This is a note to let you know that I've just added the patch titled
tmpfs: fix regression hang in fallocate undo
to the 4.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tmpfs-fix-regression-hang-in-fallocate-undo.patch
and it can be found in the queue-4.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 7f556567036cb7f89aabe2f0954b08566b4efb53 Mon Sep 17 00:00:00 2001
From: Hugh Dickins <hughd@xxxxxxxxxx>
Date: Sun, 10 Jul 2016 16:46:32 -0700
Subject: tmpfs: fix regression hang in fallocate undo
From: Hugh Dickins <hughd@xxxxxxxxxx>
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 <hughd@xxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/shmem.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2236,9 +2236,11 @@ static long shmem_fallocate(struct file
NULL);
if (error) {
/* Remove the !PageUptodate pages we added */
- shmem_undo_range(inode,
- (loff_t)start << PAGE_SHIFT,
- ((loff_t)index << PAGE_SHIFT) - 1, true);
+ if (index > start) {
+ shmem_undo_range(inode,
+ (loff_t)start << PAGE_SHIFT,
+ ((loff_t)index << PAGE_SHIFT) - 1, true);
+ }
goto undone;
}
Patches currently in stable-queue which might be from hughd@xxxxxxxxxx are
queue-4.6/tmpfs-fix-regression-hang-in-fallocate-undo.patch
queue-4.6/tmpfs-don-t-undo-fallocate-past-its-last-page.patch
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