--- /dev/null
+/* Storage object read/write
+ *
+ * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#include <linux/mount.h>
+#include <linux/slab.h>
+#include <linux/file.h>
+#include <linux/swap.h>
+#include "internal.h"
+
+/*
+ * detect wake up events generated by the unlocking of pages in which we're
+ * interested
+ * - we use this to detect read completion of backing pages
+ * - the caller holds the waitqueue lock
+ */
+static int cachefiles_read_waiter(wait_queue_t *wait, unsigned mode,
+ int sync, void *_key)
+{
+ struct cachefiles_one_read *monitor =
+ container_of(wait, struct cachefiles_one_read, monitor);
+ struct cachefiles_object *object;
+ struct wait_bit_key *key = _key;
+ struct page *page = wait->private;
+
+ ASSERT(key);
+
+ _enter("{%lu},%u,%d,{%p,%u}",
+ monitor->netfs_page->index, mode, sync,
+ key->flags, key->bit_nr);
+
+ if (key->flags != &page->flags ||
+ key->bit_nr != PG_locked)
+ return 0;
+
+ _debug("--- monitor %p %lx ---", page, page->flags);
+
+ if (!PageUptodate(page) && !PageError(page)) {
+ /* unlocked, not uptodate and not erronous? */
+ _debug("page probably truncated");
+ }
+
+ /* remove from the waitqueue */
+ list_del(&wait->task_list);
+
+ /* move onto the action list and queue for FS-Cache thread pool */
+ ASSERT(monitor->op);
+
+ object = container_of(monitor->op->op.object,
+ struct cachefiles_object, fscache);
+
+ spin_lock(&object->work_lock);
+ list_add_tail(&monitor->op_link, &monitor->op->to_do);
+ spin_unlock(&object->work_lock);
+
+ fscache_enqueue_retrieval(monitor->op);
+ return 0;
+}
+
+/*
+ * handle a probably truncated page
+ * - check to see if the page is still relevant and reissue the read if
+ * possible
+ * - return -EIO on error, -ENODATA if the page is gone, -EINPROGRESS if we
+ * must wait again and 0 if successful
+ */
+static int cachefiles_read_reissue(struct cachefiles_object *object,
+ struct cachefiles_one_read *monitor)
+{
+ struct address_space *bmapping = d_backing_inode(object->backer)->i_mapping;
+ struct page *backpage = monitor->back_page, *backpage2;
+ int ret;
+
+ _enter("{ino=%lx},{%lx,%lx}",
+ d_backing_inode(object->backer)->i_ino,
+ backpage->index, backpage->flags);
+
+ /* skip if the page was truncated away completely */
+ if (backpage->mapping != bmapping) {
+ _leave(" = -ENODATA [mapping]");
+ return -ENODATA;
+ }
+
+ backpage2 = find_get_page(bmapping, backpage->index);
+ if (!backpage2) {
+ _leave(" = -ENODATA [gone]");
+ return -ENODATA;
+ }
+
+ if (backpage != backpage2) {
+ put_page(backpage2);
+ _leave(" = -ENODATA [different]");
+ return -ENODATA;
+ }
+
+ /* the page is still there and we already have a ref on it, so we don't
+ * need a second */
+ put_page(backpage2);
+
+ INIT_LIST_HEAD(&monitor->op_link);
+ add_page_wait_queue(backpage, &monitor->monitor);
+
+ if (trylock_page(backpage)) {
+ ret = -EIO;
+ if (PageError(backpage))
+ goto unlock_discard;
+ ret = 0;
+ if (PageUptodate(backpage))
+ goto unlock_discard;
+
+ _debug("reissue read");
+ ret = bmapping->a_ops->readpage(NULL, backpage);
+ if (ret < 0)
+ goto unlock_discard;
+ }
+
