dm raid1: one kmirrord per mirror

This patch replaces the single instance of kmirrord by one instance per mirror
set.  This change is required to avoid a deadlock in kmirrord when the
persistent dirty log of a mirror itself resides on a mirror.  The single
instance of kmirrord then issues a sync write to the dirty log in write_bits
which gets deferred to kmirrord itself later in the call chain.  But kmirrord
never does the deferred work because it is still waiting for the sync
write_bits.

_mirror_sets is removed as it no longer needed, and we always flush the
workqueue before destroying it to ensure all work is complete before
destroying it.

Signed-off-by: Holger Smolinski <smolinski@de.ibm.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 27 insertions, 54 deletions

diff --git a/drivers/md/dm-raid1.c b/drivers/md/dm-raid1.c
index 23a642619bed..c8b4c108da9e 100644
--- a/drivers/md/dm-raid1.c
+++ b/drivers/md/dm-raid1.c
@@ -22,15 +22,8 @@
 
 #define DM_MSG_PREFIX "raid1"
 
-static struct workqueue_struct *_kmirrord_wq;
-static struct work_struct _kmirrord_work;
 static DECLARE_WAIT_QUEUE_HEAD(_kmirrord_recovery_stopped);
 
-static inline void wake(void)
-{
-        queue_work(_kmirrord_wq, &_kmirrord_work);
-}
-
 /*-----------------------------------------------------------------
  * Region hash
  *
@@ -136,6 +129,9 @@ struct mirror_set {
 
         struct mirror *default_mirror;  /* Default mirror */
 
+        struct workqueue_struct *kmirrord_wq;
+        struct work_struct kmirrord_work;
+
         unsigned int nr_mirrors;
         struct mirror mirror[0];
 };
@@ -153,6 +149,11 @@ static inline sector_t region_to_sector(struct region_hash *rh, region_t region)
         return region << rh->region_shift;
 }
 
+static void wake(struct mirror_set *ms)
+{
+        queue_work(ms->kmirrord_wq, &ms->kmirrord_work);
+}
+
 /* FIXME move this */
 static void queue_bio(struct mirror_set *ms, struct bio *bio, int rw);
 
@@ -471,7 +472,7 @@ static void rh_dec(struct region_hash *rh, region_t region)
         spin_unlock_irqrestore(&rh->region_lock, flags);
 
         if (should_wake)
-                wake();
+                wake(rh->ms);
 }
 
 /*
@@ -558,7 +559,7 @@ static void rh_recovery_end(struct region *reg, int success)
         list_add(&reg->list, &reg->rh->recovered_regions);
         spin_unlock_irq(&rh->region_lock);
 
-        wake();
+        wake(rh->ms);
 }
 
 static void rh_flush(struct region_hash *rh)
@@ -592,7 +593,7 @@ static void rh_start_recovery(struct region_hash *rh)
         for (i = 0; i < MAX_RECOVERY; i++)
                 up(&rh->recovery_count);
 
-        wake();
+        wake(rh->ms);
 }
 
 /*
@@ -870,11 +871,10 @@ static void do_writes(struct mirror_set *ms, struct bio_list *writes)
 /*-----------------------------------------------------------------
  * kmirrord
  *---------------------------------------------------------------*/
-static LIST_HEAD(_mirror_sets);
-static DECLARE_RWSEM(_mirror_sets_lock);
-
-static void do_mirror(struct mirror_set *ms)
+static void do_mirror(struct work_struct *work)
 {
+        struct mirror_set *ms =container_of(work, struct mirror_set,
+                                            kmirrord_work);
         struct bio_list reads, writes;
 
         spin_lock(&ms->lock);
@@ -890,16 +890,6 @@ static void do_mirror(struct mirror_set *ms)
         do_writes(ms, &writes);
 }
 
-static void do_work(struct work_struct *ignored)
-{
-        struct mirror_set *ms;
-
-        down_read(&_mirror_sets_lock);
-        list_for_each_entry (ms, &_mirror_sets, list)
-                do_mirror(ms);
-        up_read(&_mirror_sets_lock);
-}
-
 /*-----------------------------------------------------------------
  * Target functions
  *---------------------------------------------------------------*/
@@ -978,23 +968,6 @@ static int get_mirror(struct mirror_set *ms, struct dm_target *ti,
         return 0;
 }
 
-static int add_mirror_set(struct mirror_set *ms)
-{
-        down_write(&_mirror_sets_lock);
-        list_add_tail(&ms->list, &_mirror_sets);
-        up_write(&_mirror_sets_lock);
-        wake();
-
-        return 0;
-}
-
-static void del_mirror_set(struct mirror_set *ms)
-{
-        down_write(&_mirror_sets_lock);
-        list_del(&ms->list);
-        up_write(&_mirror_sets_lock);
-}
-
 /*
  * Create dirty log: log_type #log_params <log_params>
  */
@@ -1096,13 +1069,22 @@ static int mirror_ctr(struct dm_target *ti, unsigned int argc, char **argv)
         ti->private = ms;
         ti->split_io = ms->rh.region_size;
 
+        ms->kmirrord_wq = create_singlethread_workqueue("kmirrord");
+        if (!ms->kmirrord_wq) {
+                DMERR("couldn't start kmirrord");
+                free_context(ms, ti, m);
+                return -ENOMEM;
+        }
+        INIT_WORK(&ms->kmirrord_work, do_mirror);
+
         r = kcopyd_client_create(DM_IO_PAGES, &ms->kcopyd_client);
         if (r) {
+                destroy_workqueue(ms->kmirrord_wq);
                 free_context(ms, ti, ms->nr_mirrors);
                 return r;
         }
 
-        add_mirror_set(ms);
+        wake(ms);
         return 0;
 }
 
@@ -1110,8 +1092,9 @@ static void mirror_dtr(struct dm_target *ti)
 {
         struct mirror_set *ms = (struct mirror_set *) ti->private;
 
-        del_mirror_set(ms);
+        flush_workqueue(ms->kmirrord_wq);
         kcopyd_client_destroy(ms->kcopyd_client);
+        destroy_workqueue(ms->kmirrord_wq);
         free_context(ms, ti, ms->nr_mirrors);
 }
 
@@ -1127,7 +1110,7 @@ static void queue_bio(struct mirror_set *ms, struct bio *bio, int rw)
         spin_unlock(&ms->lock);
 
         if (should_wake)
-                wake();
+                wake(ms);
 }
 
 /*
@@ -1270,20 +1253,11 @@ static int __init dm_mirror_init(void)
         if (r)
                 return r;
 
-        _kmirrord_wq = create_singlethread_workqueue("kmirrord");
-        if (!_kmirrord_wq) {
-                DMERR("couldn't start kmirrord");
-                dm_dirty_log_exit();
-                return r;
-        }
-        INIT_WORK(&_kmirrord_work, do_work);
-
         r = dm_register_target(&mirror_target);
         if (r < 0) {
                 DMERR("%s: Failed to register mirror target",
                       mirror_target.name);
                 dm_dirty_log_exit();
-                destroy_workqueue(_kmirrord_wq);
         }
 
         return r;
@@ -1297,7 +1271,6 @@ static void __exit dm_mirror_exit(void)
         if (r < 0)
                 DMERR("%s: unregister failed %d", mirror_target.name, r);
 
-        destroy_workqueue(_kmirrord_wq);
         dm_dirty_log_exit();
 }