From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 15091C28D13 for ; Fri, 19 Aug 2022 22:33:32 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 2556C6B0073; Fri, 19 Aug 2022 18:33:32 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 204C36B0074; Fri, 19 Aug 2022 18:33:32 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0A69F8D0001; Fri, 19 Aug 2022 18:33:32 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id EBC2C6B0073 for ; Fri, 19 Aug 2022 18:33:31 -0400 (EDT) Received: from smtpin22.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id BEB2F16011A for ; Fri, 19 Aug 2022 22:33:31 +0000 (UTC) X-FDA: 79817795022.22.A92B1E2 Received: from mail-ed1-f44.google.com (mail-ed1-f44.google.com [209.85.208.44]) by imf29.hostedemail.com (Postfix) with ESMTP id DA7C812006F for ; Fri, 19 Aug 2022 22:31:36 +0000 (UTC) Received: by mail-ed1-f44.google.com with SMTP id z2so7244046edc.1 for ; Fri, 19 Aug 2022 15:31:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc; bh=AhRHfO8iehFCCtUowGE0tDVkHBkaER+EpAHuQQt15oc=; b=csqNUCUvJsvxtE4jVAKKtuYnZTdoPzEWZddaKZTbfqriRyKxrQIS3i7Yi/C5OPY7gt /50rUoYRzc0U7Epx0QSQyjIT9enLFPnSqL3lkshcGvgi7jH0pX4OS3kck265cQff3tdu K2jjyk/oy1hqeLqArpRYmMgyBmy3d7ddq+dVmLvOp7Mk+rAMX3wJEX9yUZBug/tfvx08 oVRPIT2a/J5iqOrYaG2WxC0uZI2OYDf4vBtn1Ukeg8BBJDPuPYIDz9Jp1UI8TlhOyoVr VWZM+DCTnSNiAgWs8qrC8uSSYcA6W0/sRGuEjTvbjNlX1NgPhxdHlfrDTy4AeNAre8hP 6g+g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc; bh=AhRHfO8iehFCCtUowGE0tDVkHBkaER+EpAHuQQt15oc=; b=Ipdwt/m85teCVnJ8OHOvmXcL6EhZi3mjQhw43tRilLjmUS6txozNgv8IxxXvk8wa/g OrQP4e9KDDpkt0GFYcVybFMF7nF8RK81QP1zA6v4KItsDPZH4pXOtHx9sh4osSVMrRPQ +OwR61Cwu4iyraFK/ADXmsRp5uOJiJ+DtcYUVLJd25DkauzgdZD38alT0XxhACAAWdHB 9SKdr7ozw2YRqGkVLZ+Gh9wnqBxf+ep7LrbETJ7XlkEshrf6bXbHVcg75HACGy+dBTGV zC2rgZkPIuGPaC0Ulh9OxJ6W1QXZs+FPE7/vSwZtdbNG9lQnn36KiCUBHgeq10wG+h+m 3V+A== X-Gm-Message-State: ACgBeo2a+j5SiL1AM2kjpvSWtZWnsENK0/i0VQmzOr80ZEMgvKwFkpUH NtCBUVJyFjy8zPW8kAyXFrw= X-Google-Smtp-Source: AA6agR4m85we7sUC2H6jAFrF9/7vo0AenPmlyIe2typeJ83W140l74mTBGmd9pjlhcmnyC+Aqk4LvA== X-Received: by 2002:a05:6402:b90:b0:446:6871:7bfa with SMTP id cf16-20020a0564020b9000b0044668717bfamr1027737edb.143.1660948295350; Fri, 19 Aug 2022 15:31:35 -0700 (PDT) Received: from opensuse.localnet (host-87-17-106-94.retail.telecomitalia.it. [87.17.106.94]) by smtp.gmail.com with ESMTPSA id 10-20020a170906218a00b0072af2460cd6sm2875378eju.30.2022.08.19.15.31.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 19 Aug 2022 15:31:33 -0700 (PDT) From: "Fabio M. De Francesco" To: Matthew Wilcox Cc: linux-fscrypt@vger.kernel.org, Eric Biggers , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] fs-verity: use kmap_local_page() instead of kmap() Date: Sat, 20 Aug 2022 00:31:31 +0200 Message-ID: <2255194.ElGaqSPkdT@opensuse> In-Reply-To: References: <20220818224010.43778-1-ebiggers@kernel.org> <44912540.fMDQidcC6G@opensuse> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1660948296; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=AhRHfO8iehFCCtUowGE0tDVkHBkaER+EpAHuQQt15oc=; b=HFKRI4mJ6isfTP9g/9rVyJRyGcIQ5JBP+grPR9H/eKhWosf3a80qt44GghHvHkv3aOUXfB Zp28TR5KlDJx/VMXedfwrQ/tNVtySDC6VmBybcR2FC1wS5WA4MRYEF8hiIg4q6P71nTn++ OifnALbpsNBTJBI8PQrjAcNyP0oJAlo= ARC-Authentication-Results: i=1; imf29.