--- /dev/null
+/*
+ * mm/truncate.c - code for taking down pages from address_spaces
+ *
+ * Copyright (C) 2002, Linus Torvalds
+ *
+ * 10Sep2002 Andrew Morton
+ * Initial version.
+ */
+
+#include <linux/kernel.h>
+#include <linux/backing-dev.h>
+#include <linux/gfp.h>
+#include <linux/mm.h>
+#include <linux/swap.h>
+#include <linux/export.h>
+#include <linux/pagemap.h>
+#include <linux/highmem.h>
+#include <linux/pagevec.h>
+#include <linux/task_io_accounting_ops.h>
+#include <linux/buffer_head.h> /* grr. try_to_release_page,
+ do_invalidatepage */
+#include <linux/cleancache.h>
+#include <linux/rmap.h>
+#include "internal.h"
+
+static void clear_exceptional_entry(struct address_space *mapping,
+ pgoff_t index, void *entry)
+{
+ struct radix_tree_node *node;
+ void **slot;
+
+ /* Handled by shmem itself */
+ if (shmem_mapping(mapping))
+ return;
+
+ spin_lock_irq(&mapping->tree_lock);
+ /*
+ * Regular page slots are stabilized by the page lock even
+ * without the tree itself locked. These unlocked entries
+ * need verification under the tree lock.
+ */
+ if (!__radix_tree_lookup(&mapping->page_tree, index, &node, &slot))
+ goto unlock;
+ if (*slot != entry)
+ goto unlock;
+ radix_tree_replace_slot(slot, NULL);
+ mapping->nrshadows--;
+ if (!node)
+ goto unlock;
+ workingset_node_shadows_dec(node);
+ /*
+ * Don't track node without shadow entries.
+ *
+ * Avoid acquiring the list_lru lock if already untracked.
+ * The list_empty() test is safe as node->private_list is
+ * protected by mapping->tree_lock.
+ */
+ if (!workingset_node_shadows(node) &&
+ !list_empty(&node->private_list)) {
+ local_lock(workingset_shadow_lock);
+ list_lru_del(&__workingset_shadow_nodes, &node->private_list);
+ local_unlock(workingset_shadow_lock);
+ }
+ __radix_tree_delete_node(&mapping->page_tree, node);
+unlock:
+ spin_unlock_irq(&mapping->tree_lock);
+}
+
+/**
+ * do_invalidatepage - invalidate part or all of a page
+ * @page: the page which is affected
+ * @offset: start of the range to invalidate
+ * @length: length of the range to invalidate
+ *
+ * do_invalidatepage() is called when all or part of the page has become
+ * invalidated by a truncate operation.
+ *
+ * do_invalidatepage() does not have to release all buffers, but it must
+ * ensure that no dirty buffer is left outside @offset and that no I/O
+ * is underway against any of the blocks which are outside the truncation
+ * point. Because the caller is about to free (and possibly reuse) those
+ * blocks on-disk.
+ */
+void do_invalidatepage(struct page *page, unsigned int offset,
+ unsigned int length)
+{
+ void (*invalidatepage)(struct page *, unsigned int, unsigned int);
+
+ invalidatepage = page->mapping->a_ops->invalidatepage;
+#ifdef CONFIG_BLOCK
+ if (!invalidatepage)
+ invalidatepage = block_invalidatepage;
+#endif
+ if (invalidatepage)
+ (*invalidatepage)(page, offset, length);
+}
+
+/*
+ * If truncate cannot remove the fs-private metadata from the page, the page
+ * becomes orphaned. It will be left on the LRU and may even be mapped into
+ * user pagetables if we're racing with filemap_fault().
+ *
+ * We need to bale out if page->mapping is no longer equal to the original
+ * mapping. This happens a) when the VM reclaimed the page while we waited on
+ * its lock, b) when a concurrent invalidate_mapping_pages got there first and
+ * c) when tmpfs swizzles a page between a tmpfs inode and swapper_space.
