Re: [PATCH 02/15] btrfs-progs: Remove root argument from btrfs_del_csums

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

On 2018年06月11日 15:02, Nikolay Borisov wrote:
> 
> 
> On 11.06.2018 07:46, Qu Wenruo wrote:
>>
>>
>> On 2018年06月08日 20:47, Nikolay Borisov wrote:
>>> It's not needed, since we can obtain a reference to fs_info from the
>>> passed transaction handle. This is needed by delayed refs code.
>>
>> This looks a little too aggressive to me.
>>
>> Normally we would expect parameters like @trans then @fs_info.
>> Although @trans only let us get @fs_info, under certain case @trans
>> could be NULL (like btrfs_search_slot).
>>
>> Although for btrfs_del_csums() @tran can be NULL, I still prefer the
>> @trans, @fs_info parameters.
> 
> The reason I'm making those prep patches i because I would like to get
> rid of the root argument from _free_extent,

For this part, I completely agree with you.

The root doesn't make sense, getting rid of it is completely fine.
The abuse of btrfs_root as parameter should be stopped, and we have tons
of such cleanup both in kernel and btrfs-progs.

The only concern is about possible NULL @trans parameter.
However it could be easily addressed by adding 'restrict' prefix.

So just adding 'restrict', and then the whole cleanup part is fine to me.

