1 files changed, 71 insertions, 4 deletions

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 0cf68b478878..52b39f335bb3 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -37,6 +37,8 @@ static const char *_name = DM_NAME;
 static unsigned int major = 0;
 static unsigned int _major = 0;
 
+static DEFINE_IDR(_minor_idr);
+
 static DEFINE_SPINLOCK(_minor_lock);
 /*
  * For bio-based dm.
@@ -109,6 +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.
@@ -313,6 +316,12 @@ static void __exit dm_exit(void)
 
         while (i--)
                 _exits[i]();
+
+        /*
+         * Should be empty by this point.
+         */
+        idr_remove_all(&_minor_idr);
+        idr_destroy(&_minor_idr);
 }
 
 /*
@@ -1171,7 +1180,8 @@ static int __clone_and_map_discard(struct clone_info *ci)
 
                 /*
                  * Even though the device advertised discard support,
-                 * reconfiguration might have changed that since the
+                 * that does not mean every target supports it, and
+                 * reconfiguration might also have changed that since the
                  * check was performed.
                  */
                 if (!ti->num_discard_requests)
@@ -1705,8 +1715,6 @@ static int dm_any_congested(void *congested_data, int bdi_bits)
 /*-----------------------------------------------------------------
  * An IDR is used to keep track of allocated minor numbers.
  *---------------------------------------------------------------*/
-static DEFINE_IDR(_minor_idr);
-
 static void free_minor(int minor)
 {
         spin_lock(&_minor_lock);
@@ -1800,7 +1808,6 @@ static void dm_init_md_queue(struct mapped_device *md)
         blk_queue_make_request(md->queue, dm_request);
         blk_queue_bounce_limit(md->queue, BLK_BOUNCE_ANY);
         blk_queue_merge_bvec(md->queue, dm_merge_bvec);
-        blk_queue_flush(md->queue, REQ_FLUSH | REQ_FUA);
 }
 
 /*
@@ -1986,6 +1993,59 @@ 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,
@@ -1995,6 +2055,7 @@ 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);
 
@@ -2020,10 +2081,16 @@ 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;