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-rw-r--r--fs/fscache/page.c79
1 files changed, 77 insertions, 2 deletions
diff --git a/fs/fscache/page.c b/fs/fscache/page.c
index 022a5da8e13..fc76798bd96 100644
--- a/fs/fscache/page.c
+++ b/fs/fscache/page.c
@@ -43,6 +43,75 @@ void __fscache_wait_on_page_write(struct fscache_cookie *cookie, struct page *pa
EXPORT_SYMBOL(__fscache_wait_on_page_write);
/*
+ * decide whether a page can be released, possibly by cancelling a store to it
+ * - we're allowed to sleep if __GFP_WAIT is flagged
+ */
+bool __fscache_maybe_release_page(struct fscache_cookie *cookie,
+ struct page *page,
+ gfp_t gfp)
+{
+ struct page *xpage;
+ void *val;
+
+ _enter("%p,%p,%x", cookie, page, gfp);
+
+ rcu_read_lock();
+ val = radix_tree_lookup(&cookie->stores, page->index);
+ if (!val) {
+ rcu_read_unlock();
+ fscache_stat(&fscache_n_store_vmscan_not_storing);
+ __fscache_uncache_page(cookie, page);
+ return true;
+ }
+
+ /* see if the page is actually undergoing storage - if so we can't get
+ * rid of it till the cache has finished with it */
+ if (radix_tree_tag_get(&cookie->stores, page->index,
+ FSCACHE_COOKIE_STORING_TAG)) {
+ rcu_read_unlock();
+ goto page_busy;
+ }
+
+ /* the page is pending storage, so we attempt to cancel the store and
+ * discard the store request so that the page can be reclaimed */
+ spin_lock(&cookie->stores_lock);
+ rcu_read_unlock();
+
+ if (radix_tree_tag_get(&cookie->stores, page->index,
+ FSCACHE_COOKIE_STORING_TAG)) {
+ /* the page started to undergo storage whilst we were looking,
+ * so now we can only wait or return */
+ spin_unlock(&cookie->stores_lock);
+ goto page_busy;
+ }
+
+ xpage = radix_tree_delete(&cookie->stores, page->index);
+ spin_unlock(&cookie->stores_lock);
+
+ if (xpage) {
+ fscache_stat(&fscache_n_store_vmscan_cancelled);
+ fscache_stat(&fscache_n_store_radix_deletes);
+ ASSERTCMP(xpage, ==, page);
+ } else {
+ fscache_stat(&fscache_n_store_vmscan_gone);
+ }
+
+ wake_up_bit(&cookie->flags, 0);
+ if (xpage)
+ page_cache_release(xpage);
+ __fscache_uncache_page(cookie, page);
+ return true;
+
+page_busy:
+ /* we might want to wait here, but that could deadlock the allocator as
+ * the slow-work threads writing to the cache may all end up sleeping
+ * on memory allocation */
+ fscache_stat(&fscache_n_store_vmscan_busy);
+ return false;
+}
+EXPORT_SYMBOL(__fscache_maybe_release_page);
+
+/*
* note that a page has finished being written to the cache
*/
static void fscache_end_page_write(struct fscache_object *object,
@@ -57,6 +126,8 @@ static void fscache_end_page_write(struct fscache_object *object,
/* delete the page from the tree if it is now no longer
* pending */
spin_lock(&cookie->stores_lock);
+ radix_tree_tag_clear(&cookie->stores, page->index,
+ FSCACHE_COOKIE_STORING_TAG);
if (!radix_tree_tag_get(&cookie->stores, page->index,
FSCACHE_COOKIE_PENDING_TAG)) {
fscache_stat(&fscache_n_store_radix_deletes);
@@ -640,8 +711,12 @@ static void fscache_write_op(struct fscache_operation *_op)
goto superseded;
}
- radix_tree_tag_clear(&cookie->stores, page->index,
- FSCACHE_COOKIE_PENDING_TAG);
+ if (page) {
+ radix_tree_tag_set(&cookie->stores, page->index,
+ FSCACHE_COOKIE_STORING_TAG);
+ radix_tree_tag_clear(&cookie->stores, page->index,
+ FSCACHE_COOKIE_PENDING_TAG);
+ }
spin_unlock(&cookie->stores_lock);
spin_unlock(&object->lock);