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Subject: Re: [PATCHv5 3/5] ext4: mballoc: Introduce pcpu seqcnt for freeing PA
 to improve ENOSPC handling
To:     Borislav Petkov <bp@alien8.de>
Cc:     Marek Szyprowski <m.szyprowski@samsung.com>,
        Ritesh Harjani <riteshh@linux.ibm.com>,
        linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        Jan Kara <jack@suse.com>, Theodore Ts'o <tytso@mit.edu>,
        "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>,
        linux-kernel@vger.kernel.org
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 <20200609102015.GA7696@zn.tnic>
From:   Ritesh Harjani <ritesh.list@gmail.com>
Message-ID: <69a26eb8-e439-6574-6f46-e557d6c852d5@gmail.com>
Date:   Tue, 9 Jun 2020 16:07:41 +0530
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On 6/9/20 3:50 PM, Borislav Petkov wrote:
> 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);
> 

That's correct. Thanks for pointing that out.
I guess in my development version of code I had seq as a u64 pointer
variable which later I had changed to u64 variable but I guess I
continued using pcpu ptr APIs for that.

Let me re-submit that patch with your Suggested-by tag and corresponding
changes.

-riteshh