+ */
+static int
+truncate_complete_page(struct address_space *mapping, struct page *page)
+{
+ if (page->mapping != mapping)
+ return -EIO;
+
+ if (page_has_private(page))
+ do_invalidatepage(page, 0, PAGE_CACHE_SIZE);
+
+ /*
+ * Some filesystems seem to re-dirty the page even after
+ * the VM has canceled the dirty bit (eg ext3 journaling).
+ * Hence dirty accounting check is placed after invalidation.
+ */
+ if (TestClearPageDirty(page))
+ account_page_cleaned(page, mapping);
+
+ ClearPageMappedToDisk(page);
+ delete_from_page_cache(page);
+ return 0;
+}
+
+/*
+ * This is for invalidate_mapping_pages(). That function can be called at
+ * any time, and is not supposed to throw away dirty pages. But pages can
+ * be marked dirty at any time too, so use remove_mapping which safely
+ * discards clean, unused pages.
+ *
+ * Returns non-zero if the page was successfully invalidated.
+ */
+static int
+invalidate_complete_page(struct address_space *mapping, struct page *page)
+{
+ int ret;
+
+ if (page->mapping != mapping)
+ return 0;
+
+ if (page_has_private(page) && !try_to_release_page(page, 0))
+ return 0;
+
+ ret = remove_mapping(mapping, page);
+
+ return ret;
+}
+
+int truncate_inode_page(struct address_space *mapping, struct page *page)
+{
+ if (page_mapped(page)) {
+ unmap_mapping_range(mapping,
+ (loff_t)page->index << PAGE_CACHE_SHIFT,
+ PAGE_CACHE_SIZE, 0);
+ }
+ return truncate_complete_page(mapping, page);
+}
+
+/*
+ * Used to get rid of pages on hardware memory corruption.
+ */
+int generic_error_remove_page(struct address_space *mapping, struct page *page)
+{
+ if (!mapping)
+ return -EINVAL;
+ /*
+ * Only punch for normal data pages for now.
+ * Handling other types like directories would need more auditing.
+ */
+ if (!S_ISREG(mapping->host->i_mode))
+ return -EIO;
+ return truncate_inode_page(mapping, page);
+}
+EXPORT_SYMBOL(generic_error_remove_page);
+
+/*
+ * Safely invalidate one page from its pagecache mapping.
+ * It only drops clean, unused pages. The page must be locked.
+ *
+ * Returns 1 if the page is successfully invalidated, otherwise 0.
+ */
+int invalidate_inode_page(struct page *page)
+{
+ struct address_space *mapping = page_mapping(page);
+ if (!mapping)
+ return 0;
+ if (PageDirty(page) || PageWriteback(page))
+ return 0;
+ if (page_mapped(page))
+ return 0;
+ return invalidate_complete_page(mapping, page);
+}
+
+/**
+ * truncate_inode_pages_range - truncate range of pages specified by start & end byte offsets
+ * @mapping: mapping to truncate
+ * @lstart: offset from which to truncate
+ * @lend: offset to which to truncate (inclusive)
+ *
+ * Truncate the page cache, removing the pages that are between
+ * specified offsets (and zeroing out partial pages
+ * if lstart or lend + 1 is not page aligned).
+ *
+ * Truncate takes two passes - the first pass is nonblocking. It will not
+ * block on page locks and it will not block on writeback. The second pass
+ * will wait. This is to prevent as much IO as possible in the affected region.
+ * The first pass will remove most pages, so the search cost of the second pass
+ * is low.
+ *
+ * We pass down the cache-hot hint to the page freeing code. Even if the
+ * mapping is large, it is probably the case that the final pages are the most
+ * recently touched, and freeing happens in ascending file offset order.
+ *
+ * Note that since ->invalidatepage() accepts range to invalidate
+ * truncate_inode_pages_range is able to handle cases where lend + 1 is not
+ * page aligned properly.
