating
+ * pages behind kswapd's direction of progress, which would
+ * cause too much scanning of the lower zones.
+ */
+ for (i = 0; i <= end_zone; i++) {
+ struct zone *zone = pgdat->node_zones + i;
+
+ if (!populated_zone(zone))
+ continue;
+
+ if (sc.priority != DEF_PRIORITY &&
+ !zone_reclaimable(zone))
+ continue;
+
+ sc.nr_scanned = 0;
+
+ nr_soft_scanned = 0;
+ /*
+ * Call soft limit reclaim before calling shrink_zone.
+ */
+ nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
+ order, sc.gfp_mask,
+ &nr_soft_scanned);
+ sc.nr_reclaimed += nr_soft_reclaimed;
+
+ /*
+ * There should be no need to raise the scanning
+ * priority if enough pages are already being scanned
+ * that that high watermark would be met at 100%
+ * efficiency.
+ */
+ if (kswapd_shrink_zone(zone, end_zone,
+ &sc, &nr_attempted))
+ raise_priority = false;
+ }
+
+ /*
+ * If the low watermark is met there is no need for processes
+ * to be throttled on pfmemalloc_wait as they should not be
+ * able to safely make forward progress. Wake them
+ */
+ if (waitqueue_active(&pgdat->pfmemalloc_wait) &&
+ pfmemalloc_watermark_ok(pgdat))
+ wake_up_all(&pgdat->pfmemalloc_wait);
+
+ /*
+ * Fragmentation may mean that the system cannot be rebalanced
+ * for high-order allocations in all zones. If twice the
+ * allocation size has been reclaimed and the zones are still
+ * not balanced then recheck the watermarks at order-0 to
+ * prevent kswapd reclaiming excessively. Assume that a
+ * process requested a high-order can direct reclaim/compact.
+ */
+ if (order && sc.nr_reclaimed >= 2UL << order)
+ order = sc.order = 0;
+
+ /* Check if kswapd should be suspending */
+ if (try_to_freeze() || kthread_should_stop())
+ break;
+
+ /*
+ * Compact if necessary and kswapd is reclaiming at least the
+ * high watermark number of pages as requsted
+ */
+ if (pgdat_needs_compaction && sc.nr_reclaimed > nr_attempted)
+ compact_pgdat(pgdat, order);
+
+ /*
+ * Raise priority if scanning rate is too low or there was no
+ * progress in reclaiming pages
+ */
+ if (raise_priority || !sc.nr_reclaimed)
+ sc.priority--;
+ } while (sc.priority >= 1 &&
+ !pgdat_balanced(pgdat, order, *classzone_idx));
+
+out:
+ /*
+ * Return the order we were reclaiming at so prepare_kswapd_sleep()
+ * makes a decision on the order we were last reclaiming at. However,
+ * if another caller entered the allocator slow path while kswapd
+ * was awake, order will remain at the higher level
+ */
+ *classzone_idx = end_zone;
+ return order;
+}
+
+static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx)
+{
+ long remaining = 0;
+ DEFINE_WAIT(wait);
+
+ if (freezing(current) || kthread_should_stop())
+ return;
+
+ prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
+
+ /* Try to sleep for a short interval */
+ if (prepare_kswapd_sleep(pgdat, order, remaining, classzone_idx)) {
+ remaining = schedule_timeout(HZ/10);
+ finish_wait(&pgdat->kswapd_wait, &wait);
+ prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
+ }
+
+ /*
+ * After a short sleep, check if it was a premature sleep. If not, then
+ * go fully to sleep until explicitly woken up.
+ */
+ if (prepare_kswapd_sleep(pgdat, order, remaining, classzone_idx)) {
+ trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
+
+ /*
+ * vmstat counters are not perfectly accurate and the estimated
+ * value for counters such as NR_FREE_PAGES can deviate from the
+ * true value by nr_online_cpus * threshold. To avoid the zone
+ * watermarks being breached while under pressure, we reduce the
+ * per-cpu vmstat threshold while kswapd is awake and restore
+ * them before going back to sleep.
