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    Subject[PATCH 5.4 015/120] iomap: iomap that extends beyond EOF should be marked dirty
    Date
    From: Chandan Babu R <chandan.babu@oracle.com>

    From: Dave Chinner <dchinner@redhat.com>

    commit 7684e2c4384d5d1f884b01ab8bff2369e4db0bff upstream.

    When doing a direct IO that spans the current EOF, and there are
    written blocks beyond EOF that extend beyond the current write, the
    only metadata update that needs to be done is a file size extension.

    However, we don't mark such iomaps as IOMAP_F_DIRTY to indicate that
    there is IO completion metadata updates required, and hence we may
    fail to correctly sync file size extensions made in IO completion
    when O_DSYNC writes are being used and the hardware supports FUA.

    Hence when setting IOMAP_F_DIRTY, we need to also take into account
    whether the iomap spans the current EOF. If it does, then we need to
    mark it dirty so that IO completion will call generic_write_sync()
    to flush the inode size update to stable storage correctly.

    Fixes: 3460cac1ca76 ("iomap: Use FUA for pure data O_DSYNC DIO writes")
    Signed-off-by: Dave Chinner <dchinner@redhat.com>
    Signed-off-by: Christoph Hellwig <hch@lst.de>
    Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
    [darrick: removed the ext4 part; they'll handle it separately]
    Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
    Acked-by: Darrick J. Wong <djwong@kernel.org>
    Signed-off-by: Chandan Babu R <chandan.babu@oracle.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    fs/xfs/xfs_iomap.c | 7 +++++++
    include/linux/iomap.h | 2 ++
    2 files changed, 9 insertions(+)

    --- a/fs/xfs/xfs_iomap.c
    +++ b/fs/xfs/xfs_iomap.c
    @@ -1055,6 +1055,13 @@ xfs_file_iomap_begin(
    trace_xfs_iomap_alloc(ip, offset, length, XFS_DATA_FORK, &imap);

    out_finish:
    + /*
    + * Writes that span EOF might trigger an IO size update on completion,
    + * so consider them to be dirty for the purposes of O_DSYNC even if
    + * there is no other metadata changes pending or have been made here.
    + */
    + if ((flags & IOMAP_WRITE) && offset + length > i_size_read(inode))
    + iomap->flags |= IOMAP_F_DIRTY;
    return xfs_bmbt_to_iomap(ip, iomap, &imap, shared);

    out_found:
    --- a/include/linux/iomap.h
    +++ b/include/linux/iomap.h
    @@ -32,6 +32,8 @@ struct vm_fault;
    *
    * IOMAP_F_DIRTY indicates the inode has uncommitted metadata needed to access
    * written data and requires fdatasync to commit them to persistent storage.
    + * This needs to take into account metadata changes that *may* be made at IO
    + * completion, such as file size updates from direct IO.
    */
    #define IOMAP_F_NEW 0x01 /* blocks have been newly allocated */
    #define IOMAP_F_DIRTY 0x02 /* uncommitted metadata */

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