Subject: [PATCH 03/14] NFSD: narrow nfsd_mutex protection in nfsd thread
From:   NeilBrown <neilb@suse.de>
To:     "J. Bruce Fields" <bfields@fieldses.org>,
        Chuck Lever <chuck.lever@oracle.com>
Cc:     linux-nfs@vger.kernel.org
Date:   Wed, 17 Nov 2021 11:46:50 +1100
Message-ID: <163711001002.5485.16884237807627303217.stgit@noble.brown>
In-Reply-To: <163710954700.5485.5622638225352156964.stgit@noble.brown>
References: <163710954700.5485.5622638225352156964.stgit@noble.brown>
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There is nothing happening in the start of nfsd() that requires
protection by the mutex, so don't take it until shutting down the thread
- which does still require protection.

Signed-off-by: NeilBrown <neilb@suse.de>
---
 fs/nfsd/nfssvc.c |    6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
index 3c6e4faac3c3..9e517ddd8d4e 100644
--- a/fs/nfsd/nfssvc.c
+++ b/fs/nfsd/nfssvc.c
@@ -934,9 +934,6 @@ nfsd(void *vrqstp)
 	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
 	int err;
 
-	/* Lock module and set up kernel thread */
-	mutex_lock(&nfsd_mutex);
-
 	/* At this point, the thread shares current->fs
 	 * with the init process. We need to create files with the
 	 * umask as defined by the client instead of init's umask. */
@@ -956,7 +953,6 @@ nfsd(void *vrqstp)
 	allow_signal(SIGINT);
 	allow_signal(SIGQUIT);
 
-	mutex_unlock(&nfsd_mutex);
 	atomic_inc(&nfsdstats.th_cnt);
 
 	set_freezable();
@@ -985,9 +981,9 @@ nfsd(void *vrqstp)
 	flush_signals(current);
 
 	atomic_dec(&nfsdstats.th_cnt);
-	mutex_lock(&nfsd_mutex);
 
 out:
+	mutex_lock(&nfsd_mutex);
 	/* Take an extra ref so that the svc_put in svc_exit_thread()
 	 * doesn't call svc_destroy()
 	 */