[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, 5 insertions, 4 deletions

diff --git a/fs/xfs/xfs_dir2_block.c b/fs/xfs/xfs_dir2_block.c
index dee225918db2..e2fa0a1d8e96 100644
--- a/fs/xfs/xfs_dir2_block.c
+++ b/fs/xfs/xfs_dir2_block.c
@@ -610,14 +610,15 @@ xfs_dir2_block_lookup(
         /*
          * Get the offset from the leaf entry, to point to the data.
          */
-        dep = (xfs_dir2_data_entry_t *)
-              ((char *)block + xfs_dir2_dataptr_to_off(mp, be32_to_cpu(blp[ent].address)));
+        dep = (xfs_dir2_data_entry_t *)((char *)block +
+                xfs_dir2_dataptr_to_off(mp, be32_to_cpu(blp[ent].address)));
         /*
-         * Fill in inode number, release the block.
+         * Fill in inode number, CI name if appropriate, release the block.
          */
         args->inumber = be64_to_cpu(dep->inumber);
+        error = xfs_dir_cilookup_result(args, dep->name, dep->namelen);
         xfs_da_brelse(args->trans, bp);
-        return XFS_ERROR(EEXIST);
+        return XFS_ERROR(error);
 }
 
 /*