+ */
+void truncate_inode_pages_range(struct address_space *mapping,
+ loff_t lstart, loff_t lend)
+{
+ pgoff_t start; /* inclusive */
+ pgoff_t end; /* exclusive */
+ unsigned int partial_start; /* inclusive */
+ unsigned int partial_end; /* exclusive */
+ struct pagevec pvec;
+ pgoff_t indices[PAGEVEC_SIZE];
+ pgoff_t index;
+ int i;
+
+ cleancache_invalidate_inode(mapping);
+ if (mapping->nrpages == 0 && mapping->nrshadows == 0)
+ return;
+
+ /* Offsets within partial pages */
+ partial_start = lstart & (PAGE_CACHE_SIZE - 1);
+ partial_end = (lend + 1) & (PAGE_CACHE_SIZE - 1);
+
+ /*
+ * 'start' and 'end' always covers the range of pages to be fully
+ * truncated. Partial pages are covered with 'partial_start' at the
+ * start of the range and 'partial_end' at the end of the range.
+ * Note that 'end' is exclusive while 'lend' is inclusive.
+ */
+ start = (lstart + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
+ if (lend == -1)
+ /*
+ * lend == -1 indicates end-of-file so we have to set 'end'
+ * to the highest possible pgoff_t and since the type is
+ * unsigned we're using -1.
+ */
+ end = -1;
+ else
+ end = (lend + 1) >> PAGE_CACHE_SHIFT;
+
+ pagevec_init(&pvec, 0);
+ index = start;
+ while (index < end && pagevec_lookup_entries(&pvec, mapping, index,
+ min(end - index, (pgoff_t)PAGEVEC_SIZE),
+ indices)) {
+ for (i = 0; i < pagevec_count(&pvec); i++) {
+ struct page *page = pvec.pages[i];
+
+ /* We rely upon deletion not changing page->index */
+ index = indices[i];
+ if (index >= end)
+ break;
+
+ if (radix_tree_exceptional_entry(page)) {
+ clear_exceptional_entry(mapping, index, page);
+ continue;
+ }
+
+ if (!trylock_page(page))
+ continue;
+ WARN_ON(page->index != index);
+ if (PageWriteback(page)) {
+ unlock_page(page);
+ continue;
+ }
+ truncate_inode_page(mapping, page);
+ unlock_page(page);
+ }
+ pagevec_remove_exceptionals(&pvec);
+ pagevec_release(&pvec);
+ cond_resched();
+ index++;
+ }
+
+ if (partial_start) {
+ struct page *page = find_lock_page(mapping, start - 1);
+ if (page) {
+ unsigned int top = PAGE_CACHE_SIZE;
+ if (start > end) {
+ /* Truncation within a single page */
+ top = partial_end;
+ partial_end = 0;
+ }
+ wait_on_page_writeback(page);
+ zero_user_segment(page, partial_start, top);
+ cleancache_invalidate_page(mapping, page);
+ if (page_has_private(page))
+ do_invalidatepage(page, partial_start,
+ top - partial_start);
+ unlock_page(page);
+ page_cache_release(page);
+ }
+ }
+ if (partial_end) {
+ struct page *page = find_lock_page(mapping, end);
+ if (page) {
+ wait_on_page_writeback(page);
+ zero_user_segment(page, 0, partial_end);
+ cleancache_invalidate_page(mapping, page);
+ if (page_has_private(page))
+ do_invalidatepage(page, 0,
+ partial_end);
+ unlock_page(page);
+ page_cache_release(page);
+ }
+ }
+ /*
+ * If the truncation happened within a single page no pages
+ * will be released, just zeroed, so we can bail out now.
