Re: [PATCH v2 5/5] btrfs: cache max and min order inside btrfs_fs_info

[Qu Wenruo <wqu@suse.com>]

在 2025/9/6 03:06, David Sterba 写道:
> On Tue, Sep 02, 2025 at 06:32:16PM +0930, Qu Wenruo wrote:
>> Inside btrfs_fs_info we cache several bits shift like sectorsize_bits.
>>
>> Apply this to max and min folio orders so that every time mapping order
>> needs to be applied we can skip the calculation.
> 
> I've checked where and how many times is btrfs_set_inode_mapping_order()
> called and it's basically once per newly accessed inode. Caching the
> values in fs_info may not make much sense compared to the other cached
> members for the shifts.

For now you're right. But the following code will need to access that 
min_order in the very soon:

- Compression
   For compressed folios.

- RAID56
- Scrub
   To match the min order so that the btrfs_bio_for_each_block*() will
   work correctly.

So it may not be that obvious for now, but will make more sense soon.

Thanks,
Qu