[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,