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    Subject[PATCH 4.2 067/120] xfs: return errors from partial I/O failures to files
    Date
    4.2-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: David Jeffery <djeffery@redhat.com>

    commit c9eb256eda4420c06bb10f5e8fbdbe1a34bc98e0 upstream.

    There is an issue with xfs's error reporting in some cases of I/O partially
    failing and partially succeeding. Calls like fsync() can report success even
    though not all I/O was successful in partial-failure cases such as one disk of
    a RAID0 array being offline.

    The issue can occur when there are more than one bio per xfs_ioend struct.
    Each call to xfs_end_bio() for a bio completing will write a value to
    ioend->io_error. If a successful bio completes after any failed bio, no
    error is reported do to it writing 0 over the error code set by any failed bio.
    The I/O error information is now lost and when the ioend is completed
    only success is reported back up the filesystem stack.

    xfs_end_bio() should only set ioend->io_error in the case of BIO_UPTODATE
    being clear. ioend->io_error is initialized to 0 at allocation so only needs
    to be updated by a failed bio. Also check that ioend->io_error is 0 so that
    the first error reported will be the error code returned.

    Signed-off-by: David Jeffery <djeffery@redhat.com>
    Reviewed-by: Dave Chinner <dchinner@redhat.com>
    Signed-off-by: Dave Chinner <david@fromorbit.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/xfs/xfs_aops.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    --- a/fs/xfs/xfs_aops.c
    +++ b/fs/xfs/xfs_aops.c
    @@ -356,7 +356,8 @@ xfs_end_bio(
    {
    xfs_ioend_t *ioend = bio->bi_private;

    - ioend->io_error = test_bit(BIO_UPTODATE, &bio->bi_flags) ? 0 : error;
    + if (!ioend->io_error && !test_bit(BIO_UPTODATE, &bio->bi_flags))
    + ioend->io_error = error;

    /* Toss bio and pass work off to an xfsdatad thread */
    bio->bi_private = NULL;



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