From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C475D2066C3; Fri, 21 Feb 2025 14:58:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740149915; cv=none; b=Dy9bzcN+AvALlWt2EbCPm+jmk7mrUR7hZMtZ7D4//0q3mfS7a5QOvfMzH43Yj1GHcsTIIYSsLtyNLU+Lc2SLcIShyV5MeMetPU/8OhxNIpczZL1ldmD4OB5LM+lhES5q1KplCbukZ/msbHSh89DlZv7obUrRcI2UYiYd0AgnOwQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740149915; c=relaxed/simple; bh=SZsrQiYPGBkSObgYWryJ6MG8RTVR89p+BMqVG/A/X6U=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=pvG7fM6xn+lIjFp56TZXFOhUAgoaKGzigLSYN9ZFiFj1yMmRa5/rwVxaMmu/ct4kTba2d0sIHe/1nJWJGRNEpATg+TexOVZ4oXKO4aa91LVeDlHNKpxcECandbD8/sLoPoEL8hg6j/FQCmdo5kOlK4+abLWSh3zEXVKAs2M0qHo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DfXbTT1j; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="DfXbTT1j" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 05C4FC4CED6; Fri, 21 Feb 2025 14:58:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1740149915; bh=SZsrQiYPGBkSObgYWryJ6MG8RTVR89p+BMqVG/A/X6U=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=DfXbTT1j7KK4xH7av5eENe+NISm1KswaObCAo3hLOpmhQK0ZrbgjOVfz610BDsEbM YgKzErDrA9tCpHN9phkCrrWmq6xjZv4Vpq9HLj4G3kROplybOqO4H0hcN7L+2TdO6C EYjhgpznb/veK/sk1B56NPU6RDMkU0HNF+LNv+PiOMkL9KBO+EbnWuPR7iyCRI2+C5 3zYmoNRqCtrx5Z2jde8WgGMIqVWN9yVA7K0JIEvV4xr0mrIyPtlrMdGxxkO+B0D6YJ hPOYNhe8+2wwipYKbJ6fijdytAhx6Kez9R4KBuOYKUGz5C6vf5uExPrjjw9G9szLId Kfr8R7zQjxxug== Message-ID: <6bdec87c369b61b515a29a6d661b1e9473fba24c.camel@kernel.org> Subject: Re: [PATCH] nfsd: decrease cl_cb_inflight if fail to queue cb_work From: Jeff Layton To: Benjamin Coddington Cc: Chuck Lever , Li Lingfeng , neilb@suse.de, okorniev@redhat.com, Dai.Ngo@oracle.com, tom@talpey.com, linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org, yukuai1@huaweicloud.com, houtao1@huawei.com, yi.zhang@huawei.com, yangerkun@huawei.com, lilingfeng@huaweicloud.com Date: Fri, 21 Feb 2025 09:58:32 -0500 In-Reply-To: <9272C75B-F102-4D42-9970-DF3D267E0629@redhat.com> References: <20250218135423.1487309-1-lilingfeng3@huawei.com> <0ae8a05272c2eb8a503102788341e1d9c49109dd.camel@kernel.org> <04ed0c70b85a1e8b66c25b9ad4d0aa4c2fb91198.camel@kernel.org> <9cea3133-d17c-48c5-8eb9-265fbfc5708b@oracle.com> 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aEZCiDOq0anx6FmOzs5E6Jqdpo/mtI8beK+BE7Va6ni7YrQlnT0i3vaTVMTiCThbqsB20VrbMjlhp f8lfK1XVNbRq/R7GZ9zHESlsa35ha60yd/j3pu5hT2xyy8krV8vGhHvnJ1XRMJBAB/UYb6FyC7S+m QZIQXVeAA+smfTT0tDrisj1U5x6ZB9b3nBg65kc= Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.54.3 (3.54.3-1.fc41) Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Fri, 2025-02-21 at 09:46 -0500, Benjamin Coddington wrote: > On 21 Feb 2025, at 9:37, Jeff Layton wrote: >=20 > > On Fri, 2025-02-21 at 09:06 -0500, Benjamin Coddington wrote: > > > On 18 Feb 2025, at 9:40, Jeff Layton wrote: > > >=20 > > > > On Tue, 2025-02-18 at 09:31 -0500, Chuck Lever wrote: > > > > > On 2/18/25 9:29 AM, Jeff Layton wrote: > > > > > > On Tue, 2025-02-18 at 08:58 -0500, Jeff Layton wrote: > > > > > > > On Tue, 2025-02-18 at 21:54 +0800, Li Lingfeng wrote: > > > > > > > > In nfsd4_run_cb, cl_cb_inflight is increased before attempt= ing to queue > > > > > > > > cb_work to callback_wq. This count can be decreased in thre= e situations: > > > > > > > > 1) If queuing fails in nfsd4_run_cb, the count will be decr= emented > > > > > > > > accordingly. > > > > > > > > 2) After cb_work is running, the count is decreased in the = exception > > > > > > > > branch of nfsd4_run_cb_work via nfsd41_destroy_cb. > > > > > > > > 3) The count is decreased in the release callback of rpc_ta= sk =E2=80=94 either > > > > > > > > directly calling nfsd41_cb_inflight_end in nfsd4_cb_probe_r= elease, or > > > > > > > > calling nfsd41_destroy_cb in . > > > > > > > >=20 > > > > > > > > However, in nfsd4_cb_release, if the current cb_work needs = to restart, the > > > > > > > > count will not be decreased, with the expectation that it w= ill be reduced > > > > > > > > once cb_work is running. > > > > > > > > If queuing fails here, then the count will leak, ultimately= causing the > > > > > > > > nfsd service to be unable to exit as shown below: > > > > > > > > [root@nfs_test2 ~]# cat /proc/2271/stack > > > > > > > > [<0>] nfsd4_shutdown_callback+0x22b/0x290 > > > > > > > > [<0>] __destroy_client+0x3cd/0x5c0 > > > > > > > > [<0>] nfs4_state_destroy_net+0xd2/0x330 > > > > > > > > [<0>] nfs4_state_shutdown_net+0x2ad/0x410 > > > > > > > > [<0>] nfsd_shutdown_net+0xb7/0x250 > > > > > > > > [<0>] nfsd_last_thread+0x15f/0x2a0 > > > > > > > > [<0>] nfsd_svc+0x388/0x3f0 > > > > > > > > [<0>] write_threads+0x17e/0x2b0 > > > > > > > > [<0>] nfsctl_transaction_write+0x91/0xf0 > > > > > > > > [<0>] vfs_write+0x1c4/0x750 > > > > > > > > [<0>] ksys_write+0xcb/0x170 > > > > > > > > [<0>] do_syscall_64+0x70/0x120 > > > > > > > > [<0>] entry_SYSCALL_64_after_hwframe+0x78/0xe2 > > > > > > > > [root@nfs_test2 ~]# > > > > > > > >=20 > > > > > > > > Fix this by decreasing cl_cb_inflight if the restart fails. > > > > > > > >=20 > > > > > > > > Fixes: cba5f62b1830 ("nfsd: fix callback restarts") > > > > > > > > Signed-off-by: Li Lingfeng > > > > > > > > --- > > > > > > > > fs/nfsd/nfs4callback.c | 10 +++++++--- > > > > > > > > 1 file changed, 7 insertions(+), 3 deletions(-) > > > > > > > >=20 > > > > > > > > diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.= c > > > > > > > > index 484077200c5d..8a7d24efdd08 100644 > > > > > > > > --- a/fs/nfsd/nfs4callback.c > > > > > > > > +++ b/fs/nfsd/nfs4callback.c > > > > > > > > @@ -1459,12 +1459,16 @@ static void nfsd4_cb_done(struct rp= c_task *task, void *calldata) > > > > > > > > static void nfsd4_cb_release(void *calldata) > > > > > > > > { > > > > > > > > struct nfsd4_callback *cb =3D calldata; > > > > > > > > + struct nfs4_client *clp =3D cb->cb_clp; > > > > > > > > + int queued; > > > > > > > >=20 > > > > > > > > trace_nfsd_cb_rpc_release(cb->cb_clp); > > > > > > > >=20 > > > > > > > > - if (cb->cb_need_restart) > > > > > > > > - nfsd4_queue_cb(cb); > > > > > > > > - else > > > > > > > > + if (cb->cb_need_restart) { > > > > > > > > + queued =3D nfsd4_queue_cb(cb); > > > > > > > > + if (!queued) > > > > > > > > + nfsd41_cb_inflight_end(clp); > > > > > > > > + } else > > > > > > > > nfsd41_destroy_cb(cb); > > > > > > > >=20 > > > > > > > > } > > > > > > >=20 > > > > > > > Good catch! > > > > > > >=20 > > > > > > > Reviewed-by: Jeff Layton > > > > > > >=20 > > > > > >=20 > > > > > > Actually, I think this is not quite right. It's a bit more subt= le than > > > > > > it first appears. The problem of course is that the callback wo= rkqueue > > > > > > jobs run in a different task than the RPC workqueue jobs, so th= ey can > > > > > > race. > > > > > >=20 > > > > > > cl_cb_inflight gets bumped when the callback is first queued, a= nd only > > > > > > gets released in nfsd41_destroy_cb(). If it fails to be queued,= it's > > > > > > because something else has queued the workqueue job in the mean= time. > > > > > >=20 > > > > > > There are two places that can occur: nfsd4_cb_release() and > > > > > > nfsd4_run_cb(). Since this is occurring in nfsd4_cb_release(), = the only > > > > > > other option is that something raced in and queued it via > > > > > > nfsd4_run_cb(). > > > > >=20 > > > > > What would be the "something" that raced in? > > > > >=20 > > > >=20 > > > > I think we may be able to get there via multiple __break_lease() ca= lls > > > > on the same layout or delegation. That could mean multiple calls to= the > > > > ->lm_break operation on the same object. > > >=20 > > > Sorry for the late response, but isn't ->lm_break() already serialize= d in > > > __break_lease for the same file_lease? We don't call lm_break(fl) if > > > lease_breaking(fl). > > >=20 > >=20 > > lease_breaking() is only checked when want_write is false. IOW, if > > you're breaking the lease for write, then lm_break is always called. > >=20 > > Is that a bug or a feature? I'm not sure, but it's been that way since > > ~2011. >=20 > Yeah.. why? >=20 > Thanks I missed that detail when I refreshed my memory of it just now. > Seems like you'd want to avoid constantly calling lm_break for both cases= , > spamming the lock manager adds nothing. 2 cents. >=20 Sorry, it doesn't get called every time. If want_write is called then we _do_ check FL_UNLOCK_PENDING. IOW, you can get a downgrade attempt first, and then a full unlock request later. nfsd doesn't do downgrades. It recalls the object either way. So, ignoring subsequent lm_break calls is the right thing to do, I think. --=20 Jeff Layton