Re: [RFC PATCH v2] dm ioctl: fix erroneous EINVAL when signaled

[Mike Snitzer <snitzer@kernel.org>]

On Wed, Jul 17, 2024 at 04:18:33PM -0700, Khazhismel Kumykov wrote:
> do_resume when loading a new map first calls dm_suspend, which could
> silently fail. When we proceeded to dm_swap_table, we would bail out
> with EINVAL. Instead, attempt to restore new_map and return ERESTARTSYS
> when signaled.
> 
> Signed-off-by: Khazhismel Kumykov <khazhy@google.com>
> ---
>  drivers/md/dm-ioctl.c | 23 +++++++++++++++++++++--
>  1 file changed, 21 insertions(+), 2 deletions(-)
> 
> v2: don't leak new_map if we can't assign it back to hc.
> 
> diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
> index c2c07bfa6471..0591455ad63c 100644
> --- a/drivers/md/dm-ioctl.c
> +++ b/drivers/md/dm-ioctl.c
> @@ -1181,8 +1181,27 @@ static int do_resume(struct dm_ioctl *param)
>  			suspend_flags &= ~DM_SUSPEND_LOCKFS_FLAG;
>  		if (param->flags & DM_NOFLUSH_FLAG)
>  			suspend_flags |= DM_SUSPEND_NOFLUSH_FLAG;
> -		if (!dm_suspended_md(md))
> -			dm_suspend(md, suspend_flags);
> +		if (!dm_suspended_md(md)) {
> +			r = dm_suspend(md, suspend_flags);
> +			if (r == -EINTR)
> +				r = -ERESTARTSYS;
> +			if (r) {
> +				down_write(&_hash_lock);
> +				hc = dm_get_mdptr(md);
> +				if (!hc)
> +					r = -ENXIO;
> +				if (hc && !hc->new_map) {
> +					hc->new_map = new_map;
> +					up_write(&_hash_lock);
> +				} else {
> +					up_write(&_hash_lock);
> +					dm_sync_table(md);
> +					dm_table_destroy(new_map);
> +				}
> +				dm_put(md);
> +				return r;
> +			}
> +		}
>  
>  		old_size = dm_get_size(md);
>  		old_map = dm_swap_table(md, new_map);
> -- 
> 2.45.2.993.g49e7a77208-goog
> 
> 

Thanks for the patch.  The header could use more context for how this
issue has caused problems in practice (you touched on that in reply to
Mikulas for v1).

But I will review this closely starting the week of July 29.  This is
a very fundamental codepath for DM so needs extended review.

Mike