+ /* but the page may have been read before the monitor was installed, so
+ * the monitor may miss the event - so we have to ensure that we do get
+ * one in such a case */
+ if (trylock_page(backpage)) {
+ _debug("jumpstart %p {%lx}", backpage, backpage->flags);
+ unlock_page(backpage);
+ }
+
+ /* it'll reappear on the todo list */
+ _leave(" = -EINPROGRESS");
+ return -EINPROGRESS;
+
+unlock_discard:
+ unlock_page(backpage);
+ spin_lock_irq(&object->work_lock);
+ list_del(&monitor->op_link);
+ spin_unlock_irq(&object->work_lock);
+ _leave(" = %d", ret);
+ return ret;
+}
+
+/*
+ * copy data from backing pages to netfs pages to complete a read operation
+ * - driven by FS-Cache's thread pool
+ */
+static void cachefiles_read_copier(struct fscache_operation *_op)
+{
+ struct cachefiles_one_read *monitor;
+ struct cachefiles_object *object;
+ struct fscache_retrieval *op;
+ int error, max;
+
+ op = container_of(_op, struct fscache_retrieval, op);
+ object = container_of(op->op.object,
+ struct cachefiles_object, fscache);
+
+ _enter("{ino=%lu}", d_backing_inode(object->backer)->i_ino);
+
+ max = 8;
+ spin_lock_irq(&object->work_lock);
+
+ while (!list_empty(&op->to_do)) {
+ monitor = list_entry(op->to_do.next,
+ struct cachefiles_one_read, op_link);
+ list_del(&monitor->op_link);
+
+ spin_unlock_irq(&object->work_lock);
+
+ _debug("- copy {%lu}", monitor->back_page->index);
+
+ recheck:
+ if (test_bit(FSCACHE_COOKIE_INVALIDATING,
+ &object->fscache.cookie->flags)) {
+ error = -ESTALE;
+ } else if (PageUptodate(monitor->back_page)) {
+ copy_highpage(monitor->netfs_page, monitor->back_page);
+ fscache_mark_page_cached(monitor->op,
+ monitor->netfs_page);
+ error = 0;
+ } else if (!PageError(monitor->back_page)) {
+ /* the page has probably been truncated */
+ error = cachefiles_read_reissue(object, monitor);
+ if (error == -EINPROGRESS)
+ goto next;
+ goto recheck;
+ } else {
+ cachefiles_io_error_obj(
+ object,
+ "Readpage failed on backing file %lx",
+ (unsigned long) monitor->back_page->flags);
+ error = -EIO;
+ }
+
+ page_cache_release(monitor->back_page);
+
+ fscache_end_io(op, monitor->netfs_page, error);
+ page_cache_release(monitor->netfs_page);
+ fscache_retrieval_complete(op, 1);
+ fscache_put_retrieval(op);
+ kfree(monitor);
+
+ next:
+ /* let the thread pool have some air occasionally */
+ max--;
+ if (max < 0 || need_resched()) {
+ if (!list_empty(&op->to_do))
+ fscache_enqueue_retrieval(op);
+ _leave(" [maxed out]");
+ return;
+ }
+
+ spin_lock_irq(&object->work_lock);
+ }
+
+ spin_unlock_irq(&object->work_lock);
+ _leave("");
+}
+
+/*
+ * read the corresponding page to the given set from the backing file
+ * - an uncertain page is simply discarded, to be tried again another time
+ */
+static int cachefiles_read_backing_file_one(struct cachefiles_object *object,
+ struct fscache_retrieval *op,
+ struct page *netpage)
+{
+ struct cachefiles_one_read *monitor;
+ struct address_space *bmapping;
+ struct page *newpage, *backpage;
+ int ret;
+
+ _enter("");
+
+ _debug("read back %p{%lu,%d}",
+ netpage, netpage->index, page_count(netpage));
