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| author | Hugh Dickins <hughd@google.com> | 2016-07-10 16:46:32 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2016-07-27 09:55:51 -0700 |
| commit | d5ec9cb62fa916687ef726f16c604f94350ff71d (patch) | |
| tree | f29f387b3ae9cf5005caaa51c8ed76e1207c7df2 | |
| parent | e187fdea9f1ebb6e1de1fcaaf38a04a03af24337 (diff) | |
| download | lwn-d5ec9cb62fa916687ef726f16c604f94350ff71d.tar.gz lwn-d5ec9cb62fa916687ef726f16c604f94350ff71d.zip | |
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.c | 8 |
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; } |