+ */
+ set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold);
+
+ /*
+ * Compaction records what page blocks it recently failed to
+ * isolate pages from and skips them in the future scanning.
+ * When kswapd is going to sleep, it is reasonable to assume
+ * that pages and compaction may succeed so reset the cache.
+ */
+ reset_isolation_suitable(pgdat);
+
+ if (!kthread_should_stop())
+ schedule();
+
+ set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold);
+ } else {
+ if (remaining)
+ count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
+ else
+ count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
+ }
+ finish_wait(&pgdat->kswapd_wait, &wait);
+}
+
+/*
+ * The background pageout daemon, started as a kernel thread
+ * from the init process.
+ *
+ * This basically trickles out pages so that we have _some_
+ * free memory available even if there is no other activity
+ * that frees anything up. This is needed for things like routing
+ * etc, where we otherwise might have all activity going on in
+ * asynchronous contexts that cannot page things out.
+ *
+ * If there are applications that are active memory-allocators
+ * (most normal use), this basically shouldn't matter.
+ */
+static int kswapd(void *p)
+{
+ unsigned long order, new_order;
+ unsigned balanced_order;
+ int classzone_idx, new_classzone_idx;
+ int balanced_classzone_idx;
+ pg_data_t *pgdat = (pg_data_t*)p;
+ struct task_struct *tsk = current;
+
+ struct reclaim_state reclaim_state = {
+ .reclaimed_slab = 0,
+ };
+ const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
+
+ lockdep_set_current_reclaim_state(GFP_KERNEL);
+
+ if (!cpumask_empty(cpumask))
+ set_cpus_allowed_ptr(tsk, cpumask);
+ current->reclaim_state = &reclaim_state;
+
+ /*
+ * Tell the memory management that we're a "memory allocator",
+ * and that if we need more memory we should get access to it
+ * regardless (see "__alloc_pages()"). "kswapd" should
+ * never get caught in the normal page freeing logic.
+ *
+ * (Kswapd normally doesn't need memory anyway, but sometimes
+ * you need a small amount of memory in order to be able to
+ * page out something else, and this flag essentially protects
+ * us from recursively trying to free more memory as we're
+ * trying to free the first piece of memory in the first place).
+ */
+ tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
+ set_freezable();
+
+ order = new_order = 0;
+ balanced_order = 0;
+ classzone_idx = new_classzone_idx = pgdat->nr_zones - 1;
+ balanced_classzone_idx = classzone_idx;
+ for ( ; ; ) {
+ bool ret;
+
+ /*
+ * If the last balance_pgdat was unsuccessful it's unlikely a
+ * new request of a similar or harder type will succeed soon
+ * so consider going to sleep on the basis we reclaimed at
+ */
+ if (balanced_classzone_idx >= new_classzone_idx &&
+ balanced_order == new_order) {
+ new_order = pgdat->kswapd_max_order;
+ new_classzone_idx = pgdat->classzone_idx;
+ pgdat->kswapd_max_order = 0;
+ pgdat->classzone_idx = pgdat->nr_zones - 1;
+ }
+
+ if (order < new_order || classzone_idx > new_classzone_idx) {
+ /*
+ * Don't sleep if someone wants a larger 'order'
+ * allocation or has tigher zone constraints
+ */
+ order = new_order;
+ classzone_idx = new_classzone_idx;
+ } else {
+ kswapd_try_to_sleep(pgdat, balanced_order,
+ balanced_classzone_idx);
+ order = pgdat->kswapd_max_order;
+ classzone_idx = pgdat->classzone_idx;
+ new_order = order;
+ new_classzone_idx = classzone_idx;
+ pgdat->kswapd_max_order = 0;
+ pgdat->classzone_idx = pgdat->nr_zones - 1;
+ }
+
+ ret = try_to_freeze();
+ if (kthread_should_stop())
+ break;
+
+ /*
+ * We can speed up thawing tasks if we don't call balance_pgdat
+ * after returning from the refrigerator
+ */
+ if (!ret) {
+ trace_mm_vmscan_kswapd_wake(pgdat->node_id, order);
+ balanced_classzone_idx = classzone_idx;
+ balanced_order = balance_pgdat(pgdat, order,
+ &balanced_classzone_idx);
+ }
+ }
+
+ tsk->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD);
+ current->reclaim_state = NULL;
+ lockdep_clear_current_reclaim_state();
+
+ return 0;
+}
+
+/*
+ * A zone is low on free memory, so wake its kswapd task to service it.
