Commit e015640f authored by Chris Mason's avatar Chris Mason
Browse files

Btrfs: Write bio checksumming outside the FS mutex 



This significantly improves streaming write performance by allowing
concurrency in the data checksumming.

Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
parent 44b8bd7e

fs/btrfs/ctree.h

+3 −1
Original line number Diff line number Diff line
@@ -1515,7 +1515,9 @@ int btrfs_lookup_file_extent(struct btrfs_trans_handle *trans, 
			     u64 bytenr, int mod);

int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans,

			   struct btrfs_root *root, struct inode *inode,

			   struct bio *bio);

			   struct bio *bio, char *sums);

int btrfs_csum_one_bio(struct btrfs_root *root,

		       struct bio *bio, char **sums_ret);

struct btrfs_csum_item *btrfs_lookup_csum(struct btrfs_trans_handle *trans,

					  struct btrfs_root *root,

					  struct btrfs_path *path,

fs/btrfs/file-item.c

+32 −14
Original line number Diff line number Diff line
@@ -134,9 +134,36 @@ int btrfs_lookup_file_extent(struct btrfs_trans_handle *trans, 
	return ret;

}



int btrfs_csum_one_bio(struct btrfs_root *root,

		       struct bio *bio, char **sums_ret)

{

	u32 *sums;

	char *data;

	struct bio_vec *bvec = bio->bi_io_vec;

	int bio_index = 0;



	sums = kmalloc(bio->bi_vcnt * BTRFS_CRC32_SIZE, GFP_NOFS);

	if (!sums)

		return -ENOMEM;

	*sums_ret = (char *)sums;



	while(bio_index < bio->bi_vcnt) {

		data = kmap_atomic(bvec->bv_page, KM_USER0);

		*sums = ~(u32)0;

		*sums = btrfs_csum_data(root, data + bvec->bv_offset,

					*sums, bvec->bv_len);

		kunmap_atomic(data, KM_USER0);

		btrfs_csum_final(*sums, (char *)sums);

		sums++;

		bio_index++;

		bvec++;

	}

	return 0;

}



int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans,

			   struct btrfs_root *root, struct inode *inode,

			   struct bio *bio)

			   struct bio *bio, char *sums)

{

	u64 objectid = inode->i_ino;

	u64 offset;
@@ -150,12 +177,11 @@ int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans, 
	struct btrfs_csum_item *item_end;

	struct extent_buffer *leaf = NULL;

	u64 csum_offset;

	u32 csum_result;

	u32 *sums32 = (u32 *)sums;

	u32 nritems;

	u32 ins_size;

	int bio_index = 0;

	struct bio_vec *bvec = bio->bi_io_vec;

	char *data;

	char *eb_map;

	char *eb_token;

	unsigned long map_len;
@@ -278,15 +304,6 @@ int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans, 
				      btrfs_item_size_nr(leaf, path->slots[0]));

	eb_token = NULL;

next_bvec:

	data = kmap_atomic(bvec->bv_page, KM_USER0);

	csum_result = ~(u32)0;

	csum_result = btrfs_csum_data(root, data + bvec->bv_offset,

				      csum_result, bvec->bv_len);

	kunmap_atomic(data, KM_USER0);

	btrfs_csum_final(csum_result, (char *)&csum_result);

	if (csum_result == 0) {

		printk("csum result is 0 for inode %lu offset %Lu\n", inode->i_ino, offset);

	}



	if (!eb_token ||

	   (unsigned long)item  + BTRFS_CRC32_SIZE >= map_start + map_len) {
@@ -304,13 +321,14 @@ int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans, 
	}

	if (eb_token) {

		memcpy(eb_token + ((unsigned long)item & (PAGE_CACHE_SIZE - 1)),

		       &csum_result, BTRFS_CRC32_SIZE);

		       sums32, BTRFS_CRC32_SIZE);

	} else {

		write_extent_buffer(leaf, &csum_result, (unsigned long)item,

		write_extent_buffer(leaf, sums32, (unsigned long)item,

				    BTRFS_CRC32_SIZE);

	}

	bio_index++;

	bvec++;

	sums32++;

	if (bio_index < bio->bi_vcnt) {

		item = (struct btrfs_csum_item *)((char *)item +

						  BTRFS_CRC32_SIZE);

fs/btrfs/inode.c

+10 −1
Original line number Diff line number Diff line
@@ -330,14 +330,23 @@ int __btrfs_submit_bio_hook(struct inode *inode, int rw, struct bio *bio, 
	struct btrfs_root *root = BTRFS_I(inode)->root;

	struct btrfs_trans_handle *trans;

	int ret = 0;

	char *sums = NULL;



	ret = btrfs_csum_one_bio(root, bio, &sums);

	BUG_ON(ret);



	mutex_lock(&root->fs_info->fs_mutex);

	trans = btrfs_start_transaction(root, 1);



	btrfs_set_trans_block_group(trans, inode);

	btrfs_csum_file_blocks(trans, root, inode, bio);

	btrfs_csum_file_blocks(trans, root, inode, bio, sums);



	ret = btrfs_end_transaction(trans, root);

	BUG_ON(ret);

	mutex_unlock(&root->fs_info->fs_mutex);



	kfree(sums);



	return btrfs_map_bio(root, rw, bio, mirror_num);

}