+
+ monitor = kzalloc(sizeof(*monitor), cachefiles_gfp);
+ if (!monitor)
+ goto nomem;
+
+ monitor->netfs_page = netpage;
+ monitor->op = fscache_get_retrieval(op);
+
+ init_waitqueue_func_entry(&monitor->monitor, cachefiles_read_waiter);
+
+ /* attempt to get hold of the backing page */
+ bmapping = d_backing_inode(object->backer)->i_mapping;
+ newpage = NULL;
+
+ for (;;) {
+ backpage = find_get_page(bmapping, netpage->index);
+ if (backpage)
+ goto backing_page_already_present;
+
+ if (!newpage) {
+ newpage = __page_cache_alloc(cachefiles_gfp |
+ __GFP_COLD);
+ if (!newpage)
+ goto nomem_monitor;
+ }
+
+ ret = add_to_page_cache_lru(newpage, bmapping,
+ netpage->index, cachefiles_gfp);
+ if (ret == 0)
+ goto installed_new_backing_page;
+ if (ret != -EEXIST)
+ goto nomem_page;
+ }
+
+ /* we've installed a new backing page, so now we need to start
+ * it reading */
+installed_new_backing_page:
+ _debug("- new %p", newpage);
+
+ backpage = newpage;
+ newpage = NULL;
+
+read_backing_page:
+ ret = bmapping->a_ops->readpage(NULL, backpage);
+ if (ret < 0)
+ goto read_error;
+
+ /* set the monitor to transfer the data across */
+monitor_backing_page:
+ _debug("- monitor add");
+
+ /* install the monitor */
+ page_cache_get(monitor->netfs_page);
+ page_cache_get(backpage);
+ monitor->back_page = backpage;
+ monitor->monitor.private = backpage;
+ add_page_wait_queue(backpage, &monitor->monitor);
+ monitor = NULL;
+
+ /* but the page may have been read before the monitor was installed, so
+ * the monitor may miss the event - so we have to ensure that we do get
+ * one in such a case */
+ if (trylock_page(backpage)) {
+ _debug("jumpstart %p {%lx}", backpage, backpage->flags);
+ unlock_page(backpage);
+ }
+ goto success;
+
+ /* if the backing page is already present, it can be in one of
+ * three states: read in progress, read failed or read okay */
+backing_page_already_present:
+ _debug("- present");
+
+ if (newpage) {
+ page_cache_release(newpage);
+ newpage = NULL;
+ }
+
+ if (PageError(backpage))
+ goto io_error;
+
+ if (PageUptodate(backpage))
+ goto backing_page_already_uptodate;
+
+ if (!trylock_page(backpage))
+ goto monitor_backing_page;
+ _debug("read %p {%lx}", backpage, backpage->flags);
+ goto read_backing_page;
+
+ /* the backing page is already up to date, attach the netfs
+ * page to the pagecache and LRU and copy the data across */
+backing_page_already_uptodate:
+ _debug("- uptodate");
+
+ fscache_mark_page_cached(op, netpage);
+
+ copy_highpage(netpage, backpage);
+ fscache_end_io(op, netpage, 0);
+ fscache_retrieval_complete(op, 1);
+
+success:
+ _debug("success");
+ ret = 0;
+
+out:
+ if (backpage)
+ page_cache_release(backpage);
+ if (monitor) {
+ fscache_put_retrieval(monitor->op);
+ kfree(monitor);
+ }
+ _leave(" = %d", ret);
+ return ret;
+
+read_error:
+ _debug("read error %d", ret);
+ if (ret == -ENOMEM) {
+ fscache_retrieval_complete(op, 1);
+ goto out;
+ }
+io_error:
+ cachefiles_io_error_obj(object, "Page read error on backing file");
+ fscache_retrieval_complete(op, 1);
+ ret = -ENOBUFS;
+ goto out;
+
+nomem_page:
