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    Subject[PATCH 005 of 5] md: Fix 'rdev->nr_pending' count when retrying barrier requests.

    When retrying a failed BIO_RW_BARRIER request, we need to
    keep the reference in ->nr_pending over the whole retry.
    Currently, we only hold the reference if the failed request is
    the *last* one to finish - which is silly, because it would normally
    be the first to finish.

    So move the rdev_dec_pending call up into the didn't-fail branch.
    As the rdev isn't used in the later code, calling rdev_dec_pending
    earlier doesn't hurt.

    Signed-off-by: Neil Brown <neilb@suse.de>

    ### Diffstat output
    ./drivers/md/raid1.c | 9 ++++-----
    1 file changed, 4 insertions(+), 5 deletions(-)

    diff ./drivers/md/raid1.c~current~ ./drivers/md/raid1.c
    --- ./drivers/md/raid1.c~current~ 2006-04-28 12:17:40.000000000 +1000
    +++ ./drivers/md/raid1.c 2006-04-28 12:17:58.000000000 +1000
    @@ -319,6 +319,7 @@ static int raid1_end_write_request(struc
    set_bit(BarriersNotsupp, &conf->mirrors[mirror].rdev->flags);
    set_bit(R1BIO_BarrierRetry, &r1_bio->state);
    r1_bio->mddev->barriers_work = 0;
    + /* Don't rdev_dec_pending in this branch - keep it for the retry */
    } else {
    /*
    * this branch is our 'one mirror IO has finished' event handler:
    @@ -365,6 +366,7 @@ static int raid1_end_write_request(struc
    }
    }
    }
    + rdev_dec_pending(conf->mirrors[mirror].rdev, conf->mddev);
    }
    /*
    *
    @@ -374,11 +376,9 @@ static int raid1_end_write_request(struc
    if (atomic_dec_and_test(&r1_bio->remaining)) {
    if (test_bit(R1BIO_BarrierRetry, &r1_bio->state)) {
    reschedule_retry(r1_bio);
    - /* Don't dec_pending yet, we want to hold
    - * the reference over the retry
    - */
    goto out;
    }
    + /* it really is the end of this request */
    if (test_bit(R1BIO_BehindIO, &r1_bio->state)) {
    /* free extra copy of the data pages */
    int i = bio->bi_vcnt;
    @@ -393,8 +393,6 @@ static int raid1_end_write_request(struc
    md_write_end(r1_bio->mddev);
    raid_end_bio_io(r1_bio);
    }
    -
    - rdev_dec_pending(conf->mirrors[mirror].rdev, conf->mddev);
    out:
    if (to_put)
    bio_put(to_put);
    @@ -1414,6 +1412,7 @@ static void raid1d(mddev_t *mddev)
    * Better resubmit without the barrier.
    * We know which devices to resubmit for, because
    * all others have had their bios[] entry cleared.
    + * We already have a nr_pending reference on these rdevs.
    */
    int i;
    clear_bit(R1BIO_BarrierRetry, &r1_bio->state);
    -
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