raid5: add a new flag to track if a stripe can be batched

A freshly new stripe with write request can be batched. Any time the stripe is
handled or new read is queued, the flag will be cleared.

Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: NeilBrown <neilb@suse.de>

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 7fb510e..49b0f23 100644 (file)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -555,6 +555,7 @@ retry:
                goto retry;
        insert_hash(conf, sh);
        sh->cpu = smp_processor_id();
+       set_bit(STRIPE_BATCH_READY, &sh->state);
 }
 
 static struct stripe_head *__find_stripe(struct r5conf *conf, sector_t sector,
@@ -2645,7 +2646,8 @@ schedule_reconstruction(struct stripe_head *sh, struct stripe_head_state *s,
  * toread/towrite point to the first in a chain.
  * The bi_next chain must be in order.
  */
-static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx, int forwrite)
+static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx,
+                         int forwrite, int previous)
 {
        struct bio **bip;
        struct r5conf *conf = sh->raid_conf;
@@ -2678,6 +2680,9 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx, in
        if (*bip && (*bip)->bi_iter.bi_sector < bio_end_sector(bi))
                goto overlap;
 
+       if (!forwrite || previous)
+               clear_bit(STRIPE_BATCH_READY, &sh->state);
+
        BUG_ON(*bip && bi->bi_next && (*bip) != bi->bi_next);
        if (*bip)
                bi->bi_next = *bip;
@@ -3824,6 +3829,7 @@ static void handle_stripe(struct stripe_head *sh)
                return;
        }
 
+       clear_bit(STRIPE_BATCH_READY, &sh->state);
        if (test_bit(STRIPE_SYNC_REQUESTED, &sh->state)) {
                spin_lock(&sh->stripe_lock);
                /* Cannot process 'sync' concurrently with 'discard' */
@@ -4793,7 +4799,7 @@ static void make_request(struct mddev *mddev, struct bio * bi)
                        }
 
                        if (test_bit(STRIPE_EXPANDING, &sh->state) ||
-                           !add_stripe_bio(sh, bi, dd_idx, rw)) {
+                           !add_stripe_bio(sh, bi, dd_idx, rw, previous)) {
                                /* Stripe is busy expanding or
                                 * add failed due to overlap.  Flush everything
                                 * and wait a while
@@ -5206,7 +5212,7 @@ static int  retry_aligned_read(struct r5conf *conf, struct bio *raid_bio)
                        return handled;
                }
 
-               if (!add_stripe_bio(sh, raid_bio, dd_idx, 0)) {
+               if (!add_stripe_bio(sh, raid_bio, dd_idx, 0, 0)) {
                        release_stripe(sh);
                        raid5_set_bi_processed_stripes(raid_bio, scnt);
                        conf->retry_read_aligned = raid_bio;

diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index 1d0f241..37644e3 100644 (file)
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -327,6 +327,7 @@ enum {
        STRIPE_ON_UNPLUG_LIST,
        STRIPE_DISCARD,
        STRIPE_ON_RELEASE_LIST,
+       STRIPE_BATCH_READY,
 };
 
 /*