The discard_alignment queue limit is named a bit misleading means the
offset into the block device at which the discard granularity starts.
On the other hand the discard_sector_alignment from the virtio 1.1 looks
similar to what Linux uses as discard granularity (even if not very well
described):
"discard_sector_alignment can be used by OS when splitting a request
based on alignment. "
And at least qemu does set it to the discard granularity.
So stop setting the discard_alignment and use the virtio
discard_sector_alignment to set the discard granularity.
Fixes: 1f23816b8eb8 ("virtio_blk: add discard and write zeroes support")
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
drivers/block/virtio_blk.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 6ccf15253dee1..d624cc8eddc3c 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -867,11 +867,12 @@ static int virtblk_probe(struct virtio_device *vdev)
blk_queue_io_opt(q, blk_size * opt_io_size);
if (virtio_has_feature(vdev, VIRTIO_BLK_F_DISCARD)) {
- q->limits.discard_granularity = blk_size;
-
virtio_cread(vdev, struct virtio_blk_config,
discard_sector_alignment, &v);
- q->limits.discard_alignment = v ? v << SECTOR_SHIFT : 0;
+ if (v)
+ q->limits.discard_granularity = v << SECTOR_SHIFT;
+ else
+ q->limits.discard_granularity = blk_size;
virtio_cread(vdev, struct virtio_blk_config,
max_discard_sectors, &v);
--
2.30.2
--
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