From: Ming Lin <min...@ssi.samsung.com>
In commit b49a087("block: remove split code in
blkdev_issue_{discard,write_same}"), discard_granularity and alignment
checks were removed. Ideally, with bio late splitting, the upper layers
shouldn't need to depend on device's limits.
Christoph reported a discard regression on the HGST Ultrastar SN100 NVMe
device when mkfs.xfs. We have not found the root cause yet.
This patch re-adds discard_granularity and alignment checks by reverting
the related changes in commit b49a087. The good thing is now we can
remove the 2G discard size cap and just use UINT_MAX to avoid bi_size
overflow.
Reviewed-by: Christoph Hellwig <h...@lst.de>
Tested-by: Christoph Hellwig <h...@lst.de>
Signed-off-by: Ming Lin <min...@ssi.samsung.com>
---
block/blk-lib.c | 31 ++++++++++++++++++++++---------
1 file changed, 22 insertions(+), 9 deletions(-)
diff --git a/block/blk-lib.c b/block/blk-lib.c
index bd40292..9ebf653 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -26,13 +26,6 @@ static void bio_batch_end_io(struct bio *bio)
bio_put(bio);
}
-/*
- * Ensure that max discard sectors doesn't overflow bi_size and hopefully
- * it is of the proper granularity as long as the granularity is a power
- * of two.
- */
-#define MAX_BIO_SECTORS ((1U << 31) >> 9)
-
/**
* blkdev_issue_discard - queue a discard
* @bdev: blockdev to issue discard for
@@ -50,6 +43,8 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t
sector,
DECLARE_COMPLETION_ONSTACK(wait);
struct request_queue *q = bdev_get_queue(bdev);
int type = REQ_WRITE | REQ_DISCARD;
+ unsigned int granularity;
+ int alignment;
struct bio_batch bb;
struct bio *bio;
int ret = 0;
@@ -61,6 +56,10 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t
sector,
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;
+
if (flags & BLKDEV_DISCARD_SECURE) {
if (!blk_queue_secdiscard(q))
return -EOPNOTSUPP;
@@ -74,7 +73,7 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t
sector,
blk_start_plug(&plug);
while (nr_sects) {
unsigned int req_sects;
- sector_t end_sect;
+ sector_t end_sect, tmp;
bio = bio_alloc(gfp_mask, 1);
if (!bio) {
@@ -82,8 +81,22 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t
sector,
break;
}
- req_sects = min_t(sector_t, nr_sects, MAX_BIO_SECTORS);
+ /* Make sure bi_size doesn't overflow */
+ req_sects = min_t(sector_t, nr_sects, UINT_MAX >> 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;
+ }
bio->bi_iter.bi_sector = sector;
bio->bi_end_io = bio_batch_end_io;
--
1.9.1
--
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