+ */
+void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
+{
+ pg_data_t *pgdat;
+
+ if (!populated_zone(zone))
+ return;
+
+ if (!cpuset_zone_allowed(zone, GFP_KERNEL | __GFP_HARDWALL))
+ return;
+ pgdat = zone->zone_pgdat;
+ if (pgdat->kswapd_max_order < order) {
+ pgdat->kswapd_max_order = order;
+ pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx);
+ }
+ if (!waitqueue_active(&pgdat->kswapd_wait))
+ return;
+ if (zone_balanced(zone, order, 0, 0))
+ return;
+
+ trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order);
+ wake_up_interruptible(&pgdat->kswapd_wait);
+}
+
+#ifdef CONFIG_HIBERNATION
+/*
+ * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
+ * freed pages.
+ *
+ * Rather than trying to age LRUs the aim is to preserve the overall
+ * LRU order by reclaiming preferentially
+ * inactive > active > active referenced > active mapped
+ */
+unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
+{
+ struct reclaim_state reclaim_state;
+ struct scan_control sc = {
+ .nr_to_reclaim = nr_to_reclaim,
+ .gfp_mask = GFP_HIGHUSER_MOVABLE,
+ .priority = DEF_PRIORITY,
+ .may_writepage = 1,
+ .may_unmap = 1,
+ .may_swap = 1,
+ .hibernation_mode = 1,
+ };
+ struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
+ struct task_struct *p = current;
+ unsigned long nr_reclaimed;
+
+ p->flags |= PF_MEMALLOC;
+ lockdep_set_current_reclaim_state(sc.gfp_mask);
+ reclaim_state.reclaimed_slab = 0;
+ p->reclaim_state = &reclaim_state;
+
+ nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
+
+ p->reclaim_state = NULL;
+ lockdep_clear_current_reclaim_state();
+ p->flags &= ~PF_MEMALLOC;
+
+ return nr_reclaimed;
+}
+#endif /* CONFIG_HIBERNATION */
+
+/* It's optimal to keep kswapds on the same CPUs as their memory, but
+ not required for correctness. So if the last cpu in a node goes
+ away, we get changed to run anywhere: as the first one comes back,
+ restore their cpu bindings. */
+static int cpu_callback(struct notifier_block *nfb, unsigned long action,
+ void *hcpu)
+{
+ int nid;
+
+ if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
+ for_each_node_state(nid, N_MEMORY) {
+ pg_data_t *pgdat = NODE_DATA(nid);
+ const struct cpumask *mask;
+
+ mask = cpumask_of_node(pgdat->node_id);
+
+ if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
+ /* One of our CPUs online: restore mask */
+ set_cpus_allowed_ptr(pgdat->kswapd, mask);
+ }
+ }
+ return NOTIFY_OK;
+}
+
+/*
+ * This kswapd start function will be called by init and node-hot-add.
+ * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
+ */
+int kswapd_run(int nid)
+{
+ pg_data_t *pgdat = NODE_DATA(nid);
+ int ret = 0;
+
+ if (pgdat->kswapd)
+ return 0;
+
+ pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
+ if (IS_ERR(pgdat->kswapd)) {
+ /* failure at boot is fatal */
+ BUG_ON(system_state == SYSTEM_BOOTING);
+ pr_err("Failed to start kswapd on node %d\n", nid);
+ ret = PTR_ERR(pgdat->kswapd);
+ pgdat->kswapd = NULL;
+ }
+ return ret;
+}
+
+/*
+ * Called by memory hotplug when all memory in a node is offlined. Caller must
+ * hold mem_hotplug_begin/end().
