Re: [PATCH 1/7] block: fail reads to offline zones early

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] block: split bios bypass early offline zone read check
--

commit 4d9e6f59ea5e83a002020d10f8ee92430c6bfa6f
Author: Damien Le Moal <dlemoal@kernel.org>

block: fail reads to offline zones early

This commit fails read commands targeting offline zones of a zoned block
device early. It checks if the sector belongs to an offline zone in
submit_bio_noacct() and sets the BIO_QUIET flag before completing the bio
with an error.

> diff --git a/block/blk-core.c b/block/blk-core.c
> index 8836c7028568b..a72aa5c18096e 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -867,6 +867,11 @@ void submit_bio_noacct(struct bio *bio)
>  
>  	switch (bio_op(bio)) {
>  	case REQ_OP_READ:
> +		if (bdev_is_zoned(bdev) &&
> +		    bdev_zone_is_offline(bdev, bio->bi_iter.bi_sector)) {
> +			bio_set_flag(bio, BIO_QUIET);
> +			goto end_io;
> +		}

[Severity: Medium]
Does this offline zone check get bypassed if a read crosses a zone boundary
into an offline zone?

If a read starts in an online zone but crosses into an offline zone, the
initial sector check passes here. The bio is later split at the zone
boundary by blk_mq_submit_bio() due to chunk_sectors alignment for zoned
devices.

The remainder of the split bio, which now starts exactly in the offline
zone, is then resubmitted by bio_submit_split_bioset() using:

block/blk-merge.c:bio_submit_split_bioset() {
	...
	else if (!blk_throtl_bio(bio))
		submit_bio_noacct_nocheck(bio, true);
	...
}

Because the remainder is submitted via submit_bio_noacct_nocheck(), it skips
submit_bio_noacct() completely. The offline remainder will be issued to
the hardware without the BIO_QUIET flag, potentially causing the noisy
device errors this code is intended to prevent.

>  		break;
>  	case REQ_OP_WRITE:
>  		if (bio->bi_opf & REQ_ATOMIC) {

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261005094632.580753-1-dlemoal@kernel.org?part=1