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Subject[PATCH, RFC] addjust discard request to be aligned with hwsect size to support SSDs with larger sector size
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The currect blkdev_issue_discard() function assumes 512 sector size.
We have seen some problem when using discard on a SSD that has larger
sector size. The following patch adjusts the starting address and size of
a discard request to be aligned with hwsect size.

Signed-off-by: Jiaying Zhang <jiayingz@google.com>

diff --git a/block/blk-barrier.c b/block/blk-barrier.c
index 6d88544..576b7a1 100644
--- a/block/blk-barrier.c
+++ b/block/blk-barrier.c
@@ -376,14 +376,22 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
DISCARD_BARRIER : DISCARD_NOBARRIER;
struct bio *bio;
struct page *page;
+ int hwsect_shift = blksize_bits(bdev_logical_block_size(bdev)) - 9;
+ int hwsect_mask = (1 << hwsect_shift) - 1;
+ sector_t end_sector;
int ret = 0;

if (!q)
return -ENXIO;

- if (!blk_queue_discard(q))
+ if (!blk_queue_discard(q) || q->limits.max_discard_sectors == 0)
return -EOPNOTSUPP;

+ if (hwsect_shift > 0) {
+ end_sector = (sector + nr_sects) & ~hwsect_mask;
+ sector = (sector + hwsect_mask) & ~hwsect_mask;
+ nr_sects = end_sector - sector;
+ }
while (nr_sects && !ret) {
unsigned int sector_size = q->limits.logical_block_size;
unsigned int max_discard_sectors =

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