cifs: add support for flock

The flock system call locks the whole file rather than a byte
range and so is currently emulated by various other file systems
by simply sending a byte range lock for the whole file.
Add flock handling for cifs.ko in similar way.

xfstest generic/504 passes with this as well

Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>

fs/cifs/cifsfs.c

@@ -1219,6 +1219,7 @@ const struct file_operations cifs_file_ops = {
 	.open = cifs_open,
 	.release = cifs_close,
 	.lock = cifs_lock,
+	.flock = cifs_flock,
 	.fsync = cifs_fsync,
 	.flush = cifs_flush,
 	.mmap  = cifs_file_mmap,
@@ -1238,6 +1239,7 @@ const struct file_operations cifs_file_strict_ops = {
 	.open = cifs_open,
 	.release = cifs_close,
 	.lock = cifs_lock,
+	.flock = cifs_flock,
 	.fsync = cifs_strict_fsync,
 	.flush = cifs_flush,
 	.mmap = cifs_file_strict_mmap,
@@ -1257,6 +1259,7 @@ const struct file_operations cifs_file_direct_ops = {
 	.open = cifs_open,
 	.release = cifs_close,
 	.lock = cifs_lock,
+	.flock = cifs_flock,
 	.fsync = cifs_fsync,
 	.flush = cifs_flush,
 	.mmap = cifs_file_mmap,

fs/cifs/cifsfs.h

@@ -108,6 +108,7 @@ extern ssize_t cifs_strict_readv(struct kiocb *iocb, struct iov_iter *to);
 extern ssize_t cifs_user_writev(struct kiocb *iocb, struct iov_iter *from);
 extern ssize_t cifs_direct_writev(struct kiocb *iocb, struct iov_iter *from);
 extern ssize_t cifs_strict_writev(struct kiocb *iocb, struct iov_iter *from);
+extern int cifs_flock(struct file *pfile, int cmd, struct file_lock *plock);
 extern int cifs_lock(struct file *, int, struct file_lock *);
 extern int cifs_fsync(struct file *, loff_t, loff_t, int);
 extern int cifs_strict_fsync(struct file *, loff_t, loff_t, int);

fs/cifs/file.c

@@ -1681,7 +1681,7 @@ cifs_setlk(struct file *file, struct file_lock *flock, __u32 type,
 		rc = server->ops->mand_unlock_range(cfile, flock, xid);
 
 out:
-	if (flock->fl_flags & FL_POSIX) {
+	if ((flock->fl_flags & FL_POSIX) || (flock->fl_flags & FL_FLOCK)) {
 		/*
 		 * If this is a request to remove all locks because we
 		 * are closing the file, it doesn't matter if the
@@ -1698,6 +1698,56 @@ out:
 	return rc;
 }
 
+int cifs_flock(struct file *file, int cmd, struct file_lock *fl)
+{
+	int rc, xid;
+	int lock = 0, unlock = 0;
+	bool wait_flag = false;
+	bool posix_lck = false;
+	struct cifs_sb_info *cifs_sb;
+	struct cifs_tcon *tcon;
+	struct cifsInodeInfo *cinode;
+	struct cifsFileInfo *cfile;
+	__u16 netfid;
+	__u32 type;
+
+	rc = -EACCES;
+	xid = get_xid();
+
+	if (!(fl->fl_flags & FL_FLOCK))
+		return -ENOLCK;
+
+	cfile = (struct cifsFileInfo *)file->private_data;
+	tcon = tlink_tcon(cfile->tlink);
+
+	cifs_read_flock(fl, &type, &lock, &unlock, &wait_flag,
+			tcon->ses->server);
+	cifs_sb = CIFS_FILE_SB(file);
+	netfid = cfile->fid.netfid;
+	cinode = CIFS_I(file_inode(file));
+
+	if (cap_unix(tcon->ses) &&
+	    (CIFS_UNIX_FCNTL_CAP & le64_to_cpu(tcon->fsUnixInfo.Capability)) &&
+	    ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NOPOSIXBRL) == 0))
+		posix_lck = true;
+
+	if (!lock && !unlock) {
+		/*
+		 * if no lock or unlock then nothing to do since we do not
+		 * know what it is
+		 */
+		free_xid(xid);
+		return -EOPNOTSUPP;
+	}
+
+	rc = cifs_setlk(file, fl, type, wait_flag, posix_lck, lock, unlock,
+			xid);
+	free_xid(xid);
+	return rc;
+
+
+}
+
 int cifs_lock(struct file *file, int cmd, struct file_lock *flock)
 {
 	int rc, xid;