linux-kernel - [PATCH 0/3] nfsd: don't allow concurrent queueing of workqueue jobs

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Message-Id: <20250218-nfsd-callback-v1-0-14f966967dd8@kernel.org>
Date: Tue, 18 Feb 2025 16:28:56 -0500
From: Jeff Layton <jlayton@...nel.org>
To: Chuck Lever <chuck.lever@...cle.com>, Neil Brown <neilb@...e.de>, 
 Olga Kornievskaia <okorniev@...hat.com>, Dai Ngo <Dai.Ngo@...cle.com>, 
 Tom Talpey <tom@...pey.com>
Cc: Li Lingfeng <lilingfeng3@...wei.com>, linux-nfs@...r.kernel.org, 
 linux-kernel@...r.kernel.org, Jeff Layton <jlayton@...nel.org>
Subject: [PATCH 0/3] nfsd: don't allow concurrent queueing of workqueue
 jobs

While looking at the problem that Li Lingfeng reported [1] around
callback queueing failures, I noticed that there were potential
scenarios where the callback workqueue jobs could run concurrently with
an rpc_task. Since they touch some of the same fields, this is incorrect
at best and potentially dangerous.

This patchset adds a new mechanism for ensuring that the same
nfsd4_callback can't run concurrently with itself, regardless of where
it is in its execution. This also gives us a more sure mechanism for
handling the places where we need to take and hold a reference on an
object while the callback is running.

This should also fix the problem that Li Lingfeng reported, since
queueing the work from nfsd4_cb_release() should never fail. Note that
the patch they sent earlier (fdf5c9413ea) should be dropped from
nfsd-testing before this will apply cleanly.

[1]: https://lore.kernel.org/linux-nfs/20250218135423.1487309-1-lilingfeng3@huawei.com/

Signed-off-by: Jeff Layton <jlayton@...nel.org>
---
Jeff Layton (3):
      nfsd: prevent callback tasks running concurrently
      nfsd: eliminate cl_ra_cblist and NFSD4_CLIENT_CB_RECALL_ANY
      nfsd: move cb_need_restart flag into cb_flags

 fs/nfsd/nfs4callback.c | 12 ++++++------
 fs/nfsd/nfs4layouts.c  |  7 ++++---
 fs/nfsd/nfs4proc.c     |  2 +-
 fs/nfsd/nfs4state.c    | 26 +++++++++++---------------
 fs/nfsd/state.h        | 13 ++++++++++---
 fs/nfsd/trace.h        |  2 +-
 6 files changed, 33 insertions(+), 29 deletions(-)
---
base-commit: 4a52e5e49d1b50fcb584e434cced6d0547ddea42
change-id: 20250218-nfsd-callback-f723b8498c78

Best regards,
-- 
Jeff Layton <jlayton@...nel.org>