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authorMing Lei <ming.lei@redhat.com>2022-04-12 11:56:15 +0300
committerMike Snitzer <snitzer@kernel.org>2022-05-06 00:31:36 +0300
commit0f14d60a023cc4fe68758e0fcdc0ce82a82dde7d (patch)
treed343453a1de1088e8f8f1b53e0b975b1c0065af0 /drivers/md
parent2e803cd99ba8b7a84be155c1d5ee28d363fdbe44 (diff)
downloadlinux-0f14d60a023cc4fe68758e0fcdc0ce82a82dde7d.tar.xz
dm: improve dm_io reference counting
Currently each dm_io's reference counter is grabbed before calling __map_bio(), this way isn't efficient since we can move this grabbing to initialization time inside alloc_io(). Meantime it becomes typical async io reference counter model: one is for submission side, the other is for completion side, and the io won't be completed until both sides are done. Signed-off-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/dm.c53
1 files changed, 39 insertions, 14 deletions
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 7cae8235fbe1..6bc2dc8071fc 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -590,7 +590,9 @@ static struct dm_io *alloc_io(struct mapped_device *md, struct bio *bio)
io = container_of(tio, struct dm_io, tio);
io->magic = DM_IO_MAGIC;
io->status = BLK_STS_OK;
- atomic_set(&io->io_count, 1);
+
+ /* one ref is for submission, the other is for completion */
+ atomic_set(&io->io_count, 2);
this_cpu_inc(*md->pending_io);
io->orig_bio = bio;
io->md = md;
@@ -955,11 +957,6 @@ static void dm_io_complete(struct dm_io *io)
}
}
-static void dm_io_inc_pending(struct dm_io *io)
-{
- atomic_inc(&io->io_count);
-}
-
/*
* Decrements the number of outstanding ios that a bio has been
* cloned into, completing the original io if necc.
@@ -1316,7 +1313,6 @@ static void __map_bio(struct bio *clone)
/*
* Map the clone.
*/
- dm_io_inc_pending(io);
tio->old_sector = clone->bi_iter.bi_sector;
if (static_branch_unlikely(&swap_bios_enabled) &&
@@ -1426,11 +1422,12 @@ static void alloc_multiple_bios(struct bio_list *blist, struct clone_info *ci,
}
}
-static void __send_duplicate_bios(struct clone_info *ci, struct dm_target *ti,
+static int __send_duplicate_bios(struct clone_info *ci, struct dm_target *ti,
unsigned num_bios, unsigned *len)
{
struct bio_list blist = BIO_EMPTY_LIST;
struct bio *clone;
+ int ret = 0;
switch (num_bios) {
case 0:
@@ -1440,6 +1437,7 @@ static void __send_duplicate_bios(struct clone_info *ci, struct dm_target *ti,
setup_split_accounting(ci, *len);
clone = alloc_tio(ci, ti, 0, len, GFP_NOIO);
__map_bio(clone);
+ ret = 1;
break;
default:
/* dm_accept_partial_bio() is not supported with shared tio->len_ptr */
@@ -1447,9 +1445,12 @@ static void __send_duplicate_bios(struct clone_info *ci, struct dm_target *ti,
while ((clone = bio_list_pop(&blist))) {
dm_tio_set_flag(clone_to_tio(clone), DM_TIO_IS_DUPLICATE_BIO);
__map_bio(clone);
+ ret += 1;
}
break;
}
+
+ return ret;
}
static void __send_empty_flush(struct clone_info *ci)
@@ -1470,8 +1471,19 @@ static void __send_empty_flush(struct clone_info *ci)
ci->sector_count = 0;
ci->io->tio.clone.bi_iter.bi_size = 0;
- while ((ti = dm_table_get_target(ci->map, target_nr++)))
- __send_duplicate_bios(ci, ti, ti->num_flush_bios, NULL);
+ while ((ti = dm_table_get_target(ci->map, target_nr++))) {
+ int bios;
+
+ atomic_add(ti->num_flush_bios, &ci->io->io_count);
+ bios = __send_duplicate_bios(ci, ti, ti->num_flush_bios, NULL);
+ atomic_sub(ti->num_flush_bios - bios, &ci->io->io_count);
+ }
+
+ /*
+ * alloc_io() takes one extra reference for submission, so the
+ * reference won't reach 0 without the following subtraction
+ */
+ atomic_sub(1, &ci->io->io_count);
bio_uninit(ci->bio);
}
@@ -1480,11 +1492,18 @@ static void __send_changing_extent_only(struct clone_info *ci, struct dm_target
unsigned num_bios)
{
unsigned len;
+ int bios;
len = min_t(sector_t, ci->sector_count,
max_io_len_target_boundary(ti, dm_target_offset(ti, ci->sector)));
- __send_duplicate_bios(ci, ti, num_bios, &len);
+ atomic_add(num_bios, &ci->io->io_count);
+ bios = __send_duplicate_bios(ci, ti, num_bios, &len);
+ /*
+ * alloc_io() takes one extra reference for submission, so the
+ * reference won't reach 0 without the following (+1) subtraction
+ */
+ atomic_sub(num_bios - bios + 1, &ci->io->io_count);
ci->sector += len;
ci->sector_count -= len;
@@ -1669,9 +1688,15 @@ out:
* Add every dm_io instance into the hlist_head which is stored in
* bio->bi_private, so that dm_poll_bio can poll them all.
*/
- if (error || !ci.submit_as_polled)
- dm_io_dec_pending(ci.io, error);
- else
+ if (error || !ci.submit_as_polled) {
+ /*
+ * In case of submission failure, the extra reference for
+ * submitting io isn't consumed yet
+ */
+ if (error)
+ atomic_dec(&io->io_count);
+ dm_io_dec_pending(io, error);
+ } else
dm_queue_poll_io(bio, io);
}