md/raid5: replace sh->lock with an 'active' flag.

sh->lock is now mainly used to ensure that two threads aren't running
in the locked part of handle_stripe[56] at the same time.

That can more neatly be achieved with an 'active' flag which we set
while running handle_stripe.  If we find the flag is set, we simply
requeue the stripe for later by setting STRIPE_HANDLE.

For safety we take ->device_lock while examining the state of the
stripe and creating a summary in 'stripe_head_state / r6_state'.
This possibly isn't needed but as shared fields like ->toread,
->towrite are checked it is safer for now at least.

We leave the label after the old 'unlock' called "unlock" because it
will disappear in a few patches, so renaming seems pointless.

This leaves the stripe 'locked' for longer as we clear STRIPE_ACTIVE
later, but that is not a problem.

Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Namhyung Kim <namhyung@gmail.com>

1 files changed, 13 insertions, 13 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 9985138f4c04..f8275b5a6fbe 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -1020,14 +1020,12 @@ ops_run_biodrain(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
                 if (test_and_clear_bit(R5_Wantdrain, &dev->flags)) {
                         struct bio *wbi;
 
-                        spin_lock(&sh->lock);
                         spin_lock_irq(&sh->raid_conf->device_lock);
                         chosen = dev->towrite;
                         dev->towrite = NULL;
                         BUG_ON(dev->written);
                         wbi = dev->written = chosen;
                         spin_unlock_irq(&sh->raid_conf->device_lock);
-                        spin_unlock(&sh->lock);
 
                         while (wbi && wbi->bi_sector <
                                 dev->sector + STRIPE_SECTORS) {
@@ -1322,7 +1320,6 @@ static int grow_one_stripe(raid5_conf_t *conf)
                 return 0;
 
         sh->raid_conf = conf;
-        spin_lock_init(&sh->lock);
         #ifdef CONFIG_MULTICORE_RAID456
         init_waitqueue_head(&sh->ops.wait_for_ops);
         #endif
@@ -1442,7 +1439,6 @@ static int resize_stripes(raid5_conf_t *conf, int newsize)
                         break;
 
                 nsh->raid_conf = conf;
-                spin_lock_init(&nsh->lock);
                 #ifdef CONFIG_MULTICORE_RAID456
                 init_waitqueue_head(&nsh->ops.wait_for_ops);
                 #endif
@@ -2148,7 +2144,6 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx, in
                 (unsigned long long)sh->sector);
 
 
-        spin_lock(&sh->lock);
         spin_lock_irq(&conf->device_lock);
         if (forwrite) {
                 bip = &sh->dev[dd_idx].towrite;
@@ -2184,7 +2179,6 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx, in
                         set_bit(R5_OVERWRITE, &sh->dev[dd_idx].flags);
         }
         spin_unlock_irq(&conf->device_lock);
-        spin_unlock(&sh->lock);
 
         pr_debug("added bi b#%llu to stripe s#%llu, disk %d.\n",
                 (unsigned long long)(*bip)->bi_sector,
@@ -2201,7 +2195,6 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx, in
  overlap:
         set_bit(R5_Overlap, &sh->dev[dd_idx].flags);
         spin_unlock_irq(&conf->device_lock);
-        spin_unlock(&sh->lock);
         return 0;
 }
 
@@ -3023,12 +3016,10 @@ static void handle_stripe5(struct stripe_head *sh)
                  atomic_read(&sh->count), sh->pd_idx, sh->check_state,
                  sh->reconstruct_state);
 
-        spin_lock(&sh->lock);
         if (test_and_clear_bit(STRIPE_SYNC_REQUESTED, &sh->state)) {
                 set_bit(STRIPE_SYNCING, &sh->state);
                 clear_bit(STRIPE_INSYNC, &sh->state);
         }
-        clear_bit(STRIPE_HANDLE, &sh->state);
         clear_bit(STRIPE_DELAYED, &sh->state);
 
         s.syncing = test_bit(STRIPE_SYNCING, &sh->state);
@@ -3037,6 +3028,7 @@ static void handle_stripe5(struct stripe_head *sh)
 
         /* Now to look around and see what can be done */
         rcu_read_lock();
+        spin_lock_irq(&conf->device_lock);
         for (i=disks; i--; ) {
                 mdk_rdev_t *rdev;
 
@@ -3099,6 +3091,7 @@ static void handle_stripe5(struct stripe_head *sh)
                         s.failed_num = i;
                 }
         }
+        spin_unlock_irq(&conf->device_lock);
         rcu_read_unlock();
 
         if (unlikely(blocked_rdev)) {
@@ -3275,7 +3268,6 @@ static void handle_stripe5(struct stripe_head *sh)
                 handle_stripe_expansion(conf, sh, NULL);
 
  unlock:
-        spin_unlock(&sh->lock);
 
         /* wait for this device to become unblocked */
         if (unlikely(blocked_rdev))
@@ -3318,12 +3310,10 @@ static void handle_stripe6(struct stripe_head *sh)
                sh->check_state, sh->reconstruct_state);
         memset(&s, 0, sizeof(s));
 
-        spin_lock(&sh->lock);
         if (test_and_clear_bit(STRIPE_SYNC_REQUESTED, &sh->state)) {
                 set_bit(STRIPE_SYNCING, &sh->state);
                 clear_bit(STRIPE_INSYNC, &sh->state);
         }
-        clear_bit(STRIPE_HANDLE, &sh->state);
         clear_bit(STRIPE_DELAYED, &sh->state);
 
         s.syncing = test_bit(STRIPE_SYNCING, &sh->state);
@@ -3332,6 +3322,7 @@ static void handle_stripe6(struct stripe_head *sh)
         /* Now to look around and see what can be done */
 
         rcu_read_lock();
+        spin_lock_irq(&conf->device_lock);
         for (i=disks; i--; ) {
                 mdk_rdev_t *rdev;
                 dev = &sh->dev[i];
@@ -3395,6 +3386,7 @@ static void handle_stripe6(struct stripe_head *sh)
                         s.failed++;
                 }
         }
+        spin_unlock_irq(&conf->device_lock);
         rcu_read_unlock();
 
         if (unlikely(blocked_rdev)) {
@@ -3580,7 +3572,6 @@ static void handle_stripe6(struct stripe_head *sh)
                 handle_stripe_expansion(conf, sh, &r6s);
 
  unlock:
-        spin_unlock(&sh->lock);
 
         /* wait for this device to become unblocked */
         if (unlikely(blocked_rdev))
@@ -3608,10 +3599,19 @@ static void handle_stripe6(struct stripe_head *sh)
 
 static void handle_stripe(struct stripe_head *sh)
 {
+        clear_bit(STRIPE_HANDLE, &sh->state);
+        if (test_and_set_bit(STRIPE_ACTIVE, &sh->state)) {
+                /* already being handled, ensure it gets handled
+                 * again when current action finishes */
+                set_bit(STRIPE_HANDLE, &sh->state);
+                return;
+        }
+
         if (sh->raid_conf->level == 6)
                 handle_stripe6(sh);
         else
                 handle_stripe5(sh);
+        clear_bit(STRIPE_ACTIVE, &sh->state);
 }
 
 static void raid5_activate_delayed(raid5_conf_t *conf)