Linux 5.15 compat: get_acl()

Kernel commits

332f606b32b6 ovl: enable RCU'd ->get_acl()
0cad6246621b vfs: add rcu argument to ->get_acl() callback

Added compatibility code to detect the new ->get_acl() interface
and correctly handle the case where the new rcu argument is set.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>

config/kernel-acl.m4

@@ -162,6 +162,9 @@ dnl #
 dnl # 3.1 API change,
 dnl # Check if inode_operations contains the function get_acl
 dnl #
+dnl # 5.15 API change,
+dnl # Added the bool rcu argument to get_acl for rcu path walk.
+dnl #
 AC_DEFUN([ZFS_AC_KERNEL_SRC_INODE_OPERATIONS_GET_ACL], [
 	ZFS_LINUX_TEST_SRC([inode_operations_get_acl], [
 		#include <linux/fs.h>
@@ -174,14 +177,32 @@ AC_DEFUN([ZFS_AC_KERNEL_SRC_INODE_OPERATIONS_GET_ACL], [
 			.get_acl = get_acl_fn,
 		};
 	],[])
+
+	ZFS_LINUX_TEST_SRC([inode_operations_get_acl_rcu], [
+		#include <linux/fs.h>
+
+		struct posix_acl *get_acl_fn(struct inode *inode, int type,
+		    bool rcu) { return NULL; }
+
+		static const struct inode_operations
+		    iops __attribute__ ((unused)) = {
+			.get_acl = get_acl_fn,
+		};
+	],[])
 ])
 
 AC_DEFUN([ZFS_AC_KERNEL_INODE_OPERATIONS_GET_ACL], [
 	AC_MSG_CHECKING([whether iops->get_acl() exists])
 	ZFS_LINUX_TEST_RESULT([inode_operations_get_acl], [
 		AC_MSG_RESULT(yes)
+		AC_DEFINE(HAVE_GET_ACL, 1, [iops->get_acl() exists])
 	],[
-		ZFS_LINUX_TEST_ERROR([iops->get_acl()])
+		ZFS_LINUX_TEST_RESULT([inode_operations_get_acl_rcu], [
+			AC_MSG_RESULT(yes)
+			AC_DEFINE(HAVE_GET_ACL_RCU, 1, [iops->get_acl() takes rcu])
+		],[
+			ZFS_LINUX_TEST_ERROR([iops->get_acl()])
+		])
 	])
 ])
 

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

@@ -70,7 +70,11 @@ extern int zpl_set_acl(struct user_namespace *userns, struct inode *ip,
 extern int zpl_set_acl(struct inode *ip, struct posix_acl *acl, int type);
 #endif /* HAVE_SET_ACL_USERNS */
 #endif /* HAVE_SET_ACL */
+#if defined(HAVE_GET_ACL_RCU)
+extern struct posix_acl *zpl_get_acl(struct inode *ip, int type, bool rcu);
+#elif defined(HAVE_GET_ACL)
 extern struct posix_acl *zpl_get_acl(struct inode *ip, int type);
+#endif
 extern int zpl_init_acl(struct inode *ip, struct inode *dir);
 extern int zpl_chmod_acl(struct inode *ip);
 #else

module/os/linux/zfs/zpl_xattr.c

@@ -1012,13 +1012,12 @@ zpl_set_acl(struct inode *ip, struct posix_acl *acl, int type)
 }
 #endif /* HAVE_SET_ACL */
 
-struct posix_acl *
-zpl_get_acl(struct inode *ip, int type)
+static struct posix_acl *
+zpl_get_acl_impl(struct inode *ip, int type)
 {
 	struct posix_acl *acl;
 	void *value = NULL;
 	char *name;
-	int size;
 
 	/*
 	 * As of Linux 3.14, the kernel get_acl will check this for us.
@@ -1042,7 +1041,7 @@ zpl_get_acl(struct inode *ip, int type)
 		return (ERR_PTR(-EINVAL));
 	}
 
-	size = zpl_xattr_get(ip, name, NULL, 0);
+	int size = zpl_xattr_get(ip, name, NULL, 0);
 	if (size > 0) {
 		value = kmem_alloc(size, KM_SLEEP);
 		size = zpl_xattr_get(ip, name, value, size);
@@ -1068,6 +1067,25 @@ zpl_get_acl(struct inode *ip, int type)
 	return (acl);
 }
 
+#if defined(HAVE_GET_ACL_RCU)
+struct posix_acl *
+zpl_get_acl(struct inode *ip, int type, bool rcu)
+{
+	if (rcu)
+		return (ERR_PTR(-ECHILD));
+
+	return (zpl_get_acl_impl(ip, type));
+}
+#elif defined(HAVE_GET_ACL)
+struct posix_acl *
+zpl_get_acl(struct inode *ip, int type)
+{
+	return (zpl_get_acl_impl(ip, type));
+}
+#else
+#error "Unsupported iops->get_acl() implementation"
+#endif /* HAVE_GET_ACL_RCU */
+
 int
 zpl_init_acl(struct inode *ip, struct inode *dir)
 {