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authorMikulas Patocka <mpatocka@redhat.com>2014-03-14 18:41:24 -0400
committerMike Snitzer <snitzer@redhat.com>2014-06-03 13:44:06 -0400
commit1dd40c3ecd9b8a4ab91dbf2e6ce10b82a3b5ae63 (patch)
treea1473eb0643c544ac9efa13911d6119a8078ed60 /drivers/md
parente0d6609a5fe34463ae2fd48d846931f70de8b37b (diff)
downloadlinux-1dd40c3ecd9b8a4ab91dbf2e6ce10b82a3b5ae63.tar.bz2
dm: introduce dm_accept_partial_bio
The function dm_accept_partial_bio allows the target to specify how many sectors of the current bio it will process. If the target only wants to accept part of the bio, it calls dm_accept_partial_bio and the DM core sends the rest of the data in next bio. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/dm.c59
1 files changed, 51 insertions, 8 deletions
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 368a20dd85c2..97940fc8c302 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1110,6 +1110,46 @@ int dm_set_target_max_io_len(struct dm_target *ti, sector_t len)
}
EXPORT_SYMBOL_GPL(dm_set_target_max_io_len);
+/*
+ * A target may call dm_accept_partial_bio only from the map routine. It is
+ * allowed for all bio types except REQ_FLUSH.
+ *
+ * dm_accept_partial_bio informs the dm that the target only wants to process
+ * additional n_sectors sectors of the bio and the rest of the data should be
+ * sent in a next bio.
+ *
+ * A diagram that explains the arithmetics:
+ * +--------------------+---------------+-------+
+ * | 1 | 2 | 3 |
+ * +--------------------+---------------+-------+
+ *
+ * <-------------- *tio->len_ptr --------------->
+ * <------- bi_size ------->
+ * <-- n_sectors -->
+ *
+ * Region 1 was already iterated over with bio_advance or similar function.
+ * (it may be empty if the target doesn't use bio_advance)
+ * Region 2 is the remaining bio size that the target wants to process.
+ * (it may be empty if region 1 is non-empty, although there is no reason
+ * to make it empty)
+ * The target requires that region 3 is to be sent in the next bio.
+ *
+ * If the target wants to receive multiple copies of the bio (via num_*bios, etc),
+ * the partially processed part (the sum of regions 1+2) must be the same for all
+ * copies of the bio.
+ */
+void dm_accept_partial_bio(struct bio *bio, unsigned n_sectors)
+{
+ struct dm_target_io *tio = container_of(bio, struct dm_target_io, clone);
+ unsigned bi_size = bio->bi_iter.bi_size >> SECTOR_SHIFT;
+ BUG_ON(bio->bi_rw & REQ_FLUSH);
+ BUG_ON(bi_size > *tio->len_ptr);
+ BUG_ON(n_sectors > bi_size);
+ *tio->len_ptr -= bi_size - n_sectors;
+ bio->bi_iter.bi_size = n_sectors << SECTOR_SHIFT;
+}
+EXPORT_SYMBOL_GPL(dm_accept_partial_bio);
+
static void __map_bio(struct dm_target_io *tio)
{
int r;
@@ -1200,11 +1240,13 @@ static struct dm_target_io *alloc_tio(struct clone_info *ci,
static void __clone_and_map_simple_bio(struct clone_info *ci,
struct dm_target *ti,
- unsigned target_bio_nr, unsigned len)
+ unsigned target_bio_nr, unsigned *len)
{
struct dm_target_io *tio = alloc_tio(ci, ti, ci->bio->bi_max_vecs, target_bio_nr);
struct bio *clone = &tio->clone;
+ tio->len_ptr = len;
+
/*
* Discard requests require the bio's inline iovecs be initialized.
* ci->bio->bi_max_vecs is BIO_INLINE_VECS anyway, for both flush
@@ -1212,13 +1254,13 @@ static void __clone_and_map_simple_bio(struct clone_info *ci,
*/
__bio_clone_fast(clone, ci->bio);
if (len)
- bio_setup_sector(clone, ci->sector, len);
+ bio_setup_sector(clone, ci->sector, *len);
__map_bio(tio);
}
static void __send_duplicate_bios(struct clone_info *ci, struct dm_target *ti,
- unsigned num_bios, unsigned len)
+ unsigned num_bios, unsigned *len)
{
unsigned target_bio_nr;
@@ -1233,13 +1275,13 @@ static int __send_empty_flush(struct clone_info *ci)
BUG_ON(bio_has_data(ci->bio));
while ((ti = dm_table_get_target(ci->map, target_nr++)))
- __send_duplicate_bios(ci, ti, ti->num_flush_bios, 0);
+ __send_duplicate_bios(ci, ti, ti->num_flush_bios, NULL);
return 0;
}
static void __clone_and_map_data_bio(struct clone_info *ci, struct dm_target *ti,
- sector_t sector, unsigned len)
+ sector_t sector, unsigned *len)
{
struct bio *bio = ci->bio;
struct dm_target_io *tio;
@@ -1254,7 +1296,8 @@ static void __clone_and_map_data_bio(struct clone_info *ci, struct dm_target *ti
for (target_bio_nr = 0; target_bio_nr < num_target_bios; target_bio_nr++) {
tio = alloc_tio(ci, ti, 0, target_bio_nr);
- clone_bio(tio, bio, sector, len);
+ tio->len_ptr = len;
+ clone_bio(tio, bio, sector, *len);
__map_bio(tio);
}
}
@@ -1306,7 +1349,7 @@ static int __send_changing_extent_only(struct clone_info *ci,
else
len = min((sector_t)ci->sector_count, max_io_len(ci->sector, ti));
- __send_duplicate_bios(ci, ti, num_bios, len);
+ __send_duplicate_bios(ci, ti, num_bios, &len);
ci->sector += len;
} while (ci->sector_count -= len);
@@ -1345,7 +1388,7 @@ static int __split_and_process_non_flush(struct clone_info *ci)
len = min_t(sector_t, max_io_len(ci->sector, ti), ci->sector_count);
- __clone_and_map_data_bio(ci, ti, ci->sector, len);
+ __clone_and_map_data_bio(ci, ti, ci->sector, &len);
ci->sector += len;
ci->sector_count -= len;