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    SubjectRe: [PATCH v2 13/26] raid5: use bio_reset()
    On Mon, 10 Sep 2012 17:22:24 -0700 Kent Overstreet <koverstreet@google.com>
    wrote:

    > Had to shuffle the code around a bit (where bi_rw and bi_end_io were
    > set), but shouldn't really be anything tricky here
    >
    > Signed-off-by: Kent Overstreet <koverstreet@google.com>
    > CC: Jens Axboe <axboe@kernel.dk>
    > CC: NeilBrown <neilb@suse.de>
    > ---
    > drivers/md/raid5.c | 28 ++++++++++++++--------------
    > 1 file changed, 14 insertions(+), 14 deletions(-)
    >
    > diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
    > index 7c19dbe..ebe43f7 100644
    > --- a/drivers/md/raid5.c
    > +++ b/drivers/md/raid5.c
    > @@ -561,14 +561,6 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
    > bi = &sh->dev[i].req;
    > rbi = &sh->dev[i].rreq; /* For writing to replacement */
    >
    > - bi->bi_rw = rw;
    > - rbi->bi_rw = rw;
    > - if (rw & WRITE) {
    > - bi->bi_end_io = raid5_end_write_request;
    > - rbi->bi_end_io = raid5_end_write_request;
    > - } else
    > - bi->bi_end_io = raid5_end_read_request;
    > -
    > rcu_read_lock();
    > rrdev = rcu_dereference(conf->disks[i].replacement);
    > smp_mb(); /* Ensure that if rrdev is NULL, rdev won't be */
    > @@ -643,7 +635,14 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
    >
    > set_bit(STRIPE_IO_STARTED, &sh->state);
    >
    > + bio_reset(bi);
    > bi->bi_bdev = rdev->bdev;
    > + bi->bi_rw = rw;
    > + bi->bi_end_io = (rw & WRITE)
    > + ? raid5_end_write_request
    > + : raid5_end_read_request;
    > + bi->bi_private = sh;
    > +
    > pr_debug("%s: for %llu schedule op %ld on disc %d\n",
    > __func__, (unsigned long long)sh->sector,
    > bi->bi_rw, i);
    > @@ -657,12 +656,9 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
    > if (test_bit(R5_ReadNoMerge, &sh->dev[i].flags))
    > bi->bi_rw |= REQ_FLUSH;
    >
    > - bi->bi_flags = 1 << BIO_UPTODATE;
    > - bi->bi_idx = 0;
    > bi->bi_io_vec[0].bv_len = STRIPE_SIZE;
    > bi->bi_io_vec[0].bv_offset = 0;
    > bi->bi_size = STRIPE_SIZE;
    > - bi->bi_next = NULL;
    > if (rrdev)
    > set_bit(R5_DOUBLE_LOCKED, &sh->dev[i].flags);
    > generic_make_request(bi);
    > @@ -674,7 +670,14 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
    >
    > set_bit(STRIPE_IO_STARTED, &sh->state);
    >
    > + bio_reset(rbi);
    > rbi->bi_bdev = rrdev->bdev;
    > + rbi->bi_rw = rw;
    > + rbi->bi_end_io = (rw & WRITE)
    > + ? raid5_end_write_request
    > + : raid5_end_read_request;

    'rbi->bi_end_io' can only ever be raid5_end_write_request. We only get here
    on a write.
    I'd be OK with
    BUG_ON(!(rw & WRITE));
    but I don't want the condition in the assignment.

    The rest looks quite sane.

    Thanks
    NeilBrown

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