nfs: introduce mount option '-olocal_lock' to make locks local

NFS clients since 2.6.12 support flock locks by emulating fcntl byte-range
locks. Due to this, some windows applications which seem to use both flock
(share mode lock mapped as flock by Samba) and fcntl locks sequentially on
the same file, can't lock as they falsely assume the file is already locked.
The problem was reported on a setup with windows clients accessing excel files
on a Samba exported share which is originally a NFS mount from a NetApp filer.

Older NFS clients (< 2.6.12) did not see this problem as flock locks were
considered local. To support legacy flock behavior, this patch adds a mount
option "-olocal_lock=" which can take the following values:

'none' - Neither flock locks nor POSIX locks are local
'flock' - flock locks are local
'posix' - fcntl/POSIX locks are local
'all' - Both flock locks and POSIX locks are local

Testing:

- This patch was tested by using -olocal_lock option with different values
and the NLM calls were noted from the network packet captured.

'none' - NLM calls were seen during both flock() and fcntl(), flock lock
was granted, fcntl was denied
'flock' - no NLM calls for flock(), NLM call was seen for fcntl(),
granted
'posix' - NLM call was seen for flock() - granted, no NLM call for fcntl()
'all' - no NLM calls were seen during both flock() and fcntl()

- No bugs were seen during NFSv4 locking/unlocking in general and NFSv4
reboot recovery.

Cc: Neil Brown <[e-mail]>
Signed-off-by: Suresh Jayaraman <[e-mail]>
Signed-off-by: Trond Myklebust <[e-mail]>

fs/nfs/client.c

···
  */
 static void nfs_destroy_server(struct nfs_server *server)
 {
-	if (!(server->flags & NFS_MOUNT_NONLM))
+	if (!(server->flags & NFS_MOUNT_LOCAL_FLOCK) ||
+			!(server->flags & NFS_MOUNT_LOCAL_FCNTL))
 		nlmclnt_done(server->nlm_host);
 }
 
···
 
 	if (nlm_init.nfs_version > 3)
 		return 0;
-	if (server->flags & NFS_MOUNT_NONLM)
+	if ((server->flags & NFS_MOUNT_LOCAL_FLOCK) &&
+			(server->flags & NFS_MOUNT_LOCAL_FCNTL))
 		return 0;
 
 	switch (clp->cl_proto) {

fs/nfs/file.c

···
 	return ret;
 }
 
-static int do_getlk(struct file *filp, int cmd, struct file_lock *fl)
+static int
+do_getlk(struct file *filp, int cmd, struct file_lock *fl, int is_local)
 {
 	struct inode *inode = filp->f_mapping->host;
 	int status = 0;
···
 	if (nfs_have_delegation(inode, FMODE_READ))
 		goto out_noconflict;
 
-	if (NFS_SERVER(inode)->flags & NFS_MOUNT_NONLM)
+	if (is_local)
 		goto out_noconflict;
 
 	status = NFS_PROTO(inode)->lock(filp, cmd, fl);
···
 	return res;
 }
 
-static int do_unlk(struct file *filp, int cmd, struct file_lock *fl)
+static int
+do_unlk(struct file *filp, int cmd, struct file_lock *fl, int is_local)
 {
 	struct inode *inode = filp->f_mapping->host;
 	int status;
···
 	 * 	If we're signalled while cleaning up locks on process exit, we
 	 * 	still need to complete the unlock.
 	 */
-	/* Use local locking if mounted with "-onolock" */
-	if (!(NFS_SERVER(inode)->flags & NFS_MOUNT_NONLM))
+	/*
+	 * Use local locking if mounted with "-onolock" or with appropriate
+	 * "-olocal_lock="
+	 */
+	if (!is_local)
 		status = NFS_PROTO(inode)->lock(filp, cmd, fl);
 	else
 		status = do_vfs_lock(filp, fl);
 	return status;
 }
 
