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 E9C8F2DCBEC; Sun, 31 May 2026 19:11:59 +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=1780254721; cv=none; b=U0eXvamqUo8lcqSQStjYESUPlCTNtML4ediircI+sqok1DUUOylvsT1ja9NtkfazrUDT7KAtIp0A98L/TlBMsbiFR1zN1sirU8TTstqE1MA7gmbB2TgO99xz+rVHqoXbMw3DtMMBxYfAqFyA+9YbMk69+AGQfzMqLQ43tbm0kIY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780254721; c=relaxed/simple; bh=sVVowetDWgw/1tCLucUDWaSHfmFN46vneB2MqMCzRgA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=leyqitNx/4P/VEYoUugK3nVM23wYApCjt/pr11l42vYgK4EZBmC4eQJWmZHoRWcJLQHK0ryg9fxcmPrv/iCgU30+3liGQM5/PVH+5LaKpVUnMc9T8vFL/2h2W0Q8X6j9oKhGCPPAOMmmhGtLP2eIbaQgtJE6WZ5Szx4sMRnCB1Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=HxsXn3w4; 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="HxsXn3w4" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 88FE61F00893; Sun, 31 May 2026 19:11:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1780254719; bh=4j/mmrMqN9cVeiG6v3MT7PKSh12sT3iMOb3Zkg1yWvI=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=HxsXn3w48nhvETfvikl1vwgfbymIGXFrRHsZTddKAZCyDvq2pmZaamPZaoMCUGJXw KkL4tM95gB98srql2xgLuVe3Yy9VrSK2K60kSZ0Ey65Qf1/7KWdOGoM+/DGWNulerX psDfrdfKwSMDYer0qdZid69g/TjAhZ3zI/gk5jR5bIJDVfOeGY5AgFOtECP3GF+lZc eqGIL98TbRgqw7Cgc9+3i7LbsyS70CXgaiC9DhF8lbn0/tI3andx0y3zK0jtR34ghq uBxKx3uNpB5BDPsXuAWlMv/TVpsoZbGkZzpfjl2JGeElVdBKisI9DGnfGxDtRXN7fU o3IsqqY0WTr5g== Message-ID: Date: Sun, 31 May 2026 21:11:53 +0200 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] fs/proc/task_mmu: do not warn on seeing non-migration pmd entry To: Dev Jain , akpm@linux-foundation.org, liam@infradead.org, ljs@kernel.org, jgg@ziepe.ca, leon@kernel.org, shuah@kernel.org Cc: vbabka@kernel.org, jannh@google.com, pfalcato@suse.de, rppt@kernel.org, surenb@google.com, mhocko@suse.com, balbirs@nvidia.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org, ryan.roberts@arm.com, anshuman.khandual@arm.com, stable@vger.kernel.org References: <20260529111704.1078346-1-dev.jain@arm.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 5/29/26 13:17, Dev Jain wrote: > pagemap_pmd_range_thp() warns if a non-present PMD is not a migration > entry. This became false once device-private entries at the PMD level were > added. > > One can hit the warning by patching hmm-tests.c with the following: > > diff --git a/tools/testing/selftests/mm/hmm-tests.c b/tools/testing/selftests/mm/hmm-tests.c > index e1c8a679a4cf3..7f0a3384f3c5f 100644 > --- a/tools/testing/selftests/mm/hmm-tests.c > +++ b/tools/testing/selftests/mm/hmm-tests.c > @@ -209,6 +209,37 @@ static int hmm_dmirror_cmd(int fd, > return 0; > } > > +static int hmm_read_self_pagemap(void *addr, unsigned long npages, > + unsigned long page_size) > +{ > + const size_t entry_size = sizeof(uint64_t); > + const off_t offset = ((uintptr_t)addr / page_size) * entry_size; > + uint64_t *entries; > + ssize_t nread; > + int fd; > + > + entries = malloc(npages * entry_size); > + if (!entries) > + return -ENOMEM; > + > + fd = open("/proc/self/pagemap", O_RDONLY); > + if (fd < 0) { > + free(entries); > + return -errno; > + } > + > + nread = pread(fd, entries, npages * entry_size, offset); > + close(fd); > + free(entries); > + > + if (nread < 0) > + return -errno; > + if ((size_t)nread != npages * entry_size) > + return -EIO; > + > + return 0; > +} > + > static void hmm_buffer_free(struct hmm_buffer *buffer) > { > if (buffer == NULL) > @@ -2314,6 +2345,10 @@ TEST_F(hmm, migrate_anon_huge_fault) > ASSERT_EQ(ret, 0); > ASSERT_EQ(buffer->cpages, npages); > > + /* Exercise pagemap on a PMD device-private entry. */ > + ret = hmm_read_self_pagemap(buffer->ptr, npages, self->page_size); > + ASSERT_EQ(ret, 0); > + > /* Check what the device read. */ > for (i = 0, ptr = buffer->mirror; i < size / sizeof(*ptr); ++i) > ASSERT_EQ(ptr[i], i); > > > Therefore, remove the stale migration-only assertion. > > Fixes: a30b48bf1b24 ("mm/migrate_device: implement THP migration of zone device pages") > Cc: stable@vger.kernel.org > Signed-off-by: Dev Jain > --- > Applies on mm-unstable (404fb4f38e8f). > > fs/proc/task_mmu.c | 1 - > 1 file changed, 1 deletion(-) > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > index 1e3a15bf46f4e..58938e62154d9 100644 > --- a/fs/proc/task_mmu.c > +++ b/fs/proc/task_mmu.c > @@ -2129,7 +2129,6 @@ static int pagemap_pmd_range_thp(pmd_t *pmdp, unsigned long addr, > flags |= PM_SOFT_DIRTY; > if (pmd_swp_uffd_wp(pmd)) > flags |= PM_UFFD_WP; > - VM_WARN_ON_ONCE(!pmd_is_migration_entry(pmd)); > page = softleaf_to_page(entry); > } > The whole thp_migration_supported() guard is a bit shaky, right? I guess device-private entries currently imply thp_migration_supported(), but that thp_migration_supported() check is really questionable and should likely just go away (else if -> else). Staring at pte_to_pagemap_entry(), likely we'd also want if (softleaf_has_pfn(entry)) page = softleaf_to_page(entry); to prepare for PMD swap entries. Anyhow, both are unrelated (can you send patches to clean it up?) Acked-by: David Hildenbrand (Arm) -- Cheers, David