dm stripe: expose correct io hints

Set sensible I/O hints for striped DM devices in the topology
infrastructure added for 2.6.31 for userspace tools to
obtain via sysfs.

Add .io_hints to 'struct target_type' to allow the I/O hints portion
(io_min and io_opt) of the 'struct queue_limits' to be set by each
target and implement this for dm-stripe.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

3 files changed, 20 insertions, 1 deletions

diff --git a/drivers/md/dm-stripe.c b/drivers/md/dm-stripe.c
index 4e0e5937e42a..3e563d251733 100644
--- a/drivers/md/dm-stripe.c
+++ b/drivers/md/dm-stripe.c
@@ -329,9 +329,19 @@ static int stripe_iterate_devices(struct dm_target *ti,
         return ret;
 }
 
+static void stripe_io_hints(struct dm_target *ti,
+                            struct queue_limits *limits)
+{
+        struct stripe_c *sc = ti->private;
+        unsigned chunk_size = (sc->chunk_mask + 1) << 9;
+
+        blk_limits_io_min(limits, chunk_size);
+        limits->io_opt = chunk_size * sc->stripes;
+}
+
 static struct target_type stripe_target = {
         .name   = "striped",
-        .version = {1, 2, 0},
+        .version = {1, 3, 0},
         .module = THIS_MODULE,
         .ctr    = stripe_ctr,
         .dtr    = stripe_dtr,
@@ -339,6 +349,7 @@ static struct target_type stripe_target = {
         .end_io = stripe_end_io,
         .status = stripe_status,
         .iterate_devices = stripe_iterate_devices,
+        .io_hints = stripe_io_hints,
 };
 
 int __init dm_stripe_init(void)
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index c90e662d2802..1a6cb3c7822e 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -1007,6 +1007,10 @@ int dm_calculate_queue_limits(struct dm_table *table,
                 ti->type->iterate_devices(ti, dm_set_device_limits,
                                           &ti_limits);
 
+                /* Set I/O hints portion of queue limits */
+                if (ti->type->io_hints)
+                        ti->type->io_hints(ti, &ti_limits);
+
                 /*
                  * Check each device area is consistent with the target's
                  * overall queue limits.
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 655e7721580a..df7607e6dce8 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -91,6 +91,9 @@ typedef int (*dm_iterate_devices_fn) (struct dm_target *ti,
                                       iterate_devices_callout_fn fn,
                                       void *data);
 
+typedef void (*dm_io_hints_fn) (struct dm_target *ti,
+                                struct queue_limits *limits);
+
 /*
  * Returns:
  *    0: The target can handle the next I/O immediately.
@@ -151,6 +154,7 @@ struct target_type {
         dm_merge_fn merge;
         dm_busy_fn busy;
         dm_iterate_devices_fn iterate_devices;
+        dm_io_hints_fn io_hints;
 
         /* For internal device-mapper use. */
         struct list_head list;