[Dazuko-devel] Bug in dazukofs_lookup()

[Lino Sanfilippo]

This patch fixes a bug in dazukofs_lookup():

If interpose fails we must not dput() the lower dentry, since at this
time the dentry operations have already been set up. This
includes the d_release() operation which already cares about dput().

This patch also removes some unnecessary lines of code:
- The check for "." and ".." dentries is not needed, since the vfs will 
never pass those
dentries down to our lookup function.
- we never have to unhash() a dentry, since after we hashed a dentry via 
d_add() (in lookup() or
interpose()), there are no errors possible.
- setting up dentry operations in interpose() is redundant (since 
already done in  lookup())

The flag passed to interpose() has been renamed, since it indicates if a 
dentry should be hashed,
not that it already has been hashed.

Please apply this patch after patch 1 that has been posted yesterday.

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diff -rup dazukofs-3.1.0-rc2-Patched/inode.c dazukofs-3.1.0-rc2-Patched2/inode.c
--- dazukofs-3.1.0-rc2-Patched/inode.c  2009-07-09 17:34:25.000000000 +0200
+++ dazukofs-3.1.0-rc2-Patched2/inode.c 2009-07-10 15:47:55.000000000 +0200
@@ -74,7 +74,7 @@ static int dazukofs_inode_set(struct ino
  * Returns 0 on success.
  */
 int dazukofs_interpose(struct dentry *lower_dentry, struct dentry *dentry,
-                      struct super_block *sb, int already_hashed)
+                      struct super_block *sb, int hash)
 {
        struct inode *inode;
        struct inode *lower_inode = igrab(lower_dentry->d_inode);
@@ -122,9 +122,7 @@ int dazukofs_interpose(struct dentry *lo
                                   lower_inode->i_rdev);
        }
 
-       dentry->d_op = &dazukofs_dops;
-
-       if (already_hashed)
+       if (hash)
                d_add(dentry, inode);
        else
                d_instantiate(dentry, inode);
@@ -156,19 +154,6 @@ static struct dentry *dazukofs_lookup(st
        struct vfsmount *lower_mnt;
        int err = 0;
 
-       /* check for "." or ".." (they are not relevant here) */
-       if (dentry->d_name.len == 1) {
-               if (dentry->d_name.name[0] == '.') {
-                       d_drop(dentry);
-                       goto out;
-               }
-       } else if (dentry->d_name.len == 2) {
-               if (dentry->d_name.name[0] == '.' &&
-                   dentry->d_name.name[1] == '.') {
-                       d_drop(dentry);
-                       goto out;
-               }
-       }
 
        dentry->d_op = &dazukofs_dops;
 
@@ -180,7 +165,6 @@ static struct dentry *dazukofs_lookup(st
        mutex_unlock(&lower_dentry_parent->d_inode->i_mutex);
        if (IS_ERR(lower_dentry)) {
                err = PTR_ERR(lower_dentry);
-               d_drop(dentry);
                goto out;
        }
 
@@ -191,9 +175,11 @@ static struct dentry *dazukofs_lookup(st
                                             GFP_KERNEL));
        if (!get_dentry_private(dentry)) {
                err = -ENOMEM;
-               goto out_dput;
+               dput(lower_dentry);
+               goto out;
        }
-
+       /* from now lower dentry and lower mount are released in 
+        * d_release() */
        fsstack_copy_attr_atime(dir, lower_dentry_parent->d_inode);
 
        lower_mnt = mntget(get_lower_mnt(dentry->d_parent));
@@ -206,15 +192,8 @@ static struct dentry *dazukofs_lookup(st
                d_add(dentry, NULL);
                goto out;
        }
-
        err = dazukofs_interpose(lower_dentry, dentry, dir->i_sb, 1);
-       if (err)
-               goto out_dput;
-       goto out;
 
-out_dput:
-       dput(lower_dentry);
-       d_drop(dentry);
 out:
        return ERR_PTR(err);
 }
Nur in dazukofs-3.1.0-rc2-Patched: .inode.c.swp.