ocfs2: implement directory read-ahead

Uptodate.c now knows about read-ahead buffers. Use some more aggressive
logic in ocfs2_readdir().

The two functions which currently use directory read-ahead are
ocfs2_find_entry() and ocfs2_readdir().

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>

1 files changed, 16 insertions, 12 deletions

diff --git a/fs/ocfs2/dir.c b/fs/ocfs2/dir.c
index 3d494d1a5f36..04e01915b86e 100644
--- a/fs/ocfs2/dir.c
+++ b/fs/ocfs2/dir.c
@@ -74,14 +74,14 @@ static int ocfs2_extend_dir(struct ocfs2_super *osb,
 int ocfs2_readdir(struct file * filp, void * dirent, filldir_t filldir)
 {
         int error = 0;
-        unsigned long offset, blk;
-        int i, num, stored;
+        unsigned long offset, blk, last_ra_blk = 0;
+        int i, stored;
         struct buffer_head * bh, * tmp;
         struct ocfs2_dir_entry * de;
         int err;
         struct inode *inode = filp->f_dentry->d_inode;
         struct super_block * sb = inode->i_sb;
-        int have_disk_lock = 0;
+        unsigned int ra_sectors = 16;
 
         mlog_entry("dirino=%llu\n",
                    (unsigned long long)OCFS2_I(inode)->ip_blkno);
@@ -95,9 +95,8 @@ int ocfs2_readdir(struct file * filp, void * dirent, filldir_t filldir)
                         mlog_errno(error);
                 /* we haven't got any yet, so propagate the error. */
                 stored = error;
-                goto bail;
+                goto bail_nolock;
         }
-        have_disk_lock = 1;
 
         offset = filp->f_pos & (sb->s_blocksize - 1);
 
@@ -113,16 +112,21 @@ int ocfs2_readdir(struct file * filp, void * dirent, filldir_t filldir)
                         continue;
                 }
 
-                /*
-                 * Do the readahead (8k)
-                 */
-                if (!offset) {
-                        for (i = 16 >> (sb->s_blocksize_bits - 9), num = 0;
+                /* The idea here is to begin with 8k read-ahead and to stay
+                 * 4k ahead of our current position.
+                 *
+                 * TODO: Use the pagecache for this. We just need to
+                 * make sure it's cluster-safe... */
+                if (!last_ra_blk
+                    || (((last_ra_blk - blk) << 9) <= (ra_sectors / 2))) {
+                        for (i = ra_sectors >> (sb->s_blocksize_bits - 9);
                              i > 0; i--) {
                                 tmp = ocfs2_bread(inode, ++blk, &err, 1);
                                 if (tmp)
                                         brelse(tmp);
                         }
+                        last_ra_blk = blk;
+                        ra_sectors = 8;
                 }
 
 revalidate:
@@ -194,9 +198,9 @@ revalidate:
 
         stored = 0;
 bail:
-        if (have_disk_lock)
-                ocfs2_meta_unlock(inode, 0);
+        ocfs2_meta_unlock(inode, 0);
 
+bail_nolock:
         mlog_exit(stored);
 
         return stored;