dm: support turning off block-core's io stats accounting

Commit bc58ba9468d9 ("block: add sysfs file for controlling io stats
accounting") allowed users to turn off disk stat accounting completely
by checking if queue flag QUEUE_FLAG_IO_STAT is set. In dm, this flag
is neither set nor checked: so block-core's io stats are continuously
counted and cannot be turned off.

Add support for turning off block-core's io stats accounting for dm.
Set QUEUE_FLAG_IO_STAT for dm's request_queue. If QUEUE_FLAG_IO_STAT
is set when an io starts, record the need for block core's io stats by
setting the DM_IO_BLK_STAT dm_io flag to avoid io stats being disabled
in the middle of the io.

DM statistics (dm-stats) is independent of block-core's io stats and
remains unchanged.

Signed-off-by: Li Nan <linan122@huawei.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

diff --git a/drivers/md/dm-core.h b/drivers/md/dm-core.h
index ce913ad..0d93661 100644 (file)
--- a/drivers/md/dm-core.h
+++ b/drivers/md/dm-core.h
@@ -306,7 +306,8 @@ struct dm_io {
  */
 enum {
        DM_IO_ACCOUNTED,
-       DM_IO_WAS_SPLIT
+       DM_IO_WAS_SPLIT,
+       DM_IO_BLK_STAT
 };
 
 static inline bool dm_io_flagged(struct dm_io *io, unsigned int bit)

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index ca2dc07..c8b3d68 100644 (file)
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -511,11 +511,14 @@ static void dm_io_acct(struct dm_io *io, bool end)
        else
                sectors = io->sectors;
 
-       if (!end)
-               bdev_start_io_acct(bio->bi_bdev, bio_op(bio), start_time);
-       else
-               bdev_end_io_acct(bio->bi_bdev, bio_op(bio), sectors,
-                                start_time);
+       if (dm_io_flagged(io, DM_IO_BLK_STAT)) {
+               if (!end)
+                       bdev_start_io_acct(bio->bi_bdev, bio_op(bio),
+                                          start_time);
+               else
+                       bdev_end_io_acct(bio->bi_bdev, bio_op(bio),
+                                        sectors, start_time);
+       }
 
        if (static_branch_unlikely(&stats_enabled) &&
            unlikely(dm_stats_used(&md->stats))) {
@@ -592,6 +595,8 @@ static struct dm_io *alloc_io(struct mapped_device *md, struct bio *bio)
        spin_lock_init(&io->lock);
        io->start_time = jiffies;
        io->flags = 0;
+       if (blk_queue_io_stat(md->queue))
+               dm_io_set_flag(io, DM_IO_BLK_STAT);
 
        if (static_branch_unlikely(&stats_enabled))
                dm_stats_record_start(&md->stats, &io->stats_aux);
@@ -2341,6 +2346,7 @@ int dm_setup_md_queue(struct mapped_device *md, struct dm_table *t)
                break;
        case DM_TYPE_BIO_BASED:
        case DM_TYPE_DAX_BIO_BASED:
+               blk_queue_flag_set(QUEUE_FLAG_IO_STAT, md->queue);
                break;
        case DM_TYPE_NONE:
                WARN_ON_ONCE(true);