[GFS2] Clean up/speed up readdir

This removes the extra filldir callback which gfs2 was using to
enclose an attempt at readahead for inodes during readdir. The
code was too complicated and also hurts performance badly in the
case that the getdents64/readdir call isn't being followed by
stat() and it wasn't even getting it right all the time when it
was.

As a result, on my test box an "ls" of a directory containing 250000
files fell from about 7mins (freshly mounted, so nothing cached) to
between about 15 to 25 seconds. When the directory content was cached,
the time taken fell from about 3mins to about 4 or 5 seconds.

Interestingly in the cached case, running "ls -l" once reduced the time
taken for subsequent runs of "ls" to about 6 secs even without this
patch. Now it turns out that there was a special case of glocks being
used for prefetching the metadata, but because of the timeouts for these
locks (set to 10 secs) the metadata was being timed out before it was
being used and this the prefetch code was constantly trying to prefetch
the same data over and over.

Calling "ls -l" meant that the inodes were brought into memory and once
the inodes are cached, the glocks are not disposed of until the inodes
are pushed out of the cache, thus extending the lifetime of the glocks,
and thus bringing down the time for subsequent runs of "ls"
considerably.

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

1 files changed, 2 insertions, 19 deletions

diff --git a/fs/gfs2/dir.h b/fs/gfs2/dir.h
index b21b33668a5b..48fe89046bba 100644
--- a/fs/gfs2/dir.h
+++ b/fs/gfs2/dir.h
@@ -16,30 +16,13 @@ struct inode;
 struct gfs2_inode;
 struct gfs2_inum;
 
-/**
- * gfs2_filldir_t - Report a directory entry to the caller of gfs2_dir_read()
- * @opaque: opaque data used by the function
- * @name: the name of the directory entry
- * @length: the length of the name
- * @offset: the entry's offset in the directory
- * @inum: the inode number the entry points to
- * @type: the type of inode the entry points to
- *
- * Returns: 0 on success, 1 if buffer full
- */
-
-typedef int (*gfs2_filldir_t) (void *opaque,
-                              const char *name, unsigned int length,
-                              u64 offset,
-                              struct gfs2_inum_host *inum, unsigned int type);
-
 int gfs2_dir_search(struct inode *dir, const struct qstr *filename,
                     struct gfs2_inum_host *inum, unsigned int *type);
 int gfs2_dir_add(struct inode *inode, const struct qstr *filename,
                  const struct gfs2_inum_host *inum, unsigned int type);
 int gfs2_dir_del(struct gfs2_inode *dip, const struct qstr *filename);
-int gfs2_dir_read(struct inode *inode, u64 * offset, void *opaque,
-                  gfs2_filldir_t filldir);
+int gfs2_dir_read(struct inode *inode, u64 *offset, void *opaque,
+                  filldir_t filldir);
 int gfs2_dir_mvino(struct gfs2_inode *dip, const struct qstr *filename,
                    struct gfs2_inum_host *new_inum, unsigned int new_type);