dm thin: optimize async discard submission
__blkdev_issue_discard_async() doesn't need to worry about further
splitting because the upper layer blkdev_issue_discard() will have
already handled splitting bios such that the bi_size isn't
overflowed.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Joe Thornber <ejt@redhat.com>
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index d2bbe8c..49e358a 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -332,9 +332,6 @@
*
* Description:
* Asynchronously issue a discard request for the sectors in question.
- * NOTE: this variant of blk-core's blkdev_issue_discard() is a stop-gap
- * that is being kept local to DM thinp until the block changes to allow
- * late bio splitting land upstream.
*/
static int __blkdev_issue_discard_async(struct block_device *bdev, sector_t sector,
sector_t nr_sects, gfp_t gfp_mask, unsigned long flags,
@@ -342,91 +339,36 @@
{
struct request_queue *q = bdev_get_queue(bdev);
int type = REQ_WRITE | REQ_DISCARD;
- unsigned int max_discard_sectors, granularity;
- int alignment;
struct bio *bio;
- int ret = 0;
- struct blk_plug plug;
- if (!q)
+ if (!q || !nr_sects)
return -ENXIO;
if (!blk_queue_discard(q))
return -EOPNOTSUPP;
- /* Zero-sector (unknown) and one-sector granularities are the same. */
- granularity = max(q->limits.discard_granularity >> 9, 1U);
- alignment = (bdev_discard_alignment(bdev) >> 9) % granularity;
-
- /*
- * Ensure that max_discard_sectors is of the proper
- * granularity, so that requests stay aligned after a split.
- */
- max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >> 9);
- max_discard_sectors -= max_discard_sectors % granularity;
- if (unlikely(!max_discard_sectors)) {
- /* Avoid infinite loop below. Being cautious never hurts. */
- return -EOPNOTSUPP;
- }
-
if (flags & BLKDEV_DISCARD_SECURE) {
if (!blk_queue_secdiscard(q))
return -EOPNOTSUPP;
type |= REQ_SECURE;
}
- blk_start_plug(&plug);
- while (nr_sects) {
- unsigned int req_sects;
- sector_t end_sect, tmp;
+ /*
+ * Required bio_put occurs in bio_endio thanks to bio_chain below
+ */
+ bio = bio_alloc(gfp_mask, 1);
+ if (!bio)
+ return -ENOMEM;
- /*
- * Required bio_put occurs in bio_endio thanks to bio_chain below
- */
- bio = bio_alloc(gfp_mask, 1);
- if (!bio) {
- ret = -ENOMEM;
- break;
- }
+ bio_chain(bio, parent_bio);
- req_sects = min_t(sector_t, nr_sects, max_discard_sectors);
+ bio->bi_iter.bi_sector = sector;
+ bio->bi_bdev = bdev;
+ bio->bi_iter.bi_size = nr_sects << 9;
- /*
- * If splitting a request, and the next starting sector would be
- * misaligned, stop the discard at the previous aligned sector.
- */
- end_sect = sector + req_sects;
- tmp = end_sect;
- if (req_sects < nr_sects &&
- sector_div(tmp, granularity) != alignment) {
- end_sect = end_sect - alignment;
- sector_div(end_sect, granularity);
- end_sect = end_sect * granularity + alignment;
- req_sects = end_sect - sector;
- }
+ submit_bio(type, bio);
- bio_chain(bio, parent_bio);
-
- bio->bi_iter.bi_sector = sector;
- bio->bi_bdev = bdev;
-
- bio->bi_iter.bi_size = req_sects << 9;
- nr_sects -= req_sects;
- sector = end_sect;
-
- submit_bio(type, bio);
-
- /*
- * We can loop for a long time in here, if someone does
- * full device discards (like mkfs). Be nice and allow
- * us to schedule out to avoid softlocking if preempt
- * is disabled.
- */
- cond_resched();
- }
- blk_finish_plug(&plug);
-
- return ret;
+ return 0;
}
static bool block_size_is_power_of_two(struct pool *pool)
@@ -1539,9 +1481,8 @@
}
/*
- * FIXME: DM local hack to defer parent bios's end_io until we
- * _know_ all chained sub range discard bios have completed.
- * Will go away once late bio splitting lands upstream!
+ * __bio_inc_remaining() is used to defer parent bios's end_io until
+ * we _know_ all chained sub range discard bios have completed.
*/
static inline void __bio_inc_remaining(struct bio *bio)
{