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 4B7F0424641 for ; Mon, 17 Aug 2026 15:52:40 +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=1786981963; cv=none; b=YyTvUeTo5f+QsHpN5MQTLJDL8PMpaUTOPVhQNU2wj3OF5y6LEuJGnZQO1tJmeHr3j67Gd0pPD2B2EdC3jkT3Ekt1wtMyfCXeFDtgZtaKenWc8WUiQDvnaPSuo9Dy5tFN6vnEfx/cAV//U79OPwuI9p7q5RM1M5m3sv+4/MZW414= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786981963; c=relaxed/simple; bh=K3Fii51FKtND0vTYWhQ7NiNl1JdkV9nLetKS/65hJo4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ZuNAA8+uVPUBRZ8yTG2uPda1v7A28ENJPZ6i5ir6UCIPyOi8PNACD6PNCorW8gIDbzm/95eZy1i8EiwUe2B8y3+4ZTzSzMqsLmDd5ogWOmQuwcdE0gL49b5i5tQuaZJf5p12NoM7R3BcGMSqvzChP4f/F2FbSH3DVvuUtkwSCtw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=iANNWR1A; 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="iANNWR1A" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5BA5A1F000E9; Mon, 17 Aug 2026 15:52:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786981959; bh=3xmAVz6xj7aLEgdSWsuJScsyd8G6EdI2tLeR0xpfNts=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=iANNWR1AAQD0uk6PzsJnNGwuL4otB9pE/sXboIVh4RmY7yBk9vkbhvRyo1P7j54Ly wtTHPl+GHBIvv2ILbyh3HPBAj68sv2f1oiUj+F3mrERGo6Yk82iY/3plgP8lbvABji eF7jvGmoQAgJAsIkeuHFtX5VqPCC6lCSKkcj/Ij8EX5PIIC4oomzWp5pNfAf/1U4a5 CuE/ncZCnvwPCF1OGErs4mFvV9nvJvD0xzsdYAheqQn06lY9oMmLIbkj0ZXXzeYypq Z9e8Bth4IKY9aAFS9J4OnSI+Zk6QX4cnC50ESKOe8nDO7LyRsK1qDRJmf6GIel8e+E EdS5Bxl9GdxIg== Message-ID: <3ae2f1e1-c784-44ed-9b2c-5edf5699d627@kernel.org> Date: Mon, 17 Aug 2026 17:52:34 +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 v4] mm: Use a folio in the softleaf_is_device_private path To: Hongfu Li , akpm@linux-foundation.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Hongfu Li References: <20260803031554.30421-1-hongfu.li@linux.dev> 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 8/3/26 05:15, Hongfu Li wrote: > From: Hongfu Li > > Use the folio APIs in the device_private migration path of do_swap_page(), > replacing four calls to compound_head() with one. > > Signed-off-by: Hongfu Li > Acked-by: David Hildenbrand (Arm) > Reviewed-by: Lorenzo Stoakes (ARM) > --- > v4: > - Drop the do_non_swap_page() extraction (patch 2/2 from v2) > - Added Reviewed-by: Lorenzo Stoakes > - Link to v2: https://lore.kernel.org/all/20260723030752.16979-1-hongfu.li@linux.dev/ > v3: > - Please ignore v3. > v2: > - Drop fault_folio, reuse the existing folio variable instead > - Refresh commit messages > - Update comment to use "folio" instead of "page" in the > device_private path > - Add Acked-by: David Hildenbrand > - Add patch 2/2 to extract do_non_swap_page() from do_swap_page() > - Link to v1: https://lore.kernel.org/all/20260721013347.65698-1-hongfu.li@linux.dev/ > --- > mm/memory.c | 11 ++++++----- > 1 file changed, 6 insertions(+), 5 deletions(-) > > diff --git a/mm/memory.c b/mm/memory.c > index 56b244552f13..bbb289ba09d3 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -4873,18 +4873,19 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) > goto unlock; > > /* > - * Get a page reference while we know the page can't be > + * Get a folio reference while we know the folio can't be > * freed. > */ > - if (trylock_page(vmf->page)) { > + folio = page_folio(vmf->page); > + if (folio_trylock(folio)) { > struct dev_pagemap *pgmap; > > - get_page(vmf->page); > + folio_get(folio); > pte_unmap_unlock(vmf->pte, vmf->ptl); > pgmap = page_pgmap(vmf->page); > ret = pgmap->ops->migrate_to_ram(vmf); > - unlock_page(vmf->page); > - put_page(vmf->page); > + folio_unlock(folio); > + folio_put(folio); > } else { > pte_unmap(vmf->pte); > softleaf_entry_wait_on_locked(entry, vmf->ptl); Okay, so this breaks the HMM selftests: # ok 30 hmm.hmm_device_private.migrate_anon_huge_fault # # RUN hmm.hmm_device_private.migrate_partial_unmap_fault ... [ 14.589125] Internal error: Oops - BUG: 00000000f2000800 [#1] SMP [ 14.589178] Modules linked in: test_hmm [ 14.589203] CPU: 25 UID: 0 PID: 653 Comm: hmm-tests Not tainted 7.2.0-rc5+ #14 PREEMPT [ 14.589243] Hardware name: linux,dummy-virt (DT) [ 14.589268] pstate: 63400005 (nZCv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--) [ 14.589300] pc : folio_unlock+0x78/0x88 [ 14.589326] lr : folio_unlock+0x78/0x88 [ 14.589349] sp : ffff80008284bb90 [ 14.589368] x29: ffff80008284bb90 x28: ffff0000cc8ce180 x27: 0000000000000000 [ 14.589406] x26: 0000000000000000 x25: ffff0000ca395dc0 x24: 0000000000000000 [ 14.589447] x23: 0000000020100073 x22: ffff0000c23d35c0 x21: ffffffffbfff8000 [ 14.589485] x20: ffffffffbfff8000 x19: ffff80008284bca0 x18: 0000000000000010 [ 14.589523] x17: 3030303030303030 x16: 2066666666666666 x15: 6630303030303030 [ 14.589562] x14: 0000000000000000 x13: 29296f696c6f6628 x12: 64656b636f6c5f74 [ 14.589603] x11: fffffffffffc7100 x10: fffffffffffc70b0 x9 : ffffb0504ff88f70 [ 14.589640] x8 : 3fffffffffffdfff x7 : ffff000c79b24bc0 x6 : 00000000000001a7 [ 14.589680] x5 : ffff000c79b24bc0 x4 : 0000000000000000 x3 : 0000000000000000 [ 14.589718] x2 : 0000000000000000 x1 : ffff0000cc8ce180 x0 : 000000000000003f [ 14.589756] Call trace: [ 14.589769] folio_unlock+0x78/0x88 (P) [ 14.589792] do_swap_page+0xf40/0x1580 [ 14.589815] __handle_mm_fault+0x648/0xe68 [ 14.589838] handle_mm_fault+0x9c/0x330 [ 14.589858] do_page_fault+0x268/0x7e0 [ 14.589882] do_translation_fault+0x5c/0x80 [ 14.589904] do_mem_abort+0x48/0xa0 [ 14.589927] el0_da+0x38/0xd0 [ 14.589948] el0t_64_sync_handler+0xd0/0xe8 [ 14.589970] el0t_64_sync+0x198/0x1a0 [ 14.589990] Code: d65f03c0 d000eec1 913c4021 94015993 (d4210000) I can only speculate that we need another folio = page_folio(vmf->page); after the migrate_to_ram() call. Let me try that real quick. -- Cheers, David