Re: [md PATCH 00/10] Simplify bio splitting and related code.

[NeilBrown <neilb@suse.com>]

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On Tue, Apr 11 2017, Shaohua Li wrote:

> On Wed, Apr 05, 2017 at 02:05:50PM +1000, Neil Brown wrote:
>> This is part of my little project to make bio splitting
>> in Linux uniform and dead-lock free, in a way that will mean
>> that we can get rid of all the bioset threads.
>> 
>> The basic approach is that when a bio needs to be split, we call
>> bio_split(), bio_chain() and then generic_make_request().
>> We then proceed to handle the remainder without further splitting.
>> Recent changes to generic_make_request() ensure that this will
>> be safe from deadlocks, providing each bioset is used only once
>> in the stack.
>> 
>> This leads to simpler code in various places.  In particular, the
>> splitting of bios that is needed to work around known bad blocks
>> is now much less complex.  There is only ever one r1bio per bio.
>> 
>> As you can see from
>>  10 files changed, 335 insertions(+), 540 deletions(-)
>> there is a net reduction in code.
>
> Looks good and makes code simpler, applied, thanks Neil! The patch 1 and 6 need
> comments in the code to explain how deadlock is avoided though. Care to send a
> new patch?

It isn't clear to me what sort of comment you want, or where it should
go.
It might make sense to have a comment near bio_split() explaining how to
use it (i.e. explaining the pattern used in various patches here), but
I don't see what sort of comments would help in raid1.c or raid10.c
??

Thanks,
NeilBrown

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