linux-ext4 - Re: [PATCHv5 3/5] ext4: mballoc: Introduce pcpu seqcnt for freeing PA to improve ENOSPC handling

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Date:   Tue, 9 Jun 2020 12:20:15 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Ritesh Harjani <ritesh.list@...il.com>
Cc:     Marek Szyprowski <m.szyprowski@...sung.com>,
        Ritesh Harjani <riteshh@...ux.ibm.com>,
        linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Jan Kara <jack@...e.com>, Theodore Ts'o <tytso@....edu>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCHv5 3/5] ext4: mballoc: Introduce pcpu seqcnt for freeing
 PA to improve ENOSPC handling

On Wed, Jun 03, 2020 at 03:40:16PM +0530, Ritesh Harjani wrote:
> Yes, this is being discussed in the community.
> I have submitted a patch which should help fix this warning msg.
> Feel free to give this a try on your setup.
> 
> https://marc.info/?l=linux-ext4&m=159110574414645&w=2

I just triggered the same thing here too. Looking at your fix and not
even pretending to know what's going on with that percpu sequence
counting, I can't help but wonder why do you wanna do:

	seq = *raw_cpu_ptr(&discard_pa_seq);

instead of simply doing:

	seq = this_cpu_read(discard_pa_seq);

?

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette