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Date:   Wed, 19 Apr 2023 19:05:04 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Suren Baghdasaryan <surenb@google.com>
Cc:     akpm@linux-foundation.org, hannes@cmpxchg.org, mhocko@suse.com,
        josef@toxicpanda.com, jack@suse.cz, ldufour@linux.ibm.com,
        laurent.dufour@fr.ibm.com, michel@lespinasse.org,
        liam.howlett@oracle.com, jglisse@google.com, vbabka@suse.cz,
        minchan@google.com, dave@stgolabs.net, punit.agrawal@bytedance.com,
        lstoakes@gmail.com, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, kernel-team@android.com
Subject: Re: [PATCH v3 1/1] mm: do not increment pgfault stats when page
 fault handler retries
Message-ID: <ZEAtUE+1lzDEPZ7E@casper.infradead.org>
References: <20230419175836.3857458-1-surenb@google.com>
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On Wed, Apr 19, 2023 at 10:58:36AM -0700, Suren Baghdasaryan wrote:
> If the page fault handler requests a retry, we will count the fault
> multiple times. This is a relatively harmless problem as the retry paths
> are not often requested, and the only user-visible problem is that the
> fault counter will be slightly higher than it should be.  Nevertheless,
> userspace only took one fault, and should not see the fact that the
> kernel had to retry the fault multiple times.
> Move page fault accounting into mm_account_fault() and skip incomplete
> faults which will be accounted upon completion.
> 
> Fixes: d065bd810b6d ("mm: retry page fault when blocking on disk transfer")
> Signed-off-by: Suren Baghdasaryan <surenb@google.com>

Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>