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 5863F33A715; Mon, 3 Aug 2026 15:07:53 +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=1785769674; cv=none; b=Jdw395hIEm6igI5s1iw4HQmLNkEFtEHjaC7E/bH4XbutRzOZaWH5eFjLV2pxgd6uYlDHhRpOcDtlYKApJBZs8ZksK7tKRNb6w0M6AW+HjIIK1xTylnCyf70ZArWH5jIqo0kB+xJQ/+li6Jkj5z6fP3Zi1GdRWcE8CgmVXTbpr+Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785769674; c=relaxed/simple; bh=Ko251mJv/SQcgstVdkYdop2Gk2wrmrPgyvD808/haAM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=LU2QYXkOMrQkW38EiI63dD7eIhSoT14dxDCDbssAlTLqLnKoqGrgdplh1czWWE00sUByQoE798QI2U3im4oxS1eQjYCtY7E9vNPhZIJuCqtXVvGaZmmieXclHsjL2HfY+qAEnG4/59cMkVxAZ8X3+XYNUucD0nD3PNEH/rkK3tA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=kTE+/Up8; 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="kTE+/Up8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0F3F21F000E9; Mon, 3 Aug 2026 15:07:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785769673; bh=2T8dsYQ/yokvFm5Hvo97P6jloDB9Jam9qmoCjWPa3ao=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=kTE+/Up8JVH3KqYp0V99R6t55UtaaF4Bc7Inu3jh3UFi/Y737TMAiYKJa88xngrEr polOoaiwAbcv7tFVfJtN8xEPRkHNpQYwlXrhfaax/OjsrG7HnDN+PAgNfq4/DsO7MB v953LXE8aEOhE2leCcJ5xkWy+eVEYGfNdUAyCyR14meMP+ZowKyYK0GWVvzmaRD66X ArtIvBTLULpTgLUKJSE0SdAq5OTIzSy6K+HDGwlz+13KpDMZmSZV/6IqpO4zRJ2wEg dExgwc6htXkMVcd9FN19bKEKTuZi0QBTqM9Qf7b2H/WD6Ts3jSOelXSAxREYW2TYd9 Noz9H8psSpAeQ== Date: Mon, 3 Aug 2026 16:07:35 +0100 From: "Lorenzo Stoakes (ARM)" To: Zi Yan Cc: Johannes Weiner , Andrew Morton , Matthew Wilcox , William Kucharski , David Hildenbrand , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v2 1/2] mm/huge_memory: use folio's memcg inside __folio_split() Message-ID: References: <20260730-add-gfp_account-to-xas_split_alloc-v2-0-5a56c2361d85@nvidia.com> <20260730-add-gfp_account-to-xas_split_alloc-v2-1-5a56c2361d85@nvidia.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Mon, Aug 03, 2026 at 11:02:30AM -0400, Zi Yan wrote: > On Sat Aug 1, 2026 at 5:36 AM EDT, Lorenzo Stoakes (ARM) wrote: > > On Thu, Jul 30, 2026 at 10:18:00PM -0400, Zi Yan wrote: > >> During a pagecache folio split, an xarray node allocation can happen and > >> needs to charge at folio's memcg instead of folio split invoker's memcg, > >> because for example folio split can happen during reclaim and reclaim's > >> active memcg might not be folio's memcg. Switch to folio's memcg at the > >> beginning and switch back afterwards. > > > > I assume this is the only allocation? I guess in general it makes sense to have > > the folio's memcg be active here regardless. > > > >> > >> Suggested-by: Johannes Weiner > >> Fixes: 6b24ca4a1a8d4 ("mm: Use multi-index entries in the page cache") > > > > Cc: stable? > > Like you said above, only xas_split_alloc() is affected. And we have not > seen related workingset regression report (like what Johannes reported > in commit 7b785645e8f13 ("mm: fix page cache convergence regression")). > It might be OK to not backport. > > Johannes, what is your take on this? > > > > >> Signed-off-by: Zi Yan > > > > Change seems reasonable overall. > > > > Acked-by: Lorenzo Stoakes (ARM) > > > >> --- > >> mm/huge_memory.c | 20 ++++++++++++++++---- > >> 1 file changed, 16 insertions(+), 4 deletions(-) > >> > >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c > >> index 04e8a6b553435..b9c2d8908e564 100644 > >> --- a/mm/huge_memory.c > >> +++ b/mm/huge_memory.c > >> @@ -4063,34 +4063,42 @@ static int __folio_split(struct folio *folio, unsigned int new_order, > >> XA_STATE(xas, &folio->mapping->i_pages, folio->index); > >> struct folio *end_folio = folio_next(folio); > >> bool is_anon = folio_test_anon(folio); > >> + struct mem_cgroup *memcg, *old_memcg; > >> struct address_space *mapping = NULL; > >> struct anon_vma *anon_vma = NULL; > >> int old_order = folio_order(folio); > >> struct folio *new_folio, *next; > >> int nr_shmem_dropped = 0; > >> enum ttu_flags ttu_flags = 0; > >> - int ret; > >> pgoff_t end = 0; > >> + int ret; > >> > >> VM_WARN_ON_ONCE_FOLIO(!folio_test_locked(folio), folio); > >> VM_WARN_ON_ONCE_FOLIO(!folio_test_large(folio), folio); > >> > >> if (folio != page_folio(split_at) || folio != page_folio(lock_at)) { > >> ret = -EINVAL; > >> - goto out; > >> + goto out_no_memcg; > >> } > >> > >> if (new_order >= old_order) { > >> ret = -EINVAL; > >> - goto out; > >> + goto out_no_memcg; > >> } > >> > >> ret = folio_check_splittable(folio, new_order, split_type); > >> if (ret) { > >> VM_WARN_ONCE(ret == -EINVAL, "Tried to split an unsplittable folio"); > >> - goto out; > >> + goto out_no_memcg; > > > > This function really badly needs splitting up and probably some cleanup.h work :) > > You mean folio_check_splittable()? You want to move -EINVAL checks a > separate one? No __folio_split(). Comment about cleanup.h really was the whole pattern of goto xxx for various levels of unwinding things. But really I mean the folio splitting code in general, there's a lot of massive-complicated-functions with a million things going on at once, __folio_freeze_and_split_unmapped() is another. Feels like we should really have this stuff in something like mm/folio.c anyway too now that's renamed :) > > -- > Best Regards, > Yan, Zi > -- Cheers, Lorenzo