locks: Use inode_is_open_for_write

Use the aptly named function rather than open coding it. No functional
changes.
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>

fs/locks.c

@@ -1766,7 +1766,7 @@ check_conflicting_open(const struct dentry *dentry, const long arg, int flags)
 	if (flags & FL_LAYOUT)
 		return 0;
 
-	if ((arg == F_RDLCK) && (atomic_read(&inode->i_writecount) > 0))
+	if ((arg == F_RDLCK) && inode_is_open_for_write(inode))
 		return -EAGAIN;
 
 	if ((arg == F_WRLCK) && ((d_count(dentry) > 1) ||