md/raid5-cache: exclude reclaiming stripes in reclaim check

stripes which are being reclaimed are still accounted into cached
stripes. The reclaim takes time. r5c_do_reclaim isn't aware of the
stripes and does unnecessary stripe reclaim. In practice, I saw one
stripe is reclaimed one time. This will cause bad IO pattern. Fixing
this by excluding the reclaing stripes in the check.

Cc: Song Liu <songliubraving@fb.com>
Signed-off-by: Shaohua Li <shli@fb.com>

3 files changed, 16 insertions, 2 deletions

diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
index a01f4daeb390..3f307be01b10 100644
--- a/drivers/md/raid5-cache.c
+++ b/drivers/md/raid5-cache.c
@@ -1327,6 +1327,10 @@ static void r5c_flush_stripe(struct r5conf *conf, struct stripe_head *sh)
         atomic_inc(&conf->active_stripes);
         r5c_make_stripe_write_out(sh);
 
+        if (test_bit(STRIPE_R5C_PARTIAL_STRIPE, &sh->state))
+                atomic_inc(&conf->r5c_flushing_partial_stripes);
+        else
+                atomic_inc(&conf->r5c_flushing_full_stripes);
         raid5_release_stripe(sh);
 }
 
@@ -1369,12 +1373,16 @@ static void r5c_do_reclaim(struct r5conf *conf)
         unsigned long flags;
         int total_cached;
         int stripes_to_flush;
+        int flushing_partial, flushing_full;
 
         if (!r5c_is_writeback(log))
                 return;
 
+        flushing_partial = atomic_read(&conf->r5c_flushing_partial_stripes);
+        flushing_full = atomic_read(&conf->r5c_flushing_full_stripes);
         total_cached = atomic_read(&conf->r5c_cached_partial_stripes) +
-                atomic_read(&conf->r5c_cached_full_stripes);
+                atomic_read(&conf->r5c_cached_full_stripes) -
+                flushing_full - flushing_partial;
 
         if (total_cached > conf->min_nr_stripes * 3 / 4 ||
             atomic_read(&conf->empty_inactive_list_nr) > 0)
@@ -1384,7 +1392,7 @@ static void r5c_do_reclaim(struct r5conf *conf)
                  */
                 stripes_to_flush = R5C_RECLAIM_STRIPE_GROUP;
         else if (total_cached > conf->min_nr_stripes * 1 / 2 ||
-                 atomic_read(&conf->r5c_cached_full_stripes) >
+                 atomic_read(&conf->r5c_cached_full_stripes) - flushing_full >
                  R5C_FULL_STRIPE_FLUSH_BATCH)
                 /*
                  * if stripe cache pressure moderate, or if there is many full
@@ -2601,11 +2609,13 @@ void r5c_finish_stripe_write_out(struct r5conf *conf,
 
         if (test_and_clear_bit(STRIPE_R5C_PARTIAL_STRIPE, &sh->state)) {
                 BUG_ON(atomic_read(&conf->r5c_cached_partial_stripes) == 0);
+                atomic_dec(&conf->r5c_flushing_partial_stripes);
                 atomic_dec(&conf->r5c_cached_partial_stripes);
         }
 
         if (test_and_clear_bit(STRIPE_R5C_FULL_STRIPE, &sh->state)) {
                 BUG_ON(atomic_read(&conf->r5c_cached_full_stripes) == 0);
+                atomic_dec(&conf->r5c_flushing_full_stripes);
                 atomic_dec(&conf->r5c_cached_full_stripes);
         }
 }
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index b0d1345c832c..e2fa88fc6a1b 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -6838,6 +6838,8 @@ static struct r5conf *setup_conf(struct mddev *mddev)
         INIT_LIST_HEAD(&conf->r5c_full_stripe_list);
         atomic_set(&conf->r5c_cached_partial_stripes, 0);
         INIT_LIST_HEAD(&conf->r5c_partial_stripe_list);
+        atomic_set(&conf->r5c_flushing_full_stripes, 0);
+        atomic_set(&conf->r5c_flushing_partial_stripes, 0);
 
         conf->level = mddev->new_level;
         conf->chunk_sectors = mddev->new_chunk_sectors;
diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index c0687df5ba06..4bb27b97bf6b 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -663,6 +663,8 @@ struct r5conf {
         struct list_head        r5c_full_stripe_list;
         atomic_t                r5c_cached_partial_stripes;
         struct list_head        r5c_partial_stripe_list;
+        atomic_t                r5c_flushing_full_stripes;
+        atomic_t                r5c_flushing_partial_stripes;
 
         atomic_t                empty_inactive_list_nr;
         struct llist_head       released_stripes;