block: Optimal I/O limit wrapper

Implement blk_limits_io_opt() and make blk_queue_io_opt() a wrapper
around it. DM needs this to avoid poking at the queue_limits directly.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

diff --git a/block/blk-settings.c b/block/blk-settings.c
index 476d870..83413ff 100644 (file)
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -427,6 +427,25 @@ void blk_queue_io_min(struct request_queue *q, unsigned int min)
 }
 EXPORT_SYMBOL(blk_queue_io_min);
 
+/**
+ * blk_limits_io_opt - set optimal request size for a device
+ * @limits: the queue limits
+ * @opt:  smallest I/O size in bytes
+ *
+ * Description:
+ *   Storage devices may report an optimal I/O size, which is the
+ *   device's preferred unit for sustained I/O.  This is rarely reported
+ *   for disk drives.  For RAID arrays it is usually the stripe width or
+ *   the internal track size.  A properly aligned multiple of
+ *   optimal_io_size is the preferred request size for workloads where
+ *   sustained throughput is desired.
+ */
+void blk_limits_io_opt(struct queue_limits *limits, unsigned int opt)
+{
+       limits->io_opt = opt;
+}
+EXPORT_SYMBOL(blk_limits_io_opt);
+
 /**
  * blk_queue_io_opt - set optimal request size for the queue
  * @q: the request queue for the device
@@ -442,7 +461,7 @@ EXPORT_SYMBOL(blk_queue_io_min);
  */
 void blk_queue_io_opt(struct request_queue *q, unsigned int opt)
 {
-       q->limits.io_opt = opt;
+       blk_limits_io_opt(&q->limits, opt);
 }
 EXPORT_SYMBOL(blk_queue_io_opt);
 

diff --git a/drivers/md/dm-stripe.c b/drivers/md/dm-stripe.c
index fde658c..e0efc1a 100644 (file)
--- a/drivers/md/dm-stripe.c
+++ b/drivers/md/dm-stripe.c
@@ -336,7 +336,7 @@ static void stripe_io_hints(struct dm_target *ti,
        unsigned chunk_size = (sc->chunk_mask + 1) << 9;
 
        blk_limits_io_min(limits, chunk_size);
-       limits->io_opt = chunk_size * sc->stripes;
+       blk_limits_io_opt(limits, chunk_size * sc->stripes);
 }
 
 static struct target_type stripe_target = {

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 8bf1a10..86c2bdf 100644 (file)
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -935,6 +935,7 @@ extern void blk_queue_alignment_offset(struct request_queue *q,
                                       unsigned int alignment);
 extern void blk_limits_io_min(struct queue_limits *limits, unsigned int min);
 extern void blk_queue_io_min(struct request_queue *q, unsigned int min);
+extern void blk_limits_io_opt(struct queue_limits *limits, unsigned int opt);
 extern void blk_queue_io_opt(struct request_queue *q, unsigned int opt);
 extern void blk_set_default_limits(struct queue_limits *lim);
 extern int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,