linux-kernel - Re: [PATCH v2 1/2] sched: Add PF_MEMALLOC

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Message-ID: <20200622191613.GB2483@worktop.programming.kicks-ass.net>
Date:   Mon, 22 Jun 2020 21:16:13 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Dave Chinner <david@...morbit.com>
Cc:     Waiman Long <longman@...hat.com>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        linux-xfs@...r.kernel.org, linux-kernel@...r.kernel.org,
        Qian Cai <cai@....pw>, Eric Sandeen <sandeen@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v2 1/2] sched: Add PF_MEMALLOC_NOLOCKDEP flag

On Thu, Jun 18, 2020 at 10:01:10AM +1000, Dave Chinner wrote:

> And, really, if we are playing "re-use existing bits" games because
> we've run out of process flags, all these memalloc flags should be
> moved to a new field in the task, say current->memalloc_flags. You
> could also move PF_SWAPWRITE, PF_LOCAL_THROTTLE, and PF_KSWAPD into
> that field as well as they are all memory allocation context process
> flags...

FWIW

There's still 23 bits free after task_struct::in_memstall. That word has
'current only' semantics, just like PF.