linux-kernel - Re: [PATCH v3 2/3] nfs4: handle async processing of F_SETLK with FL

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Date:   Mon, 3 Jan 2022 14:40:12 -0500
From:   "J. Bruce Fields" <bfields@...ldses.org>
To:     Vasily Averin <vvs@...tuozzo.com>
Cc:     Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <anna.schumaker@...app.com>, kernel@...nvz.org,
        linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org,
        Chuck Lever <chuck.lever@...cle.com>
Subject: Re: [PATCH v3 2/3] nfs4: handle async processing of F_SETLK with
 FL_SLEEP

On Wed, Dec 29, 2021 at 11:24:43AM +0300, 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 which is blocked
> for such requests. To handle them correctly FL_SLEEP flag should be
> temporarily reset before executing the locks_lock_inode_wait() function.
> 
> Additionally block flag is forced to set, to translate blocking lock to
> remote nfs server, expecting it supports async processing of the blocking
> locks too.

Seems like an improvement, but is there some way to make this more
straightforward by just calling a function that doesn't sleep in the
first place?  (posix_lock_inode(), maybe?)

--b.

> 
> https://bugzilla.kernel.org/show_bug.cgi?id=215383
> Signed-off-by: Vasily Averin <vvs@...tuozzo.com>
> ---
>  fs/nfs/nfs4proc.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
> index ee3bc79f6ca3..9b1380c4223c 100644
> --- a/fs/nfs/nfs4proc.c
> +++ b/fs/nfs/nfs4proc.c
> @@ -7094,7 +7094,7 @@ static int _nfs4_do_setlk(struct nfs4_state *state, int cmd, struct file_lock *f
>  			recovery_type == NFS_LOCK_NEW ? GFP_KERNEL : GFP_NOFS);
>  	if (data == NULL)
>  		return -ENOMEM;
> -	if (IS_SETLKW(cmd))
> +	if (IS_SETLKW(cmd) || (fl->fl_flags & FL_SLEEP))
>  		data->arg.block = 1;
>  	nfs4_init_sequence(&data->arg.seq_args, &data->res.seq_res, 1,
>  				recovery_type > NFS_LOCK_NEW);
> @@ -7200,6 +7200,9 @@ static int _nfs4_proc_setlk(struct nfs4_state *state, int cmd, struct file_lock
>  	int status;
>  
>  	request->fl_flags |= FL_ACCESS;
> +	if (((fl_flags & FL_SLEEP_POSIX) == FL_SLEEP_POSIX) && IS_SETLK(cmd))
> +		request->fl_flags &= ~FL_SLEEP;
> +
>  	status = locks_lock_inode_wait(state->inode, request);
>  	if (status < 0)
>  		goto out;
> -- 
> 2.25.1