[Qemu-devel] [PATCH v2 01/13] iscsi: Use block size as minimum zero/discard alignment

[Eric Blake <eblake@redhat.com>]

If hardware does not advertise a minimum zero/discard
alignment, we still want to guarantee that the block layer
will align requests to our blocks, rather than the arbitrary
512-byte BDRV sector size.

Signed-off-by: Eric Blake <eblake@redhat.com>
---
 block/iscsi.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/block/iscsi.c b/block/iscsi.c
index e7d5f7b..94f9974 100644
--- a/block/iscsi.c
+++ b/block/iscsi.c
@@ -1711,6 +1711,8 @@ static void iscsi_refresh_limits(BlockDriverState *bs, Error **errp)
         }
         bs->bl.discard_alignment =
             sector_limits_lun2qemu(iscsilun->bl.opt_unmap_gran, iscsilun);
+    } else {
+        bs->bl.discard_alignment = iscsilun->block_size >> BDRV_SECTOR_BITS;
     }

     if (iscsilun->bl.max_ws_len < 0xffffffff) {
@@ -1720,6 +1722,9 @@ static void iscsi_refresh_limits(BlockDriverState *bs, Error **errp)
     if (iscsilun->lbp.lbpws) {
         bs->bl.write_zeroes_alignment =
             sector_limits_lun2qemu(iscsilun->bl.opt_unmap_gran, iscsilun);
+    } else {
+        bs->bl.write_zeroes_alignment =
+            iscsilun->block_size >> BDRV_SECTOR_BITS;
     }
     bs->bl.opt_transfer_length =
         sector_limits_lun2qemu(iscsilun->bl.opt_xfer_len, iscsilun);
-- 
2.5.5