Re: [dm-devel] [PATCH] blk-settings: make sure that max_sectors is aligned on "logical_block_size" boundary.
From: John Dorminy <hidden>
Date: 2020-11-20 01:27:49
Also in:
dm-devel
Greetings; Might I suggest using SECTOR_SIZE instead of 512? Or, perhaps, >> SECTOR_SHIFT instead of / 512. I don't understand the three conditionals. I believe max_sectors is supposed to be <= min(max_dev_sectors, max_hw_sectors), but I don't understand why max_sectors being small should adjust max_hw_sectors and max_dev_sectors. Are the conditions perhaps supposed to be different, adjusting each max_*sectors up to at least PAGE_SIZE / SECTOR_SIZE? Perhaps, like e.g. blk_queue_max_hw_sectors(), the conditionals should log if they are adjusting max_*sectors up to the minimum. Thanks! John Dorminy On Thu, Nov 19, 2020 at 3:37 PM Mikulas Patocka [off-list ref] wrote:
quoted hunk ↗ jump to hunk
We get these I/O errors when we run md-raid1 on the top of dm-integrity on the top of ramdisk: device-mapper: integrity: Bio not aligned on 8 sectors: 0xff00, 0xff device-mapper: integrity: Bio not aligned on 8 sectors: 0xff00, 0xff device-mapper: integrity: Bio not aligned on 8 sectors: 0xffff, 0x1 device-mapper: integrity: Bio not aligned on 8 sectors: 0xffff, 0x1 device-mapper: integrity: Bio not aligned on 8 sectors: 0x8048, 0xff device-mapper: integrity: Bio not aligned on 8 sectors: 0x8147, 0xff device-mapper: integrity: Bio not aligned on 8 sectors: 0x8246, 0xff device-mapper: integrity: Bio not aligned on 8 sectors: 0x8345, 0xbb The ramdisk device has logical_block_size 512 and max_sectors 255. The dm-integrity device uses logical_block_size 4096 and it doesn't affect the "max_sectors" value - thus, it inherits 255 from the ramdisk. So, we have a device with max_sectors not aligned on logical_block_size. The md-raid device sees that the underlying leg has max_sectors 255 and it will split the bios on 255-sector boundary, making the bios unaligned on logical_block_size. In order to fix the bug, we round down max_sectors to logical_block_size. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Cc: stable@vger.kernel.org --- block/blk-settings.c | 10 ++++++++++ 1 file changed, 10 insertions(+) Index: linux-2.6/block/blk-settings.c ===================================================================--- linux-2.6.orig/block/blk-settings.c 2020-10-29 12:20:46.000000000 +0100 +++ linux-2.6/block/blk-settings.c 2020-11-19 21:20:18.000000000 +0100@@ -591,6 +591,16 @@ int blk_stack_limits(struct queue_limits ret = -1; } + t->max_sectors = round_down(t->max_sectors, t->logical_block_size / 512); + if (t->max_sectors < PAGE_SIZE / 512) + t->max_sectors = PAGE_SIZE / 512; + t->max_hw_sectors = round_down(t->max_hw_sectors, t->logical_block_size / 512); + if (t->max_sectors < PAGE_SIZE / 512) + t->max_hw_sectors = PAGE_SIZE / 512; + t->max_dev_sectors = round_down(t->max_dev_sectors, t->logical_block_size / 512); + if (t->max_sectors < PAGE_SIZE / 512) + t->max_dev_sectors = PAGE_SIZE / 512; + /* Discard alignment and granularity */ if (b->discard_granularity) { alignment = queue_limit_discard_alignment(b, start); --dm-devel mailing list dm-devel@redhat.com https://www.redhat.com/mailman/listinfo/dm-devel