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-rw-r--r--drivers/md/dm-table.c3
-rw-r--r--drivers/md/dm.c61
-rw-r--r--drivers/md/dm.h2
3 files changed, 64 insertions, 2 deletions
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index d58b200a3531..03516c7f5be1 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -540,8 +540,7 @@ int dm_set_device_limits(struct dm_target *ti, struct dm_dev *dev,
* If not we'll force DM to use PAGE_SIZE or
* smaller I/O, just to be safe.
*/
-
- if (q->merge_bvec_fn && !ti->type->merge)
+ if (dm_queue_merge_is_compulsory(q) && !ti->type->merge)
blk_limits_max_hw_sectors(limits,
(unsigned int) (PAGE_SIZE >> 9));
return 0;
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index aeb0fa1ccfe4..1000eaf984ef 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -111,6 +111,7 @@ EXPORT_SYMBOL_GPL(dm_get_rq_mapinfo);
#define DMF_FREEING 3
#define DMF_DELETING 4
#define DMF_NOFLUSH_SUSPENDING 5
+#define DMF_MERGE_IS_OPTIONAL 6
/*
* Work processed by per-device workqueue.
@@ -1993,6 +1994,59 @@ static void __set_size(struct mapped_device *md, sector_t size)
}
/*
+ * Return 1 if the queue has a compulsory merge_bvec_fn function.
+ *
+ * If this function returns 0, then the device is either a non-dm
+ * device without a merge_bvec_fn, or it is a dm device that is
+ * able to split any bios it receives that are too big.
+ */
+int dm_queue_merge_is_compulsory(struct request_queue *q)
+{
+ struct mapped_device *dev_md;
+
+ if (!q->merge_bvec_fn)
+ return 0;
+
+ if (q->make_request_fn == dm_request) {
+ dev_md = q->queuedata;
+ if (test_bit(DMF_MERGE_IS_OPTIONAL, &dev_md->flags))
+ return 0;
+ }
+
+ return 1;
+}
+
+static int dm_device_merge_is_compulsory(struct dm_target *ti,
+ struct dm_dev *dev, sector_t start,
+ sector_t len, void *data)
+{
+ struct block_device *bdev = dev->bdev;
+ struct request_queue *q = bdev_get_queue(bdev);
+
+ return dm_queue_merge_is_compulsory(q);
+}
+
+/*
+ * Return 1 if it is acceptable to ignore merge_bvec_fn based
+ * on the properties of the underlying devices.
+ */
+static int dm_table_merge_is_optional(struct dm_table *table)
+{
+ unsigned i = 0;
+ struct dm_target *ti;
+
+ while (i < dm_table_get_num_targets(table)) {
+ ti = dm_table_get_target(table, i++);
+
+ if (ti->type->iterate_devices &&
+ ti->type->iterate_devices(ti, dm_device_merge_is_compulsory, NULL))
+ return 0;
+ }
+
+ return 1;
+}
+
+/*
* Returns old map, which caller must destroy.
*/
static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
@@ -2002,6 +2056,7 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
struct request_queue *q = md->queue;
sector_t size;
unsigned long flags;
+ int merge_is_optional;
size = dm_table_get_size(t);
@@ -2027,10 +2082,16 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
__bind_mempools(md, t);
+ merge_is_optional = dm_table_merge_is_optional(t);
+
write_lock_irqsave(&md->map_lock, flags);
old_map = md->map;
md->map = t;
dm_table_set_restrictions(t, q, limits);
+ if (merge_is_optional)
+ set_bit(DMF_MERGE_IS_OPTIONAL, &md->flags);
+ else
+ clear_bit(DMF_MERGE_IS_OPTIONAL, &md->flags);
write_unlock_irqrestore(&md->map_lock, flags);
return old_map;
diff --git a/drivers/md/dm.h b/drivers/md/dm.h
index 1aaf16746da8..6745dbd278a4 100644
--- a/drivers/md/dm.h
+++ b/drivers/md/dm.h
@@ -66,6 +66,8 @@ int dm_table_alloc_md_mempools(struct dm_table *t);
void dm_table_free_md_mempools(struct dm_table *t);
struct dm_md_mempools *dm_table_get_md_mempools(struct dm_table *t);
+int dm_queue_merge_is_compulsory(struct request_queue *q);
+
void dm_lock_md_type(struct mapped_device *md);
void dm_unlock_md_type(struct mapped_device *md);
void dm_set_md_type(struct mapped_device *md, unsigned type);