[PATCH 3.16 116/366] block_invalidatepage(): only release page if the full page was invalidated

[Ben Hutchings]

3.16.60-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Jeff Moyer <jmoyer@xxxxxxxxxx>

commit 3172485f4f8032649c144e4aafa550e1e6179332 upstream.

Prior to commit d47992f86b30 ("mm: change invalidatepage prototype to
accept length"), an offset of 0 meant that the full page was being
invalidated.  After that commit, we need to instead check the length.

Jan said:
:
: The only possible issue is that try_to_release_page() was called more
: often than necessary.  Otherwise the issue is harmless but still it's good
: to have this fixed.

Link: http://lkml.kernel.org/r/x49fu5rtnzs.fsf@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: d47992f86b307 ("mm: change invalidatepage prototype to accept length")
Signed-off-by: Jeff Moyer <jmoyer@xxxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Cc: Lukas Czerner <lczerner@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 fs/buffer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1575,7 +1575,7 @@ void block_invalidatepage(struct page *p
 	 * The get_block cached value has been unconditionally invalidated,
 	 * so real IO is not possible anymore.
 	 */
-	if (offset == 0)
+	if (length == PAGE_SIZE)
 		try_to_release_page(page, 0);
 out:
 	return;