Initial implementation of the HTree directory index.

This is a port of NetBSD's GSoC 2012 Ext3 HTree directory indexing
by Vyacheslav Matyushin.  It was cleaned up and enhanced for FreeBSD
by Zheng Liu (lz@).

This is an excellent example of work shared among different projects:
Vyacheslav was able to look at an early prototype from Zheng Liu who
was also able to check the code from Haiku (with permission).

As in linux, the feature is not available by default and must be
enabled explicitly with tune2fs. We still do not support the
workarounds required in readdir for NFS.

Submitted by:	Zheng Liu
Tested by:	Mike Ma
Sponsored by:	Google Inc.
MFC after:	1 week

1 files changed, 7 insertions, 0 deletions

diff --git a/sys/fs/ext2fs/ext2fs.h b/sys/fs/ext2fs/ext2fs.h
index 9612cab24e93..7b16f0fcd40b 100644
--- a/sys/fs/ext2fs/ext2fs.h
+++ b/sys/fs/ext2fs/ext2fs.h
@@ -147,6 +147,7 @@ struct m_ext2fs {
 	int32_t  e2fs_contigsumsize;    /* size of cluster summary array */
 	int32_t *e2fs_maxcluster;       /* max cluster in each cyl group */
 	struct   csum *e2fs_clustersum; /* cluster summary in each cyl group */
+	int32_t  e2fs_uhash;	  /* 3 if hash should be signed, 0 if not */
 };
 
 /* cluster summary information */
@@ -228,6 +229,12 @@ struct csum {
 #define	E2FS_ISCLEAN			0x0001	/* Unmounted cleanly */
 #define	E2FS_ERRORS			0x0002	/* Errors detected */
 
+/*
+ * Filesystem miscellaneous flags
+ */
+#define E2FS_SIGNED_HASH	0x0001
+#define E2FS_UNSIGNED_HASH	0x0002
+
 /* ext2 file system block group descriptor */
 
 struct ext2_gd {