On 2020/05/16 12:55, Coly Li wrote:
> For a zoned device, e.g. host managed SMR hard drive, the request op
> REQ_OP_ZONE_RESET_ALL is to reset LBA of all zones' writer pointers to
> the start LBA of the zone they belong to. After all the write pointers
> are reset, all previously stored data is invalid and unaccessible.
> Therefore this op code changes on-disk data, belongs to WRITE request
> op code.
>
> Similar to the problem of REQ_OP_ZONE_RESET, REQ_OP_ZONE_RESET_ALL is
> even number 8, it means bios with REQ_OP_ZONE_RESET_ALL in bio->bi_opf
> will be treated as READ request by op_is_write().
>
> Same problem will happen when bcache device is created on top of zoned
> device like host managed SMR hard drive, bcache driver should invalid
> all cached data for the REQ_OP_ZONE_RESET_ALL request, but this zone
> management bio is mistakenly treated as READ request and go into bcache
> read code path, which will cause undefined behavior.
>
> This patch changes REQ_OP_ZONE_RESET_ALL value from 8 to 15, this new
> odd number will make bcache driver handle this zone management bio in
> write request code path properly.
>
> Fixes: e84e8f066395 ("block: add req op to reset all zones and flag")
> Signed-off-by: Coly Li <colyli@xxxxxxx>
> Cc: Chaitanya Kulkarni <chaitanya.kulkarni@xxxxxxx>
> Cc: Damien Le Moal <damien.lemoal@xxxxxxx>
> Cc: Hannes Reinecke <hare@xxxxxxxx>
> Cc: Jens Axboe <axboe@xxxxxxxxx>
> Cc: Johannes Thumshirn <johannes.thumshirn@xxxxxxx>
> Cc: Keith Busch <kbusch@xxxxxxxxxx>
> ---
> Changelog:
> v2: fix typo for REQ_OP_ZONE_RESET_ALL.
> v1: initial version.
>
> include/linux/blk_types.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
> index 8f7bc15a6de3..618032fa1b29 100644
> --- a/include/linux/blk_types.h
> +++ b/include/linux/blk_types.h
> @@ -284,8 +284,6 @@ enum req_opf {
> REQ_OP_SECURE_ERASE = 5,
> /* write the same sector many times */
> REQ_OP_WRITE_SAME = 7,
> - /* reset all the zone present on the device */
> - REQ_OP_ZONE_RESET_ALL = 8,
> /* write the zero filled sector many times */
> REQ_OP_WRITE_ZEROES = 9,
> /* Open a zone */
> @@ -296,6 +294,8 @@ enum req_opf {
> REQ_OP_ZONE_FINISH = 12,
> /* reset a zone write pointer */
> REQ_OP_ZONE_RESET = 13,
> + /* reset all the zone present on the device */
> + REQ_OP_ZONE_RESET_ALL = 15,
Same comment as for patch 1. And you can probably squash this patch into patch 1
to avoid repeating mostly the same explanation twice in the commit message.
REQ_OP_ZONE_RESET and REQ_OP_ZONE_RESET_ALL are very closely related. The latter
may actually be processed using the former anyway, so the op number change for
both should be a single patch to be consistent.
>
> /* SCSI passthrough using struct scsi_request */
> REQ_OP_SCSI_IN = 32,
>
--
Damien Le Moal
Western Digital Research
