linux-kernel - Re: [PATCH v2] nfs4: handle async processing of F_SETLK with FL

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Date:   Tue, 28 Dec 2021 04:04:28 +0300
From:   Vasily Averin <vvs@...tuozzo.com>
To:     Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <anna.schumaker@...app.com>
Cc:     kernel@...nvz.org, linux-nfs@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] nfs4: handle async processing of F_SETLK with FL_SLEEP

Patch is wrong,
I missed that FL_FLOCK is handled here too,
moreover locks_lock_inode_wait() is used in nfs_proc_lock and nfs3_proc_locks,
and FL_POSIX request for nfs v2 and v3 can be blocked too.

On 27.12.2021 18:51, Vasily Averin wrote:
> nfsd and lockd use F_SETLK cmd with the FL_SLEEP flag set to request
> asynchronous processing of blocking locks.
> 
> Currently nfs4 use locks_lock_inode_wait() function blocked on such requests.
> To handle such requests properly, non-blocking posix_file_lock()
> function should be used instead.
> 
> https://bugzilla.kernel.org/show_bug.cgi?id=215383
> Signed-off-by: Vasily Averin <vvs@...tuozzo.com>
> ---
> VvS: I'm not sure that request->fl_file points to the same state->inode
> used in locks_lock_inode_wait(). If it is not, posix_lock_inode() can be
> used here, but this function is static currently and should be exported first.
> 
> v2: fixed 'fl_flags && FL_SLEEP' => 'fl_flags & FL_SLEEP'
> ---
>  fs/nfs/nfs4proc.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
> index ee3bc79f6ca3..f899f4bcdae5 100644
> --- a/fs/nfs/nfs4proc.c
> +++ b/fs/nfs/nfs4proc.c
> @@ -7200,8 +7200,11 @@ static int _nfs4_proc_setlk(struct nfs4_state *state, int cmd, struct file_lock
>  	int status;
>  
>  	request->fl_flags |= FL_ACCESS;
> -	status = locks_lock_inode_wait(state->inode, request);
> -	if (status < 0)
> +	if ((request->fl_flags & FL_SLEEP) && IS_SETLK(cmd))
> +		status = posix_lock_file(request->fl_file, request, NULL);
> +	else
> +		status = locks_lock_inode_wait(state->inode, request);
> +	if (status)
>  		goto out;
>  	mutex_lock(&sp->so_delegreturn_mutex);
>  	down_read(&nfsi->rwsem);
>