| Message ID | 20171101122439.9923-1-ddiss@suse.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Nov 1, 2017 at 1:24 PM, David Disseldorp <ddiss@suse.de> wrote: > RBD devices are currently incorrectly initialised with the block queue > discard_alignment set to the underlying RADOS object size. > > As per Documentation/ABI/testing/sysfs-block: > The discard_alignment parameter indicates how many bytes the beginning > of the partition is offset from the internal allocation unit's natural > alignment. > > Correcting the discard_alignment parameter from the RADOS object size to > zero has no effect on how discard requests are propagated through the > block layer - @alignment in __blkdev_issue_discard() remains zero. > However, it does fix the UNMAP granularity alignment value advertised > to SCSI initiators via the Block Limits VPD. > > Signed-off-by: David Disseldorp <ddiss@suse.de> > --- > drivers/block/rbd.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c > index b640ad8a6d20..cd4c65843f77 100644 > --- a/drivers/block/rbd.c > +++ b/drivers/block/rbd.c > @@ -4423,7 +4423,7 @@ static int rbd_init_disk(struct rbd_device *rbd_dev) > /* enable the discard support */ > queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q); > q->limits.discard_granularity = segment_size; > - q->limits.discard_alignment = segment_size; > + q->limits.discard_alignment = 0; > blk_queue_max_discard_sectors(q, segment_size / SECTOR_SIZE); > blk_queue_max_write_zeroes_sectors(q, segment_size / SECTOR_SIZE); Hi David, Yeah, discard_alignment == discard_granularity seems bogus. The name is misleading too, but that probably comes from SBC, which talks about OPTIMAL UNMAP GRANULARITY and UNMAP GRANULARITY ALIGNMENT. 0 is the default -- let's just drop discard_alignment assignment? Also, you quoted <disk>/<partition>/discard_alignment description, but this is about <disk>/discard_alignment. This had me confused for a moment. Thanks, Ilya -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Thanks for the feedback, Ilya. On Wed, 1 Nov 2017 18:14:04 +0100, Ilya Dryomov wrote: > Yeah, discard_alignment == discard_granularity seems bogus. The name > is misleading too, but that probably comes from SBC, which talks about > OPTIMAL UNMAP GRANULARITY and UNMAP GRANULARITY ALIGNMENT. > > 0 is the default -- let's just drop discard_alignment assignment? Works for me, if you'd prefer. I'll send through a v2 with this. > Also, you quoted <disk>/<partition>/discard_alignment description, but > this is about <disk>/discard_alignment. This had me confused for > a moment. Oops, my bad. Will use the <disk> only description in the next round. Cheers, David -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c index b640ad8a6d20..cd4c65843f77 100644 --- a/drivers/block/rbd.c +++ b/drivers/block/rbd.c @@ -4423,7 +4423,7 @@ static int rbd_init_disk(struct rbd_device *rbd_dev) /* enable the discard support */ queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q); q->limits.discard_granularity = segment_size; - q->limits.discard_alignment = segment_size; + q->limits.discard_alignment = 0; blk_queue_max_discard_sectors(q, segment_size / SECTOR_SIZE); blk_queue_max_write_zeroes_sectors(q, segment_size / SECTOR_SIZE);
RBD devices are currently incorrectly initialised with the block queue discard_alignment set to the underlying RADOS object size. As per Documentation/ABI/testing/sysfs-block: The discard_alignment parameter indicates how many bytes the beginning of the partition is offset from the internal allocation unit's natural alignment. Correcting the discard_alignment parameter from the RADOS object size to zero has no effect on how discard requests are propagated through the block layer - @alignment in __blkdev_issue_discard() remains zero. However, it does fix the UNMAP granularity alignment value advertised to SCSI initiators via the Block Limits VPD. Signed-off-by: David Disseldorp <ddiss@suse.de> --- drivers/block/rbd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)