On 2018年05月18日 17:42, james harvey wrote:
> On Fri, May 18, 2018 at 1:49 AM, Qu Wenruo <quwenruo.btrfs@gmx.com> wrote:
>> And btrfs check doesn't report the same problem as the default original
>> mode doesn't have such check.
>>
>> Please also post the result of "btrfs check --mode=lowmem /dev/sda1"
> 
> Are you saying "--mode=lowmem" does more checks than without it?

Sometimes it does more check.

>  "man
> btrfs check" says it's experimental and the difference is just
> original is unoptimized regarding memory consumption and can run out
> of memory, and low memory addresses this with increased IO cost from
> re-reading blocks increasing run time.  It doesn't indicate lowmem is
> a better check.

Well, due to the fact original mode and lowmem mode use completely
different way to check, you'd better consider lowmem mode as a
completely rework.
Thus sometimes it will cause different result. (Although most of the
time lowmem is causing false alerts)

Here in this particular case, lowmem does indeed do extra check.

And overall, lowmem mode provides more human readable error output.

Thanks,
Qu