+ page_cache_release(newpage);
+nomem_monitor:
+ fscache_put_retrieval(monitor->op);
+ kfree(monitor);
+nomem:
+ fscache_retrieval_complete(op, 1);
+ _leave(" = -ENOMEM");
+ return -ENOMEM;
+}
+
+/*
+ * read a page from the cache or allocate a block in which to store it
+ * - cache withdrawal is prevented by the caller
+ * - returns -EINTR if interrupted
+ * - returns -ENOMEM if ran out of memory
+ * - returns -ENOBUFS if no buffers can be made available
+ * - returns -ENOBUFS if page is beyond EOF
+ * - if the page is backed by a block in the cache:
+ * - a read will be started which will call the callback on completion
+ * - 0 will be returned
+ * - else if the page is unbacked:
+ * - the metadata will be retained
+ * - -ENODATA will be returned
+ */
+int cachefiles_read_or_alloc_page(struct fscache_retrieval *op,
+ struct page *page,
+ gfp_t gfp)
+{
+ struct cachefiles_object *object;
+ struct cachefiles_cache *cache;
+ struct inode *inode;
+ sector_t block0, block;
+ unsigned shift;
+ int ret;
+
+ object = container_of(op->op.object,
+ struct cachefiles_object, fscache);
+ cache = container_of(object->fscache.cache,
+ struct cachefiles_cache, cache);
+
+ _enter("{%p},{%lx},,,", object, page->index);
+
+ if (!object->backer)
+ goto enobufs;
+
+ inode = d_backing_inode(object->backer);
+ ASSERT(S_ISREG(inode->i_mode));
+ ASSERT(inode->i_mapping->a_ops->bmap);
+ ASSERT(inode->i_mapping->a_ops->readpages);
+
+ /* calculate the shift required to use bmap */
+ if (inode->i_sb->s_blocksize > PAGE_SIZE)
+ goto enobufs;
+
+ shift = PAGE_SHIFT - inode->i_sb->s_blocksize_bits;
+
+ op->op.flags &= FSCACHE_OP_KEEP_FLAGS;
+ op->op.flags |= FSCACHE_OP_ASYNC;
+ op->op.processor = cachefiles_read_copier;
+
+ /* we assume the absence or presence of the first block is a good
+ * enough indication for the page as a whole
+ * - TODO: don't use bmap() for this as it is _not_ actually good
+ * enough for this as it doesn't indicate errors, but it's all we've
+ * got for the moment
+ */
+ block0 = page->index;
+ block0 <<= shift;
+
+ block = inode->i_mapping->a_ops->bmap(inode->i_mapping, block0);
+ _debug("%llx -> %llx",
+ (unsigned long long) block0,
+ (unsigned long long) block);
+
+ if (block) {
+ /* submit the apparently valid page to the backing fs to be
+ * read from disk */
+ ret = cachefiles_read_backing_file_one(object, op, page);
+ } else if (cachefiles_has_space(cache, 0, 1) == 0) {
+ /* there's space in the cache we can use */
+ fscache_mark_page_cached(op, page);
+ fscache_retrieval_complete(op, 1);
+ ret = -ENODATA;
+ } else {
+ goto enobufs;
+ }
+
+ _leave(" = %d", ret);
+ return ret;
+
+enobufs:
+ fscache_retrieval_complete(op, 1);
+ _leave(" = -ENOBUFS");
+ return -ENOBUFS;
+}
+
+/*
+ * read the corresponding pages to the given set from the backing file
+ * - any uncertain pages are simply discarded, to be tried again another time
+ */
+static int cachefiles_read_backing_file(struct cachefiles_object *object,
+ struct fscache_retrieval *op,
+ struct list_head *list)
+{
+ struct cachefiles_one_read *monitor = NULL;
