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>

1 files changed, 35 insertions, 8 deletions

diff --git a/fs/jfs/namei.c b/fs/jfs/namei.c
index 231ca4af9bce..2da1546161fa 100644
--- 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,
 };