Merge tag 'fscache-fixes-20140917' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs

Pull fs-cache fixes from David Howells:

 - Put a timeout in releasepage() to deal with a recursive hang between
   the memory allocator, writeback, ext4 and fscache under memory
   pressure.

 - Fix a pair of refcount bugs in the fscache error handling.

 - Remove a couple of unused pagevecs.

 - The cachefiles requirement that the base directory support rename
   should permit rename2 as an alternative - otherwise certain
   filesystems cannot now be used as backing stores (such as ext4).

* tag 'fscache-fixes-20140917' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs:
  CacheFiles: Handle rename2
  cachefiles: remove two unused pagevecs.
  FS-Cache: refcount becomes corrupt under vma pressure.
  FS-Cache: Reduce cookie ref count if submit fails.
  FS-Cache: Timeout for releasepage()

1 files changed, 21 insertions, 4 deletions

diff --git a/fs/fscache/page.c b/fs/fscache/page.c
index 85332b9d19d1..de33b3fccca6 100644
--- a/fs/fscache/page.c
+++ b/fs/fscache/page.c
@@ -44,6 +44,19 @@ void __fscache_wait_on_page_write(struct fscache_cookie *cookie, struct page *pa
 EXPORT_SYMBOL(__fscache_wait_on_page_write);
 
 /*
+ * wait for a page to finish being written to the cache. Put a timeout here
+ * since we might be called recursively via parent fs.
+ */
+static
+bool release_page_wait_timeout(struct fscache_cookie *cookie, struct page *page)
+{
+        wait_queue_head_t *wq = bit_waitqueue(&cookie->flags, 0);
+
+        return wait_event_timeout(*wq, !__fscache_check_page_write(cookie, page),
+                                  HZ);
+}
+
+/*
  * decide whether a page can be released, possibly by cancelling a store to it
  * - we're allowed to sleep if __GFP_WAIT is flagged
  */
@@ -115,7 +128,10 @@ page_busy:
         }
 
         fscache_stat(&fscache_n_store_vmscan_wait);
-        __fscache_wait_on_page_write(cookie, page);
+        if (!release_page_wait_timeout(cookie, page))
+                _debug("fscache writeout timeout page: %p{%lx}",
+                        page, page->index);
+
         gfp &= ~__GFP_WAIT;
         goto try_again;
 }
@@ -182,7 +198,7 @@ int __fscache_attr_changed(struct fscache_cookie *cookie)
 {
         struct fscache_operation *op;
         struct fscache_object *object;
-        bool wake_cookie;
+        bool wake_cookie = false;
 
         _enter("%p", cookie);
 
@@ -212,15 +228,16 @@ int __fscache_attr_changed(struct fscache_cookie *cookie)
 
         __fscache_use_cookie(cookie);
         if (fscache_submit_exclusive_op(object, op) < 0)
-                goto nobufs;
+                goto nobufs_dec;
         spin_unlock(&cookie->lock);
         fscache_stat(&fscache_n_attr_changed_ok);
         fscache_put_operation(op);
         _leave(" = 0");
         return 0;
 
-nobufs:
+nobufs_dec:
         wake_cookie = __fscache_unuse_cookie(cookie);
+nobufs:
         spin_unlock(&cookie->lock);
         kfree(op);
         if (wake_cookie)