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 3313E274FD1 for ; Fri, 4 Sep 2026 02:36:26 +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=1788489387; cv=none; b=lSK730uRATCpmR9Mu7lt1ebKNyITCWeDf49K9VeY7+2FyKfGBp0lXkzk+ojvjr4pFF+IypiyDmycXOHGkRsjXiKz1p2nm0BwJNZxKZyEWBmyb1D2oCAQGKFQ33z/eIDUkDvzwsgnWfrL329OEKy7FqdkJMkmWY2tE9q6ichwvKc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788489387; c=relaxed/simple; bh=ZQ71UZchkm+5sNnd6iK+uYsAPtqvLcDpKgoMi4/wPDw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=JIArecp8E+x8vhJjPSYhHpwXx3/svHAT/cKoJr9voerx1XcHefLGuQhCK/ObRxtfpn5WCRuviQwDaWa2sjLd1tc6WkXX3h1h7B3c5jk9g0+4k+1wUUUO7xu1iAYCSYVwEiCmnnnW2BaUB47xvl+wFTMOlL34fYP5JfOQF7NIDK4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Pv9nOr+E; 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="Pv9nOr+E" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6E94B1F000E9; Fri, 4 Sep 2026 02:36:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788489385; bh=48H+JzQhwLNZeSqTG3FjRi79DNXw2bGAYfRInPbUSJc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Pv9nOr+ExP2Plbo78BzVHV/ZFSEDeE32qdLgp7O7DNRcYkf5b61vNjANw3GaNTSOl 49+2bt3S25a3Bh/hogXZ5wqdwnOgSTMxVG7BmrVp8MZ5NbRK1shvZENagLk7OyP1R1 4vPucBH+ioTRE5qxHN30z7lI/Zcmy8qPSn1WgISCrv99BKmlgtp5CCOZlmX3iaZ9kL 9KSTRQoNKOxAI3wgkn09v0ybFJMXnyHETl90kD+BPnmF/a5A//i9R63YMmg/sBciWM RlRAUtjM8FPbd2dvjyVaiFxt/H6hoIEl6YUhbyg8+y8Vt9rXS++V0FTjoCd/2jaWcZ jKzv8z9d/WVWg== From: Sasha Levin To: stable@vger.kernel.org Cc: Zi Yan , Johannes Weiner , Baolin Wang , "Lorenzo Stoakes (ARM)" , Barry Song , David Hildenbrand , Dev Jain , Lance Yang , "Liam R. Howlett" , "Matthew Wilcox (Oracle)" , Ryan Roberts , William Kucharski , Andrew Morton , Sasha Levin Subject: [PATCH 6.6.y] mm/huge_memory: use folio's memcg inside __folio_split() Date: Thu, 3 Sep 2026 22:36:22 -0400 Message-ID: <20260904023622.2232975-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026090357-daybed-breach-27b2@gregkh> References: <2026090357-daybed-breach-27b2@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Zi Yan [ Upstream commit c299a2285d9d8bda4da024455de65e3d00de6f17 ] Patch series "Honor XA_FLAGS_ACCOUNT in xas_split_alloc() and charge to folio's memcg", v3. __GFP_ACCOUNT is needed for xarray node allocation accounting when XA_FLAGS_ACCOUNT is set. Commit 7b785645e8f13 ("mm: fix page cache convergence regression") fixed a workingset regression with it. xas_split_alloc() does not have it and needs to be fixed. In addition, based on Sashiko's review[1] and Johannes' confirmation[2], to charge the right memcg, folio's memcg needs to be active during folio split. Add that before adding __GFP_ACCOUNT. There is no workingset convergence regression related to missing __GFP_ACCOUNT in xas_split_alloc() and the impact to userspace should be minor. This patch (of 2): 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. Link: https://lore.kernel.org/20260804-add-gfp_account-to-xas_split_alloc-v3-0-38cb3ff325c5@nvidia.com Link: https://lore.kernel.org/20260804-add-gfp_account-to-xas_split_alloc-v3-1-38cb3ff325c5@nvidia.com Link: https://sashiko.dev/#/patchset/20260727-add-gfp_account-to-xas_split_alloc-v1-1-9fae6bf64838%40nvidia.com?part=1 [1] Link: https://lore.kernel.org/all/amtcBZ-_QVRgCd6b@cmpxchg.org/ [2] Fixes: 6b24ca4a1a8d ("mm: Use multi-index entries in the page cache") Signed-off-by: Zi Yan Suggested-by: Johannes Weiner Reviewed-by: Baolin Wang Acked-by: Lorenzo Stoakes (ARM) Acked-by: Johannes Weiner Cc: Barry Song Cc: David Hildenbrand Cc: Dev Jain Cc: Lance Yang Cc: Liam R. Howlett Cc: Matthew Wilcox (Oracle) Cc: Ryan Roberts Cc: William Kucharski Cc: Signed-off-by: Andrew Morton [ adapted get_mem_cgroup_from_folio() to the older folio_memcg()/css_tryget() sequence in split_huge_page_to_list() ] Signed-off-by: Sasha Levin --- mm/huge_memory.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 7ab6779849243..8c626f7c1aedc 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2646,6 +2646,7 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) struct folio *folio = page_folio(page); struct deferred_split *ds_queue = get_deferred_split_queue(folio); XA_STATE(xas, &folio->mapping->i_pages, folio->index); + struct mem_cgroup *memcg, *old_memcg; struct anon_vma *anon_vma = NULL; struct address_space *mapping = NULL; int extra_pins, ret; @@ -2664,6 +2665,19 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) if (folio_test_writeback(folio)) return -EBUSY; + /* + * switch to folio's memcg as xarray node allocation can happen and + * needs to charge to it. + */ +#ifdef CONFIG_MEMCG + memcg = folio_memcg(folio); + if (!memcg || WARN_ON_ONCE(!css_tryget(&memcg->css))) + memcg = root_mem_cgroup; +#else + memcg = NULL; +#endif + old_memcg = set_active_memcg(memcg); + if (folio_test_anon(folio)) { /* * The caller does not necessarily hold an mmap_lock that would @@ -2792,6 +2806,9 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) if (mapping) i_mmap_unlock_read(mapping); out: + /* restore to caller's old_memcg */ + set_active_memcg(old_memcg); + mem_cgroup_put(memcg); xas_destroy(&xas); count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED); return ret; -- 2.53.0