From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-124.freemail.mail.aliyun.com (out30-124.freemail.mail.aliyun.com [115.124.30.124]) (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 23E7918CBFE for ; Mon, 13 Jan 2025 07:00:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736751648; cv=none; b=so44VQAUlrrt7skN1Z40p1qzMv5xLhkMVfM62fy/ye7I4fLPTDE/CiJLYn0iquWAsS2zm6772ySCAJSFa8M4ir/J3+WdXLoNwqqaGEh5z2wzXK98/AmWck5axufDlRS0vM0wONaU5R8fWvaCOnb94S9k09H7Z10jjQNWq/FIO1c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736751648; c=relaxed/simple; bh=acAb8zN3Hs6F0SffW6ebAf1yqUH3Ye3AF3KF3589XdA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=pEJC4MmzOP4DopTWUbFyoo+2ugoO/ZlEYkYsj9a30dloApe2o5h1QLm0x2jMEHG5U2bypgtNOVd1LKl6yRTtqP7TsyyoGnlUlMq45exE/7yx0ySTTeC5tA/bEYGWdfG8WWhmizRbxXBQMw+MybGt8eYhRa5PvIMLNG7V5ISIjXE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=aOjQkkKi; arc=none smtp.client-ip=115.124.30.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="aOjQkkKi" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1736751637; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=CYlTVnFaSqtVQm0GJy1QXf1k66JEw/OIg3wL+iPfpow=; b=aOjQkkKiLb+Yxly9UFgHcvpoD2aen8HTBgwESS8+R8NrPDY9NGMzHBQx5WlZo3gGsXbJvrq+jHcq9KnXZLEH0i1Cl1qWaauSOwnID/ghQDnPkKppQsW9gQiMeyUJ7ke5Y7xWGqIC5Y9PgNL0pdLTfQhNGtOInShJ91+umtUMz7M= Received: from 30.74.144.122(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0WNUciYq_1736751635 cluster:ay36) by smtp.aliyun-inc.com; Mon, 13 Jan 2025 15:00:36 +0800 Message-ID: Date: Mon, 13 Jan 2025 15:00:35 +0800 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 v1 3/6] mm/migrate: don't call folio_putback_active_hugetlb() on dst hugetlb folio To: David Hildenbrand , linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, Andrew Morton , Muchun Song , "Matthew Wilcox (Oracle)" References: <20250110182149.746551-1-david@redhat.com> <20250110182149.746551-4-david@redhat.com> From: Baolin Wang In-Reply-To: <20250110182149.746551-4-david@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2025/1/11 02:21, David Hildenbrand wrote: > We replaced a simple put_page() by a putback_active_hugepage() call in > commit 3aaa76e125c1 ("mm: migrate: hugetlb: putback destination hugepage > to active list"), to set the "active" flag on the dst hugetlb folio. > > Nowadays, we decoupled the "active" list from the flag, by calling the > flag "migratable". > > Calling "putback" on something that wasn't allocated is weird and not > future proof, especially if we might reach that path when migration failed > and we just want to free the freshly allocated hugetlb folio. > > Let's simply set the "migratable" flag in move_hugetlb_state(), where we > know that allocation succeeded, and use simple folio_put() to return > our reference. > > Do we need the hugetlb_lock for setting that flag? Staring at other > users of folio_set_hugetlb_migratable(), it does not look like it. After > all, the dst folio should already be on the active list, and we are not > modifying that list. > > Signed-off-by: David Hildenbrand > --- > mm/hugetlb.c | 5 +++++ > mm/migrate.c | 8 ++++---- > 2 files changed, 9 insertions(+), 4 deletions(-) > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index da98d671088d0..b24ccf8ecbf38 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -7529,6 +7529,11 @@ void move_hugetlb_state(struct folio *old_folio, struct folio *new_folio, int re > } > spin_unlock_irq(&hugetlb_lock); > } > + /* > + * Our old folio is isolated and has "migratable" cleared until it > + * is putback. As migration succeeded, set the new folio "migratable". > + */ > + folio_set_hugetlb_migratable(new_folio); > } > > static void hugetlb_unshare_pmds(struct vm_area_struct *vma, > diff --git a/mm/migrate.c b/mm/migrate.c > index 80887cadb2774..7e23e78f1e57b 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1542,14 +1542,14 @@ static int unmap_and_move_huge_page(new_folio_t get_new_folio, > list_move_tail(&src->lru, ret); > > /* > - * If migration was not successful and there's a freeing callback, use > - * it. Otherwise, put_page() will drop the reference grabbed during > - * isolation. > + * If migration was not successful and there's a freeing callback, > + * return the folio to that special allocator. Otherwise, simply drop > + * our additional reference. > */ > if (put_new_folio) > put_new_folio(dst, private); > else > - folio_putback_active_hugetlb(dst); > + folio_put(dst); IIUC, after the changes, so the 'dst' folio might not be added into the 'h->hugepage_activelist' list (if the 'dst' is temporarily allocated), Could this cause any side effects?