This speeds up reading bitmaps from disk for very large (and full)
disks by significant amounts (i.e., up to two CPU minutes for a 4T
file system).
Addresses-Google-Bug: #7534813
Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
---
lib/ext2fs/blkmap64_rb.c | 32 +++++++++++++++++++++++++++++---
1 file changed, 29 insertions(+), 3 deletions(-)
diff --git a/lib/ext2fs/blkmap64_rb.c b/lib/ext2fs/blkmap64_rb.c
index a42eda1..0fc7c57 100644
--- a/lib/ext2fs/blkmap64_rb.c
+++ b/lib/ext2fs/blkmap64_rb.c
@@ -674,16 +674,42 @@ static errcode_t rb_set_bmap_range(ext2fs_generic_bitmap bitmap,
__u64 start, size_t num, void *in)
{
struct ext2fs_rb_private *bp;
+ unsigned char *cp = in;
size_t i;
+ int first_set = -1;
int ret;
bp = (struct ext2fs_rb_private *) bitmap->private;
for (i = 0; i < num; i++) {
- ret = ext2fs_test_bit(i, in);
- if (ret)
- rb_insert_extent(start + i - bitmap->start, 1, bp);
+ if (i & 7 == 0) {
+ unsigned char c = cp[i/8];
+ if (c == 0xFF) {
+ if (first_set == -1)
+ first_set = i;
+ i += 7;
+ continue;
+ }
+ if ((c == 0x00) && (first_set == -1)) {
+ i += 7;
+ continue;
+ }
+ }
+ if (ext2fs_test_bit(i, in)) {
+ if (first_set == -1)
+ first_set = i;
+ continue;
+ }
+ if (first_set == -1)
+ continue;
+
+ rb_insert_extent(start + first_set - bitmap->start,
+ i - first_set, bp);
+ first_set = -1;
}
+ if (first_set != -1)
+ rb_insert_extent(start + first_set - bitmap->start,
+ num - first_set, bp);
return 0;
}
--
1.7.12.rc0.22.gcdd159b
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
