Re: [md PATCH 10/15] md/raid1: stop using bi_phys_segment

Shaohua Li
2017-03-16T03:36:37Z

On Thu, Mar 16, 2017 at 01:49:57PM +1100, Neil Brown wrote:
> On Wed, Mar 15 2017, Shaohua Li wrote:
>
> > On Wed, Mar 15, 2017 at 02:05:14PM +1100, Neil Brown wrote:
> >> Change to use bio->__bi_remaining to count number of r1bio attached
> >> to a bio.
> >> See precious raid10 patch for more details.
> >>
> >> Like the raid10.c patch, this fixes a bug as nr_queued and nr_pending
> >> used to measure different things, but were being compared.
> >>
> >> This patch fixes another bug in that nr_pending previously did not
> >> could write-behind requests, so behind writes could continue while
> >> resync was happening. How that nr_pending counts all r1_bio,
> >> the resync cannot commence until the behind writes have completed.
> >>
> >> Signed-off-by: NeilBrown <neilb@suse.com>
> >> ---
> >> drivers/md/raid1.c | 87 +++++++++++++---------------------------------------
> >> 1 file changed, 22 insertions(+), 65 deletions(-)
> >>
> >> diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
> >> index 7e509a894f15..e566407b196f 100644
> >> --- a/drivers/md/raid1.c
> >> +++ b/drivers/md/raid1.c
> >> @@ -246,35 +246,18 @@ static void reschedule_retry(struct r1bio *r1_bio)
> >> static void call_bio_endio(struct r1bio *r1_bio)
> >> {
> >> struct bio *bio = r1_bio->master_bio;
> >> - int done;
> >> struct r1conf *conf = r1_bio->mddev->private;
> >> sector_t bi_sector = bio->bi_iter.bi_sector;
> >>
> >> - if (bio->bi_phys_segments) {
> >> - unsigned long flags;
> >> - spin_lock_irqsave(&conf->device_lock, flags);
> >> - bio->bi_phys_segments--;
> >> - done = (bio->bi_phys_segments == 0);
> >> - spin_unlock_irqrestore(&conf->device_lock, flags);
> >> - /*
> >> - * make_request() might be waiting for
> >> - * bi_phys_segments to decrease
> >> - */
> >> - wake_up(&conf->wait_barrier);
> >> - } else
> >> - done = 1;
> >> -
> >> if (!test_bit(R1BIO_Uptodate, &r1_bio->state))
> >> bio->bi_error = -EIO;
> >>
> >> - if (done) {
> >> - bio_endio(bio);
> >> - /*
> >> - * Wake up any possible resync thread that waits for the device
> >> - * to go idle.
> >> - */
> >> - allow_barrier(conf, bi_sector);
> >> - }
> >> + bio_endio(bio);
> >> + /*
> >> + * Wake up any possible resync thread that waits for the device
> >> + * to go idle.
> >> + */
> >> + allow_barrier(conf, bi_sector);
> >
> > I think this one should be r1_bio->sector instead of master_bio->sector,
> > because multiple r1_bio could be attached to a master_bio. Maybe not change
> > anything, because both sector should be in the same barrier unit, but we'd
> > better to be consistent.
>
> Yes, I agree. Both that it won't make a practical difference and that
> it should be changed.
> I just noticed another little problem with this patch.
> The chunk in handle_read_error() should have added inc_pending()
> near where it added bio_inc_remaining().
>
> Shall I just resend the individual patch (and the raid5 one?).

Please send a fix, I'll integrate it to original patches.

Thanks,
Shaohua