Re: [PATCH] btrfs: scrub: avoid use-after-free when chunk end is not 64K aligned

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

On 2024/1/15 22:39, Johannes Thumshirn wrote:
[...]
>
>> - Make sure scrub_submit_initial_read() only to read the chunk range
>>     This is done by calculating the real number of sectors we need to
>>     read, and add sector-by-sector to the bio.
>
> Why can't you do it the same way the RST version does it by checking the
> extent_sector_bitmap and then add sector-by-sector from it?

Sure, we can, although the whole new scrub code is before RST, and at
that time, the whole 64K read behavior is considered as a better option,
as it reduces the IOPS for a fragmented stripe.

And initially to make the code much simpler, but it turns out that the
"simpler" code is also less robust, requiring very strict never-be-split
condition, and finally leading to the bug.

Thanks,
Qu