[PATCH 3/5] block: add a blk_alloc_discard_bio helper

Christoph Hellwig
2024-03-12T14:45:47Z

Factor out a helper from __blkdev_issue_discard that chews off as much as
possible from a discard range and allocates a bio for it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
block/blk-lib.c | 58 ++++++++++++++++++++++++++-------------------
include/linux/bio.h | 3 +++
2 files changed, 37 insertions(+), 24 deletions(-)

diff --git a/block/blk-lib.c b/block/blk-lib.c
index 50923508a32466..fd97f4dd34e7f4 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -55,36 +55,46 @@ static void await_bio_chain(struct bio *bio)
blk_wait_io(&done);
}

+struct bio *blk_alloc_discard_bio(struct block_device *bdev,
+ sector_t *sector, sector_t *nr_sects, gfp_t gfp_mask)
+{
+ sector_t bio_sects = min(*nr_sects, bio_discard_limit(bdev, *sector));
+ struct bio *bio;
+
+ if (WARN_ON_ONCE(!(gfp_mask & __GFP_RECLAIM)))
+ return NULL;
+ if (!bio_sects)
+ return NULL;
+
+ bio = bio_alloc(bdev, 0, REQ_OP_DISCARD, gfp_mask);
+ bio->bi_iter.bi_sector = *sector;
+ bio->bi_iter.bi_size = bio_sects << SECTOR_SHIFT;
+ *sector += bio_sects;
+ *nr_sects -= bio_sects;
+ /*
+ * 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();
+ return bio;
+}
+
int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
sector_t nr_sects, gfp_t gfp_mask, struct bio **biop)
{
- struct bio *bio = *biop;
-
- while (nr_sects) {
- sector_t req_sects =
- min(nr_sects, bio_discard_limit(bdev, sector));
+ struct bio *bio;

- bio = blk_next_bio(bio, bdev, 0, REQ_OP_DISCARD, gfp_mask);
- bio->bi_iter.bi_sector = sector;
- bio->bi_iter.bi_size = req_sects << 9;
- sector += req_sects;
- nr_sects -= req_sects;
-
- /*
- * 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();
- if (fatal_signal_pending(current)) {
- await_bio_chain(bio);
- return -EINTR;
- }
+ while (!fatal_signal_pending(current)) {
+ bio = blk_alloc_discard_bio(bdev, &sector, &nr_sects, gfp_mask);
+ if (!bio)
+ return 0;
+ *biop = bio_chain_and_submit(*biop, bio);
}

- *biop = bio;
- return 0;
+ if (*biop)
+ await_bio_chain(*biop);
+ return -EINTR;
}
EXPORT_SYMBOL(__blkdev_issue_discard);

diff --git a/include/linux/bio.h b/include/linux/bio.h
index 643d61b7cb82f7..74138c815657fd 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -826,4 +826,7 @@ struct bio *blk_next_bio(struct bio *bio, struct block_device *bdev,
unsigned int nr_pages, blk_opf_t opf, gfp_t gfp);
struct bio *bio_chain_and_submit(struct bio *prev, struct bio *new);

+struct bio *blk_alloc_discard_bio(struct block_device *bdev,
+ sector_t *sector, sector_t *nr_sects, gfp_t gfp_mask);
+
#endif /* __LINUX_BIO_H */
--
2.39.2