btrfs: provide simple rcu-walk ACL implementation

This simple implementation just checks for no ACLs on the inode, and
if so, then the rcu-walk may proceed, otherwise fail it.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>

1 files changed, 12 insertions, 9 deletions

diff --git a/fs/btrfs/acl.c b/fs/btrfs/acl.c
index cb518a4b917c..6ae2c8cac9d5 100644
--- a/fs/btrfs/acl.c
+++ b/fs/btrfs/acl.c
@@ -187,18 +187,21 @@ static int btrfs_xattr_acl_set(struct dentry *dentry, const char *name,
 
 int btrfs_check_acl(struct inode *inode, int mask, unsigned int flags)
 {
-        struct posix_acl *acl;
         int error = -EAGAIN;
 
-        if (flags & IPERM_FLAG_RCU)
-                return -ECHILD;
+        if (flags & IPERM_FLAG_RCU) {
+                if (!negative_cached_acl(inode, ACL_TYPE_ACCESS))
+                        error = -ECHILD;
 
-        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);
+        } 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);
+                }
         }
 
         return error;