bcache/md: Use raid stripe size

Now that we've got code for raid5/6 stripe awareness, bcache just needs
to know about the stripes and when writing partial stripes is expensive
- we probably don't want to enable this optimization for raid1 or 10,
even though they have stripes. So add a flag to queue_limits.

Signed-off-by: Kent Overstreet <kmo@daterainc.com>

4 files changed, 12 insertions, 0 deletions

diff --git a/block/blk-settings.c b/block/blk-settings.c
index 05e826793e4e..5d21239bc859 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -592,6 +592,10 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
                 ret = -1;
         }
 
+        t->raid_partial_stripes_expensive =
+                max(t->raid_partial_stripes_expensive,
+                    b->raid_partial_stripes_expensive);
+
         /* Find lowest common alignment_offset */
         t->alignment_offset = lcm(t->alignment_offset, alignment)
                 & (max(t->physical_block_size, t->io_min) - 1);
diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 63ebef78df4a..e363efcf2b76 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -1134,6 +1134,12 @@ static int cached_dev_init(struct cached_dev *dc, unsigned block_size)
                 hlist_add_head(&io->hash, dc->io_hash + RECENT_IO);
         }
 
+        dc->disk.stripe_size = q->limits.io_opt >> 9;
+
+        if (dc->disk.stripe_size)
+                dc->partial_stripes_expensive =
+                        q->limits.raid_partial_stripes_expensive;
+
         ret = bcache_device_init(&dc->disk, block_size,
                          dc->bdev->bd_part->nr_sects - dc->sb.data_offset);
         if (ret)
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index eea63372e4d3..1cfb22c025b6 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -6101,6 +6101,7 @@ static int run(struct mddev *mddev)
                 blk_queue_io_min(mddev->queue, chunk_size);
                 blk_queue_io_opt(mddev->queue, chunk_size *
                                  (conf->raid_disks - conf->max_degraded));
+                mddev->queue->limits.raid_partial_stripes_expensive = 1;
                 /*
                  * We can only discard a whole stripe. It doesn't make sense to
                  * discard data disk but write parity disk
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 02cb6f0ea71d..0375654adb28 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -291,6 +291,7 @@ struct queue_limits {
         unsigned char           discard_misaligned;
         unsigned char           cluster;
         unsigned char           discard_zeroes_data;
+        unsigned char           raid_partial_stripes_expensive;
 };
 
 struct request_queue {