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>
diff --git a/fs/hpfs/map.c b/fs/hpfs/map.c
index 803d3da..3aa66ae 100644
--- a/fs/hpfs/map.c
+++ b/fs/hpfs/map.c
@@ -17,6 +17,7 @@
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 @@
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));
}
/*
