diff options
author | Eryu Guan <eguan@redhat.com> | 2017-11-01 21:43:50 -0700 |
---|---|---|
committer | Darrick J. Wong <darrick.wong@oracle.com> | 2017-11-03 09:45:56 -0700 |
commit | 350976ae21873b0d36584ea005076356431b8f79 (patch) | |
tree | 6ab1b1d6d5cdb01f556bec178aa1c58404aaf499 /fs/xfs/scrub | |
parent | 5d0eda0307ca20c5c58b1abd2a8ba822e0763b43 (diff) | |
download | op-kernel-dev-350976ae21873b0d36584ea005076356431b8f79.zip op-kernel-dev-350976ae21873b0d36584ea005076356431b8f79.tar.gz |
xfs: truncate pagecache before writeback in xfs_setattr_size()
On truncate down, if new size is not block size aligned, we zero the
rest of block to avoid exposing stale data to user, and
iomap_truncate_page() skips zeroing if the range is already in
unwritten state or a hole. Then we writeback from on-disk i_size to
the new size if this range hasn't been written to disk yet, and
truncate page cache beyond new EOF and set in-core i_size.
The problem is that we could write data between di_size and newsize
before removing the page cache beyond newsize, as the extents may
still be in unwritten state right after a buffer write. As such, the
page of data that newsize lies in has not been zeroed by page cache
invalidation before it is written, and xfs_do_writepage() hasn't
triggered it's "zero data beyond EOF" case because we haven't
updated in-core i_size yet. Then a subsequent mmap read could see
non-zeros past EOF.
I occasionally see this in fsx runs in fstests generic/112, a
simplified fsx operation sequence is like (assuming 4k block size
xfs):
fallocate 0x0 0x1000 0x0 keep_size
write 0x0 0x1000 0x0
truncate 0x0 0x800 0x1000
punch_hole 0x0 0x800 0x800
mapread 0x0 0x800 0x800
where fallocate allocates unwritten extent but doesn't update
i_size, buffer write populates the page cache and extent is still
unwritten, truncate skips zeroing page past new EOF and writes the
page to disk, punch_hole invalidates the page cache, at last mapread
reads the block back and sees non-zero beyond EOF.
Fix it by moving truncate_setsize() to before writeback so the page
cache invalidation zeros the partial page at the new EOF. This also
triggers "zero data beyond EOF" in xfs_do_writepage() at writeback
time, because newsize has been set and page straddles the newsize.
Also fixed the wrong 'end' param of filemap_write_and_wait_range()
call while we're at it, the 'end' is inclusive and should be
'newsize - 1'.
Suggested-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>
Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Diffstat (limited to 'fs/xfs/scrub')
0 files changed, 0 insertions, 0 deletions