Thanks,
Qu

> since if you look at the
> later delayed refs patches - patch 12/15 you'd see that the adapter
> function __free_extent2 doesn't really have a root pointer as an
> argument. If you also take a look at 10/15 (add delayed refs
> infrastructure), the functions which create the delayed refs also don't
> take a struct btrfs_root as an argument.
> 
> Alternatively I can perhaps wire up a call to btrfs_read_fs_root in
> __free_extent which will be using the "ref->root" id to obtain struct
> btrfs_root. However, due to the way FST fixup is implemented (I still
> haven't sent that code) it's possible that we call __free_extent2 with
> the freespace root set to 0 so if btrfs_read_fs_root is called it will
> return an -ENOENT.
> 
> In conclusion what you suggest *could* be done but it will require
> re-engineering the currently-tested FST code + delayed refs code. Given
> the purpose of the root argument in this callchain I'd rather eliminate
> it altogether and not bother with it.
> 
>>
>> Thanks,
>> Qu
>>
>>
>>>
>>> Signed-off-by: Nikolay Borisov <nborisov@suse.com>
>>> ---
>>>  btrfs-corrupt-block.c |  2 +-
>>>  ctree.h               |  3 +--
>>>  extent-tree.c         |  2 +-
>>>  file-item.c           | 20 ++++++++++----------
>>>  4 files changed, 13 insertions(+), 14 deletions(-)
>>>
>>> diff --git a/btrfs-corrupt-block.c b/btrfs-corrupt-block.c
>>> index 4fbea26cda20..3add8e63b7bb 100644
>>> --- a/btrfs-corrupt-block.c
>>> +++ b/btrfs-corrupt-block.c
>>> @@ -926,7 +926,7 @@ static int delete_csum(struct btrfs_root *root, u64 bytenr, u64 bytes)
>>>  		return PTR_ERR(trans);
>>>  	}
>>>  
>>> -	ret = btrfs_del_csums(trans, root, bytenr, bytes);
>>> +	ret = btrfs_del_csums(trans, bytenr, bytes);
>>>  	if (ret)
>>>  		fprintf(stderr, "Error deleting csums %d\n", ret);
>>>  	btrfs_commit_transaction(trans, root);
>>> diff --git a/ctree.h b/ctree.h
>>> index de4b1b7e6416..082726238b91 100644
>>> --- a/ctree.h
>>> +++ b/ctree.h
>>> @@ -2752,8 +2752,7 @@ int btrfs_del_inode_ref(struct btrfs_trans_handle *trans,
>>>  			u64 ino, u64 parent_ino, u64 *index);
>>>  
>>>  /* file-item.c */
>>> -int btrfs_del_csums(struct btrfs_trans_handle *trans,
>>> -		    struct btrfs_root *root, u64 bytenr, u64 len);
>>> +int btrfs_del_csums(struct btrfs_trans_handle *trans, u64 bytenr, u64 len);
>>>  int btrfs_insert_file_extent(struct btrfs_trans_handle *trans,
>>>  			     struct btrfs_root *root,
>>>  			     u64 objectid, u64 pos, u64 offset,
>>> diff --git a/extent-tree.c b/extent-tree.c
>>> index cbc022f6cef6..c6f09b52800f 100644
>>> --- a/extent-tree.c
>>> +++ b/extent-tree.c
>>> @@ -2372,7 +2372,7 @@ static int __free_extent(struct btrfs_trans_handle *trans,
>>>  		btrfs_release_path(path);
>>>  
>>>  		if (is_data) {
>>> -			ret = btrfs_del_csums(trans, root, bytenr, num_bytes);
>>> +			ret = btrfs_del_csums(trans, bytenr, num_bytes);
>>>  			BUG_ON(ret);
>>>  		}
>>>  
>>> diff --git a/file-item.c b/file-item.c
>>> index 7b0ff3585509..71d4e89f78d1 100644
>>> --- a/file-item.c
>>> +++ b/file-item.c
>>> @@ -394,8 +394,7 @@ static noinline int truncate_one_csum(struct btrfs_root *root,
>>>   * deletes the csum items from the csum tree for a given
>>>   * range of bytes.
>>>   */
>>> -int btrfs_del_csums(struct btrfs_trans_handle *trans,
>>> -		    struct btrfs_root *root, u64 bytenr, u64 len)
>>> +int btrfs_del_csums(struct btrfs_trans_handle *trans, u64 bytenr, u64 len)
>>>  {
>>>  	struct btrfs_path *path;
>>>  	struct btrfs_key key;
>>> @@ -403,11 +402,10 @@ int btrfs_del_csums(struct btrfs_trans_handle *trans,
>>>  	u64 csum_end;
>>>  	struct extent_buffer *leaf;
>>>  	int ret;
>>> -	u16 csum_size =
>>> -		btrfs_super_csum_size(root->fs_info->super_copy);
>>> -	int blocksize = root->fs_info->sectorsize;
>>> +	u16 csum_size = btrfs_super_csum_size(trans->fs_info->super_copy);
>>> +	int blocksize = trans->fs_info->sectorsize;
>>> +	struct btrfs_root *csum_root = trans->fs_info->csum_root;
>>>  
>>> -	root = root->fs_info->csum_root;
>>>  
>>>  	path = btrfs_alloc_path();
>>>  	if (!path)
>>> @@ -418,7 +416,7 @@ int btrfs_del_csums(struct btrfs_trans_handle *trans,
>>>  		key.offset = end_byte - 1;
>>>  		key.type = BTRFS_EXTENT_CSUM_KEY;
>>>  
>>> -		ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
>>> +		ret = btrfs_search_slot(trans, csum_root, &key, path, -1, 1);
>>>  		if (ret > 0) {
>>>  			if (path->slots[0] == 0)
>>>  				goto out;
>>> @@ -445,7 +443,7 @@ int btrfs_del_csums(struct btrfs_trans_handle *trans,
>>>  
>>>  		/* delete the entire item, it is inside our range */
>>>  		if (key.offset >= bytenr && csum_end <= end_byte) {
>>> -			ret = btrfs_del_item(trans, root, path);
>>> +			ret = btrfs_del_item(trans, csum_root, path);
>>>  			BUG_ON(ret);
>>>  		} else if (key.offset < bytenr && csum_end > end_byte) {
>>>  			unsigned long offset;
>>> @@ -485,12 +483,14 @@ int btrfs_del_csums(struct btrfs_trans_handle *trans,
>>>  			 * btrfs_split_item returns -EAGAIN when the
>>>  			 * item changed size or key
>>>  			 */
>>> -			ret = btrfs_split_item(trans, root, path, &key, offset);
>>> +			ret = btrfs_split_item(trans, csum_root, path, &key,
>>> +					       offset);
>>>  			BUG_ON(ret && ret != -EAGAIN);
>>>  
>>>  			key.offset = end_byte - 1;
>>>  		} else {
>>> -			ret = truncate_one_csum(root, path, &key, bytenr, len);
>>> +			ret = truncate_one_csum(csum_root, path, &key, bytenr,
>>> +						len);
>>>  			BUG_ON(ret);
>>>  		}
>>>  		btrfs_release_path(path);
>>>
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