Skip to content

K
Kernel

openeuler / Kernel
接近 2 年 前同步成功

通知 8
Star 0
Fork 0
K
Kernel
切换分支/标签
  1. 07 7月, 2020 3 次提交
  3. 10 6月, 2020 1 次提交
  5. 20 5月, 2020 1 次提交
  7. 06 4月, 2020 2 次提交
  9. 16 1月, 2020 1 次提交
  11. 23 11月, 2019 1 次提交
  13. 01 11月, 2019 1 次提交
    • D
      xfs: properly serialise fallocate against AIO+DIO · 249bd908
      由 Dave Chinner 提交于 
      AIO+DIO can extend the file size on IO completion, and it holds
no inode locks while the IO is in flight. Therefore, a race
condition exists in file size updates if we do something like this:

aio-thread			fallocate-thread

lock inode
submit IO beyond inode->i_size
unlock inode
.....
				lock inode
				break layouts
				if (off + len > inode->i_size)
					new_size = off + len
				.....
				inode_dio_wait()
				<blocks>
.....
completes
inode->i_size updated
inode_dio_done()
....
				<wakes>
				<does stuff no long beyond EOF>
				if (new_size)
					xfs_vn_setattr(inode, new_size)


Yup, that attempt to extend the file size in the fallocate code
turns into a truncate - it removes the whatever the aio write
allocated and put to disk, and reduced the inode size back down to
where the fallocate operation ends.

Fundamentally, xfs_file_fallocate()  not compatible with racing
AIO+DIO completions, so we need to move the inode_dio_wait() call
up to where the lock the inode and break the layouts.

Secondly, storing the inode size and then using it unchecked without
holding the ILOCK is not safe; we can only do such a thing if we've
locked out and drained all IO and other modification operations,
which we don't do initially in xfs_file_fallocate.

It should be noted that some of the fallocate operations are
compound operations - they are made up of multiple manipulations
that may zero data, and so we may need to flush and invalidate the
file multiple times during an operation. However, we only need to
lock out IO and other space manipulation operations once, as that
lockout is maintained until the entire fallocate operation has been
completed.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-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>
      249bd908
  15. 29 10月, 2019 1 次提交
  17. 28 10月, 2019 2 次提交
  19. 22 10月, 2019 2 次提交
  21. 15 10月, 2019 2 次提交
  23. 20 9月, 2019 2 次提交
  25. 31 8月, 2019 1 次提交
  27. 06 7月, 2019 1 次提交
  29. 01 7月, 2019 1 次提交
  31. 29 6月, 2019 1 次提交
  33. 10 6月, 2019 1 次提交
  35. 23 4月, 2019 1 次提交
  37. 26 3月, 2019 1 次提交
    • B
      xfs: serialize unaligned dio writes against all other dio writes · 2032a8a2
      由 Brian Foster 提交于 
      XFS applies more strict serialization constraints to unaligned
direct writes to accommodate things like direct I/O layer zeroing,
unwritten extent conversion, etc. Unaligned submissions acquire the
exclusive iolock and wait for in-flight dio to complete to ensure
multiple submissions do not race on the same block and cause data
corruption.

This generally works in the case of an aligned dio followed by an
unaligned dio, but the serialization is lost if I/Os occur in the
opposite order. If an unaligned write is submitted first and
immediately followed by an overlapping, aligned write, the latter
submits without the typical unaligned serialization barriers because
there is no indication of an unaligned dio still in-flight. This can
lead to unpredictable results.

To provide proper unaligned dio serialization, require that such
direct writes are always the only dio allowed in-flight at one time
for a particular inode. We already acquire the exclusive iolock and
drain pending dio before submitting the unaligned dio. Wait once
more after the dio submission to hold the iolock across the I/O and
prevent further submissions until the unaligned I/O completes. This
is heavy handed, but consistent with the current pre-submission
serialization for unaligned direct writes.
Signed-off-by: NBrian Foster <bfoster@redhat.com>
Reviewed-by: NAllison Henderson <allison.henderson@oracle.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>
      2032a8a2
  39. 24 2月, 2019 1 次提交
  41. 21 2月, 2019 2 次提交
    • C
      xfs: introduce an always_cow mode · 66ae56a5
      由 Christoph Hellwig 提交于 
      Add a mode where XFS never overwrites existing blocks in place.  This
is to aid debugging our COW code, and also put infatructure in place
for things like possible future support for zoned block devices, which
can't support overwrites.

This mode is enabled globally by doing a:

    echo 1 > /sys/fs/xfs/debug/always_cow

Note that the parameter is global to allow running all tests in xfstests
easily in this mode, which would not easily be possible with a per-fs
sysfs file.

In always_cow mode persistent preallocations are disabled, and fallocate
will fail when called with a 0 mode (with our without
FALLOC_FL_KEEP_SIZE), and not create unwritten extent for zeroed space
when called with FALLOC_FL_ZERO_RANGE or FALLOC_FL_UNSHARE_RANGE.

There are a few interesting xfstests failures when run in always_cow
mode:

 - generic/392 fails because the bytes used in the file used to test
   hole punch recovery are less after the log replay.  This is
   because the blocks written and then punched out are only freed
   with a delay due to the logging mechanism.
 - xfs/170 will fail as the already fragile file streams mechanism
   doesn't seem to interact well with the COW allocator
 - xfs/180 xfs/182 xfs/192 xfs/198 xfs/204 and xfs/208 will claim
   the file system is badly fragmented, but there is not much we
   can do to avoid that when always writing out of place
 - xfs/205 fails because overwriting a file in always_cow mode
   will require new space allocation and the assumption in the
   test thus don't work anymore.
 - xfs/326 fails to modify the file at all in always_cow mode after
   injecting the refcount error, leading to an unexpected md5sum
   after the remount, but that again is expected
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>
      66ae56a5
    • C
      xfs: fix SEEK_DATA for speculative COW fork preallocation · 60271ab7
      由 Christoph Hellwig 提交于 
      We speculatively allocate extents in the COW fork to reduce
fragmentation.  But when we write data into such COW fork blocks that
do now shadow an allocation in the data fork SEEK_DATA will not
correctly report it, as it only looks at the data fork extents.
The only reason why that hasn't been an issue so far is because
we even use these speculative COW fork preallocations over holes in
the data fork at all for buffered writes, and blocks in the COW
fork that are written by direct writes are moved into the data
fork immediately at I/O completion time.

Add a new set of iomap_ops for SEEK_HOLE/SEEK_DATA which looks into
both the COW and data fork, and reports all COW extents as unwritten
to the iomap layer.  While this isn't strictly true for COW fork
extents that were already converted to real extents, the practical
semantics that you can't read data from them until they are moved
into the data fork are very similar, and this will force the iomap
layer into probing the extents for actually present data.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>
      60271ab7
  43. 20 11月, 2018 1 次提交
  45. 30 10月, 2018 5 次提交
  47. 18 8月, 2018 1 次提交
  49. 12 8月, 2018 1 次提交
  51. 12 7月, 2018 1 次提交
  53. 07 7月, 2018 2 次提交