[dm-devel] [PATCH 3/3] block: fail writes to read-only devices

[Mike Snitzer]

On Thu, Jun 01 2023 at  3:28P -0400,
Christoph Hellwig <hch at lst.de> wrote:

> Currently callers can happily submit writes to block devices that are
> marked read-only, including to drivers that don't even support writes
> and will crash when fed such bios.
> 
> While bio submitter should check for read-only devices, that's not a
> very robust way of dealing with this.
> 
> Note that the last attempt to do this got reverted by Linus in commit
> a32e236eb93e ("Partially revert "block: fail op_is_write() requests to
> read-only partitions") because device mapper relyied on not enforcing
> the read-only state when used together with older lvm-tools.
> 
> The lvm side got fixed in:
> 
>     https://sourceware.org/git/?p=lvm2.git;a=commit;h=a6fdb9d9d70f51c49ad11a87ab4243344e6701a3
> 
> but if people still have older lvm2 tools in use we probably need
> to find a workaround for this in device mapper rather than lacking
> the core block layer checks.
> 
> Signed-off-by: Christoph Hellwig <hch at lst.de>

Reviewed-by: Mike Snitzer <snitzer at kernel.org>