hpfs: implement prefetch to improve performance

This patch implements prefetch to improve performance.  It helps mostly
when scanning the bitmaps to calculate free space.

Signed-off-by: Mikulas Patocka <mpatocka@artax.karlin.mff.cuni.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 18 insertions, 1 deletions

diff --git a/fs/hpfs/map.c b/fs/hpfs/map.c
index 803d3da3a0fe..3aa66ae1031e 100644
--- a/fs/hpfs/map.c
+++ b/fs/hpfs/map.c
@@ -17,6 +17,7 @@ __le32 *hpfs_map_bitmap(struct super_block *s, unsigned bmp_block,
                          struct quad_buffer_head *qbh, char *id)
 {
         secno sec;
+        __le32 *ret;
         unsigned n_bands = (hpfs_sb(s)->sb_fs_size + 0x3fff) >> 14;
         if (hpfs_sb(s)->sb_chk) if (bmp_block >= n_bands) {
                 hpfs_error(s, "hpfs_map_bitmap called with bad parameter: %08x at %s", bmp_block, id);
@@ -27,7 +28,23 @@ __le32 *hpfs_map_bitmap(struct super_block *s, unsigned bmp_block,
                 hpfs_error(s, "invalid bitmap block pointer %08x -> %08x at %s", bmp_block, sec, id);
                 return NULL;
         }
-        return hpfs_map_4sectors(s, sec, qbh, 4);
+        ret = hpfs_map_4sectors(s, sec, qbh, 4);
+        if (ret) hpfs_prefetch_bitmap(s, bmp_block + 1);
+        return ret;
+}
+
+void hpfs_prefetch_bitmap(struct super_block *s, unsigned bmp_block)
+{
+        unsigned to_prefetch, next_prefetch;
+        unsigned n_bands = (hpfs_sb(s)->sb_fs_size + 0x3fff) >> 14;
+        if (unlikely(bmp_block >= n_bands))
+                return;
+        to_prefetch = le32_to_cpu(hpfs_sb(s)->sb_bmp_dir[bmp_block]);
+        if (unlikely(bmp_block + 1 >= n_bands))
+                next_prefetch = 0;
+        else
+                next_prefetch = le32_to_cpu(hpfs_sb(s)->sb_bmp_dir[bmp_block + 1]);
+        hpfs_prefetch_sectors(s, to_prefetch, 4 + 4 * (to_prefetch + 4 == next_prefetch));
 }
 
 /*