=======================
Beyond the obvious open coded bits cleanup, going forward, this schema
will allow adding more common FT_ values and for file systems to catch up
with them at will. For example, if FT_WHT were to be added to the common
file types, xfs could join the party with existing v3 format by adding
a single line to private conversion table:
[FT_WHT] = XFS_DIR3_FT_WHT,
and other fs could join the FT_WHT party after sorting out whatever
feature flags that need to be sorted out.
I envision adding some opaque 'hint bits' to common ftype -
file systems that will support the opaque hint bits will store them as is
on-disk and repair tools will mask them out when comparing to inode mode.
Think of those bits as a way to white list or black list objects on a
file system for a very fast low-level directory tree iteration.
There is one such use case for overlayfs, but I am sure there are more.
The hint bits are not supposed to be set nor cleared during the life time
of the directory entry. Setting a file type hint bit should only be possible
at directory entry creation time (i.e. create,mknod,mkdir,symlink,rename).
v2:
- add private conversion from common to on-disk values
v1:
- use common conversion functions to get on-disk values
@@ -37,21 +37,45 @@ struct xfs_name xfs_name_dotdot = { (unsigned char *)"..", 2, XFS_DIR3_FT_DIR };
/*
* @mode, if set, indicates that the type field needs to be set up.
- * This uses the transformation from file mode to DT_* as defined in linux/fs.h
- * for file type specification. This will be propagated into the directory
- * structure if appropriate for the given operation and filesystem config.
+ * readdir(2) DT_* file types and fs common FT_* file types are defined
+ * in linux/file_type.h.
+ *
+ * These tables define the transformation from common FT_* file types to on-disk
+ * file types and from on-disk file types to readdir(2) DT_* file types.
+ *
+ * The on-disk file types will be propagated into the directory structure if
+ * appropriate for the given operation and filesystem config.
+ *
+ * NOTE that the common_to_dir3_ftype table is an indentity transformation -
+ * the common values are an exact reflection on the xfs v3 on-disk values.
+ * The dir3_ftype_to_dtype table is identical to the common fs_dtype_by_ftype
+ * table in linux/file_type.h with an additional single entry for the
+ * never used value of XFS_DIR3_FT_WHT.
*/
-const unsigned char xfs_mode_to_ftype[S_IFMT >> S_SHIFT] = {
- [0] = XFS_DIR3_FT_UNKNOWN,
- [S_IFREG >> S_SHIFT] = XFS_DIR3_FT_REG_FILE,
- [S_IFDIR >> S_SHIFT] = XFS_DIR3_FT_DIR,
- [S_IFCHR >> S_SHIFT] = XFS_DIR3_FT_CHRDEV,
- [S_IFBLK >> S_SHIFT] = XFS_DIR3_FT_BLKDEV,
- [S_IFIFO >> S_SHIFT] = XFS_DIR3_FT_FIFO,
- [S_IFSOCK >> S_SHIFT] = XFS_DIR3_FT_SOCK,
- [S_IFLNK >> S_SHIFT] = XFS_DIR3_FT_SYMLINK,
+const unsigned char xfs_common_to_dir3_ftype[FT_MAX] = {
+ [FT_UNKNOWN] = XFS_DIR3_FT_UNKNOWN,
+ [FT_REG_FILE] = XFS_DIR3_FT_REG_FILE,
+ [FT_DIR] = XFS_DIR3_FT_DIR,
+ [FT_CHRDEV] = XFS_DIR3_FT_CHRDEV,
+ [FT_BLKDEV] = XFS_DIR3_FT_BLKDEV,
+ [FT_FIFO] = XFS_DIR3_FT_FIFO,
+ [FT_SOCK] = XFS_DIR3_FT_SOCK,
+ [FT_SYMLINK] = XFS_DIR3_FT_SYMLINK,
};
+const unsigned char xfs_dir3_ftype_to_dtype[XFS_DIR3_FT_MAX] = {
+ [XFS_DIR3_FT_UNKNOWN] = DT_UNKNOWN,
+ [XFS_DIR3_FT_REG_FILE] = DT_REG,
+ [XFS_DIR3_FT_DIR] = DT_DIR,
+ [XFS_DIR3_FT_CHRDEV] = DT_CHR,
+ [XFS_DIR3_FT_BLKDEV] = DT_BLK,
+ [XFS_DIR3_FT_FIFO] = DT_FIFO,
+ [XFS_DIR3_FT_SOCK] = DT_SOCK,
+ [XFS_DIR3_FT_SYMLINK] = DT_LNK,
+ [XFS_DIR3_FT_WHT] = DT_WHT,
+};
+
+
/*
* ASCII case-insensitive (ie. A-Z) support for directories that was
* used in IRIX.
