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authorMilan Broz <mbroz@redhat.com>2008-07-21 12:00:37 +0100
committerAlasdair G Kergon <agk@redhat.com>2008-07-21 12:00:37 +0100
commitf6fccb1213ba3d661baeb2a5eee0a9701dc03e1b (patch)
tree456671e791f8a61b40e0d622591b902ca1351ae7 /drivers/md
parent92e868122edf08b9fc06b112e7e0c80ab94c1f93 (diff)
dm: introduce merge_bvec_fn
Introduce a bvec merge function for device mapper devices for dynamic size restrictions. This code ensures the requested biovec lies within a single target and then calls a target-specific function to check against any constraints imposed by underlying devices. Signed-off-by: Milan Broz <mbroz@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/dm.c44
1 files changed, 44 insertions, 0 deletions
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index efe96907492..bca448e1187 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -829,6 +829,49 @@ static int __split_bio(struct mapped_device *md, struct bio *bio)
* CRUD END
*---------------------------------------------------------------*/
+static int dm_merge_bvec(struct request_queue *q,
+ struct bvec_merge_data *bvm,
+ struct bio_vec *biovec)
+{
+ struct mapped_device *md = q->queuedata;
+ struct dm_table *map = dm_get_table(md);
+ struct dm_target *ti;
+ sector_t max_sectors;
+ int max_size;
+
+ if (unlikely(!map))
+ return 0;
+
+ ti = dm_table_find_target(map, bvm->bi_sector);
+
+ /*
+ * Find maximum amount of I/O that won't need splitting
+ */
+ max_sectors = min(max_io_len(md, bvm->bi_sector, ti),
+ (sector_t) BIO_MAX_SECTORS);
+ max_size = (max_sectors << SECTOR_SHIFT) - bvm->bi_size;
+ if (max_size < 0)
+ max_size = 0;
+
+ /*
+ * merge_bvec_fn() returns number of bytes
+ * it can accept at this offset
+ * max is precomputed maximal io size
+ */
+ if (max_size && ti->type->merge)
+ max_size = ti->type->merge(ti, bvm, biovec, max_size);
+
+ /*
+ * Always allow an entire first page
+ */
+ if (max_size <= biovec->bv_len && !(bvm->bi_size >> SECTOR_SHIFT))
+ max_size = biovec->bv_len;
+
+ dm_table_put(map);
+
+ return max_size;
+}
+
/*
* The request function that just remaps the bio built up by
* dm_merge_bvec.
@@ -1032,6 +1075,7 @@ static struct mapped_device *alloc_dev(int minor)
blk_queue_make_request(md->queue, dm_request);
blk_queue_bounce_limit(md->queue, BLK_BOUNCE_ANY);
md->queue->unplug_fn = dm_unplug_all;
+ blk_queue_merge_bvec(md->queue, dm_merge_bvec);
md->io_pool = mempool_create_slab_pool(MIN_IOS, _io_cache);
if (!md->io_pool)