Changes since last update:
- Fix a bunch of static checker complaints about uninitialized variables
  and insufficient range checks.
- Avoid a crash when incore extent map data are corrupt.
- Disallow FITRIM when we haven't recovered the log and know the
  metadata are stale.
- Fix a data corruption when doing unaligned overlapping dio writes.
-----BEGIN PGP SIGNATURE-----
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=iNqS
-----END PGP SIGNATURE-----
xfs: serialize unaligned dio writes against all other dio writes

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: Brian Foster <bfoster@redhat.com>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
1 file changed