jfs: dont overwrite dentry name in d_revalidate

Use vfat's method for dealing with negative dentries to preserve case,
rather than overwrite dentry name in d_revalidate, which is a bit ugly
and also gets in the way of doing lock-free path walking.

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

diff --git a/fs/jfs/namei.c b/fs/jfs/namei.c
index 231ca4a..2da1546 100644 (file)
--- a/fs/jfs/namei.c
+++ b/fs/jfs/namei.c
@@ -18,6 +18,7 @@
  */
 
 #include <linux/fs.h>
+#include <linux/namei.h>
 #include <linux/ctype.h>
 #include <linux/quotaops.h>
 #include <linux/exportfs.h>
@@ -1597,21 +1598,47 @@ static int jfs_ci_compare(struct dentry *dir, struct qstr *a, struct qstr *b)
                        goto out;
        }
        result = 0;
+out:
+       return result;
+}
 
+static int jfs_ci_revalidate(struct dentry *dentry, struct nameidata *nd)
+{
        /*
-        * We want creates to preserve case.  A negative dentry, a, that
-        * has a different case than b may cause a new entry to be created
-        * with the wrong case.  Since we can't tell if a comes from a negative
-        * dentry, we blindly replace it with b.  This should be harmless if
-        * a is not a negative dentry.
+        * This is not negative dentry. Always valid.
+        *
+        * Note, rename() to existing directory entry will have ->d_inode,
+        * and will use existing name which isn't specified name by user.
+        *
+        * We may be able to drop this positive dentry here. But dropping
+        * positive dentry isn't good idea. So it's unsupported like
+        * rename("filename", "FILENAME") for now.
         */
-       memcpy((unsigned char *)a->name, b->name, a->len);
-out:
-       return result;
+       if (dentry->d_inode)
+               return 1;
+
+       /*
+        * This may be nfsd (or something), anyway, we can't see the
+        * intent of this. So, since this can be for creation, drop it.
+        */
+       if (!nd)
+               return 0;
+
+       /*
+        * Drop the negative dentry, in order to make sure to use the
+        * case sensitive name which is specified by user if this is
+        * for creation.
+        */
+       if (!(nd->flags & (LOOKUP_CONTINUE | LOOKUP_PARENT))) {
+               if (nd->flags & (LOOKUP_CREATE | LOOKUP_RENAME_TARGET))
+                       return 0;
+       }
+       return 1;
 }
 
 const struct dentry_operations jfs_ci_dentry_operations =
 {
        .d_hash = jfs_ci_hash,
        .d_compare = jfs_ci_compare,
+       .d_revalidate = jfs_ci_revalidate,
 };