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Date:   Sun, 15 Mar 2020 03:17:13 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To:     Sean Christopherson <sean.j.christopherson@intel.com>
Cc:     linux-kernel@vger.kernel.org, x86@kernel.org,
        linux-sgx@vger.kernel.org, akpm@linux-foundation.org,
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        haitao.huang@intel.com, andriy.shevchenko@linux.intel.com,
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        linux-mm@kvack.org, Ismo Puustinen <ismo.puustinen@intel.com>,
        Mark Shanahan <mark.shanahan@intel.com>,
        Mikko Ylinen <mikko.ylinen@intel.com>,
        Derek Bombien <derek.bombien@intel.com>
Subject: Re: [PATCH v28 16/22] x86/sgx: Add a page reclaimer
Message-ID: <20200315011713.GB208715@linux.intel.com>
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On Sun, Mar 15, 2020 at 02:27:46AM +0200, Jarkko Sakkinen wrote:
> On Thu, Mar 12, 2020 at 11:38:24AM -0700, Sean Christopherson wrote:
> > On Fri, Mar 06, 2020 at 08:47:02PM +0200, Jarkko Sakkinen wrote:
> > > On Thu, Mar 05, 2020 at 11:03:54AM -0800, Sean Christopherson wrote:
> > > > We've also discussed taking a file descriptor to hold the backing, but
> > > > unless I'm misreading the pagecache code, that doesn't solve the incorrect
> > > > accounting problem because the current task, i.e. evicting task, would be
> > > > charged.  In other words, whether the backing is kernel or user controlled
> > > > is purely an ABI question.
> > > 
> > > Even if the file is owned by a different process the account happens
> > > to "current"?
> > 
> > Yes.  Which makes sense as files do not have a 1:1 association with tasks.
> 
> Yeah, that makes sense. Looking at mm/memory.c.
> 
> Looking at finish_fault/alloc_set_pte/inc_mm_counter_fast code path that
> is also what happens.

Ugh, I meant __set_page_dirty/account_page_dirtied/task_io_account_write
path :-/ Anyway.

/Jarkko