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=csqNUCUv; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf29.hostedemail.com: domain of fmdefrancesco@gmail.com designates 209.85.208.44 as permitted sender) smtp.mailfrom=fmdefrancesco@gmail.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1660948296; a=rsa-sha256; cv=none; b=c+CoF2nWChyD4bTDs1hw/llJUqO52q0luPDm2AgUvs8H64J636O/Fo2jdz4JoXxP53FYXi wvGOUdQMD1asdGV4UoDHKupZBmG+Tx6AeQdzrUZ5cGPLvuvwBPQvQhFQAKA+VVN887D3s2 PQFgM90h7W75fIZHGHGovAdQajVfMh8= Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=csqNUCUv; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf29.hostedemail.com: domain of fmdefrancesco@gmail.com designates 209.85.208.44 as permitted sender) smtp.mailfrom=fmdefrancesco@gmail.com X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: DA7C812006F X-Stat-Signature: hihcg5xformkg35cahd4djhgwbpp3xzj X-Rspam-User: X-HE-Tag: 1660948296-331219 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On venerd=C3=AC 19 agosto 2022 20:29:31 CEST Matthew Wilcox wrote: > On Fri, Aug 19, 2022 at 09:50:37AM +0200, Fabio M. De Francesco wrote: > > On venerd=C3=AC 19 agosto 2022 00:40:10 CEST Eric Biggers wrote: > > > From: Eric Biggers > > >=20 > > > Convert the use of kmap() to its recommended replacement > > > kmap_local_page(). This avoids the overhead of doing a non-local > > > mapping, which is unnecessary in this case. > > >=20 > > > Signed-off-by: Eric Biggers > > > --- > > >=20 > > > fs/verity/read_metadata.c | 6 +++--- > > > 1 file changed, 3 insertions(+), 3 deletions(-) > >=20 > > It looks good to me... > >=20 > > > - virt =3D kmap(page); > > > + virt =3D kmap_local_page(page); > > >=20 > > > if (copy_to_user(buf, virt + offs_in_page, bytes_to_copy)) > >=20 > > { > >=20 > > > - kunmap(page); > > > + kunmap_local(virt); > > >=20 > > > put_page(page); > > > err =3D -EFAULT; > > > break; > > > =09 > > > } > > >=20 > > > - kunmap(page); > > > + kunmap_local(virt); >=20 > Is this a common pattern? eg do we want something like: >=20 > static inline int copy_user_page(void __user *dst, struct page *page, > size_t offset, size_t len) > { > char *src =3D kmap_local_page(page) + offset; > int err =3D 0; >=20 > VM_BUG_ON(offset + len > PAGE_SIZE); > if (copy_to_user(dst, src, len)) > err =3D -EFAULT; >=20 > kunmap_local(src); > return err; > } >=20 > in highmem.h? Not sure that it is much common... Can the following command provide any insight? opensuse:/usr/src/git/kernels/linux> grep -rn copy_to_user -B7 . --exclude- dir\=3DDocumentation | grep kmap =2E/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c-2306- ptr =3D=20 kmap_local_page(p); =2E/drivers/gpu/drm/i915/i915_gem.c-215- vaddr =3D kmap_local_page(page); =2E/drivers/gpu/drm/radeon/radeon_ttm.c-872- ptr =3D=20 kmap(page); =2E/drivers/vfio/pci/mlx5/main.c-182- from_buff =3D=20 kmap_local_page(page); =2E/arch/parisc/kernel/cache.c-580- kto =3D kmap_local_page(to); =2E/mm/memory.c-5474- maddr =3D kmap(page); =2E/fs/verity/read_metadata.c-56- virt =3D kmap(page); =2E/fs/aio.c-1252- ev =3D kmap_local_page(page); =2E/fs/exec.c-883- char *src =3D kmap_local_page(bprm->page[= index])=20 + offset; If this command is good to provide any hint, it suggests that having=20 copy_to_user() in highmem.h is not probably worth. Thanks, =46abio=20