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: Chris Mason <chris.mason@oracle.com>

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 1d2b541..70e143b 100644 (file)
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -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,

diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
index 10a4c74..482a2b6 100644 (file)
--- a/fs/btrfs/file-item.c
+++ b/fs/btrfs/file-item.c
@@ -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) {

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 02d802c..7efc047 100644 (file)
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -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);