This allows a target to dynamically tell dm core how many copies of a
bio it needs. The dm-cache target will make use of this for it's
write-through support.
Introduce __split_and_issue_bio_to_target to allow split_bvec to be used
with get_num_duplicates.
We already have hard coded instances of this (eg, num_flush_requests,
num_discard_requests). These have been left for now, we can switch
everything over to use get_num_duplicates later.
(Based heavily on Joe's original work; ported to work with Mikulas' new
bio cloning via front padding)
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Cc: Joe Thornber <ejt@xxxxxxxxxx>
---
drivers/md/dm.c | 83 ++++++++++++++++++++++++++++++-----------
include/linux/device-mapper.h | 8 ++++
2 files changed, 69 insertions(+), 22 deletions(-)
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 08eea14..506c73a 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1038,7 +1038,7 @@ struct clone_info {
*/
static void split_bvec(struct dm_target_io *tio, struct bio *bio,
sector_t sector, unsigned short idx, unsigned int offset,
- unsigned int len, struct bio_set *bs)
+ unsigned int len)
{
struct bio *clone = &tio->clone;
struct bio_vec *bv = bio->bi_io_vec + idx;
@@ -1104,6 +1104,20 @@ static struct dm_target_io *alloc_tio(struct clone_info *ci,
return tio;
}
+static unsigned num_duplicate_bios_needed(struct dm_target *ti, struct bio *bio)
+{
+ if (bio->bi_rw & REQ_FLUSH)
+ return ti->num_flush_requests;
+
+ if (bio->bi_rw & REQ_DISCARD)
+ return ti->num_discard_requests;
+
+ if (ti->type->get_num_duplicates)
+ return ti->type->get_num_duplicates(ti, bio);
+
+ return 1;
+}
+
static void __issue_target_request(struct clone_info *ci, struct dm_target *ti,
unsigned request_nr, sector_t len)
{
@@ -1128,12 +1142,12 @@ static void __issue_target_request(struct clone_info *ci, struct dm_target *ti,
}
static void __issue_target_requests(struct clone_info *ci, struct dm_target *ti,
- unsigned num_requests, sector_t len)
+ sector_t len)
{
- unsigned request_nr;
+ unsigned i, num_requests = num_duplicate_bios_needed(ti, ci->bio);
- for (request_nr = 0; request_nr < num_requests; request_nr++)
- __issue_target_request(ci, ti, request_nr, len);
+ for (i = 0; i < num_requests; i++)
+ __issue_target_request(ci, ti, i, len);
}
static int __clone_and_map_empty_flush(struct clone_info *ci)
@@ -1143,23 +1157,54 @@ static int __clone_and_map_empty_flush(struct clone_info *ci)
BUG_ON(bio_has_data(ci->bio));
while ((ti = dm_table_get_target(ci->map, target_nr++)))
- __issue_target_requests(ci, ti, ti->num_flush_requests, 0);
+ __issue_target_requests(ci, ti, 0);
return 0;
}
+static void __issue_bio_to_target(struct clone_info *ci, struct dm_target *ti,
+ struct bio *bio, sector_t sector,
+ unsigned short idx, unsigned bv_count,
+ unsigned len, struct bio_set *bs)
+{
+ unsigned i, num_duplicates = num_duplicate_bios_needed(ti, bio);
+ struct dm_target_io *tio;
+
+ for (i = 0; i < num_duplicates; i++) {
+ tio = alloc_tio(ci, ti, bio->bi_max_vecs);
+ tio->target_request_nr = i;
+ clone_bio(tio, bio, sector, idx, bv_count, len, bs);
+ __map_bio(ti, tio);
+ }
+}
+
+static void __split_and_issue_bio_to_target(struct clone_info *ci,
+ struct dm_target *ti,
+ struct bio *bio, sector_t sector,
+ unsigned short idx, unsigned bv_count,
+ unsigned len)
+{
+ unsigned i, num_duplicates = num_duplicate_bios_needed(ti, bio);
+ struct dm_target_io *tio;
+
+ for (i = 0; i < num_duplicates; i++) {
+ tio = alloc_tio(ci, ti, 1);
+ tio->target_request_nr = i;
+ split_bvec(tio, bio, sector, idx, bv_count, len);
+ __map_bio(ti, tio);
+ }
+}
+
/*
* Perform all io with a single clone.
*/
static void __clone_and_map_simple(struct clone_info *ci, struct dm_target *ti)
{
struct bio *bio = ci->bio;
- struct dm_target_io *tio;
- tio = alloc_tio(ci, ti, bio->bi_max_vecs);
- clone_bio(tio, bio, ci->sector, ci->idx, bio->bi_vcnt - ci->idx,
- ci->sector_count, ci->md->bs);
- __map_bio(ti, tio);
+ __issue_bio_to_target(ci, ti, bio, ci->sector, ci->idx,
+ bio->bi_vcnt - ci->idx, ci->sector_count,
+ ci->md->bs);
ci->sector_count = 0;
}
@@ -1187,7 +1232,7 @@ static int __clone_and_map_discard(struct clone_info *ci)
else
len = min(ci->sector_count, max_io_len(ci->sector, ti));
- __issue_target_requests(ci, ti, ti->num_discard_requests, len);
+ __issue_target_requests(ci, ti, len);
ci->sector += len;
} while (ci->sector_count -= len);
@@ -1200,7 +1245,6 @@ static int __clone_and_map(struct clone_info *ci)
struct bio *bio = ci->bio;
struct dm_target *ti;
sector_t len = 0, max;
- struct dm_target_io *tio;
if (unlikely(bio->bi_rw & REQ_DISCARD))
return __clone_and_map_discard(ci);
@@ -1237,10 +1281,8 @@ static int __clone_and_map(struct clone_info *ci)
len += bv_len;
}
- tio = alloc_tio(ci, ti, bio->bi_max_vecs);
- clone_bio(tio, bio, ci->sector, ci->idx, i - ci->idx, len,
- ci->md->bs);
- __map_bio(ti, tio);
+ __issue_bio_to_target(ci, ti, bio, ci->sector, ci->idx,
+ i - ci->idx, len, ci->md->bs);
ci->sector += len;
ci->sector_count -= len;
@@ -1265,11 +1307,8 @@ static int __clone_and_map(struct clone_info *ci)
len = min(remaining, max);
- tio = alloc_tio(ci, ti, 1);
- split_bvec(tio, bio, ci->sector, ci->idx,
- bv->bv_offset + offset, len, ci->md->bs);
-
- __map_bio(ti, tio);
+ __split_and_issue_bio_to_target(ci, ti, bio, ci->sector, ci->idx,
+ bv->bv_offset + offset, len);
ci->sector += len;
ci->sector_count -= len;
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 1687f9e..2d65c70 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -39,6 +39,13 @@ typedef int (*dm_ctr_fn) (struct dm_target *target,
typedef void (*dm_dtr_fn) (struct dm_target *ti);
/*
+ * Some targets need to process multiple copies of a bio. For instance a
+ * cache target in 'writethrough' mode will need to issue io to both the
+ * fast and slow devices.
+ */
+typedef unsigned (*dm_get_num_duplicates_fn)(struct dm_target *ti, struct bio *bio);
+
+/*
* The map function must return:
* < 0: error
* = 0: The target will handle the io by resubmitting it later
@@ -131,6 +138,7 @@ struct target_type {
unsigned version[3];
dm_ctr_fn ctr;
dm_dtr_fn dtr;
+ dm_get_num_duplicates_fn get_num_duplicates;
dm_map_fn map;
dm_map_request_fn map_rq;
dm_endio_fn end_io;
--
1.7.1
--
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