+ struct address_space *bmapping = d_backing_inode(object->backer)->i_mapping;
+ struct page *newpage = NULL, *netpage, *_n, *backpage = NULL;
+ int ret = 0;
+
+ _enter("");
+
+ list_for_each_entry_safe(netpage, _n, list, lru) {
+ list_del(&netpage->lru);
+
+ _debug("read back %p{%lu,%d}",
+ netpage, netpage->index, page_count(netpage));
+
+ if (!monitor) {
+ monitor = kzalloc(sizeof(*monitor), cachefiles_gfp);
+ if (!monitor)
+ goto nomem;
+
+ monitor->op = fscache_get_retrieval(op);
+ init_waitqueue_func_entry(&monitor->monitor,
+ cachefiles_read_waiter);
+ }
+
+ for (;;) {
+ backpage = find_get_page(bmapping, netpage->index);
+ if (backpage)
+ goto backing_page_already_present;
+
+ if (!newpage) {
+ newpage = __page_cache_alloc(cachefiles_gfp |
+ __GFP_COLD);
+ if (!newpage)
+ goto nomem;
+ }
+
+ ret = add_to_page_cache_lru(newpage, bmapping,
+ netpage->index,
+ cachefiles_gfp);
+ if (ret == 0)
+ goto installed_new_backing_page;
+ if (ret != -EEXIST)
+ goto nomem;
+ }
+
+ /* we've installed a new backing page, so now we need
+ * to start it reading */
+ installed_new_backing_page:
+ _debug("- new %p", newpage);
+
+ backpage = newpage;
+ newpage = NULL;
+
+ reread_backing_page:
+ ret = bmapping->a_ops->readpage(NULL, backpage);
+ if (ret < 0)
+ goto read_error;
+
+ /* add the netfs page to the pagecache and LRU, and set the
+ * monitor to transfer the data across */
+ monitor_backing_page:
+ _debug("- monitor add");
+
+ ret = add_to_page_cache_lru(netpage, op->mapping,
+ netpage->index, cachefiles_gfp);
+ if (ret < 0) {
+ if (ret == -EEXIST) {
+ page_cache_release(netpage);
+ fscache_retrieval_complete(op, 1);
+ continue;
+ }
+ goto nomem;
+ }
+
+ /* install a monitor */
+ page_cache_get(netpage);
+ monitor->netfs_page = netpage;
+
+ page_cache_get(backpage);
+ monitor->back_page = backpage;
+ monitor->monitor.private = backpage;
+ add_page_wait_queue(backpage, &monitor->monitor);
+ monitor = NULL;
+
+ /* but the page may have been read before the monitor was
+ * installed, so the monitor may miss the event - so we have to
+ * ensure that we do get one in such a case */
+ if (trylock_page(backpage)) {
+ _debug("2unlock %p {%lx}", backpage, backpage->flags);
+ unlock_page(backpage);
+ }
+
+ page_cache_release(backpage);
+ backpage = NULL;
+
+ page_cache_release(netpage);
+ netpage = NULL;
+ continue;
+
+ /* if the backing page is already present, it can be in one of
+ * three states: read in progress, read failed or read okay */
+ backing_page_already_present:
+ _debug("- present %p", backpage);
+
+ if (PageError(backpage))
+ goto io_error;
+
+ if (PageUptodate(backpage))
+ goto backing_page_already_uptodate;
+
+ _debug("- not ready %p{%lx}", backpage, backpage->flags);
+
+ if (!trylock_page(backpage))
+ goto monitor_backing_page;
+
+ if (PageError(backpage)) {
+ _debug("error %lx", backpage->flags);
+ unlock_page(backpage);
+ goto io_error;
+ }
+
+ if (PageUptodate(backpage))
+ goto backing_page_already_uptodate_unlock;
+
+ /* we've locked a page that's neither up to date nor erroneous,
+ * so we need to attempt to read it again */
+ goto reread_backing_page;
