On Wed, 2 Jan 2013 10:42:49 -0500 (EST) Joe Lawrence
<Joe.Lawrence@xxxxxxxxxxx> wrote:
> On Fri, 14 Dec 2012, Joe Lawrence wrote:
>
> > Submitting patch for review... This sets the max_write_same_sectors for
> > the mdev request queue to its chunk_sectors (before merging its member
> > disk limits). I believe this should keep the write same LBA sector count
> > inside the write intent bitmap granularity, but I'm not sure if the sector
> > range could cross bits and how could would be handled. Any insight into
> > the bitmap side of things would be appreciated.
> >
> > Thanks,
> >
> > -- Joe
> >
> > From d31c4569b3883475f293403fa4eed63f107616bb Mon Sep 17 00:00:00 2001
> > From: Joe Lawrence <joe.lawrence@xxxxxxxxxxx>
> > Date: Fri, 14 Dec 2012 11:25:27 -0500
> > Subject: [PATCH] md: raid1,10: Handle REQ_WRITE_SAME flag in write bios
> >
> > Set mddev queue's max_write_same_sectors to its chunk_sector value (before
> > disk_stack_limits merges the underlying disk limits.) With that in place,
> > be sure to handle writes coming down from the block layer that have the
> > REQ_WRITE_SAME flag set. That flag needs to be copied into any newly cloned
> > write bio.
> >
> > Signed-off-by: Joe Lawrence <joe.lawrence@xxxxxxxxxxx>
> > ---
> > drivers/md/raid1.c | 5 ++++-
> > drivers/md/raid10.c | 8 ++++++--
> > 2 files changed, 10 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
> > index a0f7309..c9ef213 100644
> > --- a/drivers/md/raid1.c
> > +++ b/drivers/md/raid1.c
> > @@ -1001,6 +1001,7 @@ static void make_request(struct mddev *mddev, struct bio * bio)
> > const unsigned long do_flush_fua = (bio->bi_rw & (REQ_FLUSH | REQ_FUA));
> > const unsigned long do_discard = (bio->bi_rw
> > & (REQ_DISCARD | REQ_SECURE));
> > + const unsigned long do_same = (bio->bi_rw & REQ_WRITE_SAME);
> > struct md_rdev *blocked_rdev;
> > struct blk_plug_cb *cb;
> > struct raid1_plug_cb *plug = NULL;
> > @@ -1302,7 +1303,8 @@ read_again:
> > conf->mirrors[i].rdev->data_offset);
> > mbio->bi_bdev = conf->mirrors[i].rdev->bdev;
> > mbio->bi_end_io = raid1_end_write_request;
> > - mbio->bi_rw = WRITE | do_flush_fua | do_sync | do_discard;
> > + mbio->bi_rw =
> > + WRITE | do_flush_fua | do_sync | do_discard | do_same;
> > mbio->bi_private = r1_bio;
> >
> > atomic_inc(&r1_bio->remaining);
> > @@ -2819,6 +2821,7 @@ static int run(struct mddev *mddev)
> > if (IS_ERR(conf))
> > return PTR_ERR(conf);
> >
> > + blk_queue_max_write_same_sectors(mddev->queue, mddev->chunk_sectors);
> > rdev_for_each(rdev, mddev) {
> > if (!mddev->gendisk)
> > continue;
> > diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
> > index c9acbd7..3d77a92 100644
> > --- a/drivers/md/raid10.c
> > +++ b/drivers/md/raid10.c
> > @@ -1106,6 +1106,7 @@ static void make_request(struct mddev *mddev, struct bio * bio)
> > const unsigned long do_fua = (bio->bi_rw & REQ_FUA);
> > const unsigned long do_discard = (bio->bi_rw
> > & (REQ_DISCARD | REQ_SECURE));
> > + const unsigned long do_same = (bio->bi_rw & REQ_WRITE_SAME);
> > unsigned long flags;
> > struct md_rdev *blocked_rdev;
> > struct blk_plug_cb *cb;
> > @@ -1461,7 +1462,8 @@ retry_write:
> > rdev));
> > mbio->bi_bdev = rdev->bdev;
> > mbio->bi_end_io = raid10_end_write_request;
> > - mbio->bi_rw = WRITE | do_sync | do_fua | do_discard;
> > + mbio->bi_rw =
> > + WRITE | do_sync | do_fua | do_discard | do_same;
> > mbio->bi_private = r10_bio;
> >
> > atomic_inc(&r10_bio->remaining);
> > @@ -1503,7 +1505,8 @@ retry_write:
> > r10_bio, rdev));
> > mbio->bi_bdev = rdev->bdev;
> > mbio->bi_end_io = raid10_end_write_request;
> > - mbio->bi_rw = WRITE | do_sync | do_fua | do_discard;
> > + mbio->bi_rw =
> > + WRITE | do_sync | do_fua | do_discard | do_same;
> > mbio->bi_private = r10_bio;
> >
> > atomic_inc(&r10_bio->remaining);
> > @@ -3578,6 +3581,7 @@ static int run(struct mddev *mddev)
> > (conf->geo.raid_disks / conf->geo.near_copies));
> > }
> >
> > + blk_queue_max_write_same_sectors(mddev->queue, mddev->chunk_sectors);
> > rdev_for_each(rdev, mddev) {
> > long long diff;
> > struct request_queue *q;
> > --
> > 1.7.11.7
> >
> >
>
> Hi Neil,
>
> Happy new year -- any comments on this bug / patch? I can rebase and
> test against 3.8, though I don't believe any related code has changed yet.
>
Thanks. I've added Martin's and and queue it up.
Assuming that a REQ_WRITE_SAME is just like a normal write except for the
iovec being shorter (is that right?) there should be no interesting issues
with bitmaps - it should just work.
NeilBrown
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