+ */
+ if (start >= end)
+ return;
+
+ index = start;
+ for ( ; ; ) {
+ cond_resched();
+ if (!pagevec_lookup_entries(&pvec, mapping, index,
+ min(end - index, (pgoff_t)PAGEVEC_SIZE), indices)) {
+ /* If all gone from start onwards, we're done */
+ if (index == start)
+ break;
+ /* Otherwise restart to make sure all gone */
+ index = start;
+ continue;
+ }
+ if (index == start && indices[0] >= end) {
+ /* All gone out of hole to be punched, we're done */
+ pagevec_remove_exceptionals(&pvec);
+ pagevec_release(&pvec);
+ break;
+ }
+ for (i = 0; i < pagevec_count(&pvec); i++) {
+ struct page *page = pvec.pages[i];
+
+ /* We rely upon deletion not changing page->index */
+ index = indices[i];
+ if (index >= end) {
+ /* Restart punch to make sure all gone */
+ index = start - 1;
+ break;
+ }
+
+ if (radix_tree_exceptional_entry(page)) {
+ clear_exceptional_entry(mapping, index, page);
+ continue;
+ }
+
+ lock_page(page);
+ WARN_ON(page->index != index);
+ wait_on_page_writeback(page);
+ truncate_inode_page(mapping, page);
+ unlock_page(page);
+ }
+ pagevec_remove_exceptionals(&pvec);
+ pagevec_release(&pvec);
+ index++;
+ }
+ cleancache_invalidate_inode(mapping);
+}
+EXPORT_SYMBOL(truncate_inode_pages_range);
+
+/**
+ * truncate_inode_pages - truncate *all* the pages from an offset
+ * @mapping: mapping to truncate
+ * @lstart: offset from which to truncate
+ *
+ * Called under (and serialised by) inode->i_mutex.
+ *
+ * Note: When this function returns, there can be a page in the process of
+ * deletion (inside __delete_from_page_cache()) in the specified range. Thus
+ * mapping->nrpages can be non-zero when this function returns even after
+ * truncation of the whole mapping.
+ */
+void truncate_inode_pages(struct address_space *mapping, loff_t lstart)
+{
+ truncate_inode_pages_range(mapping, lstart, (loff_t)-1);
+}
+EXPORT_SYMBOL(truncate_inode_pages);
+
+/**
+ * truncate_inode_pages_final - truncate *all* pages before inode dies
+ * @mapping: mapping to truncate
+ *
+ * Called under (and serialized by) inode->i_mutex.
+ *
+ * Filesystems have to use this in the .evict_inode path to inform the
+ * VM that this is the final truncate and the inode is going away.
+ */
+void truncate_inode_pages_final(struct address_space *mapping)
+{
+ unsigned long nrshadows;
+ unsigned long nrpages;
+
+ /*
+ * Page reclaim can not participate in regular inode lifetime
+ * management (can't call iput()) and thus can race with the
+ * inode teardown. Tell it when the address space is exiting,
+ * so that it does not install eviction information after the
+ * final truncate has begun.
+ */
+ mapping_set_exiting(mapping);
+
+ /*
+ * When reclaim installs eviction entries, it increases
+ * nrshadows first, then decreases nrpages. Make sure we see
+ * this in the right order or we might miss an entry.
+ */
+ nrpages = mapping->nrpages;
+ smp_rmb();
+ nrshadows = mapping->nrshadows;
+
+ if (nrpages || nrshadows) {
+ /*
+ * As truncation uses a lockless tree lookup, cycle
+ * the tree lock to make sure any ongoing tree
+ * modification that does not see AS_EXITING is
+ * completed before starting the final truncate.
+ */
+ spin_lock_irq(&mapping->tree_lock);
+ spin_unlock_irq(&mapping->tree_lock);
+
+ truncate_inode_pages(mapping, 0);
+ }
+}
+EXPORT_SYMBOL(truncate_inode_pages_final);
+
+/**
+ * invalidate_mapping_pages - Invalidate all the unlocked pages of one inode
+ * @mapping: the address_space which holds the pages to invalidate
+ * @start: the offset 'from' which to invalidate
+ * @end: the offset 'to' which to invalidate (inclusive)
+ *
+ * This function only removes the unlocked pages, if you want to
+ * remove all the pages of one inode, you must call truncate_inode_pages.
+ *
+ * invalidate_mapping_pages() will not block on IO activity. It will not
+ * invalidate pages which are dirty, locked, under writeback or mapped into
+ * pagetables.
