diff options
| author | Mike Snitzer <snitzer@redhat.com> | 2012-10-12 21:02:07 +0100 |
|---|---|---|
| committer | Alasdair G Kergon <agk@redhat.com> | 2012-10-12 21:02:07 +0100 |
| commit | 28eed34e7662d7602da6753b0ba2563006b8e7a2 (patch) | |
| tree | 0aeeda160b7cccfb77be58d47084a8e606905bf7 /drivers | |
| parent | 0bcf08798eb9fc3cd0fe2e6b74b25f3f57fa8af2 (diff) | |
| download | lwn-28eed34e7662d7602da6753b0ba2563006b8e7a2.tar.gz lwn-28eed34e7662d7602da6753b0ba2563006b8e7a2.zip | |
dm thin: support discard with non power of two block size
Support discards when the pool's block size is not a power of 2.
The block layer assumes discard_granularity is a power of 2 (in
blkdev_issue_discard), so we set this to the largest power of 2 that is
a divides into the number of sectors in each block, but never less than
DATA_DEV_BLOCK_SIZE_MIN_SECTORS.
This patch eliminates the "Discard support must be disabled when the
block size is not a power of 2" constraint that was imposed in commit
55f2b8b ("dm thin: support for non power of 2 pool blocksize"). That
commit was incomplete: using a block size that is not a power of 2
shouldn't mean disabling discard support on the device completely.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/md/dm-thin.c | 23 |
1 files changed, 13 insertions, 10 deletions
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c index c29410af1e22..df20a115136f 100644 --- a/drivers/md/dm-thin.c +++ b/drivers/md/dm-thin.c @@ -2272,15 +2272,6 @@ static int pool_ctr(struct dm_target *ti, unsigned argc, char **argv) goto out_flags_changed; } - /* - * The block layer requires discard_granularity to be a power of 2. - */ - if (pf.discard_enabled && !is_power_of_2(block_size)) { - ti->error = "Discard support must be disabled when the block size is not a power of 2"; - r = -EINVAL; - goto out_flags_changed; - } - pt->pool = pool; pt->ti = ti; pt->metadata_dev = metadata_dev; @@ -2762,6 +2753,11 @@ static int pool_merge(struct dm_target *ti, struct bvec_merge_data *bvm, return min(max_size, q->merge_bvec_fn(q, bvm, biovec)); } +static bool block_size_is_power_of_two(struct pool *pool) +{ + return pool->sectors_per_block_shift >= 0; +} + static void set_discard_limits(struct pool_c *pt, struct queue_limits *limits) { struct pool *pool = pt->pool; @@ -2775,8 +2771,15 @@ static void set_discard_limits(struct pool_c *pt, struct queue_limits *limits) if (pt->adjusted_pf.discard_passdown) { data_limits = &bdev_get_queue(pt->data_dev->bdev)->limits; limits->discard_granularity = data_limits->discard_granularity; - } else + } else if (block_size_is_power_of_two(pool)) limits->discard_granularity = pool->sectors_per_block << SECTOR_SHIFT; + else + /* + * Use largest power of 2 that is a factor of sectors_per_block + * but at least DATA_DEV_BLOCK_SIZE_MIN_SECTORS. + */ + limits->discard_granularity = max(1 << (ffs(pool->sectors_per_block) - 1), + DATA_DEV_BLOCK_SIZE_MIN_SECTORS) << SECTOR_SHIFT; } static void pool_io_hints(struct dm_target *ti, struct queue_limits *limits) |