From: Hugh Dickins <hughd@google.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Anthony Romano <anthony.romano@coreos.com>,
Brandon Philips <brandon@ifup.co>,
Andrew Morton <akpm@linux-foundation.org>,
Vlastimil Babka <vbabka@suse.cz>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: [PATCH] tmpfs: fix regression hang in fallocate undo
Date: Sun, 10 Jul 2016 16:46:32 -0700 (PDT) [thread overview]
Message-ID: <alpine.LSU.2.11.1607101637420.6514@eggly.anvils> (raw)
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")
Cc: stable@vger.kernel.org
Signed-off-by: Hugh Dickins <hughd@google.com>
---
mm/shmem.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
--- 4.7-rc6/mm/shmem.c 2016-06-26 22:02:27.543373427 -0700
+++ linux/mm/shmem.c 2016-07-10 15:19:24.000000000 -0700
@@ -2225,9 +2225,11 @@ static long shmem_fallocate(struct file
error = shmem_getpage(inode, index, &page, SGP_FALLOC);
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;
}
--
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reply other threads:[~2016-07-10 23:46 UTC|newest]
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