+
+ /* the backing page is already up to date, attach the netfs
+ * page to the pagecache and LRU and copy the data across */
+ backing_page_already_uptodate_unlock:
+ _debug("uptodate %lx", backpage->flags);
+ unlock_page(backpage);
+ backing_page_already_uptodate:
+ _debug("- uptodate");
+
+ ret = add_to_page_cache_lru(netpage, op->mapping,
+ netpage->index, cachefiles_gfp);
+ if (ret < 0) {
+ if (ret == -EEXIST) {
+ page_cache_release(netpage);
+ fscache_retrieval_complete(op, 1);
+ continue;
+ }
+ goto nomem;
+ }
+
+ copy_highpage(netpage, backpage);
+
+ page_cache_release(backpage);
+ backpage = NULL;
+
+ fscache_mark_page_cached(op, netpage);
+
+ /* the netpage is unlocked and marked up to date here */
+ fscache_end_io(op, netpage, 0);
+ page_cache_release(netpage);
+ netpage = NULL;
+ fscache_retrieval_complete(op, 1);
+ continue;
+ }
+
+ netpage = NULL;
+
+ _debug("out");
+
+out:
+ /* tidy up */
+ if (newpage)
+ page_cache_release(newpage);
+ if (netpage)
+ page_cache_release(netpage);
+ if (backpage)
+ page_cache_release(backpage);
+ if (monitor) {
+ fscache_put_retrieval(op);
+ kfree(monitor);
+ }
+
+ list_for_each_entry_safe(netpage, _n, list, lru) {
+ list_del(&netpage->lru);
+ page_cache_release(netpage);
+ fscache_retrieval_complete(op, 1);
+ }
+
+ _leave(" = %d", ret);
+ return ret;
+
+nomem:
+ _debug("nomem");
+ ret = -ENOMEM;
+ goto record_page_complete;
+
+read_error:
+ _debug("read error %d", ret);
+ if (ret == -ENOMEM)
+ goto record_page_complete;
+io_error:
+ cachefiles_io_error_obj(object, "Page read error on backing file");
+ ret = -ENOBUFS;
+record_page_complete:
+ fscache_retrieval_complete(op, 1);
+ goto out;
+}
+
+/*
+ * read a list of pages from the cache or allocate blocks in which to store
+ * them
+ */
+int cachefiles_read_or_alloc_pages(struct fscache_retrieval *op,
+ struct list_head *pages,
+ unsigned *nr_pages,
+ gfp_t gfp)
+{
+ struct cachefiles_object *object;
+ struct cachefiles_cache *cache;
+ struct list_head backpages;
+ struct pagevec pagevec;
+ struct inode *inode;
+ struct page *page, *_n;
+ unsigned shift, nrbackpages;
+ int ret, ret2, space;
+
+ object = container_of(op->op.object,
+ struct cachefiles_object, fscache);
+ cache = container_of(object->fscache.cache,
+ struct cachefiles_cache, cache);
+
+ _enter("{OBJ%x,%d},,%d,,",
+ object->fscache.debug_id, atomic_read(&op->op.usage),
+ *nr_pages);
+
+ if (!object->backer)
+ goto all_enobufs;
+
+ space = 1;
+ if (cachefiles_has_space(cache, 0, *nr_pages) < 0)
+ space = 0;
+
+ inode = d_backing_inode(object->backer);
+ ASSERT(S_ISREG(inode->i_mode));
+ ASSERT(inode->i_mapping->a_ops->bmap);
+ ASSERT(inode->i_mapping->a_ops->readpages);
+
+ /* calculate the shift required to use bmap */
+ if (inode->i_sb->s_blocksize > PAGE_SIZE)
+ goto all_enobufs;
+
+ shift = PAGE_SHIFT - inode->i_sb->s_blocksize_bits;
+
+ pagevec_init(&pagevec, 0);
+
+ op->op.flags &= FSCACHE_OP_KEEP_FLAGS;
+ op->op.flags |= FSCACHE_OP_ASYNC;
+ op->op.processor = cachefiles_read_copier;
+
+ INIT_LIST_HEAD(&backpages);
+ nrbackpages = 0;
+
+ ret = space ? -ENODATA : -ENOBUFS;