+ */
+unsigned long invalidate_mapping_pages(struct address_space *mapping,
+ pgoff_t start, pgoff_t end)
+{
+ pgoff_t indices[PAGEVEC_SIZE];
+ struct pagevec pvec;
+ pgoff_t index = start;
+ unsigned long ret;
+ unsigned long count = 0;
+ int i;
+
+ pagevec_init(&pvec, 0);
+ while (index <= end && pagevec_lookup_entries(&pvec, mapping, index,
+ min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1,
+ indices)) {
+ for (i = 0; i < pagevec_count(&pvec); i++) {
+ struct page *page = pvec.pages[i];
+
+ /* We rely upon deletion not changing page->index */
+ index = indices[i];
+ if (index > end)
+ break;
+
+ if (radix_tree_exceptional_entry(page)) {
+ clear_exceptional_entry(mapping, index, page);
+ continue;
+ }
+
+ if (!trylock_page(page))
+ continue;
+ WARN_ON(page->index != index);
+ ret = invalidate_inode_page(page);
+ unlock_page(page);
+ /*
+ * Invalidation is a hint that the page is no longer
+ * of interest and try to speed up its reclaim.
+ */
+ if (!ret)
+ deactivate_file_page(page);
+ count += ret;
+ }
+ pagevec_remove_exceptionals(&pvec);
+ pagevec_release(&pvec);
+ cond_resched();
+ index++;
+ }
+ return count;
+}
+EXPORT_SYMBOL(invalidate_mapping_pages);
+
+/*
+ * This is like invalidate_complete_page(), except it ignores the page's
+ * refcount. We do this because invalidate_inode_pages2() needs stronger
+ * invalidation guarantees, and cannot afford to leave pages behind because
+ * shrink_page_list() has a temp ref on them, or because they're transiently
+ * sitting in the lru_cache_add() pagevecs.
+ */
+static int
+invalidate_complete_page2(struct address_space *mapping, struct page *page)
+{
+ if (page->mapping != mapping)
+ return 0;
+
+ if (page_has_private(page) && !try_to_release_page(page, GFP_KERNEL))
+ return 0;
+
+ spin_lock_irq(&mapping->tree_lock);
+ if (PageDirty(page))
+ goto failed;
+
+ BUG_ON(page_has_private(page));
+ __delete_from_page_cache(page, NULL);
+ spin_unlock_irq(&mapping->tree_lock);
+
+ if (mapping->a_ops->freepage)
+ mapping->a_ops->freepage(page);
+
+ page_cache_release(page); /* pagecache ref */
+ return 1;
+failed:
+ spin_unlock_irq(&mapping->tree_lock);
+ return 0;
+}
+
+static int do_launder_page(struct address_space *mapping, struct page *page)
+{
+ if (!PageDirty(page))
+ return 0;
+ if (page->mapping != mapping || mapping->a_ops->launder_page == NULL)
+ return 0;
+ return mapping->a_ops->launder_page(page);
+}
+
+/**
+ * invalidate_inode_pages2_range - remove range of pages from an address_space
+ * @mapping: the address_space
+ * @start: the page offset 'from' which to invalidate
+ * @end: the page offset 'to' which to invalidate (inclusive)
+ *
+ * Any pages which are found to be mapped into pagetables are unmapped prior to
+ * invalidation.
+ *
+ * Returns -EBUSY if any pages could not be invalidated.
+ */
+int invalidate_inode_pages2_range(struct address_space *mapping,
+ pgoff_t start, pgoff_t end)
+{
+ pgoff_t indices[PAGEVEC_SIZE];
+ struct pagevec pvec;
+ pgoff_t index;
+ int i;
+ int ret = 0;
+ int ret2 = 0;
+ int did_range_unmap = 0;
+
+ cleancache_invalidate_inode(mapping);
+ pagevec_init(&pvec, 0);
+ index = start;
+ while (index <= end && pagevec_lookup_entries(&pvec, mapping, index,
+ min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1,
+ indices)) {
+ for (i = 0; i < pagevec_count(&pvec); i++) {
+ struct page *page = pvec.pages[i];
+
+ /* We rely upon deletion not changing page->index */
+ index = indices[i];
+ if (index > end)
+ break;
+
+ if (radix_tree_exceptional_entry(page)) {
+ clear_exceptional_entry(mapping, index, page);
+ continue;
+ }
+
+ lock_page(page);
+ WARN_ON(page->index != index);
+ if (page->mapping != mapping) {
+ unlock_page(page);
+ continue;
+ }
+ wait_on_page_writeback(page);
+ if (page_mapped(page)) {
+ if (!did_range_unmap) {
+ /*
+ * Zap the rest of the file in one hit.
