Btrfs: remove btrfs_sector_sum structure
Using the structure btrfs_sector_sum to keep the checksum value is
unnecessary, because the extents that btrfs_sector_sum points to are
continuous, we can find out the expected checksums by btrfs_ordered_sum's
bytenr and the offset, so we can remove btrfs_sector_sum's bytenr. After
removing bytenr, there is only one member in the structure, so it makes
no sense to keep the structure, just remove it, and use a u32 array to
store the checksum value.
By this change, we don't use the while loop to get the checksums one by
one. Now, we can get several checksum value at one time, it improved the
performance by ~74% on my SSD (31MB/s -> 54MB/s).
test command:
# dd if=/dev/zero of=/mnt/btrfs/file0 bs=1M count=1024 oflag=sync
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
diff --git a/fs/btrfs/ordered-data.h b/fs/btrfs/ordered-data.h
index d082d43..68844d5 100644
--- a/fs/btrfs/ordered-data.h
+++ b/fs/btrfs/ordered-data.h
@@ -26,18 +26,6 @@
struct rb_node *last;
};
-/*
- * these are used to collect checksums done just before bios submission.
- * They are attached via a list into the ordered extent, and
- * checksum items are inserted into the tree after all the blocks in
- * the ordered extent are on disk
- */
-struct btrfs_sector_sum {
- /* bytenr on disk */
- u64 bytenr;
- u32 sum;
-};
-
struct btrfs_ordered_sum {
/* bytenr is the start of this extent on disk */
u64 bytenr;
@@ -45,10 +33,10 @@
/*
* this is the length in bytes covered by the sums array below.
*/
- unsigned long len;
+ int len;
struct list_head list;
- /* last field is a variable length array of btrfs_sector_sums */
- struct btrfs_sector_sum sums[];
+ /* last field is a variable length array of csums */
+ u32 sums[];
};
/*
@@ -149,11 +137,8 @@
static inline int btrfs_ordered_sum_size(struct btrfs_root *root,
unsigned long bytes)
{
- unsigned long num_sectors = (bytes + root->sectorsize - 1) /
- root->sectorsize;
- num_sectors++;
- return sizeof(struct btrfs_ordered_sum) +
- num_sectors * sizeof(struct btrfs_sector_sum);
+ int num_sectors = (int)DIV_ROUND_UP(bytes, root->sectorsize);
+ return sizeof(struct btrfs_ordered_sum) + num_sectors * sizeof(u32);
}
static inline void