xfs: Add read-only support for dirent filetype field

Add support for the file type field in directory entries so that
readdir can return the type of the inode the dirent points to to
userspace without first having to read the inode off disk.

The encoding of the type field is a single byte that is added to the
end of the directory entry name length. For all intents and
purposes, it appends a "hidden" byte to the name field which
contains the type information. As the directory entry is already of
dynamic size, helpers are already required to access and decode the
direct entry structures.

Hence the relevent extraction and iteration helpers are updated to
understand the hidden byte.  Helpers for reading and writing the
filetype field from the directory entries are also added. Only the
read helpers are used by this patch.  It also adds all the code
necessary to read the type information out of the dirents on disk.

Further we add the superblock feature bit and helpers to indicate
that we understand the on-disk format change. This is not a
compatible change - existing kernels cannot read the new format
successfully - so an incompatible feature flag is added. We don't
yet allow filesystems to mount with this flag yet - that will be
added once write support is added.

Finally, the code to take the type from the VFS, convert it to an
XFS on-disk type and put it into the xfs_name structures passed
around is added, but the directory code does not use this field yet.
That will be in the next patch.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/fs/xfs/xfs_dir2_priv.h b/fs/xfs/xfs_dir2_priv.h
index 6d2a99c224b7..1bad84c40829 100644
--- a/fs/xfs/xfs_dir2_priv.h
+++ b/fs/xfs/xfs_dir2_priv.h
@@ -18,6 +18,8 @@
 #ifndef __XFS_DIR2_PRIV_H__
 #define __XFS_DIR2_PRIV_H__
 
+struct dir_context;
+
 /* xfs_dir2.c */
 extern int xfs_dir_ino_validate(struct xfs_mount *mp, xfs_ino_t ino);
 extern int xfs_dir2_grow_inode(struct xfs_da_args *args, int space,
@@ -25,6 +27,13 @@ extern int xfs_dir2_grow_inode(struct xfs_da_args *args, int space,
 extern int xfs_dir_cilookup_result(struct xfs_da_args *args,
 				const unsigned char *name, int len);
 
+#define S_SHIFT 12
+extern const unsigned char xfs_mode_to_ftype[];
+
+extern unsigned char xfs_dir3_get_dtype(struct xfs_mount *mp,
+					__uint8_t filetype);
+
+
 /* xfs_dir2_block.c */
 extern int xfs_dir3_block_read(struct xfs_trans *tp, struct xfs_inode *dp,
 			       struct xfs_buf **bpp);