+ */
+ unmap_mapping_range(mapping,
+ (loff_t)index << PAGE_CACHE_SHIFT,
+ (loff_t)(1 + end - index)
+ << PAGE_CACHE_SHIFT,
+ 0);
+ did_range_unmap = 1;
+ } else {
+ /*
+ * Just zap this page
+ */
+ unmap_mapping_range(mapping,
+ (loff_t)index << PAGE_CACHE_SHIFT,
+ PAGE_CACHE_SIZE, 0);
+ }
+ }
+ BUG_ON(page_mapped(page));
+ ret2 = do_launder_page(mapping, page);
+ if (ret2 == 0) {
+ if (!invalidate_complete_page2(mapping, page))
+ ret2 = -EBUSY;
+ }
+ if (ret2 < 0)
+ ret = ret2;
+ unlock_page(page);
+ }
+ pagevec_remove_exceptionals(&pvec);
+ pagevec_release(&pvec);
+ cond_resched();
+ index++;
+ }
+ cleancache_invalidate_inode(mapping);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range);
+
+/**
+ * invalidate_inode_pages2 - remove all pages from an address_space
+ * @mapping: the address_space
+ *
+ * Any pages which are found to be mapped into pagetables are unmapped prior to
+ * invalidation.
+ *
+ * Returns -EBUSY if any pages could not be invalidated.
+ */
+int invalidate_inode_pages2(struct address_space *mapping)
+{
+ return invalidate_inode_pages2_range(mapping, 0, -1);
+}
+EXPORT_SYMBOL_GPL(invalidate_inode_pages2);
+
+/**
+ * truncate_pagecache - unmap and remove pagecache that has been truncated
+ * @inode: inode
+ * @newsize: new file size
+ *
+ * inode's new i_size must already be written before truncate_pagecache
+ * is called.
+ *
+ * This function should typically be called before the filesystem
+ * releases resources associated with the freed range (eg. deallocates
+ * blocks). This way, pagecache will always stay logically coherent
+ * with on-disk format, and the filesystem would not have to deal with
+ * situations such as writepage being called for a page that has already
+ * had its underlying blocks deallocated.
+ */
+void truncate_pagecache(struct inode *inode, loff_t newsize)
+{
+ struct address_space *mapping = inode->i_mapping;
+ loff_t holebegin = round_up(newsize, PAGE_SIZE);
+
+ /*
+ * unmap_mapping_range is called twice, first simply for
+ * efficiency so that truncate_inode_pages does fewer
+ * single-page unmaps. However after this first call, and
+ * before truncate_inode_pages finishes, it is possible for
+ * private pages to be COWed, which remain after
+ * truncate_inode_pages finishes, hence the second
+ * unmap_mapping_range call must be made for correctness.
+ */
+ unmap_mapping_range(mapping, holebegin, 0, 1);
+ truncate_inode_pages(mapping, newsize);
+ unmap_mapping_range(mapping, holebegin, 0, 1);
+}
+EXPORT_SYMBOL(truncate_pagecache);
+
+/**
+ * truncate_setsize - update inode and pagecache for a new file size
+ * @inode: inode
+ * @newsize: new file size
+ *
+ * truncate_setsize updates i_size and performs pagecache truncation (if
+ * necessary) to @newsize. It will be typically be called from the filesystem's
+ * setattr function when ATTR_SIZE is passed in.
+ *
+ * Must be called with a lock serializing truncates and writes (generally
+ * i_mutex but e.g. xfs uses a different lock) and before all filesystem
+ * specific block truncation has been performed.
