hollalinux
/
linux-sg2042
mirror of https://github.com/sophgo/linux-riscv.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

xfs: skip delalloc COW blocks in xfs_reflink_end_cow 

The iomap direct I/O code issues a single ->end_io call for the whole
I/O request, and if some of the extents cowered needed a COW operation
it will call xfs_reflink_end_cow over the whole range.

When we do AIO writes we drop the iolock after doing the initial setup,
but before the I/O completion.  Between dropping the lock and completing
the I/O we can have a racing buffered write create new delalloc COW fork
extents in the region covered by the outstanding direct I/O write, and
thus see delalloc COW fork extents in xfs_reflink_end_cow.  As
concurrent writes are fundamentally racy and no guarantees are given we
can simply skip those.

This can be easily reproduced with xfstests generic/208 in always_cow
mode.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
This commit is contained in:
Christoph Hellwig 2018-09-29 13:49:58 +10:00 committed by Dave Chinner
parent f369a13cea
commit f5f3f959b7
1 changed files with 4 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
fs/xfs/xfs_reflink.c
View File

@ -693,14 +693,12 @@ xfs_reflink_end_cow(
if (!del.br_blockcount)
goto prev_extent;
ASSERT(!isnullstartblock(got.br_startblock));
/*
* Don't remap unwritten extents; these are
* speculatively preallocated CoW extents that have been
* allocated but have not yet been involved in a write.
* Only remap real extent that contain data. With AIO
* speculatively preallocations can leak into the range we
* are called upon, and we need to skip them.
*/
if (got.br_state == XFS_EXT_UNWRITTEN)
if (!xfs_bmap_is_real_extent(&got))
goto prev_extent;
/* Unmap the old blocks in the data fork. */