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

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Message-ID: <34139e33-3e7-4895-bd4-2d9f7727e9fb@redhat.com>
Date: Tue, 23 Jul 2024 14:51:45 +0200 (CEST)
From: Mikulas Patocka <mpatocka@...hat.com>
To: Khazhismel Kumykov <khazhy@...omium.org>
cc: Alasdair Kergon <agk@...hat.com>, Mike Snitzer <snitzer@...nel.org>, 
    Zdenek Kabelac <zkabelac@...hat.com>, Joe Thornber <thornber@...hat.com>, 
    Heinz Mauelshagen <heinzm@...hat.com>, dm-devel@...ts.linux.dev, 
    linux-kernel@...r.kernel.org, Khazhismel Kumykov <khazhy@...gle.com>
Subject: Re: [RFC PATCH v2] dm ioctl: fix erroneous EINVAL when signaled



On Wed, 17 Jul 2024, 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@...gle.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;

I'd like to ask why the "EINTR -> ERESTARTSYS" conversion is here and why 
it isn't in dm_suspend?

What do libdevmapper+lvm maintainers think about it? Does lvm hadle EINTR 
by restarting the ioctl syscall? Should we return ERESTARTSYS when suspend 
is interrupted?

Mikulas