+ list_for_each_entry_safe(page, _n, pages, lru) {
+ sector_t block0, block;
+
+ /* we assume the absence or presence of the first block is a
+ * good enough indication for the page as a whole
+ * - TODO: don't use bmap() for this as it is _not_ actually
+ * good enough for this as it doesn't indicate errors, but
+ * it's all we've got for the moment
+ */
+ block0 = page->index;
+ block0 <<= shift;
+
+ block = inode->i_mapping->a_ops->bmap(inode->i_mapping,
+ block0);
+ _debug("%llx -> %llx",
+ (unsigned long long) block0,
+ (unsigned long long) block);
+
+ if (block) {
+ /* we have data - add it to the list to give to the
+ * backing fs */
+ list_move(&page->lru, &backpages);
+ (*nr_pages)--;
+ nrbackpages++;
+ } else if (space && pagevec_add(&pagevec, page) == 0) {
+ fscache_mark_pages_cached(op, &pagevec);
+ fscache_retrieval_complete(op, 1);
+ ret = -ENODATA;
+ } else {
+ fscache_retrieval_complete(op, 1);
+ }
+ }
+
+ if (pagevec_count(&pagevec) > 0)
+ fscache_mark_pages_cached(op, &pagevec);
+
+ if (list_empty(pages))
+ ret = 0;
+
+ /* submit the apparently valid pages to the backing fs to be read from
+ * disk */
+ if (nrbackpages > 0) {
+ ret2 = cachefiles_read_backing_file(object, op, &backpages);
+ if (ret2 == -ENOMEM || ret2 == -EINTR)
+ ret = ret2;
+ }
+
+ _leave(" = %d [nr=%u%s]",
+ ret, *nr_pages, list_empty(pages) ? " empty" : "");
+ return ret;
+
+all_enobufs:
+ fscache_retrieval_complete(op, *nr_pages);
+ return -ENOBUFS;
+}
+
+/*
+ * allocate a block in the cache in which to store a page
+ * - cache withdrawal is prevented by the caller
+ * - returns -EINTR if interrupted
+ * - returns -ENOMEM if ran out of memory
+ * - returns -ENOBUFS if no buffers can be made available
+ * - returns -ENOBUFS if page is beyond EOF
+ * - otherwise:
+ * - the metadata will be retained
+ * - 0 will be returned
+ */
+int cachefiles_allocate_page(struct fscache_retrieval *op,
+ struct page *page,
+ gfp_t gfp)
+{
+ struct cachefiles_object *object;
+ struct cachefiles_cache *cache;
+ int ret;
+
+ object = container_of(op->op.object,
+ struct cachefiles_object, fscache);
+ cache = container_of(object->fscache.cache,
+ struct cachefiles_cache, cache);
+
+ _enter("%p,{%lx},", object, page->index);
+
+ ret = cachefiles_has_space(cache, 0, 1);
+ if (ret == 0)
+ fscache_mark_page_cached(op, page);
+ else
+ ret = -ENOBUFS;
+
+ fscache_retrieval_complete(op, 1);
+ _leave(" = %d", ret);
+ return ret;
+}
+
+/*
+ * allocate blocks in the cache in which to store a set of pages
+ * - cache withdrawal is prevented by the caller
+ * - returns -EINTR if interrupted
+ * - returns -ENOMEM if ran out of memory
+ * - returns -ENOBUFS if some buffers couldn't be made available
+ * - returns -ENOBUFS if some pages are beyond EOF
+ * - otherwise:
+ * - -ENODATA will be returned
+ * - metadata will be retained for any page marked
+ */
+int cachefiles_allocate_pages(struct fscache_retrieval *op,
+ struct list_head *pages,
+ unsigned *nr_pages,
+ gfp_t gfp)
+{
+ struct cachefiles_object *object;
+ struct cachefiles_cache *cache;
+ struct pagevec pagevec;
