GFS2: Cache dir hash table in a contiguous buffer

This patch adds a cache for the hash table to the directory code
in order to help simplify the way in which the hash table is
accessed. This is intended to be a first step towards introducing
some performance improvements in the directory code.

There are two follow ups that I'm hoping to see fairly shortly. One
is to simplify the hash table reading code now that we always read the
complete hash table, whether we want one entry or all of them. The
other is to introduce readahead on the heads of the hash chains
which are referred to from the table.

The hash table is a maximum of 128k in size, so it is not worth trying
to read it in small chunks.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/gfs2/dir.h b/fs/gfs2/dir.h
index e686af11becd..ff5772fbf024 100644
--- a/fs/gfs2/dir.h
+++ b/fs/gfs2/dir.h
@@ -35,6 +35,7 @@ extern int gfs2_diradd_alloc_required(struct inode *dir,
 				      const struct qstr *filename);
 extern int gfs2_dir_get_new_buffer(struct gfs2_inode *ip, u64 block,
 				   struct buffer_head **bhp);
+extern void gfs2_dir_hash_inval(struct gfs2_inode *ip);
 
 static inline u32 gfs2_disk_hash(const char *data, int len)
 {