@@ -34,8 +34,8 @@ extern struct xfs_name xfs_name_dotdot;
/*
* directory filetype conversion tables.
*/
-#define S_SHIFT 12
-extern const unsigned char xfs_mode_to_ftype[];
+extern const unsigned char xfs_common_to_dir3_ftype[];
+extern const unsigned char xfs_dir3_ftype_to_dtype[];
/*
* directory operations vector for encode/decode routines
@@ -36,11 +36,6 @@
/*
* Directory file type support functions
*/
-static unsigned char xfs_dir3_filetype_table[] = {
- DT_UNKNOWN, DT_REG, DT_DIR, DT_CHR, DT_BLK,
- DT_FIFO, DT_SOCK, DT_LNK, DT_WHT,
-};
-
static unsigned char
xfs_dir3_get_dtype(
struct xfs_mount *mp,
@@ -52,7 +47,7 @@ xfs_dir3_get_dtype(
if (filetype >= XFS_DIR3_FT_MAX)
return DT_UNKNOWN;
- return xfs_dir3_filetype_table[filetype];
+ return xfs_dir3_ftype_to_dtype[filetype];
}
STATIC int
@@ -103,7 +103,7 @@ xfs_dentry_to_name(
{
namep->name = dentry->d_name.name;
namep->len = dentry->d_name.len;
- namep->type = xfs_mode_to_ftype[(mode & S_IFMT) >> S_SHIFT];
+ namep->type = xfs_common_to_dir3_ftype[fs_umode_to_ftype(mode)];
}
STATIC void
Deduplicate the common bits of the file type conversion implementation. Use private conversion tables to convert from fs common FT_* file types to on-disk file types and from on-disk file types to readdir(2) DT_* file types. NOTE that the common_to_dir3_ftype table is an indentity transformation - the common FT_* values are an exact reflection of the v3 on-disk values. The dir3_ftype_to_dtype table is identical to the common fs_dtype_by_ftype table in linux/file_type.h with an additional single entry for the never used value of XFS_DIR3_FT_WHT. Signed-off-by: Amir Goldstein <amir73il@gmail.com> --- fs/xfs/libxfs/xfs_dir2.c | 48 +++++++++++++++++++++++++++++++++++------------ fs/xfs/libxfs/xfs_dir2.h | 4 ++-- fs/xfs/xfs_dir2_readdir.c | 7 +------ fs/xfs/xfs_iops.c | 2 +- 4 files changed, 40 insertions(+), 21 deletions(-) Ted, Chris and Dave, I would appreciate a NACK or ACK on this xfs example implementation. If the major fs maintainers are on board, I will apply this approach to all other fs. This is a draft for the mid grounds approach suggested by Dave, which keeps the control of on-disk bits in the hands of the the file system code and still uses some of the common implementation. As a code deduplication patch, one can argue that it does a pretty lousy job, removing only a single line of common code (#define S_SHIFT 12), but I do think that the result is cleaner without all the open coded >> S_SHIFT conversions. In any case, all for all the small file systems, this cleanup should be a win (exofs ACKed already), so it would be nice to get feedback from more maintainers. Amir. Extra food for thought: