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authorMike Snitzer <snitzer@redhat.com>2012-10-12 21:02:07 +0100
committerAlasdair G Kergon <agk@redhat.com>2012-10-12 21:02:07 +0100
commit28eed34e7662d7602da6753b0ba2563006b8e7a2 (patch)
tree0aeeda160b7cccfb77be58d47084a8e606905bf7
parent0bcf08798eb9fc3cd0fe2e6b74b25f3f57fa8af2 (diff)
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>
-rw-r--r--drivers/md/dm-thin.c23
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)