Thread (7 messages) 7 messages, 3 authors, 2022-11-02

Re: [bisected] RAID1 direct IO redirecting sector loop since 6.0

From: Keith Busch <kbusch@kernel.org>
Date: 2022-11-01 21:21:32
Also in: linux-block, lkml

On Tue, Nov 01, 2022 at 11:51:44PM +0300, Dmitrii Tcvetkov wrote:
It also doesn't reproduce with 4096 sector loop:
# lsblk -t -a                                                                           
NAME                 ALIGNMENT MIN-IO OPT-IO PHY-SEC LOG-SEC ROTA SCHED RQ-SIZE  RA WSAME
loop0                        0   4096      0    4096    4096    0 none      128 128    0B
└─md2                        0   4096      0    4096    4096    0           128 128    0B
  ├─4096lvmraid-zfs          0   4096      0    4096    4096    0           128 128    0B
  └─4096lvmraid-wrk          0   4096      0    4096    4096    0           128 128    0B
loop1                        0   4096      0    4096    4096    0 none      128 128    0B
└─md2                        0   4096      0    4096    4096    0           128 128    0B
  ├─4096lvmraid-zfs          0   4096      0    4096    4096    0           128 128    0B
  └─4096lvmraid-wrk          0   4096      0    4096    4096    0           128 128    0B

where:
# losetup --sector-size 4096 -f /dev/sdd4
# losetup --sector-size 4096 -f /dev/sde4
# mdadm --create --level=1 --metadata=1.2 \
	--raid-devices=2 /dev/md2 /dev/loop0 /dev/loop1
# pvcreate /dev/md2
# vgcreate 4096lvmraid /dev/md2

Indeed then something is wrong in LUKS.
Thanks, this helps narrow down where to consider. The offending commit
definitely wasn't supposed to break crypto device mappers, but it seems I may
have missed a case depending on the previous behavior's implicit constraints.
I'll look more into this area.
 
quoted
For a different experiment, it may be safer to just force all
alignment for stacking drivers. Could you try the following and see
if that gets it working again? 

---
diff --git a/block/blk-settings.c b/block/blk-settings.c
index 8bb9eef5310e..5c16fdb00c6f 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -646,6 +646,7 @@ int blk_stack_limits(struct queue_limits *t,
struct queue_limits *b, t->misaligned = 1;
 		ret = -1;
 	}
+	blk_queue_dma_alignment(t, t->logical_block_size - 1);
 
 	t->max_sectors = blk_round_down_sectors(t->max_sectors,
t->logical_block_size); t->max_hw_sectors =
blk_round_down_sectors(t->max_hw_sectors, t->logical_block_size); --
This doesn't compile:
Oh shoot, sorry about that! Should have been this:
@@ -703,6 +702,7 @@ void disk_stack_limits(struct gendisk *disk, struct block_device *bdev,
                pr_notice("%s: Warning: Device %pg is misaligned\n",
                        disk->disk_name, bdev);

+       blk_queue_dma_alignment(t, queue_logical_block_size(t) - 1);
        disk_update_readahead(disk);
 }
 EXPORT_SYMBOL(disk_stack_limits);
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