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Message-ID: <a1e7f5c1-76ef-19e5-91db-a62f7615b28a@yandex.ru>
Date:   Tue, 20 Jun 2023 15:57:23 +0500
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Subject: Re: [PATCH 2/3] fd/locks: allow get the lock owner by F_OFD_GETLK
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To:     Jeff Layton <jlayton@kernel.org>, linux-kernel@vger.kernel.org
Cc:     Chuck Lever <chuck.lever@oracle.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Christian Brauner <brauner@kernel.org>,
        linux-fsdevel@vger.kernel.org
References: <20230620095507.2677463-1-stsp2@yandex.ru>
 <20230620095507.2677463-3-stsp2@yandex.ru>
 <5728ebda22a723b0eb209ae078e8f132d7b4ac7b.camel@kernel.org>
From:   stsp <stsp2@yandex.ru>
In-Reply-To: <5728ebda22a723b0eb209ae078e8f132d7b4ac7b.camel@kernel.org>
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Hello,

20.06.2023 15:51, Jeff Layton пишет:
> On Tue, 2023-06-20 at 14:55 +0500, Stas Sergeev wrote:
>> Currently F_OFD_GETLK sets the pid of the lock owner to -1.
>> Remove such behavior to allow getting the proper owner's pid.
>> This may be helpful when you want to send some message (like SIGKILL)
>> to the offending locker.
>>
>> Signed-off-by: Stas Sergeev <stsp2@yandex.ru>
>>
>> CC: Jeff Layton <jlayton@kernel.org>
>> CC: Chuck Lever <chuck.lever@oracle.com>
>> CC: Alexander Viro <viro@zeniv.linux.org.uk>
>> CC: Christian Brauner <brauner@kernel.org>
>> CC: linux-fsdevel@vger.kernel.org
>> CC: linux-kernel@vger.kernel.org
>>
>> ---
>>   fs/locks.c | 2 --
>>   1 file changed, 2 deletions(-)
>>
>> diff --git a/fs/locks.c b/fs/locks.c
>> index 210766007e63..ee265e166542 100644
>> --- a/fs/locks.c
>> +++ b/fs/locks.c
>> @@ -2158,8 +2158,6 @@ static pid_t locks_translate_pid(struct file_lock *fl, struct pid_namespace *ns)
>>   	pid_t vnr;
>>   	struct pid *pid;
>>   
>> -	if (IS_OFDLCK(fl))
>> -		return -1;
>>   	if (IS_REMOTELCK(fl))
>>   		return fl->fl_pid;
>>   	/*
> NACK on this one.
>
> OFD locks are not owned by processes. They are owned by the file
> description (hence the name). Because of this, returning a pid here is
> wrong.

But fd is owned by a process.
PID has a meaning, you can send SIGKILL
to the returned PID, and the lock is clear.
Was there any reason to hide the PID at
a first place?


> This precedent comes from BSD, where flock() and POSIX locks can
> conflict. BSD returns -1 for the pid if you call F_GETLK on a file
> locked with flock(). Since OFD locks have similar ownership semantics to
> flock() locks, we use the same convention here.
OK if you insist I can drop this one and
search the PID by some other means.
Just a bit unsure what makes it so important
to overwrite the potentially useful info
with -1.

So in case you insist on that, then should
I send a v2 or can you just drop the patch
yourself?