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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>
This commit is contained in:
Mike Snitzer 2015-08-18 10:31:09 -04:00
parent 76c44f6d80
commit 84f8bd86cc
1 changed files with 15 additions and 74 deletions
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73
drivers/md/dm-thin.c
View File

@ -332,9 +332,6 @@ struct thin_c {
*
* 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 @@ static int __blkdev_issue_discard_async(struct block_device *bdev, sector_t sect
{
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) {
ret = -ENOMEM;
break;
}
req_sects = min_t(sector_t, nr_sects, max_discard_sectors);
/*
* 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;
}
if (!bio)
return -ENOMEM;
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;
bio->bi_iter.bi_size = nr_sects << 9;
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 @@ static void process_discard_cell_no_passdown(struct thin_c *tc,
}
/*
* 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)
{