Re: [PATCH 2/2] btrfs: zoned: fix compressed writes

[Johannes Thumshirn <Johannes.Thumshirn@wdc.com>]

On 17/05/2021 11:15, David Sterba wrote:
> On Mon, May 17, 2021 at 07:07:04AM +0000, Johannes Thumshirn wrote:
>> On 12/05/2021 16:44, David Sterba wrote:
>>> On Wed, May 12, 2021 at 11:01:40PM +0900, Johannes Thumshirn wrote:
>>>> +	if (use_append) {
>>>> +		struct extent_map *em;
>>>> +		struct map_lookup *map;
>>>> +
>>>> +		em = btrfs_get_chunk_map(fs_info, disk_start, PAGE_SIZE);
>>>
>>> The caller already does the em lookup, so this is duplicate, allocating
>>> memory, taking locks and doing a tree lookup. All happening on write out
>>> path so this seems heavy.
>>
>> Right, I did not check this, sorry. Is it OK to add another patch as 
>> preparation swapping some of the parameters to btrfs_submit_compressed_write()
>> from the em?
> 
> That would be another prep patch for the fix, I can't say now if this
> would be still suitable for stable.
> 
>> Otherwise btrfs_submit_compressed_write() will have 10 parameters
>> which sounds awefull.
> 
> In case the fix would have to be in one patch, extending the parameters
> to 10 would be acceptable, if followed by reduction cleanup (that won't
> have to be backported).

OK, then I'll do that.

> If you check the only caller of btrfs_submit_compressed_write, four
> parameters are from async_extent, and two are async_chunk, where
> async_extent = list_entry(async_chunk->extents.next, ...) so that should
> be easy to reduce.
> 

Right