vfs: move ACL cache lookup into generic code

This moves logic for checking the cached ACL values from low-level
filesystems into generic code.  The end result is a streamlined ACL
check that doesn't need to load the inode->i_op->check_acl pointer at
all for the common cached case.

The filesystems also don't need to check for a non-blocking RCU walk
case in their acl_check() functions, because that is all handled at a
VFS layer.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/btrfs/acl.c b/fs/btrfs/acl.c
index 9f62ab2..c13ea9f 100644
--- a/fs/btrfs/acl.c
+++ b/fs/btrfs/acl.c
@@ -198,19 +198,14 @@
 int btrfs_check_acl(struct inode *inode, int mask)
 {
 	int error = -EAGAIN;
+	struct posix_acl *acl;
 
-	if (mask & MAY_NOT_BLOCK) {
-		if (!negative_cached_acl(inode, ACL_TYPE_ACCESS))
-			error = -ECHILD;
-	} else {
-		struct posix_acl *acl;
-		acl = btrfs_get_acl(inode, ACL_TYPE_ACCESS);
-		if (IS_ERR(acl))
-			return PTR_ERR(acl);
-		if (acl) {
-			error = posix_acl_permission(inode, acl, mask);
-			posix_acl_release(acl);
-		}
+	acl = btrfs_get_acl(inode, ACL_TYPE_ACCESS);
+	if (IS_ERR(acl))
+		return PTR_ERR(acl);
+	if (acl) {
+		error = posix_acl_permission(inode, acl, mask);
+		posix_acl_release(acl);
 	}
 
 	return error;