ext2,3,4: 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>

3 files changed, 15 insertions, 6 deletions

diff --git a/fs/ext2/acl.c b/fs/ext2/acl.c
index dd9bb3f0c8d7..7b4180554a62 100644
--- a/fs/ext2/acl.c
+++ b/fs/ext2/acl.c
@@ -236,8 +236,11 @@ ext2_check_acl(struct inode *inode, int mask, unsigned int flags)
 {
         struct posix_acl *acl;
 
-        if (flags & IPERM_FLAG_RCU)
-                return -ECHILD;
+        if (flags & IPERM_FLAG_RCU) {
+                if (!negative_cached_acl(inode, ACL_TYPE_ACCESS))
+                        return -ECHILD;
+                return -EAGAIN;
+        }
 
         acl = ext2_get_acl(inode, ACL_TYPE_ACCESS);
         if (IS_ERR(acl))
diff --git a/fs/ext3/acl.c b/fs/ext3/acl.c
index 9e49da8302d3..e4fa49e6c539 100644
--- a/fs/ext3/acl.c
+++ b/fs/ext3/acl.c
@@ -244,8 +244,11 @@ ext3_check_acl(struct inode *inode, int mask, unsigned int flags)
 {
         struct posix_acl *acl;
 
-        if (flags & IPERM_FLAG_RCU)
-                return -ECHILD;
+        if (flags & IPERM_FLAG_RCU) {
+                if (!negative_cached_acl(inode, ACL_TYPE_ACCESS))
+                        return -ECHILD;
+                return -EAGAIN;
+        }
 
         acl = ext3_get_acl(inode, ACL_TYPE_ACCESS);
         if (IS_ERR(acl))
diff --git a/fs/ext4/acl.c b/fs/ext4/acl.c
index 373dcaeedba9..e0270d1f8d82 100644
--- a/fs/ext4/acl.c
+++ b/fs/ext4/acl.c
@@ -242,8 +242,11 @@ ext4_check_acl(struct inode *inode, int mask, unsigned int flags)
 {
         struct posix_acl *acl;
 
-        if (flags & IPERM_FLAG_RCU)
-                return -ECHILD;
+        if (flags & IPERM_FLAG_RCU) {
+                if (!negative_cached_acl(inode, ACL_TYPE_ACCESS))
+                        return -ECHILD;
+                return -EAGAIN;
+        }
 
         acl = ext4_get_acl(inode, ACL_TYPE_ACCESS);
         if (IS_ERR(acl))