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, 59 insertions, 10 deletions

diff --git a/fs/xfs/xfs_dir2_readdir.c b/fs/xfs/xfs_dir2_readdir.c
index 5f4f705eebbb..8993ec17452c 100644
--- a/fs/xfs/xfs_dir2_readdir.c
+++ b/fs/xfs/xfs_dir2_readdir.c
@@ -36,6 +36,44 @@
 #include "xfs_trace.h"
 #include "xfs_bmap.h"
 
+/*
+ * 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,
+};
+
+unsigned char
+xfs_dir3_get_dtype(
+        struct xfs_mount        *mp,
+        __uint8_t               filetype)
+{
+        if (!xfs_sb_version_hasftype(&mp->m_sb))
+                return DT_UNKNOWN;
+
+        if (filetype >= XFS_DIR3_FT_MAX)
+                return DT_UNKNOWN;
+
+        return xfs_dir3_filetype_table[filetype];
+}
+/*
+ * @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.
+ */
+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,
+};
+
 STATIC int
 xfs_dir2_sf_getdents(
         xfs_inode_t             *dp,            /* incore directory inode */
@@ -109,20 +147,23 @@ xfs_dir2_sf_getdents(
          */
         sfep = xfs_dir2_sf_firstentry(sfp);
         for (i = 0; i < sfp->count; i++) {
+                __uint8_t filetype;
+
                 off = xfs_dir2_db_off_to_dataptr(mp, mp->m_dirdatablk,
                                 xfs_dir2_sf_get_offset(sfep));
 
                 if (ctx->pos > off) {
-                        sfep = xfs_dir2_sf_nextentry(sfp, sfep);
+                        sfep = xfs_dir3_sf_nextentry(mp, sfp, sfep);
                         continue;
                 }
 
-                ino = xfs_dir2_sfe_get_ino(sfp, sfep);
+                ino = xfs_dir3_sfe_get_ino(mp, sfp, sfep);
+                filetype = xfs_dir3_sfe_get_ftype(mp, sfp, sfep);
                 ctx->pos = off & 0x7fffffff;
-                if (!dir_emit(ctx, (char *)sfep->name, sfep->namelen,
-                            ino, DT_UNKNOWN))
+                if (!dir_emit(ctx, (char *)sfep->name, sfep->namelen, ino,
+                            xfs_dir3_get_dtype(mp, filetype)))
                         return 0;
-                sfep = xfs_dir2_sf_nextentry(sfp, sfep);
+                sfep = xfs_dir3_sf_nextentry(mp, sfp, sfep);
         }
 
         ctx->pos = xfs_dir2_db_off_to_dataptr(mp, mp->m_dirdatablk + 1, 0) &
@@ -180,6 +221,8 @@ xfs_dir2_block_getdents(
          * Each object is a real entry (dep) or an unused one (dup).
          */
         while (ptr < endptr) {
+                __uint8_t filetype;
+
                 dup = (xfs_dir2_data_unused_t *)ptr;
                 /*
                  * Unused, skip it.
@@ -194,7 +237,7 @@ xfs_dir2_block_getdents(
                 /*
                  * Bump pointer for the next iteration.
                  */
-                ptr += xfs_dir2_data_entsize(dep->namelen);
+                ptr += xfs_dir3_data_entsize(mp, dep->namelen);
                 /*
                  * The entry is before the desired starting point, skip it.
                  */
@@ -205,11 +248,13 @@ xfs_dir2_block_getdents(
                                             (char *)dep - (char *)hdr);
 
                 ctx->pos = cook & 0x7fffffff;
+                filetype = xfs_dir3_dirent_get_ftype(mp, dep);
                 /*
                  * If it didn't fit, set the final offset to here & return.
                  */
                 if (!dir_emit(ctx, (char *)dep->name, dep->namelen,
-                            be64_to_cpu(dep->inumber), DT_UNKNOWN)) {
+                            be64_to_cpu(dep->inumber),
+                            xfs_dir3_get_dtype(mp, filetype))) {
                         xfs_trans_brelse(NULL, bp);
                         return 0;
                 }
@@ -500,6 +545,8 @@ xfs_dir2_leaf_getdents(
          * Get more blocks and readahead as necessary.
          */
         while (curoff < XFS_DIR2_LEAF_OFFSET) {
+                __uint8_t filetype;
+
                 /*
                  * If we have no buffer, or we're off the end of the
                  * current buffer, need to get another one.
@@ -554,7 +601,7 @@ xfs_dir2_leaf_getdents(
                                         }
                                         dep = (xfs_dir2_data_entry_t *)ptr;
                                         length =
-                                           xfs_dir2_data_entsize(dep->namelen);
+                                           xfs_dir3_data_entsize(mp, dep->namelen);
                                         ptr += length;
                                 }
                                 /*
@@ -585,11 +632,13 @@ xfs_dir2_leaf_getdents(
                 }
 
                 dep = (xfs_dir2_data_entry_t *)ptr;
-                length = xfs_dir2_data_entsize(dep->namelen);
+                length = xfs_dir3_data_entsize(mp, dep->namelen);
+                filetype = xfs_dir3_dirent_get_ftype(mp, dep);
 
                 ctx->pos = xfs_dir2_byte_to_dataptr(mp, curoff) & 0x7fffffff;
                 if (!dir_emit(ctx, (char *)dep->name, dep->namelen,
-                            be64_to_cpu(dep->inumber), DT_UNKNOWN))
+                            be64_to_cpu(dep->inumber),
+                            xfs_dir3_get_dtype(mp, filetype)))
                         break;
 
                 /*