[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, 3 insertions, 2 deletions

diff --git a/fs/xfs/xfs_dir2_leaf.c b/fs/xfs/xfs_dir2_leaf.c
index 2ebbed4f1b0d..f110242d6dfc 100644
--- a/fs/xfs/xfs_dir2_leaf.c
+++ b/fs/xfs/xfs_dir2_leaf.c
@@ -1299,12 +1299,13 @@ xfs_dir2_leaf_lookup(
               ((char *)dbp->data +
                xfs_dir2_dataptr_to_off(dp->i_mount, be32_to_cpu(lep->address)));
         /*
-         * Return the found inode number.
+         * Return the found inode number & CI name if appropriate
          */
         args->inumber = be64_to_cpu(dep->inumber);
+        error = xfs_dir_cilookup_result(args, dep->name, dep->namelen);
         xfs_da_brelse(tp, dbp);
         xfs_da_brelse(tp, lbp);
-        return XFS_ERROR(EEXIST);
+        return XFS_ERROR(error);
 }
 
 /*