[XFS] Name operation vector for hash and compare

Adds two pieces of functionality for the basis of case-insensitive support
in XFS:

1. A comparison result enumerated type: xfs_dacmp. It represents an

exact match, case-insensitive match or no match at all. This patch

only implements different and exact results.

2. xfs_nameops vector for specifying how to perform the hash generation

of filenames and comparision methods. In this patch the hash vector

points to the existing xfs_da_hashname function and the comparison

method does a length compare, and if the same, does a memcmp and

return the xfs_dacmp result.

All filename functions that use the hash (create, lookup remove, rename,
etc) now use the xfs_nameops.hashname function and all directory lookup
functions also use the xfs_nameops.compname function.

The lookup functions also handle case-insensitive results even though the
default comparison function cannot return that. And important aspect of
the lookup functions is that an exact match always has precedence over a
case-insensitive. So while a case-insensitive match is found, we have to
keep looking just in case there is an exact match. In the meantime, the
info for the first case-insensitive match is retained if no exact match is
found.

SGI-PV: 981519
SGI-Modid: xfs-linux-melb:xfs-kern:31205a

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

1 files changed, 22 insertions, 0 deletions

diff --git a/fs/xfs/xfs_da_btree.c b/fs/xfs/xfs_da_btree.c
index 294780427abb..ae4b18c7726b 100644
--- a/fs/xfs/xfs_da_btree.c
+++ b/fs/xfs/xfs_da_btree.c
@@ -1530,6 +1530,28 @@ xfs_da_hashname(const uchar_t *name, int namelen)
         }
 }
 
+enum xfs_dacmp
+xfs_da_compname(
+        struct xfs_da_args *args,
+        const char      *name,
+        int             len)
+{
+        return (args->namelen == len && memcmp(args->name, name, len) == 0) ?
+                                        XFS_CMP_EXACT : XFS_CMP_DIFFERENT;
+}
+
+static xfs_dahash_t
+xfs_default_hashname(
+        struct xfs_name *name)
+{
+        return xfs_da_hashname(name->name, name->len);
+}
+
+const struct xfs_nameops xfs_default_nameops = {
+        .hashname       = xfs_default_hashname,
+        .compname       = xfs_da_compname
+};
+
 /*
  * Add a block to the btree ahead of the file.
  * Return the new block number to the caller.