[PATCH 1/2] block: add BLKDEV_DISCARD_SYNC flag

Jens Axboe
2018-04-30T15:32:51Z

By default, blkdev_issue_discard() will build potentially big
bio chains, even when the discard size has been limited by the
user. Add a BLKDEV_DISCARD_SYNC flag, telling blkdev_issue_discard()
to wait for completion of each discard.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
block/blk-lib.c | 33 ++++++++++++++++++++++++---------
include/linux/blkdev.h | 1 +
2 files changed, 25 insertions(+), 9 deletions(-)

diff --git a/block/blk-lib.c b/block/blk-lib.c
index a676084d4740..1d0263c13c9c 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -11,13 +11,18 @@
#include "blk.h"

static struct bio *next_bio(struct bio *bio, unsigned int nr_pages,
- gfp_t gfp)
+ gfp_t gfp, bool do_sync)
{
struct bio *new = bio_alloc(gfp, nr_pages);

if (bio) {
- bio_chain(bio, new);
- submit_bio(bio);
+ if (do_sync) {
+ submit_bio_wait(bio);
+ bio_put(bio);
+ } else {
+ bio_chain(bio, new);
+ submit_bio(bio);
+ }
}

return new;
@@ -30,7 +35,7 @@ int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
struct request_queue *q = bdev_get_queue(bdev);
struct bio *bio = *biop;
unsigned int granularity;
- unsigned int op;
+ unsigned int op, max_sectors;
int alignment;
sector_t bs_mask;

@@ -58,12 +63,17 @@ int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
granularity = max(q->limits.discard_granularity >> 9, 1U);
alignment = (bdev_discard_alignment(bdev) >> 9) % granularity;

+ if (flags & BLKDEV_DISCARD_SYNC)
+ max_sectors = q->limits.max_discard_sectors;
+ else
+ max_sectors = UINT_MAX >> 9;
+
while (nr_sects) {
unsigned int req_sects;
sector_t end_sect, tmp;

/* Make sure bi_size doesn't overflow */
- req_sects = min_t(sector_t, nr_sects, UINT_MAX >> 9);
+ req_sects = min_t(sector_t, nr_sects, max_sectors);

/**
* If splitting a request, and the next starting sector would be
@@ -79,7 +89,7 @@ int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
req_sects = end_sect - sector;
}

- bio = next_bio(bio, 0, gfp_mask);
+ bio = next_bio(bio, 0, gfp_mask, flags & BLKDEV_DISCARD_SYNC);
bio->bi_iter.bi_sector = sector;
bio_set_dev(bio, bdev);
bio_set_op_attrs(bio, op, 0);
@@ -97,6 +107,11 @@ int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
cond_resched();
}

+ if (bio && (flags & BLKDEV_DISCARD_SYNC)) {
+ submit_bio_wait(bio);
+ bio_put(bio);
+ bio = NULL;
+ }
*biop = bio;
return 0;
}
@@ -173,7 +188,7 @@ static int __blkdev_issue_write_same(struct block_device *bdev, sector_t sector,
max_write_same_sectors = UINT_MAX >> 9;

while (nr_sects) {
- bio = next_bio(bio, 1, gfp_mask);
+ bio = next_bio(bio, 1, gfp_mask, false);
bio->bi_iter.bi_sector = sector;
bio_set_dev(bio, bdev);
bio->bi_vcnt = 1;
@@ -249,7 +264,7 @@ static int __blkdev_issue_write_zeroes(struct block_device *bdev,
return -EOPNOTSUPP;

while (nr_sects) {
- bio = next_bio(bio, 0, gfp_mask);
+ bio = next_bio(bio, 0, gfp_mask, false);
bio->bi_iter.bi_sector = sector;
bio_set_dev(bio, bdev);
bio->bi_opf = REQ_OP_WRITE_ZEROES;
@@ -301,7 +316,7 @@ static int __blkdev_issue_zero_pages(struct block_device *bdev,

while (nr_sects != 0) {
bio = next_bio(bio, __blkdev_sectors_to_bio_pages(nr_sects),
- gfp_mask);
+ gfp_mask, false);
bio->bi_iter.bi_sector = sector;
bio_set_dev(bio, bdev);
bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 5c4eee043191..e90388004029 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1396,6 +1396,7 @@ extern int blkdev_issue_write_same(struct block_device *bdev, sector_t sector,
sector_t nr_sects, gfp_t gfp_mask, struct page *page);

#define BLKDEV_DISCARD_SECURE (1 << 0) /* issue a secure erase */
+#define BLKDEV_DISCARD_SYNC (1 << 1)

extern int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
sector_t nr_sects, gfp_t gfp_mask, unsigned long flags);
--
2.7.4