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, 160 insertions, 23 deletions

diff --git a/fs/xfs/xfs_dir2_format.h b/fs/xfs/xfs_dir2_format.h
index 2095e17b75cb..a0961a61ac1a 100644
--- a/fs/xfs/xfs_dir2_format.h
+++ b/fs/xfs/xfs_dir2_format.h
@@ -69,6 +69,23 @@
 #define	XFS_DIR3_FREE_MAGIC	0x58444633	/* XDF3: free index blocks */
 
 /*
+ * Dirents in version 3 directories have a file type field. Additions to this
+ * list are an on-disk format change, requiring feature bits. Valid values
+ * are as follows:
+ */
+#define XFS_DIR3_FT_UNKNOWN		0
+#define XFS_DIR3_FT_REG_FILE		1
+#define XFS_DIR3_FT_DIR			2
+#define XFS_DIR3_FT_CHRDEV		3
+#define XFS_DIR3_FT_BLKDEV		4
+#define XFS_DIR3_FT_FIFO		5
+#define XFS_DIR3_FT_SOCK		6
+#define XFS_DIR3_FT_SYMLINK		7
+#define XFS_DIR3_FT_WHT			8
+
+#define XFS_DIR3_FT_MAX			9
+
+/*
  * Byte offset in data block and shortform entry.
  */
 typedef	__uint16_t	xfs_dir2_data_off_t;
@@ -138,6 +155,9 @@ typedef struct xfs_dir2_sf_entry {
 	xfs_dir2_sf_off_t	offset;		/* saved offset */
 	__u8			name[];		/* name, variable size */
 	/*
+	 * A single byte containing the file type field follows the inode
+	 * number for version 3 directory entries.
+	 *
 	 * A xfs_dir2_ino8_t or xfs_dir2_ino4_t follows here, at a
 	 * variable offset after the name.
 	 */
@@ -162,16 +182,6 @@ xfs_dir2_sf_put_offset(xfs_dir2_sf_entry_t *sfep, xfs_dir2_data_aoff_t off)
 	put_unaligned_be16(off, &sfep->offset.i);
 }
 
-static inline int
-xfs_dir2_sf_entsize(struct xfs_dir2_sf_hdr *hdr, int len)
-{
-	return sizeof(struct xfs_dir2_sf_entry) +	/* namelen + offset */
-		len +					/* name */
-		(hdr->i8count ?				/* ino */
-		 sizeof(xfs_dir2_ino8_t) :
-		 sizeof(xfs_dir2_ino4_t));
-}
-
 static inline struct xfs_dir2_sf_entry *
 xfs_dir2_sf_firstentry(struct xfs_dir2_sf_hdr *hdr)
 {
@@ -179,14 +189,78 @@ xfs_dir2_sf_firstentry(struct xfs_dir2_sf_hdr *hdr)
 		((char *)hdr + xfs_dir2_sf_hdr_size(hdr->i8count));
 }
 
+static inline int
+xfs_dir3_sf_entsize(
+	struct xfs_mount	*mp,
+	struct xfs_dir2_sf_hdr	*hdr,
+	int			len)
+{
+	int count = sizeof(struct xfs_dir2_sf_entry); 	/* namelen + offset */
+
+	count += len;					/* name */
+	count += hdr->i8count ? sizeof(xfs_dir2_ino8_t) :
+				sizeof(xfs_dir2_ino4_t); /* ino # */
+	if (xfs_sb_version_hasftype(&mp->m_sb))
+		count += sizeof(__uint8_t);		/* file type */
+	return count;
+}
+
 static inline struct xfs_dir2_sf_entry *
-xfs_dir2_sf_nextentry(struct xfs_dir2_sf_hdr *hdr,
-		struct xfs_dir2_sf_entry *sfep)
+xfs_dir3_sf_nextentry(
+	struct xfs_mount	*mp,
+	struct xfs_dir2_sf_hdr	*hdr,
+	struct xfs_dir2_sf_entry *sfep)
 {
 	return (struct xfs_dir2_sf_entry *)
-		((char *)sfep + xfs_dir2_sf_entsize(hdr, sfep->namelen));
+		((char *)sfep + xfs_dir3_sf_entsize(mp, hdr, sfep->namelen));
 }
 
