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

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Message-ID: <99266e5d-de9d-4d31-a1f2-d003bddb7b44@gmail.com>
Date: Tue, 23 Jul 2024 15:11:37 +0200
From: Zdenek Kabelac <zdenek.kabelac@...il.com>
To: Mikulas Patocka <mpatocka@...hat.com>,
 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

Dne 23. 07. 24 v 14:51 Mikulas Patocka napsal(a):
> 
> 
> 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?

In general - with suspend failures - we are just stopping whole operation - 
and restoring previous state - so user can run operation again.

There is no special check for exact reason of ioctl failure.

Regards

Zdenek