Enable the striped target to support discard requests by splitting a
single discard into N discards on a stripe chunk size boundary.
Follow on core block layer work to merge discards would be helpful.
This work relies on DM's clone_bio() always having BIO_RW_BARRIER set
for discard requests. Without BIO_RW_BARRIER the block layer will spew
"blk: request botched" warnings for discards that were split by DM.
- this clearly needs further investigation!
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
---
drivers/md/dm-stripe.c | 1 +
drivers/md/dm-table.c | 6 ------
drivers/md/dm.c | 37 +++++++++++++++++++++++++++++++++----
3 files changed, 34 insertions(+), 10 deletions(-)
diff --git a/drivers/md/dm-stripe.c b/drivers/md/dm-stripe.c
index e610725..052f254 100644
--- a/drivers/md/dm-stripe.c
+++ b/drivers/md/dm-stripe.c
@@ -349,6 +349,7 @@ static struct target_type stripe_target = {
.status = stripe_status,
.iterate_devices = stripe_iterate_devices,
.io_hints = stripe_io_hints,
+ .features = DM_TARGET_SUPPORTS_DISCARDS,
};
int __init dm_stripe_init(void)
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index a825a7b..b38fdb3 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -911,12 +911,6 @@ int dm_table_complete(struct dm_table *t)
int r = 0;
unsigned int leaf_nodes;
- /*
- * We only support discards if there is exactly one underlying device.
- */
- if (!list_is_singular(&t->devices))
- t->discards_supported = 0;
-
/* how many indexes will the btree have ? */
leaf_nodes = dm_div_up(t->num_targets, KEYS_PER_NODE);
t->depth = 1 + int_log(leaf_nodes, CHILDREN_PER_NODE);
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 232332a..a08b1d3 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1137,7 +1137,12 @@ static struct bio *clone_bio(struct bio *bio, sector_t sector,
clone = bio_alloc_bioset(GFP_NOIO, bio->bi_max_vecs, bs);
__bio_clone(clone, bio);
- clone->bi_rw &= ~(1 << BIO_RW_BARRIER);
+ if (!bio_rw_flagged(bio, BIO_RW_DISCARD))
+ clone->bi_rw &= ~(1 << BIO_RW_BARRIER);
+ else if (!bio_rw_flagged(bio, BIO_RW_BARRIER)) {
+ /* discard w/o barrier results in "blk: request botched" */
+ clone->bi_rw |= (1 << BIO_RW_BARRIER);
+ }
clone->bi_destructor = dm_bio_destructor;
clone->bi_sector = sector;
clone->bi_idx = idx;
@@ -1217,7 +1222,7 @@ static void __clone_and_map_simple(struct clone_info *ci, struct dm_target *ti)
static int __clone_and_map_discard(struct clone_info *ci)
{
struct dm_target *ti;
- sector_t max;
+ sector_t len = 0, max;
if (!dm_table_supports_discards(ci->map))
return -EOPNOTSUPP;
@@ -1232,9 +1237,33 @@ static int __clone_and_map_discard(struct clone_info *ci)
__clone_and_map_simple(ci, ti);
else {
/*
- * FIXME: Handle a discard that spans two or more targets.
+ * Handle a discard that spans two or more targets.
*/
- return -EOPNOTSUPP;
+ struct bio *clone;
+ struct dm_target_io *tio;
+ sector_t remaining = ci->sector_count;
+ unsigned int offset = 0;
+
+ do {
+ if (offset) {
+ ti = dm_table_find_target(ci->map, ci->sector);
+ if (!dm_target_is_valid(ti))
+ return -EIO;
+
+ max = max_io_len(ci->md, ci->sector, ti);
+ }
+
+ len = min(remaining, max);
+
+ tio = alloc_tio(ci, ti);
+ clone = clone_bio(ci->bio, ci->sector, 0,
+ 0, len, ci->md->bs);
+ __map_bio(ti, clone, tio);
+
+ ci->sector += len;
+ ci->sector_count -= len;
+ offset += to_bytes(len);
+ } while (remaining -= len);
}
return 0;
--
1.6.5.rc2
--
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