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

[Nikolay Borisov <nborisov@suse.com>]

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, 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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