+ */
+void kswapd_stop(int nid)
+{
+ struct task_struct *kswapd = NODE_DATA(nid)->kswapd;
+
+ if (kswapd) {
+ kthread_stop(kswapd);
+ NODE_DATA(nid)->kswapd = NULL;
+ }
+}
+
+static int __init kswapd_init(void)
+{
+ int nid;
+
+ swap_setup();
+ for_each_node_state(nid, N_MEMORY)
+ kswapd_run(nid);
+ hotcpu_notifier(cpu_callback, 0);
+ return 0;
+}
+
+module_init(kswapd_init)
+
+#ifdef CONFIG_NUMA
+/*
+ * Zone reclaim mode
+ *
+ * If non-zero call zone_reclaim when the number of free pages falls below
+ * the watermarks.
+ */
+int zone_reclaim_mode __read_mostly;
+
+#define RECLAIM_OFF 0
+#define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
+#define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
+#define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
+
+/*
+ * Priority for ZONE_RECLAIM. This determines the fraction of pages
+ * of a node considered for each zone_reclaim. 4 scans 1/16th of
+ * a zone.
+ */
+#define ZONE_RECLAIM_PRIORITY 4
+
+/*
+ * Percentage of pages in a zone that must be unmapped for zone_reclaim to
+ * occur.
+ */
+int sysctl_min_unmapped_ratio = 1;
+
+/*
+ * If the number of slab pages in a zone grows beyond this percentage then
+ * slab reclaim needs to occur.
+ */
+int sysctl_min_slab_ratio = 5;
+
+static inline unsigned long zone_unmapped_file_pages(struct zone *zone)
+{
+ unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
+ unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
+ zone_page_state(zone, NR_ACTIVE_FILE);
+
+ /*
+ * It's possible for there to be more file mapped pages than
+ * accounted for by the pages on the file LRU lists because
+ * tmpfs pages accounted for as ANON can also be FILE_MAPPED
+ */
+ return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
+}
+
+/* Work out how many page cache pages we can reclaim in this reclaim_mode */
+static long zone_pagecache_reclaimable(struct zone *zone)
+{
+ long nr_pagecache_reclaimable;
+ long delta = 0;
+
+ /*
+ * If RECLAIM_SWAP is set, then all file pages are considered
+ * potentially reclaimable. Otherwise, we have to worry about
+ * pages like swapcache and zone_unmapped_file_pages() provides
+ * a better estimate
+ */
+ if (zone_reclaim_mode & RECLAIM_SWAP)
+ nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
+ else
+ nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);
+
+ /* If we can't clean pages, remove dirty pages from consideration */
+ if (!(zone_reclaim_mode & RECLAIM_WRITE))
+ delta += zone_page_state(zone, NR_FILE_DIRTY);
+
+ /* Watch for any possible underflows due to delta */
+ if (unlikely(delta > nr_pagecache_reclaimable))
+ delta = nr_pagecache_reclaimable;
+
+ return nr_pagecache_reclaimable - delta;
+}
+
+/*
+ * Try to free up some pages from this zone through reclaim.
+ */
+static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
+{
+ /* Minimum pages needed in order to stay on node */
+ const unsigned long nr_pages = 1 << order;
+ struct task_struct *p = current;
+ struct reclaim_state reclaim_state;
+ struct scan_control sc = {
+ .nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
+ .gfp_mask = (gfp_mask = memalloc_noio_flags(gfp_mask)),
+ .order = order,
+ .priority = ZONE_RECLAIM_PRIORITY,
+ .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
+ .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
+ .may_swap = 1,
+ };
+
+ cond_resched();
+ /*
+ * We need to be able to allocate from the reserves for RECLAIM_SWAP
+ * and we also need to be able to write out pages for RECLAIM_WRITE
+ * and RECLAIM_SWAP.
+ */
+ p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
+ lockdep_set_current_reclaim_state(gfp_mask);
+ reclaim_state.reclaimed_slab = 0;
+ p->reclaim_state = &reclaim_state;
+
+ if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
+ /*
+ * Free memory by calling shrink zone with increasing
+ * priorities until we have enough memory freed.
