git: f84ac01e1829 - stable/13 - nfsd: Make modifying vfs.nfsd.enable_locallocks safe

The branch stable/13 has been updated by rmacklem:

URL: https://cgit.FreeBSD.org/src/commit/?id=f84ac01e1829a6f3e48af076041120692c00ccb0

commit f84ac01e1829a6f3e48af076041120692c00ccb0
Author:     Rick Macklem <rmacklem@FreeBSD.org>
AuthorDate: 2024-06-23 22:47:22 +0000
Commit:     Rick Macklem <rmacklem@FreeBSD.org>
CommitDate: 2024-07-23 00:35:02 +0000

    nfsd: Make modifying vfs.nfsd.enable_locallocks safe
    
    Commit dfaeeacc2cc2 modified clientID handling so that it could be done
    with only a mutex lock held when vfs.nfsd.enable_locallocks is 0.
    This makes it unsafe to change the setting of vfs.nfsd.enable_locallocks
    when nfsd threads are active.
    
    This patch forces all nfsd threads to be blocked when the value
    of vfs.nfsd.enable_locallocks is changed, so that it is done safely.
    
    (cherry picked from commit 67284d32e5e0d5f015d73eeac4342974277263f5)
---
 sys/fs/nfsserver/nfs_nfsdport.c | 35 +++++++++++++++++++++++++++++++++--
 1 file changed, 33 insertions(+), 2 deletions(-)

diff --git a/sys/fs/nfsserver/nfs_nfsdport.c b/sys/fs/nfsserver/nfs_nfsdport.c
index 46be3e051056..f412451e4e35 100644
--- a/sys/fs/nfsserver/nfs_nfsdport.c
+++ b/sys/fs/nfsserver/nfs_nfsdport.c
@@ -70,6 +70,7 @@ extern int nfsrv_maxpnfsmirror;
 extern uint32_t nfs_srvmaxio;
 extern int nfs_bufpackets;
 extern u_long sb_max_adj;
+extern struct nfsv4lock nfsv4rootfs_lock;
 
 NFSD_VNET_DECLARE(int, nfsrv_numnfsd);
 NFSD_VNET_DECLARE(struct nfsrv_stablefirst, nfsrv_stablefirst);
@@ -177,8 +178,6 @@ SYSCTL_INT(_vfs_nfsd, OID_AUTO, commit_miss, CTLFLAG_RW, &nfs_commit_miss,
     0, "");
 SYSCTL_INT(_vfs_nfsd, OID_AUTO, issue_delegations, CTLFLAG_RW,
     &nfsrv_issuedelegs, 0, "Enable nfsd to issue delegations");
-SYSCTL_INT(_vfs_nfsd, OID_AUTO, enable_locallocks, CTLFLAG_RW,
-    &nfsrv_dolocallocks, 0, "Enable nfsd to acquire local locks on files");
 SYSCTL_INT(_vfs_nfsd, OID_AUTO, debuglevel, CTLFLAG_RW, &nfsd_debuglevel,
     0, "Debug level for NFS server");
 NFSD_VNET_DECLARE(int, nfsd_enable_stringtouid);
@@ -293,6 +292,38 @@ SYSCTL_PROC(_vfs_nfsd, OID_AUTO, srvmaxio,
     CTLTYPE_UINT | CTLFLAG_MPSAFE | CTLFLAG_RW, NULL, 0,
     sysctl_srvmaxio, "IU", "Maximum I/O size in bytes");
 
+static int
+sysctl_dolocallocks(SYSCTL_HANDLER_ARGS)
+{
+	int error, igotlock, newdolocallocks;
+
+	newdolocallocks = nfsrv_dolocallocks;
+	error = sysctl_handle_int(oidp, &newdolocallocks, 0, req);
+	if (error != 0 || req->newptr == NULL)
+		return (error);
+	if (newdolocallocks == nfsrv_dolocallocks)
+		return (0);
+	if (jailed(curthread->td_ucred))
+		return (EINVAL);
+
+	NFSLOCKV4ROOTMUTEX();
+	do {
+		igotlock = nfsv4_lock(&nfsv4rootfs_lock, 1, NULL,
+		    NFSV4ROOTLOCKMUTEXPTR, NULL);
+	} while (!igotlock);
+	NFSUNLOCKV4ROOTMUTEX();
+
+	nfsrv_dolocallocks = newdolocallocks;
+
+	NFSLOCKV4ROOTMUTEX();
+	nfsv4_unlock(&nfsv4rootfs_lock, 0);
+	NFSUNLOCKV4ROOTMUTEX();
+	return (0);
+}
+SYSCTL_PROC(_vfs_nfsd, OID_AUTO, enable_locallocks,
+    CTLTYPE_INT | CTLFLAG_MPSAFE | CTLFLAG_RW, NULL, 0,
+    sysctl_dolocallocks, "IU", "Enable nfsd to acquire local locks on files");
+
 #define	MAX_REORDERED_RPC	16
 #define	NUM_HEURISTIC		1031
 #define	NHUSE_INIT		64