Call the filesystem back whenever a page is removed from the page cache

NFS needs to be able to release objects that are stored in the page
cache once the page itself is no longer visible from the page cache.

This patch adds a callback to the address space operations that allows
filesystems to perform page cleanups once the page has been removed
from the page cache.

Original patch by: Linus Torvalds <torvalds@linux-foundation.org>
[trondmy: cover the cases of invalidate_inode_pages2() and
          truncate_inode_pages()]
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index d31d7ce52c0e..9ca587c69274 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -494,9 +494,16 @@ static int __remove_mapping(struct address_space *mapping, struct page *page)
                 spin_unlock_irq(&mapping->tree_lock);
                 swapcache_free(swap, page);
         } else {
+                void (*freepage)(struct page *);
+
+                freepage = mapping->a_ops->freepage;
+
                 __remove_from_page_cache(page);
                 spin_unlock_irq(&mapping->tree_lock);
                 mem_cgroup_uncharge_cache_page(page);
+
+                if (freepage != NULL)
+                        freepage(page);
         }
 
         return 1;