linux-kernel - Re: [PATCH] block: fix unintended fallthrough in generic_make_request

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Date:   Mon, 5 Dec 2016 07:55:09 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     Nicolai Stange <nicstange@...il.com>
Cc:     Chaitanya Kulkarni <chaitanya.kulkarni@...t.com>,
        Shaun Tancheff <shaun.tancheff@...gate.com>,
        Damien Le Moal <damien.lemoal@...t.com>,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] block: fix unintended fallthrough in
 generic_make_request_checks()

On 12/04/2016 06:56 AM, Nicolai Stange wrote:
> Since commit e73c23ff736e ("block: add async variant of
> blkdev_issue_zeroout") messages like the following show up:
> 
>   EXT4-fs (dm-1): Delayed block allocation failed for inode 2368848 at
>                   logical offset 0 with max blocks 1 with error 95
>   EXT4-fs (dm-1): This should not happen!! Data will be lost
> 
> Due to the following fallthrough introduced with
> commit 2d253440b5af ("block: Define zoned block device operations"),
> generic_make_request_checks() would accept a REQ_OP_WRITE_SAME bio only
> if the block device supports "write same" *and* is a zoned one:
> 
>   switch (bio_op(bio)) {
>   [...]
>   case REQ_OP_WRITE_SAME:
>         if (!bdev_write_same(bio->bi_bdev))
>                 goto not_supported;
>   case REQ_OP_ZONE_REPORT:
>   case REQ_OP_ZONE_RESET:
>                 if (!bdev_is_zoned(bio->bi_bdev))
>                         goto not_supported;
>                 break;
>   [...]
>   }
> 
> Thus, although the bio setup as done by __blkdev_issue_write_same() from
> commit e73c23ff736e ("block: add async variant of blkdev_issue_zeroout")
> would succeed, its actual submission would not, resulting in the
> EOPNOTSUPP == 95.
> 
> Fix this by removing the fallthrough which, due to the lack of an explicit
> comment, seems to be unintended anyway.
> 
> Fixes: e73c23ff736e ("block: add async variant of blkdev_issue_zeroout")
> Fixes: 2d253440b5af ("block: Define zoned block device operations")
> Signed-off-by: Nicolai Stange <nicstange@...il.com>

Added, thanks.

-- 
Jens Axboe