+/*
+ * in dir3 shortform directories, the file type field is stored at a variable
+ * offset after the inode number. Because it's only a single byte, endian
+ * conversion is not necessary.
+ */
+static inline __uint8_t *
+xfs_dir3_sfe_ftypep(
+	struct xfs_dir2_sf_hdr	*hdr,
+	struct xfs_dir2_sf_entry *sfep)
+{
+	return (__uint8_t *)&sfep->name[sfep->namelen];
+}
+
+static inline __uint8_t
+xfs_dir3_sfe_get_ftype(
+	struct xfs_mount	*mp,
+	struct xfs_dir2_sf_hdr	*hdr,
+	struct xfs_dir2_sf_entry *sfep)
+{
+	__uint8_t	*ftp;
+
+	if (!xfs_sb_version_hasftype(&mp->m_sb))
+		return XFS_DIR3_FT_UNKNOWN;
+
+	ftp = xfs_dir3_sfe_ftypep(hdr, sfep);
+	if (*ftp >= XFS_DIR3_FT_MAX)
+		return XFS_DIR3_FT_UNKNOWN;
+	return *ftp;
+}
+
+static inline void
+xfs_dir3_sfe_put_ftype(
+	struct xfs_mount	*mp,
+	struct xfs_dir2_sf_hdr	*hdr,
+	struct xfs_dir2_sf_entry *sfep,
+	__uint8_t		ftype)
+{
+	__uint8_t	*ftp;
+
+	ASSERT(ftype < XFS_DIR3_FT_MAX);
+
+	if (!xfs_sb_version_hasftype(&mp->m_sb))
+		return;
+	ftp = xfs_dir3_sfe_ftypep(hdr, sfep);
+	*ftp = ftype;
+}
 
 /*
  * Data block structures.
@@ -286,12 +360,18 @@ xfs_dir3_data_bestfree_p(struct xfs_dir2_data_hdr *hdr)
  * Active entry in a data block.
  *
  * Aligned to 8 bytes.  After the variable length name field there is a
- * 2 byte tag field, which can be accessed using xfs_dir2_data_entry_tag_p.
+ * 2 byte tag field, which can be accessed using xfs_dir3_data_entry_tag_p.
+ *
+ * For dir3 structures, there is file type field between the name and the tag.
+ * This can only be manipulated by helper functions. It is packed hard against
+ * the end of the name so any padding for rounding is between the file type and
+ * the tag.
  */
 typedef struct xfs_dir2_data_entry {
 	__be64			inumber;	/* inode number */
 	__u8			namelen;	/* name length */
 	__u8			name[];		/* name bytes, no null */
+     /* __u8			filetype; */	/* type of inode we point to */
      /*	__be16                  tag; */		/* starting offset of us */
 } xfs_dir2_data_entry_t;
 
@@ -311,20 +391,67 @@ typedef struct xfs_dir2_data_unused {
 /*
  * Size of a data entry.
  */
-static inline int xfs_dir2_data_entsize(int n)
+static inline int
+__xfs_dir3_data_entsize(
+	bool	ftype,
+	int	n)
 {
-	return (int)roundup(offsetof(struct xfs_dir2_data_entry, name[0]) + n +
-		 (uint)sizeof(xfs_dir2_data_off_t), XFS_DIR2_DATA_ALIGN);
+	int	size = offsetof(struct xfs_dir2_data_entry, name[0]);
+
+	size += n;
+	size += sizeof(xfs_dir2_data_off_t);
+	if (ftype)
+		size += sizeof(__uint8_t);
+	return roundup(size, XFS_DIR2_DATA_ALIGN);
+}
+static inline int
+xfs_dir3_data_entsize(
+	struct xfs_mount	*mp,
+	int			n)
+{
+	bool ftype = xfs_sb_version_hasftype(&mp->m_sb) ? true : false;
+	return __xfs_dir3_data_entsize(ftype, n);
+}
+
+static inline __uint8_t
+xfs_dir3_dirent_get_ftype(
+	struct xfs_mount	*mp,
+	struct xfs_dir2_data_entry *dep)
+{
+	if (xfs_sb_version_hasftype(&mp->m_sb)) {
+		__uint8_t	type = dep->name[dep->namelen];
+
+		ASSERT(type < XFS_DIR3_FT_MAX);
+		if (type < XFS_DIR3_FT_MAX)
+			return type;
+
+	}
+	return XFS_DIR3_FT_UNKNOWN;
+}
+
+static inline void
+xfs_dir3_dirent_put_ftype(
+	struct xfs_mount	*mp,
+	struct xfs_dir2_data_entry *dep,
+	__uint8_t		type)
+{
+	ASSERT(type < XFS_DIR3_FT_MAX);
+	ASSERT(dep->namelen != 0);
+
+	if (xfs_sb_version_hasftype(&mp->m_sb))
+		dep->name[dep->namelen] = type;
 }
 
