From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6111235FF6E for ; Mon, 13 Jul 2026 10:34:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783938897; cv=none; b=FogIKy/sTB61R+4s4/aq4BB9n6d4kTWZ5+0CEyOfTx8EotL0n2YaYlZ9mZC94rE5YHIRjcIvjRYCDDLvU8lo1xeTbPNqaoTVOIwUM7fni6AibZ84Sd1VfflQRcZhWMb95zAnV87gRve264kvPnxRvokN3zMmThPXBuls0dG56q0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783938897; c=relaxed/simple; bh=UAaSk21FJHS+OAzjnr9EjhTvEeZbRnIvl3ShhRdryHQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=K/thbUMYXG5KcvH4XN7KDoPABqptjHDDHLzLt5btfKp8HoDsrXwJ15qIX6lMd56rpFRFqpwne6QyzhowkIUztARTdYvIl2eP5iBkhNGGl6S5E3YRAmi+0npnfGOql40i9lXQv0K4CLkyMk/TJVRGzRS8k4kk0B88AirJaj4GKgI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=hsRXNUQK; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="hsRXNUQK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A04371F000E9; Mon, 13 Jul 2026 10:34:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783938895; bh=8Gg6zcvzOEOlwfKtfjKwTjYa7q99CzNlGtktYSfy79w=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=hsRXNUQKVx+rEC++ym4RrSK7/O9TMsKUyCkHp2Fg5BaNtVwEVYxvkkmgaR+Wguu09 AJ5HFafZ1LjP7/u3Fgc8gxcHzxLjfx4zXcIRFIYi6BvOLgrr07hM+Ta+QWh6fjcb+l wve84ooRTdU7Qzf6CjmIrgUpzVfPSdQlFAmkalqu1snmaYobmTcGZX9jmYQnjMRlTB 1E/twWmbcCOvsOE9bVKwCXN/0nk5W7IoMpjbhNabWDtFckxXER+Sjc9oGXAE2tnDWp 5Xm3brj5LRdA0NE1lkvKXyTB6+5JUsiNhwRkti1osmsmy3Plx6bClzAdgcXJdUtdTP zyQheO9XMUW3Q== Message-ID: Date: Mon, 13 Jul 2026 12:34:52 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/5] mm/rmap: Add try_to_unmap_hugetlb_one To: Dev Jain , akpm@linux-foundation.org, ljs@kernel.org, muchun.song@linux.dev, osalvador@suse.de Cc: riel@surriel.com, liam@infradead.org, vbabka@kernel.org, harry@kernel.org, jannh@google.com, lance.yang@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, ryan.roberts@arm.com, anshuman.khandual@arm.com References: <20260710055915.638659-1-dev.jain@arm.com> <20260710055915.638659-3-dev.jain@arm.com> <49b408b9-6d10-4892-916f-ad8e7ef875e5@arm.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/10/26 15:16, Dev Jain wrote: > > > On 10/07/26 11:29 am, Dev Jain wrote: >> Simplify try_to_unmap_one() by separating the hugetlb parts into >> try_to_unmap_hugetlb_one(). >> >> To understand the correctness of the refactoring, the following points >> are noted: >> >> 1. try_to_unmap() is called for hugetlb folios only when they are >> hwpoisoned. >> >> 2. A hugetlb VMA cannot be mlocked. >> >> 3. page_vma_mapped_walk() returns at most one hugetlb mapping in a VMA, >> and that mapping points at the head PFN. >> >> 4. We won't ever process a softleaf entry that encodes a hugetlb folio; >> hugetlb folios are never swapped out, migration entries will be >> skipped (PVMW_MIGRATION not passed), and device-exclusive does not >> work for hugetlb. >> >> 5. The hwpoison entry is constructed from the poisoned folio, just as in >> the pre-refactor code. Any previous uffd-wp state is deliberately not >> preserved for the hwpoison entry. >> >> 6. TTU_HWPOISON is always present; for it to not be present, either the >> folio has to be in swapcache, or mapping_can_writeback() is true (see >> unmap_poisoned_folio), none of which is true for hugetlb folios. >> >> 7. Hugetlb uses separate counters from normal rss counters, therefore >> update_highwater_rss() need not be called. >> >> While at it: >> >> - Change VM_BUG_* to VM_WARN_*. >> >> - Do not declare variables which are only used once. >> >> - Constify some variables. >> >> - Add some more VM_WARN_* to assert some invariants. >> >> Except the above 4 points, no functional change intended. >> >> Suggested-by: David Hildenbrand (Arm) >> Acked-by: David Hildenbrand (Arm) >> Signed-off-by: Dev Jain >> --- > > Andrew, could you squash the following diff: > > diff --git a/mm/rmap.c b/mm/rmap.c > index cf02b315a2ead..b61051b879c4c 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -2229,8 +2229,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, > update_hiwater_rss(mm); > > /* > - * With TTU_HWPOISON, we only expect small folios or hugetlb > - * folios here for now. > + * With TTU_HWPOISON, we only expect small folios here. > */ > if (folio_test_hwpoison(folio) && (flags & TTU_HWPOISON)) { > pteval = swp_entry_to_pte(make_hwpoison_entry(subpage)); Note that the comment likely fits into a single line now. -- Cheers, David