From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 29E2C3C3BF7; Mon, 11 May 2026 12:57:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778504268; cv=none; b=LdVz7bvFQjGevn0MQsv9HFQ+BRUH6SPs+ySt3Bfnb5WxH8RCjtPaUkxGujDRWMELCkjCArsKLxP5zJSw2lgG22WXcGn4CdsKd1e0qnuGSIpCq0U1vETprBaxwVJWfeI9LvCaRXp5SmzqGovKixgdBukaUm4G/VgXGlgMCoTmm6k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778504268; c=relaxed/simple; bh=pnCvFrJE0VGOM9kfqQ8BIn8SlSghwRxC2pKIrOTqydY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=CZlkx6R1mC+ns/keXMylYT0gcetWPITIs150+yPKsvIzrXT5AMlyuEKaMCR7YxukvXUKjLqIQ6eIFkSMvA1FNcVla8b8ZbcZ6y63kFsui+hyyaUS3gxrfMMJ3Knk/zcrCWH/KwgcD+5U0L1/pvuMIazhJxLlb6OEvBLrFesB6C8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=t7jqbSZF; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="t7jqbSZF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9E005C2BCB0; Mon, 11 May 2026 12:57:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778504267; bh=pnCvFrJE0VGOM9kfqQ8BIn8SlSghwRxC2pKIrOTqydY=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=t7jqbSZFr3aZel5TYWb7wvgfkOqbIuSCCQhv5vWBYMcitaFAZbPI7FjQuTUqGmnxc GmvP3xbJd2VI26TGuyFvOj5PSqTIJPxFKwZEh0HFxEL73kWoi2q28+Ar67TttguY0A 0v32iA5RjBZ6mjT39FrQpF7U3MwoghIspc8gCCZSDBHIeOhbybrnCBHs6kE/grtGkP 46lx1Pwwy3tEQSDbkVIIxRc9LbSZ0ZPYHYFaOqwjp8b3vyYguudoggJTPlIxcGXUII VGB2r0kdTa/gotgzy0upOOHUjAVW/m+zw5g9yAakxfxsxH3qpnmGMlimZ2DlMHBnOV btNlhzCCupXCg== Message-ID: <675e9027-9fb5-47b5-9a2d-c9a416a27d0d@kernel.org> Date: Mon, 11 May 2026 14:57:41 +0200 Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 05/12] mm, swap: unify large folio allocation To: kasong@tencent.com, linux-mm@kvack.org Cc: Andrew Morton , Zi Yan , Baolin Wang , Barry Song , Hugh Dickins , Chris Li , Kemeng Shi , Nhat Pham , Baoquan He , Johannes Weiner , Youngjun Park , Chengming Zhou , Roman Gushchin , Shakeel Butt , Muchun Song , Qi Zheng , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Yosry Ahmed , Lorenzo Stoakes , Dev Jain , Lance Yang , Michal Hocko , Michal Hocko , Suren Baghdasaryan , Axel Rasmussen References: <20260421-swap-table-p4-v3-0-2f23759a76bc@tencent.com> <20260421-swap-table-p4-v3-5-2f23759a76bc@tencent.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 4/21/26 08:16, Kairui Song via B4 Relay wrote: > From: Kairui Song > > Now that direct large order allocation is supported in the swap cache, > both anon and shmem can use it instead of implementing their own methods. > This unifies the fallback and swap cache check, which also reduces the > TOCTOU race window of swap cache state: previously, high order swapin > required checking swap cache states first, then allocating and falling > back separately. Now all these steps happen in the same compact loop. > > Order fallback and statistics are also unified, callers just need to > check and pass the acceptable order bitmask. > > There is basically no behavior change. This only makes things more > unified and prepares for later commits. Cgroup and zero map checks can > also be moved into the compact loop, further reducing race windows and > redundancy > You should spell out the rename from swapin_folio() to swapin_entry() [and why it is done]. swapin_readahead() vs. swapin_entry() looks a bit odd, fiven that both consume an entry. > Signed-off-by: Kairui Song > --- > mm/memory.c | 77 ++++++------------------------ > mm/shmem.c | 94 +++++++++--------------------------- > mm/swap.h | 30 ++---------- > mm/swap_state.c | 145 ++++++++++---------------------------------------------- > mm/swapfile.c | 3 +- > 5 files changed, 67 insertions(+), 282 deletions(-) > > diff --git a/mm/memory.c b/mm/memory.c > index ea6568571131..404734a5bcff 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -4593,26 +4593,6 @@ static vm_fault_t handle_pte_marker(struct vm_fault *vmf) > return VM_FAULT_SIGBUS; > } > > -static struct folio *__alloc_swap_folio(struct vm_fault *vmf) > -{ > - struct vm_area_struct *vma = vmf->vma; > - struct folio *folio; > - softleaf_t