Make zpl_permission work with 5.12+ kernels

The "permission" inode operation takes a new `struct user_namespace *`
parameter starting in Linux 5.12.

Add a configure check and adapt accordingly.

Signed-off-by: Ryan Moeller <[email protected]>

Author: Ryan Moeller

include/os/linux/zfs/sys/zpl.h

@@ -91,7 +91,12 @@ zpl_chmod_acl(struct inode *ip)
 }
 #endif /* CONFIG_FS_POSIX_ACL */
 
+#if defined(HAVE_IOPS_PERMISSION_USERNS)
+extern int zpl_permission(struct user_namespace *userns, struct inode *ip,
+    int mask);
+#else
 extern int zpl_permission(struct inode *ip, int mask);
+#endif
 
 extern xattr_handler_t *zpl_xattr_handlers[];
 

module/os/linux/zfs/zpl_xattr.c

@@ -1449,7 +1449,11 @@ static xattr_handler_t zpl_xattr_acl_default_handler = {
 #endif /* CONFIG_FS_POSIX_ACL */
 
 int
+#if defined(HAVE_IOPS_PERMISSION_USERNS)
+zpl_permission(struct user_namespace *userns, struct inode *ip, int mask)
+#else
 zpl_permission(struct inode *ip, int mask)
+#endif
 {
 	int to_check = 0, i, ret;
 	cred_t *cr = NULL;
@@ -1462,7 +1466,11 @@ zpl_permission(struct inode *ip, int mask)
 	 */
 	if ((ITOZSB(ip)->z_acl_type != ZFS_ACLTYPE_NFSV4) ||
 	    ((ITOZ(ip)->z_pflags & ZFS_ACL_TRIVIAL && GENERIC_MASK(mask)))) {
+#if defined(HAVE_IOPS_PERMISSION_USERNS)
+		return (generic_permission(userns, ip, mask));
+#else
 		return (generic_permission(ip, mask));
+#endif
 	}
 
 	for (i = 0; i < ARRAY_SIZE(mask2zfs); i++) {
@@ -1476,7 +1484,11 @@ zpl_permission(struct inode *ip, int mask)
 	 * NFSv4 ACE. Pass back to default kernel permissions check.
 	 */
 	if (to_check == 0) {
+#if defined(HAVE_IOPS_PERMISSION_USERNS)
+		return (generic_permission(userns, ip, mask));
+#else
 		return (generic_permission(ip, mask));
+#endif
 	}
 
 	/*