From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B8E74C433FE for ; Tue, 18 Jan 2022 22:35:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1350008AbiARWfJ (ORCPT ); Tue, 18 Jan 2022 17:35:09 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56152 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237457AbiARWfH (ORCPT ); Tue, 18 Jan 2022 17:35:07 -0500 Received: from fieldses.org (fieldses.org [IPv6:2600:3c00:e000:2f7::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3DC7AC061574; Tue, 18 Jan 2022 14:35:06 -0800 (PST) Received: by fieldses.org (Postfix, from userid 2815) id BDC453DDA; Tue, 18 Jan 2022 17:35:05 -0500 (EST) DKIM-Filter: OpenDKIM Filter v2.11.0 fieldses.org BDC453DDA DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fieldses.org; s=default; t=1642545305; bh=t2AsXyVLAWmqYQGBLsOjhjyKdu16wtjBmE5q6ZDtIgI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Dl7RqCM/OQvD2DSoj+7Ntl1r4n7BRlbqZIXAkO7Fg/cg5U/MzRV9bQXFI7SFKSleW rWh0BVNfsEpLSmQN4XpDXIKdi0FT4IJiPZoM7kwHomtE9q01dhmycP/LudlMVz23S9 bR+XxAlemLZU9B9qo3Bu7w2jdZQyQCJPue8Feyp4= Date: Tue, 18 Jan 2022 17:35:05 -0500 From: "J. Bruce Fields" To: Vasily Averin Cc: Trond Myklebust , Anna Schumaker , kernel@openvz.org, linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org, Chuck Lever Subject: Re: [PATCH v3 2/3] nfs4: handle async processing of F_SETLK with FL_SLEEP Message-ID: <20220118223505.GE16108@fieldses.org> References: <1f354cec-d2d6-ddf5-56e0-325c10fe26ee@virtuozzo.com> <00d1e0fa-55dd-82a5-2607-70d4552cc7f4@virtuozzo.com> <20220103195333.GG21514@fieldses.org> <7666958f-6215-a8eb-3412-b613158406db@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7666958f-6215-a8eb-3412-b613158406db@virtuozzo.com> User-Agent: Mutt/1.5.21 (2010-09-15) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Jan 16, 2022 at 03:44:21PM +0300, Vasily Averin wrote: > On 03.01.2022 22:53, J. Bruce Fields wrote: > > 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. > > > > But this on its own isn't enough for the client to support asynchronous > > blocking locks, right? Don't we also need the logic that calls knfsd's > > lm_notify when it gets a CB_NOTIFY_LOCK from the server? > > No, I think this should be enough. > We are here a nfs client, > we can get F_SETLK with FL_SLEEP from nfsd only (i.e. in re-export case) > we need to avoid blocking if lock is already taken, > so we need to call locks_lock_inode_wait without FL_SLEEP, > then we submit _sleeping_ request to NFS server (i.e. set )data->arg.block = 1) > and waiting for reply from server. > > Here we rely that server will NOT block on such request too, so our reply wel not be blocked too. Just on that one point: if there's a lock conflict, an NFSv4 server will return NFS4ERR_DENIED immediately and leave it to the client to poll. Or if you're using NFS version >= 4.1, the server has the option of calling back to the client with a CB_NOTIFY_LOCK to let the client know when the lock might be available. (See https://datatracker.ietf.org/doc/html/rfc8881#section-20.11 for details.) But if a server that blocked and didn't reply to the original LOCK request until the lock became available, that would be a bug. (Apologies for responding just to that one point, I'm also trying to get caught back up again here....). --b. > Under "block" I mean that handler can sleep or process request for a very long time > but it will NOT BE BLOCKED if lock is taken already, it WILL NOT WAIT when lock will be released, > it just return some error in this case. > > I think it is correct. > Do you think I am wrong or maybe I missed something? > > Thank you, > Vasily Averin > > However I noticed now that past is incorrect, > temporally dropped FL_SLEEP should be restored back in _nfs4_proc_setlk before _nfs4_do_setlk() call. > I'll fix it in next version of this patch-set. > > >> https://bugzilla.kernel.org/show_bug.cgi?id=215383 > >> Signed-off-by: Vasily Averin > >> --- > >> 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