Commit f578d4bd authored by Chris Mason's avatar Chris Mason
Browse files

Btrfs: Optimize csum insertion to create larger items when possible 



This reduces the number of calls to btrfs_extend_item and greatly lowers
the cpu usage while writing large files.

Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
parent 5ee78ac7

fs/btrfs/ctree.h

+1 −0
Original line number Diff line number Diff line
@@ -991,6 +991,7 @@ int btrfs_lookup_file_extent(struct btrfs_trans_handle *trans, 
			     u64 bytenr, int mod);

int btrfs_csum_file_block(struct btrfs_trans_handle *trans,

			  struct btrfs_root *root,

			  struct inode *inode,

			  u64 objectid, u64 offset,

			  char *data, size_t len);

struct btrfs_csum_item *btrfs_lookup_csum(struct btrfs_trans_handle *trans,

fs/btrfs/file-item.c

+36 −1
Original line number Diff line number Diff line
@@ -133,17 +133,22 @@ int btrfs_lookup_file_extent(struct btrfs_trans_handle *trans, 


int btrfs_csum_file_block(struct btrfs_trans_handle *trans,

			  struct btrfs_root *root,

			  struct inode *inode,

			  u64 objectid, u64 offset,

			  char *data, size_t len)

{

	int ret;

	struct btrfs_key file_key;

	struct btrfs_key found_key;

	u64 next_offset = (u64)-1;

	int found_next = 0;

	struct btrfs_path *path;

	struct btrfs_csum_item *item;

	struct extent_buffer *leaf = NULL;

	u64 csum_offset;

	u32 csum_result = ~(u32)0;

	u32 nritems;

	u32 ins_size;



	path = btrfs_alloc_path();

	BUG_ON(!path);
@@ -168,7 +173,27 @@ int btrfs_csum_file_block(struct btrfs_trans_handle *trans, 
			goto insert;

		}

	} else {

		int slot = path->slots[0] + 1;

		/* we didn't find a csum item, insert one */

		nritems = btrfs_header_nritems(path->nodes[0]);

		if (path->slots[0] >= nritems - 1) {

			ret = btrfs_next_leaf(root, path);

			if (ret == 1) {

				found_next = 1;

			} else if (ret == 0) {

				slot = 0;

			} else {

				goto insert;

			}

		}

		btrfs_item_key_to_cpu(path->nodes[0], &found_key, slot);

		if (found_key.objectid != objectid ||

		    found_key.type != BTRFS_CSUM_ITEM_KEY) {

			found_next = 1;

			goto insert;

		}

		next_offset = found_key.offset;

		found_next = 1;

		goto insert;

	}
@@ -211,8 +236,18 @@ int btrfs_csum_file_block(struct btrfs_trans_handle *trans, 
insert:

	btrfs_release_path(root, path);

	csum_offset = 0;

	if (found_next) {

		u64 tmp = min((u64)i_size_read(inode), next_offset);

		tmp -= offset + root->sectorsize - 1;

		tmp >>= root->fs_info->sb->s_blocksize_bits;

		tmp = max((u64)1, tmp);

		tmp = min(tmp, (u64)MAX_CSUM_ITEMS(root));

		ins_size = BTRFS_CRC32_SIZE * tmp;

	} else {

		ins_size = BTRFS_CRC32_SIZE;

	}

	ret = btrfs_insert_empty_item(trans, root, path, &file_key,

				      BTRFS_CRC32_SIZE);

				      ins_size);

	if (ret < 0)

		goto fail;

	if (ret != 0) {

fs/btrfs/inode.c

+1 −1
Original line number Diff line number Diff line
@@ -118,7 +118,7 @@ int btrfs_writepage_io_hook(struct page *page, u64 start, u64 end) 
	trans = btrfs_start_transaction(root, 1);

	btrfs_set_trans_block_group(trans, inode);

	kaddr = kmap(page);

	btrfs_csum_file_block(trans, root, inode->i_ino,

	btrfs_csum_file_block(trans, root, inode, inode->i_ino,

			      start, kaddr + offset, end - start + 1);

	kunmap(page);

	ret = btrfs_end_transaction(trans, root);