+ struct page *page;
+ int ret;
+
+ object = container_of(op->op.object,
+ struct cachefiles_object, fscache);
+ cache = container_of(object->fscache.cache,
+ struct cachefiles_cache, cache);
+
+ _enter("%p,,,%d,", object, *nr_pages);
+
+ ret = cachefiles_has_space(cache, 0, *nr_pages);
+ if (ret == 0) {
+ pagevec_init(&pagevec, 0);
+
+ list_for_each_entry(page, pages, lru) {
+ if (pagevec_add(&pagevec, page) == 0)
+ fscache_mark_pages_cached(op, &pagevec);
+ }
+
+ if (pagevec_count(&pagevec) > 0)
+ fscache_mark_pages_cached(op, &pagevec);
+ ret = -ENODATA;
+ } else {
+ ret = -ENOBUFS;
+ }
+
+ fscache_retrieval_complete(op, *nr_pages);
+ _leave(" = %d", ret);
+ return ret;
+}
+
+/*
+ * request a page be stored in the cache
+ * - cache withdrawal is prevented by the caller
+ * - this request may be ignored if there's no cache block available, in which
+ * case -ENOBUFS will be returned
+ * - if the op is in progress, 0 will be returned
+ */
+int cachefiles_write_page(struct fscache_storage *op, struct page *page)
+{
+ struct cachefiles_object *object;
+ struct cachefiles_cache *cache;
+ struct file *file;
+ struct path path;
+ loff_t pos, eof;
+ size_t len;
+ void *data;
+ int ret;
+
+ ASSERT(op != NULL);
+ ASSERT(page != NULL);
+
+ object = container_of(op->op.object,
+ struct cachefiles_object, fscache);
+
+ _enter("%p,%p{%lx},,,", object, page, page->index);
+
+ if (!object->backer) {
+ _leave(" = -ENOBUFS");
+ return -ENOBUFS;
+ }
+
+ ASSERT(d_is_reg(object->backer));
+
+ cache = container_of(object->fscache.cache,
+ struct cachefiles_cache, cache);
+
+ /* write the page to the backing filesystem and let it store it in its
+ * own time */
+ path.mnt = cache->mnt;
+ path.dentry = object->backer;
+ file = dentry_open(&path, O_RDWR | O_LARGEFILE, cache->cache_cred);
+ if (IS_ERR(file)) {
+ ret = PTR_ERR(file);
+ } else {
+ pos = (loff_t) page->index << PAGE_SHIFT;
+
+ /* we mustn't write more data than we have, so we have
+ * to beware of a partial page at EOF */
+ eof = object->fscache.store_limit_l;
+ len = PAGE_SIZE;
+ if (eof & ~PAGE_MASK) {
+ ASSERTCMP(pos, <, eof);
+ if (eof - pos < PAGE_SIZE) {
+ _debug("cut short %llx to %llx",
+ pos, eof);
+ len = eof - pos;
+ ASSERTCMP(pos + len, ==, eof);
+ }
+ }
+
+ data = kmap(page);
+ ret = __kernel_write(file, data, len, &pos);
+ kunmap(page);
+ if (ret != len)
+ ret = -EIO;
+ fput(file);
+ }
+
+ if (ret < 0) {
+ if (ret == -EIO)
+ cachefiles_io_error_obj(
+ object, "Write page to backing file failed");
+ ret = -ENOBUFS;
+ }
+
+ _leave(" = %d", ret);
+ return ret;
+}
+
+/*
+ * detach a backing block from a page
+ * - cache withdrawal is prevented by the caller
+ */
+void cachefiles_uncache_page(struct fscache_object *_object, struct page *page)
+{
+ struct cachefiles_object *object;
+ struct cachefiles_cache *cache;
+
+ object = container_of(_object, struct cachefiles_object, fscache);
+ cache = container_of(object->fscache.cache,
+ struct cachefiles_cache, cache);
+
+ _enter("%p,{%lu}", object, page->index);
+
+ spin_unlock(&object->fscache.cookie->lock);
+}
Code Review / kvmfornfv.git / blobdiff