Skip to content

K
Kernel

openeuler / Kernel
1 年多 前同步成功

通知 8
Star 0
Fork 0
K
Kernel
切换分支/标签
  1. 27 10月, 2017 14 次提交
  3. 17 10月, 2017 1 次提交
    • B
      xfs: trim writepage mapping to within eof · 40214d12
      由 Brian Foster 提交于 
      The writeback rework in commit fbcc0256 ("xfs: Introduce
writeback context for writepages") introduced a subtle change in
behavior with regard to the block mapping used across the
->writepages() sequence. The previous xfs_cluster_write() code would
only flush pages up to EOF at the time of the writepage, thus
ensuring that any pages due to file-extending writes would be
handled on a separate cycle and with a new, updated block mapping.

The updated code establishes a block mapping in xfs_writepage_map()
that could extend beyond EOF if the file has post-eof preallocation.
Because we now use the generic writeback infrastructure and pass the
cached mapping to each writepage call, there is no implicit EOF
limit in place. If eofblocks trimming occurs during ->writepages(),
any post-eof portion of the cached mapping becomes invalid. The
eofblocks code has no means to serialize against writeback because
there are no pages associated with post-eof blocks. Therefore if an
eofblocks trim occurs and is followed by a file-extending buffered
write, not only has the mapping become invalid, but we could end up
writing a page to disk based on the invalid mapping.

Consider the following sequence of events:

- A buffered write creates a delalloc extent and post-eof
  speculative preallocation.
- Writeback starts and on the first writepage cycle, the delalloc
  extent is converted to real blocks (including the post-eof blocks)
  and the mapping is cached.
- The file is closed and xfs_release() trims post-eof blocks. The
  cached writeback mapping is now invalid.
- Another buffered write appends the file with a delalloc extent.
- The concurrent writeback cycle picks up the just written page
  because the writeback range end is LLONG_MAX. xfs_writepage_map()
  attributes it to the (now invalid) cached mapping and writes the
  data to an incorrect location on disk (and where the file offset is
  still backed by a delalloc extent).

This problem is reproduced by xfstests test generic/464, which
triggers racing writes, appends, open/closes and writeback requests.

To address this problem, trim the mapping used during writeback to
within EOF when the mapping is validated. This ensures the mapping
is revalidated for any pages encountered beyond EOF as of the time
the current mapping was cached or last validated.
Reported-by: NEryu Guan <eguan@redhat.com>
Diagnosed-by: NEryu Guan <eguan@redhat.com>
Signed-off-by: NBrian Foster <bfoster@redhat.com>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>
      40214d12
  5. 12 10月, 2017 1 次提交
  7. 27 9月, 2017 1 次提交
  9. 02 9月, 2017 10 次提交
  11. 26 7月, 2017 1 次提交
  13. 21 7月, 2017 1 次提交
  15. 28 6月, 2017 1 次提交
  17. 19 6月, 2017 1 次提交
    • D
      xfs: try to avoid blowing out the transaction reservation when bunmaping a shared extent · e1a4e37c
      由 Darrick J. Wong 提交于 
      In a pathological scenario where we are trying to bunmapi a single
extent in which every other block is shared, it's possible that trying
to unmap the entire large extent in a single transaction can generate so
many EFIs that we overflow the transaction reservation.

Therefore, use a heuristic to guess at the number of blocks we can
safely unmap from a reflink file's data fork in an single transaction.
This should prevent problems such as the log head slamming into the tail
and ASSERTs that trigger because we've exceeded the transaction
reservation.

Note that since bunmapi can fail to unmap the entire range, we must also
teach the deferred unmap code to roll into a new transaction whenever we
get low on reservation.
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>
[hch: random edits, all bugs are my fault]
Signed-off-by: NChristoph Hellwig <hch@lst.de>
      e1a4e37c
  19. 17 5月, 2017 2 次提交
    • D
      xfs: fix warnings about unused stack variables · 6e747506
      由 Darrick J. Wong 提交于 
      Reduce stack usage and get rid of compiler warnings by eliminating
unused variables.
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NCarlos Maiolino <cmaiolino@redhat.com>
      6e747506
    • B
      xfs: fix indlen accounting error on partial delalloc conversion · 0daaecac
      由 Brian Foster 提交于 
      The delalloc -> real block conversion path uses an incorrect
calculation in the case where the middle part of a delalloc extent
is being converted. This is documented as a rare situation because
XFS generally attempts to maximize contiguity by converting as much
of a delalloc extent as possible.

If this situation does occur, the indlen reservation for the two new
delalloc extents left behind by the conversion of the middle range
is calculated and compared with the original reservation. If more
blocks are required, the delta is allocated from the global block
pool. This delta value can be characterized as the difference
between the new total requirement (temp + temp2) and the currently
available reservation minus those blocks that have already been
allocated (startblockval(PREV.br_startblock) - allocated).

The problem is that the current code does not account for previously
allocated blocks correctly. It subtracts the current allocation
count from the (new - old) delta rather than the old indlen
reservation. This means that more indlen blocks than have been
allocated end up stashed in the remaining extents and free space
accounting is broken as a result.

Fix up the calculation to subtract the allocated block count from
the original extent indlen and thus correctly allocate the
reservation delta based on the difference between the new total
requirement and the unused blocks from the original reservation.
Also remove a bogus assert that contradicts the fact that the new
indlen reservation can be larger than the original indlen
reservation.
Signed-off-by: NBrian Foster <bfoster@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>
      0daaecac
  21. 26 4月, 2017 7 次提交