+ */
+void truncate_setsize(struct inode *inode, loff_t newsize)
+{
+ loff_t oldsize = inode->i_size;
+
+ i_size_write(inode, newsize);
+ if (newsize > oldsize)
+ pagecache_isize_extended(inode, oldsize, newsize);
+ truncate_pagecache(inode, newsize);
+}
+EXPORT_SYMBOL(truncate_setsize);
+
+/**
+ * pagecache_isize_extended - update pagecache after extension of i_size
+ * @inode: inode for which i_size was extended
+ * @from: original inode size
+ * @to: new inode size
+ *
+ * Handle extension of inode size either caused by extending truncate or by
+ * write starting after current i_size. We mark the page straddling current
+ * i_size RO so that page_mkwrite() is called on the nearest write access to
+ * the page. This way filesystem can be sure that page_mkwrite() is called on
+ * the page before user writes to the page via mmap after the i_size has been
+ * changed.
+ *
+ * The function must be called after i_size is updated so that page fault
+ * coming after we unlock the page will already see the new i_size.
+ * The function must be called while we still hold i_mutex - this not only
+ * makes sure i_size is stable but also that userspace cannot observe new
+ * i_size value before we are prepared to store mmap writes at new inode size.
+ */
+void pagecache_isize_extended(struct inode *inode, loff_t from, loff_t to)
+{
+ int bsize = 1 << inode->i_blkbits;
+ loff_t rounded_from;
+ struct page *page;
+ pgoff_t index;
+
+ WARN_ON(to > inode->i_size);
+
+ if (from >= to || bsize == PAGE_CACHE_SIZE)
+ return;
+ /* Page straddling @from will not have any hole block created? */
+ rounded_from = round_up(from, bsize);
+ if (to <= rounded_from || !(rounded_from & (PAGE_CACHE_SIZE - 1)))
+ return;
+
+ index = from >> PAGE_CACHE_SHIFT;
+ page = find_lock_page(inode->i_mapping, index);
+ /* Page not cached? Nothing to do */
+ if (!page)
+ return;
+ /*
+ * See clear_page_dirty_for_io() for details why set_page_dirty()
+ * is needed.
+ */
+ if (page_mkclean(page))
+ set_page_dirty(page);
+ unlock_page(page);
+ page_cache_release(page);
+}
+EXPORT_SYMBOL(pagecache_isize_extended);
+
+/**
+ * truncate_pagecache_range - unmap and remove pagecache that is hole-punched
+ * @inode: inode
+ * @lstart: offset of beginning of hole
+ * @lend: offset of last byte of hole
+ *
+ * This function should typically be called before the filesystem
+ * releases resources associated with the freed range (eg. deallocates
+ * blocks). This way, pagecache will always stay logically coherent
+ * with on-disk format, and the filesystem would not have to deal with
+ * situations such as writepage being called for a page that has already
+ * had its underlying blocks deallocated.
+ */
+void truncate_pagecache_range(struct inode *inode, loff_t lstart, loff_t lend)
+{
+ struct address_space *mapping = inode->i_mapping;
+ loff_t unmap_start = round_up(lstart, PAGE_SIZE);
+ loff_t unmap_end = round_down(1 + lend, PAGE_SIZE) - 1;
+ /*
+ * This rounding is currently just for example: unmap_mapping_range
+ * expands its hole outwards, whereas we want it to contract the hole
+ * inwards. However, existing callers of truncate_pagecache_range are
+ * doing their own page rounding first. Note that unmap_mapping_range
+ * allows holelen 0 for all, and we allow lend -1 for end of file.
+ */
+
+ /*
+ * Unlike in truncate_pagecache, unmap_mapping_range is called only
+ * once (before truncating pagecache), and without "even_cows" flag:
+ * hole-punching should not remove private COWed pages from the hole.
+ */
+ if ((u64)unmap_end > (u64)unmap_start)
+ unmap_mapping_range(mapping, unmap_start,
+ 1 + unmap_end - unmap_start, 0);
+ truncate_inode_pages_range(mapping, lstart, lend);
+}
+EXPORT_SYMBOL(truncate_pagecache_range);
Code Review / kvmfornfv.git / blobdiff