dm: introduce target callbacks and congestion callback

DM currently implements congestion checking by checking on congestion
in each component device.  For raid456 we need to also check if the
stripe cache is congested.

Add per-target congestion checker callback support.

Extending the target_callbacks structure with additional callback
functions allows for establishing multiple callbacks per-target (a
callback is also needed for unplug).

Cc: linux-raid@vger.kernel.org
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 985c20a4f30e14c5a0c00d6749a3b7bcf79e9f6a..7e2ec3c055502fe21b0d9b01153cbc67e83111db 100644 (file)
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -71,6 +71,8 @@ struct dm_table {
        void *event_context;
 
        struct dm_md_mempools *mempools;
+
+       struct list_head target_callbacks;
 };
 
 /*
@@ -204,6 +206,7 @@ int dm_table_create(struct dm_table **result, fmode_t mode,
                return -ENOMEM;
 
        INIT_LIST_HEAD(&t->devices);
+       INIT_LIST_HEAD(&t->target_callbacks);
        atomic_set(&t->holders, 0);
        t->discards_supported = 1;
 
@@ -1225,10 +1228,17 @@ int dm_table_resume_targets(struct dm_table *t)
        return 0;
 }
 
+void dm_table_add_target_callbacks(struct dm_table *t, struct dm_target_callbacks *cb)
+{
+       list_add(&cb->list, &t->target_callbacks);
+}
+EXPORT_SYMBOL_GPL(dm_table_add_target_callbacks);
+
 int dm_table_any_congested(struct dm_table *t, int bdi_bits)
 {
        struct dm_dev_internal *dd;
        struct list_head *devices = dm_table_get_devices(t);
+       struct dm_target_callbacks *cb;
        int r = 0;
 
        list_for_each_entry(dd, devices, list) {
@@ -1243,6 +1253,10 @@ int dm_table_any_congested(struct dm_table *t, int bdi_bits)
                                     bdevname(dd->dm_dev.bdev, b));
        }
 
+       list_for_each_entry(cb, &t->target_callbacks, list)
+               if (cb->congested_fn)
+                       r |= cb->congested_fn(cb, bdi_bits);
+
        return r;
 }
 

diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 2970022faa632715461ab11ea8955cf3aa0fb1c0..4b1c63d478ab972e328e279486255650b84e75d1 100644 (file)
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -193,6 +193,12 @@ struct dm_target {
        char *error;
 };
 
+/* Each target can link one of these into the table */
+struct dm_target_callbacks {
+       struct list_head list;
+       int (*congested_fn) (struct dm_target_callbacks *, int);
+};
+
 int dm_register_target(struct target_type *t);
 void dm_unregister_target(struct target_type *t);
 
@@ -268,6 +274,11 @@ int dm_table_create(struct dm_table **result, fmode_t mode,
 int dm_table_add_target(struct dm_table *t, const char *type,
                        sector_t start, sector_t len, char *params);
 
+/*
+ * Target_ctr should call this if it needs to add any callbacks.
+ */
+void dm_table_add_target_callbacks(struct dm_table *t, struct dm_target_callbacks *cb);
+
 /*
  * Finally call this to make the table ready for use.
  */