https://github.com/torvalds/linux
Revision 0929d8580071c6a1cec1a7916a8f674c243ceee1 authored by Dave Chinner on 19 November 2018, 21:31:10 UTC, committed by Darrick J. Wong on 21 November 2018, 18:10:53 UTC
When we write into an unwritten extent via direct IO, we dirty metadata on IO completion to convert the unwritten extent to written. However, when we do the FUA optimisation checks, the inode may be clean and so we issue a FUA write into the unwritten extent. This means we then bypass the generic_write_sync() call after unwritten extent conversion has ben done and we don't force the modified metadata to stable storage. This violates O_DSYNC semantics. The window of exposure is a single IO, as the next DIO write will see the inode has dirty metadata and hence will not use the FUA optimisation. Calling generic_write_sync() after completion of the second IO will also sync the first write and it's metadata. Fix this by avoiding the FUA optimisation when writing to unwritten extents. Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
1 parent 9230a0b
Tip revision: 0929d8580071c6a1cec1a7916a8f674c243ceee1 authored by Dave Chinner on 19 November 2018, 21:31:10 UTC
iomap: FUA is wrong for DIO O_DSYNC writes into unwritten extents
iomap: FUA is wrong for DIO O_DSYNC writes into unwritten extents
Tip revision: 0929d85
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