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authorHugh Dickins <hughd@google.com>2016-07-10 16:46:32 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-07-27 09:55:51 -0700
commitd5ec9cb62fa916687ef726f16c604f94350ff71d (patch)
treef29f387b3ae9cf5005caaa51c8ed76e1207c7df2
parente187fdea9f1ebb6e1de1fcaaf38a04a03af24337 (diff)
tmpfs: fix regression hang in fallocate undo
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@google.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--mm/shmem.c8
1 files changed, 5 insertions, 3 deletions
diff --git a/mm/shmem.c b/mm/shmem.c
index 7a8a6e5a7da8..8791289974c3 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1893,9 +1893,11 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset,
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;
}