[XFS] Return case-insensitive match for dentry cache

This implements the code to store the actual filename found during a
lookup in the dentry cache and to avoid multiple entries in the dcache
pointing to the same inode.

To avoid polluting the dcache, we implement a new directory inode
operations for lookup. xfs_vn_ci_lookup() stores the correct case name in
the dcache.

The "actual name" is only allocated and returned for a case- insensitive
match and not an actual match.

Another unusual interaction with the dcache is not storing negative
dentries like other filesystems doing a d_add(dentry, NULL) when an ENOENT
is returned. During the VFS lookup, if a dentry returned has no inode,
dput is called and ENOENT is returned. By not doing a d_add, this actually
removes it completely from the dcache to be reused. create/rename have to
be modified to support unhashed dentries being passed in.

SGI-PV: 981521
SGI-Modid: xfs-linux-melb:xfs-kern:31208a

Signed-off-by: Barry Naujok <bnaujok@sgi.com>
Signed-off-by: Christoph Hellwig <hch@infradead.org>

1 files changed, 56 insertions, 1 deletions

diff --git a/fs/xfs/linux-2.6/xfs_iops.c b/fs/xfs/linux-2.6/xfs_iops.c
index 13b6cfd366c2..9f0f8ee8d44d 100644
--- a/fs/xfs/linux-2.6/xfs_iops.c
+++ b/fs/xfs/linux-2.6/xfs_iops.c
@@ -382,7 +382,7 @@ xfs_vn_lookup(
 		return ERR_PTR(-ENAMETOOLONG);
 
 	xfs_dentry_to_name(&name, dentry);
-	error = xfs_lookup(XFS_I(dir), &name, &cip);
+	error = xfs_lookup(XFS_I(dir), &name, &cip, NULL);
 	if (unlikely(error)) {
 		if (unlikely(error != ENOENT))
 			return ERR_PTR(-error);
@@ -393,6 +393,42 @@ xfs_vn_lookup(
 	return d_splice_alias(cip->i_vnode, dentry);
 }
 
+STATIC struct dentry *
+xfs_vn_ci_lookup(
+	struct inode	*dir,
+	struct dentry	*dentry,
+	struct nameidata *nd)
+{
+	struct xfs_inode *ip;
+	struct xfs_name	xname;
+	struct xfs_name ci_name;
+	struct qstr	dname;
+	int		error;
+
+	if (dentry->d_name.len >= MAXNAMELEN)
+		return ERR_PTR(-ENAMETOOLONG);
+
+	xfs_dentry_to_name(&xname, dentry);
+	error = xfs_lookup(XFS_I(dir), &xname, &ip, &ci_name);
+	if (unlikely(error)) {
+		if (unlikely(error != ENOENT))
+			return ERR_PTR(-error);
+		d_add(dentry, NULL);
+		return NULL;
+	}
+
+	/* if exact match, just splice and exit */
+	if (!ci_name.name)
+		return d_splice_alias(ip->i_vnode, dentry);
+
+	/* else case-insensitive match... */
+	dname.name = ci_name.name;
+	dname.len = ci_name.len;
+	dentry = d_add_ci(ip->i_vnode, dentry, &dname);
+	kmem_free(ci_name.name);
+	return dentry;
+}
+
 STATIC int
 xfs_vn_link(
 	struct dentry	*old_dentry,
@@ -892,6 +928,25 @@ const struct inode_operations xfs_dir_inode_operations = {
 	.removexattr		= xfs_vn_removexattr,
 };
 
+const struct inode_operations xfs_dir_ci_inode_operations = {
+	.create			= xfs_vn_create,
+	.lookup			= xfs_vn_ci_lookup,
+	.link			= xfs_vn_link,
+	.unlink			= xfs_vn_unlink,
+	.symlink		= xfs_vn_symlink,
+	.mkdir			= xfs_vn_mkdir,
+	.rmdir			= xfs_vn_rmdir,
+	.mknod			= xfs_vn_mknod,
+	.rename			= xfs_vn_rename,
+	.permission		= xfs_vn_permission,
+	.getattr		= xfs_vn_getattr,
+	.setattr		= xfs_vn_setattr,
+	.setxattr		= xfs_vn_setxattr,
+	.getxattr		= xfs_vn_getxattr,
+	.listxattr		= xfs_vn_listxattr,
+	.removexattr		= xfs_vn_removexattr,
+};
+
 const struct inode_operations xfs_symlink_inode_operations = {
 	.readlink		= generic_readlink,
 	.follow_link		= xfs_vn_follow_link,