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b=ePHnLnjC++XvojUVKd/BioxVavElfpLaXW3WK+6BYE6qBGUJ/b1aud5whdp1KQYDw ZtzgLxJ3Q1eV4ZNT+DivuCFM0UCNDK/Cj2ggZZxOxGQvbXExjKEQQKZ9wcv0M51jvk BA3JxyBdJr3e5VPvhNPJBXtuiKvaBAGYhkbsTxU7cHXLBYY52/B8B1BhZKgqBoh1cu eU57qdTZnBw+AZpKNTwyDHxCrin6ioJKb+2A6U4pHLPGOqDUKra7ncHmmoaixbFHv0 PsyAul+BvYzKh0z6Dw93KDuotgBQlmN/aZPaXT5K9yLrTwvrK8SppYHorvfL7DEOGO 7s7jfE9aFKyeg== Date: Wed, 26 Aug 2026 09:11:41 +0100 From: "Lorenzo Stoakes (ARM)" To: "David Hildenbrand (Arm)" Cc: Vernon Yang , akpm@linux-foundation.org, nico.pache@linux.dev, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, usama.arif@linux.dev, zokeefe@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org, Vernon Yang Subject: Re: [PATCH v3 1/3] mm: khugepaged: fix swap entry value to folio_pfn() Message-ID: References: <20260824092935.73892-1-vernon2gm@gmail.com> <20260824092935.73892-2-vernon2gm@gmail.com> <6a9c2369-5589-4f2a-bcfe-c6e3b46a1ccd@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: z7ndbgf8nrkknoc5agq9875bezec4c9h X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 21AE2C0002 X-Rspam-User: X-HE-Tag: 1787731908-656023 X-HE-Meta: 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 LWjwNis4 Y6RJ941/Kaj6SUU65x7IHVRSfavaf9AE+5lntNVZZYEgz0FOkuoSWc/26AAVv3H912udSP3uEx2lDyP6voVaRO5TKZqfIpNLpUbN6Rxdv/4IJruNbh9VWiNMHcOho62/g5g0v1jUMduuXPGuhUx/EzWHPXpDcYDR8f8CopylfQOazl4hh2bCRAEb2/lIkBWtCHXqomqj2HMmTEXPNX/fdsXbv8ImiOYqIYKC9TZ+QizmuAaBP969K7aynzUTy8eBzMFv79ydD9uIwawkoNIkGDBeexmFFrMrr9SZN7qUx0VjaZKY= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Aug 26, 2026 at 10:08:58AM +0200, David Hildenbrand (Arm) wrote: > On 8/26/26 10:07, Lorenzo Stoakes (ARM) wrote: > > On Wed, Aug 26, 2026 at 09:57:05AM +0200, David Hildenbrand (Arm) wrote: > >> On 8/26/26 04:44, Vernon Yang wrote: > >>> > >>> When the `xas_for_each()` iteration to terminate and the folio operation > >>> preceding is normal, but pfn will be incorrect. > >> > >> The PFN is only relevant when a folio participated in the failure. Maybe the > >> following would be cleanest? > >> > >> diff --git a/mm/khugepaged.c b/mm/khugepaged.c > >> index 75639298efc27..371ee0b16d10c 100644 > >> --- a/mm/khugepaged.c > >> +++ b/mm/khugepaged.c > >> @@ -2683,6 +2683,7 @@ static enum scan_result collapse_scan_file(struct > >> mm_struct *mm, > >> int present, swap; > >> int node = NUMA_NO_NODE; > >> enum scan_result result = SCAN_SUCCEED; > >> + unsigned long problematic_pfn = -1; > > > > I find this name... problematic :) > > Elaborate. It's overly long, I read it and am confused as to what is 'problematic' or not, it reads weirdly in English and pfn_xxx is the usual convention for naming of pfn's anyway. I made a suggestion in the reply as to how to refactor this to avoid the need for assigning the name like that anyway, if you branch the result == SCAN_SUCCEED then it's implied. I did wonder about pfn_folio but then that's confusing wrt the function, maybe pfn_fail if you really want the name not to be pfn. > > -- > Cheers, > > David -- Cheers, Lorenzo