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 053131DC98F for ; Fri, 10 Jul 2026 02:28:56 +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=1783650538; cv=none; b=XGOuyfD6z2uDKVeZM6Hcktst9yHLHLn0K117NLb/JzPNa/OJvevnAyPtqsd1XqQLEAWiU+V2IPBIn7eq93R8RHBhgajEcDom8NEgswamv4uNLiDKxg2xI6iMBHwn33t//EqPmhRRVL2a0QbsOtkbLjUxBkFaXxtdNgUsSUgof0Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783650538; c=relaxed/simple; bh=oIsj/B1+2+AWMiiT+QQ+CdWaNJUI7ibxzLtpYTJGoRQ=; h=Date:To:From:Subject:Message-Id; b=EKcXZRMOwLQRERIVZebfaq7zi7C3CLwYK6A60CtyfIKOv104o+DBk/IgxWHjf5MK6vQrPMRSgcqMsNzPaBqXVVIJ8exlwy0eatTOEfTv6jBhTUerjzwHP7jDyskZxZEYA8DElWPO7fiC6xv+T1lDmBzx8m1V1USqwuQkzgx3p+Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=oqQQipSM; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="oqQQipSM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6B2021F000E9; Fri, 10 Jul 2026 02:28:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1783650536; bh=M+JJfX0eM7ykwf2+IVxuhuFr+RdTSHxPdf/Ik4Ji4wQ=; h=Date:To:From:Subject; b=oqQQipSMvBJvoqLg0BTeOnsIolvawDosjHK7/Ky4YbTe1sK/RnEeQn+lL/9RCyDkp lExYFI8GcetyvC66zwqLdtTygHkcrdPqczIz6/3JZBbTueKKhjjGkVg8U1TE3z9XJ+ 7iAk9eBtwSED79F58wAmiwa45/OZJpI3m8AXIOMA= Date: Thu, 09 Jul 2026 19:28:56 -0700 To: mm-commits@vger.kernel.org,ziy@nvidia.com,sougupta@nvidia.com,david@kernel.org,balbirs@nvidia.com,apopple@nvidia.com,jhubbard@nvidia.com,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-gup-fix-gup-fast-fallback-for-null-mapping-order-0-folios.patch added to mm-new branch Message-Id: <20260710022856.6B2021F000E9@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm/gup: fix GUP-fast fallback for NULL-mapping order-0 folios has been added to the -mm mm-new branch. Its filename is mm-gup-fix-gup-fast-fallback-for-null-mapping-order-0-folios.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-gup-fix-gup-fast-fallback-for-null-mapping-order-0-folios.patch This patch will later appear in the mm-new branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Note, mm-new is a provisional staging ground for work-in-progress patches, and acceptance into mm-new is a notification for others take notice and to finish up reviews. Please do not hesitate to respond to review feedback and post updated versions to replace or incrementally fixup patches in mm-new. The mm-new branch of mm.git is not included in linux-next If a few days of testing in mm-new is successful, the patch will me moved into mm.git's mm-unstable branch, which is included in linux-next Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: John Hubbard Subject: mm/gup: fix GUP-fast fallback for NULL-mapping order-0 folios Date: Tue, 7 Jul 2026 17:57:45 -0700 Since commit f002882ca369 ("mm: merge folio_is_secretmem() and folio_fast_pin_allowed() into gup_fast_folio_allowed()"), gup_fast_folio_allowed() falls back to the slow path for any order-0 folio with a NULL mapping when CONFIG_SECRETMEM=y. This causes a performance regression for drivers that allocate pages with alloc_page() and insert them into VMAs via vm_insert_page(). These pages legitimately have a NULL folio->mapping, but they cannot be secretmem pages. Secretmem pages are always added to the secretmem inode's page cache via filemap_add_folio(), which sets folio->mapping to the inode's i_mapping. A folio with a NULL mapping can never be a secretmem folio. The NULL-mapping check was intended to handle truncated file-backed pages (a reject_file_backed concern), not secretmem detection. When only check_secretmem is true (and reject_file_backed is false), a NULL mapping is sufficient to prove the folio is not secretmem, so the fast path can proceed. Link: https://lore.kernel.org/20260708005745.164928-1-jhubbard@nvidia.com Fixes: f002882ca369 ("mm: merge folio_is_secretmem() and folio_fast_pin_allowed() into gup_fast_folio_allowed()") Signed-off-by: John Hubbard Tested-by: Sourab Gupta Acked-by: David Hildenbrand (Arm) Cc: Alistair Popple Cc: Balbir Singh Cc: Zi Yan Signed-off-by: Andrew Morton --- mm/gup.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) --- a/mm/gup.c~mm-gup-fix-gup-fast-fallback-for-null-mapping-order-0-folios +++ a/mm/gup.c @@ -2784,12 +2784,17 @@ static bool gup_fast_folio_allowed(struc mapping = READ_ONCE(folio->mapping); /* - * The mapping may have been truncated, in any case we cannot determine - * if this mapping is safe - fall back to slow path to determine how to - * proceed. + * If the mapping is NULL (truncated, or never set), we cannot + * determine whether the folio is file-backed, so a long-term writable + * pin must fall back to the slow path. + * + * Otherwise, a NULL mapping proves this is not a secretmem folio + * (secretmem folios always have a valid mapping to the secretmem + * inode's address_space), so in that case, we can continue with the + * fast path. */ if (!mapping) - return false; + return !reject_file_backed; /* Anonymous folios pose no problem. */ mapping_flags = (unsigned long)mapping & FOLIO_MAPPING_FLAGS; _ Patches currently in -mm which might be from jhubbard@nvidia.com are mm-gup-fix-gup-fast-fallback-for-null-mapping-order-0-folios.patch