linux-kernel - Re: [PATCH 08/15] mm/filemap: add read support for RWF

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Message-ID: <27cd53e0-981e-42f0-b965-e9e2cf3d5894@kernel.dk>
Date: Wed, 13 Nov 2024 07:07:19 -0700
From: Jens Axboe <axboe@...nel.dk>
To: Brian Foster <bfoster@...hat.com>
Cc: Christoph Hellwig <hch@...radead.org>,
 "Kirill A. Shutemov" <kirill@...temov.name>, linux-mm@...ck.org,
 linux-fsdevel@...r.kernel.org, hannes@...xchg.org, clm@...a.com,
 linux-kernel@...r.kernel.org, willy@...radead.org
Subject: Re: [PATCH 08/15] mm/filemap: add read support for RWF_UNCACHED

On 11/12/24 1:25 PM, Jens Axboe wrote:
>>>>>> BTW, I should have also mentioned that fsx is also useful for longer
>>>>>> soak testing. I.e., fstests will provide a decent amount of coverage as
>>>>>> is via the various preexisting tests, but I'll occasionally run fsx
>>>>>> directly and let it run overnight or something to get the op count at
>>>>>> least up in the 100 millions or so to have a little more confidence
>>>>>> there isn't some rare/subtle bug lurking. That might be helpful with
>>>>>> something like this. JFYI.
>>>>>
>>>>> Good suggestion, I can leave it running overnight here as well. Since
>>>>> I'm not super familiar with it, what would be a good set of parameters
>>>>> to run it with?
>>>>>
>>>>
>>>> Most things are on by default, so I'd probably just go with that. -p is
>>>> useful to get occasional status output on how many operations have
>>>> completed and you could consider increasing the max file size with -l,
>>>> but usually I don't use more than a few MB or so if I increase it at
>>>> all.
>>>
>>> When you say default, I'd run it without arguments. And then it does
>>> nothing :-)
>>>
>>> Not an fs guy, I never run fsx. I run xfstests if I make changes that
>>> may impact the page cache, writeback, or file systems.
>>>
>>> IOW, consider this a "I'm asking my mom to run fsx, I need to be pretty
>>> specific" ;-)
>>>
>>
>> Heh. In that case I'd just run something like this:
>>
>> 	fsx -p 100000 <file>
>>
>> ... and see how long it survives. It may not necessarily be an uncached
>> I/O problem if it fails, but depending on how reproducible a failure is,
>> that's where a cli knob comes in handy.
> 
> OK good, will give that a spin.

Ran overnight, no issues seen. Just terminated the process. For funsies,
I also added RWF_UNCACHED support to qemu and had the vm booted with
that as well, to get some host side testing too. Everything looks fine.
This is running:

https://git.kernel.dk/cgit/linux/log/?h=buffered-uncached.7

which is the current branch.

-- 
Jens Axboe