entry; > - > - folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, vma, vmf->address); > - if (!folio) > - return NULL; > - > - entry = softleaf_from_pte(vmf->orig_pte); > - if (mem_cgroup_swapin_charge_folio(folio, vma->vm_mm, > - GFP_KERNEL, entry)) { > - folio_put(folio); > - return NULL; > - } > - > - return folio; > -} > - > #ifdef CONFIG_TRANSPARENT_HUGEPAGE > /* > * Check if the PTEs within a range are contiguous swap entries > @@ -4642,8 +4622,6 @@ static bool can_swapin_thp(struct vm_fault *vmf, pte_t *ptep, int nr_pages) > */ > if (unlikely(swap_zeromap_batch(entry, nr_pages, NULL) != nr_pages)) > return false; > - if (unlikely(non_swapcache_batch(entry, nr_pages) != nr_pages)) > - return false; > This should also be pointed out in the patch description. (and why it is ok) > return true; > } > @@ -4671,16 +4649,14 @@ static inline unsigned long thp_swap_suitable_orders(pgoff_t swp_offset, > return orders; > } > > -static struct folio *alloc_swap_folio(struct vm_fault *vmf) > +static unsigned long thp_swapin_suitable_orders(struct vm_fault *vmf) > { > struct vm_area_struct *vma = vmf->vma; > unsigned long orders; > - struct folio *folio; > unsigned long addr; > softleaf_t entry; > spinlock_t *ptl; > pte_t *pte; > - gfp_t gfp; > int order; > > /* > @@ -4688,7 +4664,7 @@ static struct folio *alloc_swap_folio(struct vm_fault *vmf) > * maintain the uffd semantics. > */ > if (unlikely(userfaultfd_armed(vma))) > - goto fallback; > + return 0; > > /* > * A large swapped out folio could be partially or fully in zswap. We > @@ -4696,7 +4672,7 @@ static struct folio *alloc_swap_folio(struct vm_fault *vmf) > * folio. > */ > if (!zswap_never_enabled()) > - goto fallback; > + return 0; > > entry = softleaf_from_pte(vmf->orig_pte); > /* > @@ -4710,12 +4686,12 @@ static struct folio *alloc_swap_folio(struct vm_fault *vmf) > vmf->address, orders); > > if (!orders) > - goto fallback; > + return 0; > > pte = pte_offset_map_lock(vmf->vma->vm_mm, vmf->pmd, > vmf->address & PMD_MASK, &ptl); > if (unlikely(!pte)) > - goto fallback; > + return 0; > > /* > * For do_swap_page, find the highest order where the aligned range is > @@ -4731,29 +4707,12 @@ static struct folio *alloc_swap_folio(struct vm_fault *vmf) > > pte_unmap_unlock(pte, ptl); > > - /* Try allocating the highest of the remaining orders. */ > - gfp = vma_thp_gfp_mask(vma); > - while (orders) { > - addr = ALIGN_DOWN(vmf->address, PAGE_SIZE << order); > - folio = vma_alloc_folio(gfp, order, vma, addr); > - if (folio) { > - if (!mem_cgroup_swapin_charge_folio(folio, vma->vm_mm, > - gfp, entry)) > - return folio; > - count_mthp_stat(order, MTHP_STAT_SWPIN_FALLBACK_CHARGE); > - folio_put(folio); > - } > - count_mthp_stat(order, MTHP_STAT_SWPIN_FALLBACK); > - order = next_order(&orders, order); > - } > - > -fallback: > - return __alloc_swap_folio(vmf); > + return orders; > } > #else /* !CONFIG_TRANSPARENT_HUGEPAGE */ > -static struct folio *alloc_swap_folio(struct vm_fault *vmf) > +static unsigned long thp_swapin_suitable_orders(struct vm_fault *vmf) > { > - return __alloc_swap_folio(vmf); > + return 0; > } > #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ > > @@ -4859,21 +4818,13 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) > if (folio) > swap_update_readahead(folio, vma, vmf->address); > if (!folio) { > - if (data_race(si->flags & SWP_SYNCHRONOUS_IO)) { > - folio = alloc_swap_folio(vmf); > - if (folio) { > - /* > - * folio is charged, so swapin can only fail due > - * to raced swapin and return NULL. > - */ > - swapcache = swapin_folio(entry, folio); > - if (swapcache != folio) > - folio_put(folio); > - folio = swapcache; > - } > - } else { > + /* Swapin bypasses readahead for SWP_SYNCHRONOUS_IO devices */ > + if (data_race(si->flags & SWP_SYNCHRONOUS_IO)) > + folio = swapin_entry(entry, GFP_HIGHUSER_MOVABLE, > + thp_swapin_suitable_orders(vmf), > + vmf, NULL, 0); > + else > folio = swapin_readahead(entry, GFP_HIGHUSER_MOVABLE, vmf); > - } > > if (!folio) { > /* Nothing else jumped at me in memory.c -- Cheers, David