Re: [PATCH 2/4] XFS: Return case-insensitive match for dentry cache

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On Mon, 21 Apr 2008 18:59:47 +1000, Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote:

+STATIC struct dentry *
+xfs_ci_dentry_update(
+	struct dentry	*dent,
+	struct inode	*dent_inode,
+	struct xfs_name	*name)
+{
+	int		err;
+	struct dentry	*real_dent;
+	struct dentry	*new_dent;
+	struct qstr	nls_name;

This helper should go into fs/dcache.c with a slightly move descritive
name (d_add_ci?).

Also the naming is rather odd, please replace every occurance of
dent with dentry, and the variable dent_inode should be just inode.

Also when moving this to dcache.c please provide a nice big kerneldoc
comment describing it like Anton did for the ntfs lookup instance.
of the

+	/*
+	 * following code from ntfs_lookup() in fs/ntfs/namei.c
+	 */

Not a very helpful comment :)

+		new_dent = d_splice_alias(dent_inode, real_dent);
+		if (new_dent)
+			dput(real_dent);
+		else
+			new_dent = real_dent;
+		return new_dent;

I think this would be more readable as

		if (new_dentry) {
			dput(real_dentry);
			return new_dentry;
		}
		return real_dentry;

+	/* Matching dentry exists, check if it is negative. */
+	if (real_dent->d_inode) {
+		if (unlikely(real_dent->d_inode != dent_inode)) {
+			/* This can happen because bad inodes are unhashed. */
+			BUG_ON(!is_bad_inode(dent_inode));
+			BUG_ON(!is_bad_inode(real_dent->d_inode));
+		}

Shouldn't this be a can't above?

+		 * Already have the inode and the dentry attached, decrement
+		 * the reference count to balance the xfs_lookup() we did
+		 * earlier on.  We found the dentry using d_lookup() so it
+		 * cannot be disconnected and thus we do not need to worry
+		 * about any NFS/disconnectedness issues here.

		s/xfs_lookup/iget/

This whole function (other than the xfs_blah) is a direct copy of
Anton's code, I left the variable names etc the same.

+kmem_zone_t	*xfs_name_zone;

What about just using kmalloc here?  We know the length of the name
anyway, so there is no point of allocating the maximum possible size.

Not with the CI/NLS, the length could be different.

 	error = xfs_iget(dp->i_mount, NULL, inum, 0, 0, ipp, 0);
-	if (error)
+	if (error) {
+		if (ci_match && *ci_match)
+			xfs_name_free(name->name);
 		goto out;
+	}

All the allocation and freeing for ci_match looks odd and error prone
to me.  I think the low-level directory code should never allocate
args->value unless it's explicitly asked for a CI match.  That way
there's only one place in xfs_ci_lookup to free it either.

Yes, I could do that, it is a neater, cleaner implementation. I did it
this way to only alloc as required rather than an alloc for every lookup.

Barry.
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