3.16.37-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Hugh Dickins <hu...@google.com>
commit 7f556567036cb7f89aabe2f0954b08566b4efb53 upstream.
The well-spotted fallocate undo fix is good in most cases, but not when
fallocate failed on the very first page. index 0 then passes lend -1
to shmem_undo_range(), and that has two bad effects: (a) that it will
undo every fallocation throughout the file, unrestricted by the current
range; but more importantly (b) it can cause the undo to hang, because
lend -1 is treated as truncation, which makes it keep on retrying until
every page has gone, but those already fully instantiated will never go
away. Big thank you to xfstests generic/269 which demonstrates this.
Fixes: b9b4bb26af01 ("tmpfs: don't undo fallocate past its last page")
Signed-off-by: Hugh Dickins <hu...@google.com>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
[bwh: Backported to 3.16: use PAGE_CACHE_SHIFT instead of PAGE_SHIFT]
Signed-off-by: Ben Hutchings <b...@decadent.org.uk>
---
mm/shmem.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1865,9 +1865,11 @@ static long shmem_fallocate(struct file
NULL);
if (error) {
/* Remove the !PageUptodate pages we added */
- shmem_undo_range(inode,
- (loff_t)start << PAGE_CACHE_SHIFT,
- ((loff_t)index << PAGE_CACHE_SHIFT) - 1, true);
+ if (index > start) {
+ shmem_undo_range(inode,
+ (loff_t)start << PAGE_CACHE_SHIFT,
+ ((loff_t)index << PAGE_CACHE_SHIFT) - 1,
true);
+ }
goto undone;
}
