split do_revalidate() into RCU and non-RCU cases

fixing oopsen in lookup_one_len()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 30 insertions, 17 deletions

diff --git a/fs/namei.c b/fs/namei.c
index 7609bacc704..a98f7f14178 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -592,12 +592,10 @@ static int d_revalidate(struct dentry *dentry, struct nameidata *nd)
         return status;
 }
 
-static inline struct dentry *
+static struct dentry *
 do_revalidate(struct dentry *dentry, struct nameidata *nd)
 {
-        int status;
-
-        status = d_revalidate(dentry, nd);
+        int status = d_revalidate(dentry, nd);
         if (unlikely(status <= 0)) {
                 /*
                  * The dentry failed validation.
@@ -606,24 +604,39 @@ do_revalidate(struct dentry *dentry, struct nameidata *nd)
                  * to return a fail status.
                  */
                 if (status < 0) {
-                        /* If we're in rcu-walk, we don't have a ref */
-                        if (!(nd->flags & LOOKUP_RCU))
-                                dput(dentry);
+                        dput(dentry);
                         dentry = ERR_PTR(status);
-
-                } else {
-                        /* Don't d_invalidate in rcu-walk mode */
-                        if (nameidata_dentry_drop_rcu_maybe(nd, dentry))
-                                return ERR_PTR(-ECHILD);
-                        if (!d_invalidate(dentry)) {
-                                dput(dentry);
-                                dentry = NULL;
-                        }
+                } else if (!d_invalidate(dentry)) {
+                        dput(dentry);
+                        dentry = NULL;
                 }
         }
         return dentry;
 }
 
+static inline struct dentry *
+do_revalidate_rcu(struct dentry *dentry, struct nameidata *nd)
+{
+        int status = dentry->d_op->d_revalidate(dentry, nd);
+        if (likely(status > 0))
+                return dentry;
+        if (status == -ECHILD) {
+                if (nameidata_dentry_drop_rcu(nd, dentry))
+                        return ERR_PTR(-ECHILD);
+                return do_revalidate(dentry, nd);
+        }
+        if (status < 0)
+                return ERR_PTR(status);
+        /* Don't d_invalidate in rcu-walk mode */
+        if (nameidata_dentry_drop_rcu(nd, dentry))
+                return ERR_PTR(-ECHILD);
+        if (!d_invalidate(dentry)) {
+                dput(dentry);
+                dentry = NULL;
+        }
+        return dentry;
+}
+
 static inline int need_reval_dot(struct dentry *dentry)
 {
         if (likely(!(dentry->d_flags & DCACHE_OP_REVALIDATE)))
@@ -1260,7 +1273,7 @@ static int do_lookup(struct nameidata *nd, struct qstr *name,
 
                 nd->seq = seq;
                 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) {
-                        dentry = do_revalidate(dentry, nd);
+                        dentry = do_revalidate_rcu(dentry, nd);
                         if (!dentry)
                                 goto need_lookup;
                         if (IS_ERR(dentry))