 /*
  * Pointer to an entry's tag word.
  */
 static inline __be16 *
-xfs_dir2_data_entry_tag_p(struct xfs_dir2_data_entry *dep)
+xfs_dir3_data_entry_tag_p(
+	struct xfs_mount	*mp,
+	struct xfs_dir2_data_entry *dep)
 {
 	return (__be16 *)((char *)dep +
-		xfs_dir2_data_entsize(dep->namelen) - sizeof(__be16));
+		xfs_dir3_data_entsize(mp, dep->namelen) - sizeof(__be16));
 }
 
 /*
@@ -375,13 +502,17 @@ xfs_dir3_data_unused_p(struct xfs_dir2_data_hdr *hdr)
  * data block header because the sfe embeds the block offset of the entry into
  * it so that it doesn't change when format conversion occurs. Bad Things Happen
  * if we don't follow this rule.
+ *
+ * XXX: there is scope for significant optimisation of the logic here. Right
+ * now we are checking for "dir3 format" over and over again. Ideally we should
+ * only do it once for each operation.
  */
 #define	XFS_DIR3_DATA_DOT_OFFSET(mp)	\
 	xfs_dir3_data_hdr_size(xfs_sb_version_hascrc(&(mp)->m_sb))
 #define	XFS_DIR3_DATA_DOTDOT_OFFSET(mp)	\
-	(XFS_DIR3_DATA_DOT_OFFSET(mp) + xfs_dir2_data_entsize(1))
+	(XFS_DIR3_DATA_DOT_OFFSET(mp) + xfs_dir3_data_entsize(mp, 1))
 #define	XFS_DIR3_DATA_FIRST_OFFSET(mp)		\
-	(XFS_DIR3_DATA_DOTDOT_OFFSET(mp) + xfs_dir2_data_entsize(2))
+	(XFS_DIR3_DATA_DOTDOT_OFFSET(mp) + xfs_dir3_data_entsize(mp, 2))
 
 static inline xfs_dir2_data_aoff_t
 xfs_dir3_data_dot_offset(struct xfs_dir2_data_hdr *hdr)
@@ -392,13 +523,19 @@ xfs_dir3_data_dot_offset(struct xfs_dir2_data_hdr *hdr)
 static inline xfs_dir2_data_aoff_t
 xfs_dir3_data_dotdot_offset(struct xfs_dir2_data_hdr *hdr)
 {
-	return xfs_dir3_data_dot_offset(hdr) + xfs_dir2_data_entsize(1);
+	bool dir3 = hdr->magic == cpu_to_be32(XFS_DIR3_DATA_MAGIC) ||
+		    hdr->magic == cpu_to_be32(XFS_DIR3_BLOCK_MAGIC);
+	return xfs_dir3_data_dot_offset(hdr) +
+		__xfs_dir3_data_entsize(dir3, 1);
 }
 
 static inline xfs_dir2_data_aoff_t
 xfs_dir3_data_first_offset(struct xfs_dir2_data_hdr *hdr)
 {
-	return xfs_dir3_data_dotdot_offset(hdr) + xfs_dir2_data_entsize(2);
+	bool dir3 = hdr->magic == cpu_to_be32(XFS_DIR3_DATA_MAGIC) ||
+		    hdr->magic == cpu_to_be32(XFS_DIR3_BLOCK_MAGIC);
+	return xfs_dir3_data_dotdot_offset(hdr) +
+		__xfs_dir3_data_entsize(dir3, 2);
 }
 
 /*