dm: remove the pending IO accounting

Remove the "pending" atomic counters, that duplicate block-core's
in_flight counters, and update md_in_flight() to look at percpu
in_flight counters.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/md/dm-core.h b/drivers/md/dm-core.h
index 224d445..6fe883f 100644 (file)
--- a/drivers/md/dm-core.h
+++ b/drivers/md/dm-core.h
@@ -65,7 +65,6 @@ struct mapped_device {
         */
        struct work_struct work;
        wait_queue_head_t wait;
-       atomic_t pending[2];
        spinlock_t deferred_lock;
        struct bio_list deferred;
 
@@ -119,7 +118,6 @@ struct mapped_device {
        struct srcu_struct io_barrier;
 };
 
-int md_in_flight(struct mapped_device *md);
 void disable_write_same(struct mapped_device *md);
 void disable_write_zeroes(struct mapped_device *md);
 

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 33100e5..70568f8 100644 (file)
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -646,25 +646,30 @@ static void free_tio(struct dm_target_io *tio)
        bio_put(&tio->clone);
 }
 
-int md_in_flight(struct mapped_device *md)
+static bool md_in_flight(struct mapped_device *md)
 {
-       return atomic_read(&md->pending[READ]) +
-              atomic_read(&md->pending[WRITE]);
+       int cpu;
+       struct hd_struct *part = &dm_disk(md)->part0;
+
+       for_each_possible_cpu(cpu) {
+               if (part_stat_local_read_cpu(part, in_flight[0], cpu) ||
+                   part_stat_local_read_cpu(part, in_flight[1], cpu))
+                       return true;
+       }
+
+       return false;
 }
 
 static void start_io_acct(struct dm_io *io)
 {
        struct mapped_device *md = io->md;
        struct bio *bio = io->orig_bio;
-       int rw = bio_data_dir(bio);
 
        io->start_time = jiffies;
 
        generic_start_io_acct(md->queue, bio_op(bio), bio_sectors(bio),
                              &dm_disk(md)->part0);
 
-       atomic_inc(&md->pending[rw]);
-
        if (unlikely(dm_stats_used(&md->stats)))
                dm_stats_account_io(&md->stats, bio_data_dir(bio),
                                    bio->bi_iter.bi_sector, bio_sectors(bio),
@@ -676,8 +681,6 @@ static void end_io_acct(struct dm_io *io)
        struct mapped_device *md = io->md;
        struct bio *bio = io->orig_bio;
        unsigned long duration = jiffies - io->start_time;
-       int pending;
-       int rw = bio_data_dir(bio);
 
        generic_end_io_acct(md->queue, bio_op(bio), &dm_disk(md)->part0,
                            io->start_time);
@@ -687,16 +690,11 @@ static void end_io_acct(struct dm_io *io)
                                    bio->bi_iter.bi_sector, bio_sectors(bio),
                                    true, duration, &io->stats_aux);
 
-       /*
-        * After this is decremented the bio must not be touched if it is
-        * a flush.
-        */
-       pending = atomic_dec_return(&md->pending[rw]);
-       pending += atomic_read(&md->pending[rw^0x1]);
-
        /* nudge anyone waiting on suspend queue */
-       if (!pending)
-               wake_up(&md->wait);
+       if (unlikely(waitqueue_active(&md->wait))) {
+               if (!md_in_flight(md))
+                       wake_up(&md->wait);
+       }
 }
 
 /*
@@ -1915,8 +1913,6 @@ static struct mapped_device *alloc_dev(int minor)
        if (!md->disk)
                goto bad;
 
-       atomic_set(&md->pending[0], 0);
-       atomic_set(&md->pending[1], 0);
        init_waitqueue_head(&md->wait);
        INIT_WORK(&md->work, dm_wq_work);
        init_waitqueue_head(&md->eventq);