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Btrfs: Add mount option to turn off data cow

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A number of workloads do not require copy on write data or checksumming.
mount -o nodatasum to disable checksums and -o nodatacow to disable
both copy on write and checksumming.

In nodatacow mode, copy on write is still performed when a given extent
is under snapshot.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
This commit is contained in:
Chris Mason
2007-12-17 20:14:01 -05:00
parent b6cda9bcb4
commit be20aa9dba
5 changed files with 293 additions and 25 deletions
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53
fs/btrfs/ctree.c
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@@ -70,7 +70,58 @@ void btrfs_release_path(struct btrfs_root *root, struct btrfs_path *p)
memset(p, 0, sizeof(*p));
}
static int __btrfs_cow_block(struct btrfs_trans_handle *trans,
int btrfs_copy_root(struct btrfs_trans_handle *trans,
struct btrfs_root *root,
struct extent_buffer *buf,
struct extent_buffer **cow_ret, u64 new_root_objectid)
{
struct extent_buffer *cow;
u32 nritems;
int ret = 0;
int level;
struct btrfs_key first_key;
struct btrfs_root new_root;
memcpy(&new_root, root, sizeof(new_root));
new_root.root_key.objectid = new_root_objectid;
WARN_ON(root->ref_cows && trans->transid !=
root->fs_info->running_transaction->transid);
WARN_ON(root->ref_cows && trans->transid != root->last_trans);
level = btrfs_header_level(buf);
nritems = btrfs_header_nritems(buf);
if (nritems) {
if (level == 0)
btrfs_item_key_to_cpu(buf, &first_key, 0);
else
btrfs_node_key_to_cpu(buf, &first_key, 0);
} else {
first_key.objectid = 0;
}
cow = __btrfs_alloc_free_block(trans, &new_root, buf->len,
new_root_objectid,
trans->transid, first_key.objectid,
level, buf->start, 0);
if (IS_ERR(cow))
return PTR_ERR(cow);
copy_extent_buffer(cow, buf, 0, 0, cow->len);
btrfs_set_header_bytenr(cow, cow->start);
btrfs_set_header_generation(cow, trans->transid);
btrfs_set_header_owner(cow, new_root_objectid);
WARN_ON(btrfs_header_generation(buf) > trans->transid);
ret = btrfs_inc_ref(trans, &new_root, buf);
if (ret)
return ret;
btrfs_mark_buffer_dirty(cow);
*cow_ret = cow;
return 0;
}
int __btrfs_cow_block(struct btrfs_trans_handle *trans,
struct btrfs_root *root,
struct extent_buffer *buf,
struct extent_buffer *parent, int parent_slot,