Add trivial acl helpers

The zfs acl code makes use of the two OpenSolaris helper functions
acl_trivial_access_masks() and ace_trivial_common().  Since they are
only called from zfs_acl.c I've brought them over from OpenSolaris
and added them as static function to this file.  This way I don't
need to reimplement this functionality from scratch in the SPL.

Long term once I take a more careful look at the acl implementation
it may be the case that these functions really aren't needed.  If
that turns out to be the case they can then be removed.

module/zfs/zfs_acl.c

@@ -53,7 +53,6 @@
 #include <sys/zap.h>
 #include <sys/sa.h>
 #include "fs/fs_subr.h"
-#include <acl/acl_common.h>
 
 #define	ALLOW	ACE_ACCESS_ALLOWED_ACE_TYPE
 #define	DENY	ACE_ACCESS_DENIED_ACE_TYPE
@@ -1166,6 +1165,126 @@ zfs_acl_chown_setattr(znode_t *zp)
 	return (error);
 }
 
+static void
+acl_trivial_access_masks(mode_t mode, uint32_t *allow0, uint32_t *deny1,
+    uint32_t *deny2, uint32_t *owner, uint32_t *group, uint32_t *everyone)
+{
+	*deny1 = *deny2 = *allow0 = *group = 0;
+
+	if (!(mode & S_IRUSR) && (mode & (S_IRGRP|S_IROTH)))
+		*deny1 |= ACE_READ_DATA;
+	if (!(mode & S_IWUSR) && (mode & (S_IWGRP|S_IWOTH)))
+		*deny1 |= ACE_WRITE_DATA;
+	if (!(mode & S_IXUSR) && (mode & (S_IXGRP|S_IXOTH)))
+		*deny1 |= ACE_EXECUTE;
+
+	if (!(mode & S_IRGRP) && (mode & S_IROTH))
+		*deny2 = ACE_READ_DATA;
+	if (!(mode & S_IWGRP) && (mode & S_IWOTH))
+		*deny2 |= ACE_WRITE_DATA;
+	if (!(mode & S_IXGRP) && (mode & S_IXOTH))
+		*deny2 |= ACE_EXECUTE;
+
+	if ((mode & S_IRUSR) && (!(mode & S_IRGRP) && (mode & S_IROTH)))
+		*allow0 |= ACE_READ_DATA;
+	if ((mode & S_IWUSR) && (!(mode & S_IWGRP) && (mode & S_IWOTH)))
+		*allow0 |= ACE_WRITE_DATA;
+	if ((mode & S_IXUSR) && (!(mode & S_IXGRP) && (mode & S_IXOTH)))
+		*allow0 |= ACE_EXECUTE;
+
+	*owner = ACE_WRITE_ATTRIBUTES|ACE_WRITE_OWNER|ACE_WRITE_ACL|
+	    ACE_WRITE_NAMED_ATTRS|ACE_READ_ACL|ACE_READ_ATTRIBUTES|
+	    ACE_READ_NAMED_ATTRS|ACE_SYNCHRONIZE;
+	if (mode & S_IRUSR)
+		*owner |= ACE_READ_DATA;
+	if (mode & S_IWUSR)
+		*owner |= ACE_WRITE_DATA|ACE_APPEND_DATA;
+	if (mode & S_IXUSR)
+		*owner |= ACE_EXECUTE;
+
+	*group = ACE_READ_ACL|ACE_READ_ATTRIBUTES| ACE_READ_NAMED_ATTRS|
+	    ACE_SYNCHRONIZE;
+	if (mode & S_IRGRP)
+		*group |= ACE_READ_DATA;
+	if (mode & S_IWGRP)
+		*group |= ACE_WRITE_DATA|ACE_APPEND_DATA;
+	if (mode & S_IXGRP)
+		*group |= ACE_EXECUTE;
+
+	*everyone = ACE_READ_ACL|ACE_READ_ATTRIBUTES| ACE_READ_NAMED_ATTRS|
+	    ACE_SYNCHRONIZE;
+	if (mode & S_IROTH)
+		*everyone |= ACE_READ_DATA;
+	if (mode & S_IWOTH)
+		*everyone |= ACE_WRITE_DATA|ACE_APPEND_DATA;
+	if (mode & S_IXOTH)
+		*everyone |= ACE_EXECUTE;
+}
+
+/*
+ * ace_trivial:
+ * determine whether an ace_t acl is trivial
+ *
+ * Trivialness implies that the acl is composed of only
+ * owner, group, everyone entries.  ACL can't
+ * have read_acl denied, and write_owner/write_acl/write_attributes
+ * can only be owner@ entry.
+ */
+static int
+ace_trivial_common(void *acep, int aclcnt,
+    uint64_t (*walk)(void *, uint64_t, int aclcnt,
+    uint16_t *, uint16_t *, uint32_t *))
+{
+	uint16_t flags;
+	uint32_t mask;
+	uint16_t type;
+	uint64_t cookie = 0;
+
+	while ((cookie = walk(acep, cookie, aclcnt, &flags, &type, &mask))) {
+		switch (flags & ACE_TYPE_FLAGS) {
+		case ACE_OWNER:
+		case ACE_GROUP|ACE_IDENTIFIER_GROUP:
+		case ACE_EVERYONE:
+			break;
+		default:
+			return (1);
+		}
+
+		if (flags & (ACE_FILE_INHERIT_ACE|
+		    ACE_DIRECTORY_INHERIT_ACE|ACE_NO_PROPAGATE_INHERIT_ACE|
+		    ACE_INHERIT_ONLY_ACE))
+			return (1);
+
+		/*
+		 * Special check for some special bits
+		 *
+		 * Don't allow anybody to deny reading basic
+		 * attributes or a files ACL.
+		 */
+		if ((mask & (ACE_READ_ACL|ACE_READ_ATTRIBUTES)) &&
+		    (type == ACE_ACCESS_DENIED_ACE_TYPE))
+			return (1);
+
+		/*
+		 * Delete permissions are never set by default
+		 */
+		if (mask & (ACE_DELETE|ACE_DELETE_CHILD))
+			return (1);
+		/*
+		 * only allow owner@ to have
+		 * write_acl/write_owner/write_attributes/write_xattr/
+		 */
+		if (type == ACE_ACCESS_ALLOWED_ACE_TYPE &&
+		    (!(flags & ACE_OWNER) && (mask &
+		    (ACE_WRITE_OWNER|ACE_WRITE_ACL| ACE_WRITE_ATTRIBUTES|
+		    ACE_WRITE_NAMED_ATTRS))))
+			return (1);
+
+	}
+
+	return (0);
+}
+
 /*
  * common code for setting ACLs.
  *