Split discard requests as follows:
* If the start sector is not aligned, an initial write request up
to the first aligned sector.
* A discard request from the first aligned sector in the range up
to the last aligned sector in the discarded range.
* If the end sector is not aligned, a final write request from the
last aligned sector up to the end.
Note: if the start and/or end sectors are not aligned and if the
range is small enough the discard request will be submitted with
bi_size == 0.
Signed-off-by: Bart Van Assche <bart.vanassche@xxxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Mike Snitzer <snitzer@xxxxxxxxxx>
Cc: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Cc: Dmitry Monakhov <dmonakhov@xxxxxxxxxx>
---
block/blk-lib.c | 4 ++--
block/blk-merge.c | 55 ++++++++++++++++++++++++++++++-------------------------
block/blk.h | 3 +++
3 files changed, 35 insertions(+), 27 deletions(-)
diff --git a/block/blk-lib.c b/block/blk-lib.c
index 1a60b3f..da0a744 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -30,7 +30,7 @@ static void bio_batch_end_io(struct bio *bio)
* Return the largest number that is less than or equal to @s and for which
* the remainder of the division by @granularity is @alignment.
*/
-static sector_t blk_round_sect_down(sector_t s, u32 granularity, u32 alignment)
+sector_t blk_round_sect_down(sector_t s, u32 granularity, u32 alignment)
{
sector_t tmp = s, res = s;
u32 remainder;
@@ -219,7 +219,7 @@ int blkdev_issue_write_same(struct block_device *bdev, sector_t sector,
}
EXPORT_SYMBOL(blkdev_issue_write_same);
-static void bio_add_zero_pages(struct bio *bio, sector_t nr_sects)
+void bio_add_zero_pages(struct bio *bio, sector_t nr_sects)
{
unsigned sz;
int ret;
diff --git a/block/blk-merge.c b/block/blk-merge.c
index e01405a..2ce5a78 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -14,42 +14,47 @@ static struct bio *blk_bio_discard_split(struct request_queue *q,
struct bio_set *bs,
unsigned *nsegs)
{
+ struct bio *wr;
unsigned int max_discard_sectors, granularity;
int alignment;
- sector_t tmp;
- unsigned split_sectors;
+ sector_t start, start_r, end, end_r, skip;
*nsegs = 1;
/* Zero-sector (unknown) and one-sector granularities are the same. */
granularity = max(q->limits.discard_granularity >> 9, 1U);
-
+ alignment = (q->limits.discard_alignment >> 9) % granularity;
max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >> 9);
- max_discard_sectors -= max_discard_sectors % granularity;
-
- if (unlikely(!max_discard_sectors)) {
- /* XXX: warn */
- return NULL;
- }
-
- if (bio_sectors(bio) <= max_discard_sectors)
- return NULL;
-
- split_sectors = max_discard_sectors;
+ WARN_ON_ONCE(max_discard_sectors == 0);
/*
- * If the next starting sector would be misaligned, stop the discard at
- * the previous aligned sector.
+ * If the start or end sector are misaligned, issue a write same
+ * same request if the discard_zeroes_data flag has been set.
*/
- alignment = (q->limits.discard_alignment >> 9) % granularity;
-
- tmp = bio->bi_iter.bi_sector + split_sectors - alignment;
- tmp = sector_div(tmp, granularity);
-
- if (split_sectors > tmp)
- split_sectors -= tmp;
-
- return bio_split(bio, split_sectors, GFP_NOIO, bs);
+ start = bio->bi_iter.bi_sector;
+ start_r = blk_round_sect_down(start, granularity, alignment);
+ end = start + min(max_discard_sectors, bio_sectors(bio));
+ end_r = blk_round_sect_down(end, granularity, alignment);
+ if (start == start_r && start < end_r) {
+ if (end == end_r && bio_sectors(bio) == end_r - start)
+ return NULL;
+ return bio_split(bio, end_r - start, GFP_NOIO, bs);
+ } else if (q->limits.discard_zeroes_data) {
+ end = min(end, start_r + granularity);
+ wr = bio_alloc_bioset(GFP_NOIO, end - start, bs);
+ if (WARN_ON_ONCE(!wr))
+ return NULL;
+ wr->bi_rw = REQ_WRITE;
+ wr->bi_iter.bi_sector = start;
+ wr->bi_bdev = bio->bi_bdev;
+ bio_add_zero_pages(wr, end - start);
+ bio_advance(bio, wr->bi_iter.bi_size);
+ return wr;
+ } else {
+ skip = (min(start_r + granularity, end) - start) << 9;
+ bio_advance(bio, skip);
+ return NULL;
+ }
}
static struct bio *blk_bio_write_same_split(struct request_queue *q,
diff --git a/block/blk.h b/block/blk.h
index c43926d..e043c34 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -36,6 +36,9 @@ extern struct kmem_cache *request_cachep;
extern struct kobj_type blk_queue_ktype;
extern struct ida blk_queue_ida;
+sector_t blk_round_sect_down(sector_t s, u32 granularity, u32 alignment);
+void bio_add_zero_pages(struct bio *bio, sector_t nr_sects);
+
static inline struct blk_flush_queue *blk_get_flush_queue(
struct request_queue *q, struct blk_mq_ctx *ctx)
{
--
2.1.4
--
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