-static int do_setlk(struct file *filp, int cmd, struct file_lock *fl)
+static int
+do_setlk(struct file *filp, int cmd, struct file_lock *fl, int is_local)
 {
 	struct inode *inode = filp->f_mapping->host;
 	int status;
···
 	if (status != 0)
 		goto out;
 
-	/* Use local locking if mounted with "-onolock" */
-	if (!(NFS_SERVER(inode)->flags & NFS_MOUNT_NONLM))
+	/*
+	 * Use local locking if mounted with "-onolock" or with appropriate
+	 * "-olocal_lock="
+	 */
+	if (!is_local)
 		status = NFS_PROTO(inode)->lock(filp, cmd, fl);
 	else
 		status = do_vfs_lock(filp, fl);
···
 {
 	struct inode *inode = filp->f_mapping->host;
 	int ret = -ENOLCK;
+	int is_local = 0;
 
 	dprintk("NFS: lock(%s/%s, t=%x, fl=%x, r=%lld:%lld)\n",
 			filp->f_path.dentry->d_parent->d_name.name,
···
 	if (__mandatory_lock(inode) && fl->fl_type != F_UNLCK)
 		goto out_err;
 
+	if (NFS_SERVER(inode)->flags & NFS_MOUNT_LOCAL_FCNTL)
+		is_local = 1;
+
 	if (NFS_PROTO(inode)->lock_check_bounds != NULL) {
 		ret = NFS_PROTO(inode)->lock_check_bounds(fl);
 		if (ret < 0)
···
 	}
 
 	if (IS_GETLK(cmd))
-		ret = do_getlk(filp, cmd, fl);
+		ret = do_getlk(filp, cmd, fl, is_local);
 	else if (fl->fl_type == F_UNLCK)
-		ret = do_unlk(filp, cmd, fl);
+		ret = do_unlk(filp, cmd, fl, is_local);
 	else
-		ret = do_setlk(filp, cmd, fl);
+		ret = do_setlk(filp, cmd, fl, is_local);
 out_err:
 	return ret;
 }
···
  */
 static int nfs_flock(struct file *filp, int cmd, struct file_lock *fl)
 {
+	struct inode *inode = filp->f_mapping->host;
+	int is_local = 0;
+
 	dprintk("NFS: flock(%s/%s, t=%x, fl=%x)\n",
 			filp->f_path.dentry->d_parent->d_name.name,
 			filp->f_path.dentry->d_name.name,
···
 	if (!(fl->fl_flags & FL_FLOCK))
 		return -ENOLCK;
 
+	if (NFS_SERVER(inode)->flags & NFS_MOUNT_LOCAL_FLOCK)
+		is_local = 1;
+
 	/* We're simulating flock() locks using posix locks on the server */
 	fl->fl_owner = (fl_owner_t)filp;
 	fl->fl_start = 0;
 	fl->fl_end = OFFSET_MAX;
 
 	if (fl->fl_type == F_UNLCK)
-		return do_unlk(filp, cmd, fl);
-	return do_setlk(filp, cmd, fl);
+		return do_unlk(filp, cmd, fl, is_local);
+	return do_setlk(filp, cmd, fl, is_local);
 }
 
 /*

fs/nfs/super.c

···
 	Opt_addr, Opt_mountaddr, Opt_clientaddr,
 	Opt_lookupcache,
 	Opt_fscache_uniq,
+	Opt_local_lock,
 
 	/* Special mount options */
 	Opt_userspace, Opt_deprecated, Opt_sloppy,
···
 
 	{ Opt_lookupcache, "lookupcache=%s" },
 	{ Opt_fscache_uniq, "fsc=%s" },
+	{ Opt_local_lock, "local_lock=%s" },
 
