linux-kernel - Re: [PATCH] xfs: Drop setting redundant PF

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Message-Id: <f60c57f4-c7e2-9ae0-38e8-80c3f77f65e0@linux.vnet.ibm.com>
Date:   Fri, 25 Aug 2017 09:32:14 +0530
From:   Anshuman Khandual <khandual@...ux.vnet.ibm.com>
To:     Dave Chinner <david@...morbit.com>,
        Michal Hocko <mhocko@...nel.org>
Cc:     Anshuman Khandual <khandual@...ux.vnet.ibm.com>,
        linux-mm@...ck.org, linux-xfs@...r.kernel.org,
        linux-kernel@...r.kernel.org, dchinner@...hat.com,
        bfoster@...hat.com, sandeen@...deen.net
Subject: Re: [PATCH] xfs: Drop setting redundant PF_KSWAPD in kswapd context

On 08/25/2017 05:31 AM, Dave Chinner wrote:
> On Thu, Aug 24, 2017 at 12:56:35PM +0200, Michal Hocko wrote:
>> On Thu 24-08-17 16:12:47, Anshuman Khandual wrote:
>>> xfs_btree_split() calls xfs_btree_split_worker() with args.kswapd set
>>> if current->flags alrady has PF_KSWAPD. Hence we should not again add
>>> PF_KSWAPD into the current flags inside kswapd context. So drop this
>>> redundant flag addition.
>>
>> I am not familiar with the code but your change seems incorect. The
>> whole point of args->kswapd is to convey the kswapd context to the
>> worker which is obviously running in a different context. So this patch
>> loses the kswapd context.
> 
> Yup. That's what the code does, and removing the PF_KSWAPD from it
> will break it.

The worker thread need to inherit these flags. Thanks for pointing out.