+ */
+ do {
+ shrink_zone(zone, &sc, true);
+ } while (sc.nr_reclaimed < nr_pages && --sc.priority >= 0);
+ }
+
+ p->reclaim_state = NULL;
+ current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
+ lockdep_clear_current_reclaim_state();
+ return sc.nr_reclaimed >= nr_pages;
+}
+
+int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
+{
+ int node_id;
+ int ret;
+
+ /*
+ * Zone reclaim reclaims unmapped file backed pages and
+ * slab pages if we are over the defined limits.
+ *
+ * A small portion of unmapped file backed pages is needed for
+ * file I/O otherwise pages read by file I/O will be immediately
+ * thrown out if the zone is overallocated. So we do not reclaim
+ * if less than a specified percentage of the zone is used by
+ * unmapped file backed pages.
+ */
+ if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
+ zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
+ return ZONE_RECLAIM_FULL;
+
+ if (!zone_reclaimable(zone))
+ return ZONE_RECLAIM_FULL;
+
+ /*
+ * Do not scan if the allocation should not be delayed.
+ */
+ if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
+ return ZONE_RECLAIM_NOSCAN;
+
+ /*
+ * Only run zone reclaim on the local zone or on zones that do not
+ * have associated processors. This will favor the local processor
+ * over remote processors and spread off node memory allocations
+ * as wide as possible.
+ */
+ node_id = zone_to_nid(zone);
+ if (node_state(node_id, N_CPU) && node_id != numa_node_id())
+ return ZONE_RECLAIM_NOSCAN;
+
+ if (test_and_set_bit(ZONE_RECLAIM_LOCKED, &zone->flags))
+ return ZONE_RECLAIM_NOSCAN;
+
+ ret = __zone_reclaim(zone, gfp_mask, order);
+ clear_bit(ZONE_RECLAIM_LOCKED, &zone->flags);
+
+ if (!ret)
+ count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
+
+ return ret;
+}
+#endif
+
+/*
+ * page_evictable - test whether a page is evictable
+ * @page: the page to test
+ *
+ * Test whether page is evictable--i.e., should be placed on active/inactive
+ * lists vs unevictable list.
+ *
+ * Reasons page might not be evictable:
+ * (1) page's mapping marked unevictable
+ * (2) page is part of an mlocked VMA
+ *
+ */
+int page_evictable(struct page *page)
+{
+ return !mapping_unevictable(page_mapping(page)) && !PageMlocked(page);
+}
+
+#ifdef CONFIG_SHMEM
+/**
+ * check_move_unevictable_pages - check pages for evictability and move to appropriate zone lru list
+ * @pages: array of pages to check
+ * @nr_pages: number of pages to check
+ *
+ * Checks pages for evictability and moves them to the appropriate lru list.
+ *
+ * This function is only used for SysV IPC SHM_UNLOCK.
+ */
+void check_move_unevictable_pages(struct page **pages, int nr_pages)
+{
+ struct lruvec *lruvec;
+ struct zone *zone = NULL;
+ int pgscanned = 0;
+ int pgrescued = 0;
+ int i;
+
+ for (i = 0; i < nr_pages; i++) {
+ struct page *page = pages[i];
+ struct zone *pagezone;
+
+ pgscanned++;
+ pagezone = page_zone(page);
+ if (pagezone != zone) {
+ if (zone)
+ spin_unlock_irq(&zone->lru_lock);
+ zone = pagezone;
+ spin_lock_irq(&zone->lru_lock);
+ }
+ lruvec = mem_cgroup_page_lruvec(page, zone);
+
+ if (!PageLRU(page) || !PageUnevictable(page))
+ continue;
+
+ if (page_evictable(page)) {
+ enum lru_list lru = page_lru_base_type(page);
+
+ VM_BUG_ON_PAGE(PageActive(page), page);
+ ClearPageUnevictable(page);
+ del_page_from_lru_list(page, lruvec, LRU_UNEVICTABLE);
+ add_page_to_lru_list(page, lruvec, lru);
+ pgrescued++;
+ }
+ }
+
+ if (zone) {
+ __count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
+ __count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned);
+ spin_unlock_irq(&zone->lru_lock);
+ }
+}
+#endif /* CONFIG_SHMEM */
Code Review / kvmfornfv.git / blobdiff