 	{ Opt_err, NULL }
 };
···
 	{ Opt_lookupcache_none, "none" },
 
 	{ Opt_lookupcache_err, NULL }
+};
+
+enum {
+	Opt_local_lock_all, Opt_local_lock_flock, Opt_local_lock_posix,
+	Opt_local_lock_none,
+
+	Opt_local_lock_err
+};
+
+static match_table_t nfs_local_lock_tokens = {
+	{ Opt_local_lock_all, "all" },
+	{ Opt_local_lock_flock, "flock" },
+	{ Opt_local_lock_posix, "posix" },
+	{ Opt_local_lock_none, "none" },
+
+	{ Opt_local_lock_err, NULL }
 };
 
 
···
 			break;
 		case Opt_lock:
 			mnt->flags &= ~NFS_MOUNT_NONLM;
+			mnt->flags &= ~(NFS_MOUNT_LOCAL_FLOCK |
+					NFS_MOUNT_LOCAL_FCNTL);
 			break;
 		case Opt_nolock:
 			mnt->flags |= NFS_MOUNT_NONLM;
+			mnt->flags |= (NFS_MOUNT_LOCAL_FLOCK |
+				       NFS_MOUNT_LOCAL_FCNTL);
 			break;
 		case Opt_v2:
 			mnt->flags &= ~NFS_MOUNT_VER3;
···
 			kfree(mnt->fscache_uniq);
 			mnt->fscache_uniq = string;
 			mnt->options |= NFS_OPTION_FSCACHE;
+			break;
+		case Opt_local_lock:
+			string = match_strdup(args);
+			if (string == NULL)
+				goto out_nomem;
+			token = match_token(string, nfs_local_lock_tokens,
+					args);
+			kfree(string);
+			switch (token) {
+			case Opt_local_lock_all:
+				mnt->flags |= (NFS_MOUNT_LOCAL_FLOCK |
+					       NFS_MOUNT_LOCAL_FCNTL);
+				break;
+			case Opt_local_lock_flock:
+				mnt->flags |= NFS_MOUNT_LOCAL_FLOCK;
+				break;
+			case Opt_local_lock_posix:
+				mnt->flags |= NFS_MOUNT_LOCAL_FCNTL;
+				break;
+			case Opt_local_lock_none:
+				mnt->flags &= ~(NFS_MOUNT_LOCAL_FLOCK |
+						NFS_MOUNT_LOCAL_FCNTL);
+				break;
+			default:
+				dfprintk(MOUNT, "NFS:	invalid	"
+						"local_lock argument\n");
+				return 0;
+			};
 			break;
 
 		/*
···
 		if (!args->nfs_server.hostname)
 			goto out_nomem;
 
+		if (!(data->flags & NFS_MOUNT_NONLM))
+			args->flags &= ~(NFS_MOUNT_LOCAL_FLOCK|
+					 NFS_MOUNT_LOCAL_FCNTL);
+		else
+			args->flags |= (NFS_MOUNT_LOCAL_FLOCK|
+					NFS_MOUNT_LOCAL_FCNTL);
 		/*
 		 * The legacy version 6 binary mount data from userspace has a
 		 * field used only to transport selinux information into the
···
 
 static void nfs4_validate_mount_flags(struct nfs_parsed_mount_data *args)
 {
-	args->flags &= ~(NFS_MOUNT_NONLM|NFS_MOUNT_NOACL|NFS_MOUNT_VER3);
+	args->flags &= ~(NFS_MOUNT_NONLM|NFS_MOUNT_NOACL|NFS_MOUNT_VER3|
+			 NFS_MOUNT_LOCAL_FLOCK|NFS_MOUNT_LOCAL_FCNTL);
 }
 
 static int nfs4_validate_text_mount_data(void *options,

include/linux/nfs_mount.h

···
 #define NFS_MOUNT_NORESVPORT		0x40000
 #define NFS_MOUNT_LEGACY_INTERFACE	0x80000
 
+#define NFS_MOUNT_LOCAL_FLOCK	0x100000
+#define NFS_MOUNT_LOCAL_FCNTL	0x200000
+
 #endif