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 X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D216BC282DD for ; Wed, 17 Apr 2019 13:00:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 98E1F21773 for ; Wed, 17 Apr 2019 13:00:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="BjZsvhO3" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732196AbfDQNA6 (ORCPT ); Wed, 17 Apr 2019 09:00:58 -0400 Received: from mail-lf1-f66.google.com ([209.85.167.66]:45828 "EHLO mail-lf1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729318AbfDQNA5 (ORCPT ); Wed, 17 Apr 2019 09:00:57 -0400 Received: by mail-lf1-f66.google.com with SMTP id t11so14315225lfl.12 for ; Wed, 17 Apr 2019 06:00:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=nD5N/gZK0Hc9/leGn/iw1G+jz11LpAQc97DIEWLBEH0=; b=BjZsvhO3f2TtZdypKM0jxF9FMvsBQgKsjOjoxn88+v7JSDK6dBNSiffPm+ktPRILcE HmWGSWZxWZHKnDwj5FtEyQyi0yj7N3sx12LtX22qusLXABFr0uNQaTgY4ME5c+GsOW5/ cdEURgaDBigSxdcG2kpRozIdV+yh2dtTvlQyqrQdcX1l+FHwwNxp3WKEhssRK+Dtj5ML bol8BNRZ/nTq/h9U2713ozFZCt/zN6G1HMOANjAJqqVeRne08HkFoDLPlb2H/asmksvu e57LwlEC/XyHZJILatdvhwGcZTcgiOGrP3JA0IsDCg6RlFrY0cwU1y9ZqEANl9d65w8L IoVA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=nD5N/gZK0Hc9/leGn/iw1G+jz11LpAQc97DIEWLBEH0=; b=W4rLrWCXX+R0xchzbOgVF9V7yWo+8FYdWM1K2tvHbPr6EHXt8OqjtGnB8zb85BaLuj Gq3pZxWJFQTLYgXXfSuQiq6lp4eYtAG2fmDF/0Lp6WO+LyXoAi73BrTz3nLWSc4uYriq O4x75VXgeozLDYS55a2mjD3exr4ehiOtx/2YB/ufKBNTiwBGeDYCZAcOI5gGlhEwi4k8 hqpQAFPBsJswqy8D+AKgsEivCUiy2599JEj/g1aE8Hd+ta0gSuFv/INwzQQZwUZ2Zg64 CIwjJ22AhI88wiuqMxd5U/V2BasHAPlhbcK5zDUYlAK/nZw94fe9axmCbks1gjzrP+0b JqNg== X-Gm-Message-State: APjAAAWIImzd3AvJzx8Ce/0zwB1Z2Mfp/6Hxq2cU0zWUPhlhxXIUdAjX 2m5IHgNGYwDJBn5IFcVm4aypm2sczgWw0k4S2RA= X-Google-Smtp-Source: APXvYqzYJsHEPZUdZi7dgUmK7iczzP/OpZWI0kCGkirNZhXZR65KeukbkI/1y7q+0vV1rRiXwgEe0vywbPgmOrs7Vcs= X-Received: by 2002:a19:3f09:: with SMTP id m9mr14983716lfa.36.1555506054907; Wed, 17 Apr 2019 06:00:54 -0700 (PDT) MIME-Version: 1.0 References: <20190412160338.64994-1-thellstrom@vmware.com> <20190412160338.64994-2-thellstrom@vmware.com> In-Reply-To: From: Souptick Joarder Date: Wed, 17 Apr 2019 18:30:43 +0530 Message-ID: Subject: Re: [PATCH 1/9] mm: Allow the [page|pfn]_mkwrite callbacks to drop the mmap_sem To: Thomas Hellstrom Cc: "linux-kernel@vger.kernel.org" , "peterz@infradead.org" , "willy@infradead.org" , "linux-mm@kvack.org" , "akpm@linux-foundation.org" , "minchan@kernel.org" , "jglisse@redhat.com" , "dri-devel@lists.freedesktop.org" , "will.deacon@arm.com" , Linux-graphics-maintainer , "mhocko@suse.com" , "ying.huang@intel.com" , "riel@surriel.com" Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 17, 2019 at 4:28 PM Thomas Hellstrom wr= ote: > > Hi, Souptick, > > On Sat, 2019-04-13 at 20:41 +0530, Souptick Joarder wrote: > > On Fri, Apr 12, 2019 at 9:34 PM Thomas Hellstrom < > > thellstrom@vmware.com> wrote: > > > Driver fault callbacks are allowed to drop the mmap_sem when > > > expecting > > > long hardware waits to avoid blocking other mm users. Allow the > > > mkwrite > > > callbacks to do the same by returning early on VM_FAULT_RETRY. > > > > > > In particular we want to be able to drop the mmap_sem when waiting > > > for > > > a reservation object lock on a GPU buffer object. These locks may > > > be > > > held while waiting for the GPU. > > > > > > Cc: Andrew Morton > > > Cc: Matthew Wilcox > > > Cc: Will Deacon > > > Cc: Peter Zijlstra > > > Cc: Rik van Riel > > > Cc: Minchan Kim > > > Cc: Michal Hocko > > > Cc: Huang Ying > > > Cc: Souptick Joarder > > > Cc: "J=C3=A9r=C3=B4me Glisse" > > > Cc: linux-mm@kvack.org > > > Cc: linux-kernel@vger.kernel.org > > > > > > Signed-off-by: Thomas Hellstrom > > > --- > > > mm/memory.c | 10 ++++++---- > > > 1 file changed, 6 insertions(+), 4 deletions(-) > > > > > > diff --git a/mm/memory.c b/mm/memory.c > > > index e11ca9dd823f..a95b4a3b1ae2 100644 > > > --- a/mm/memory.c > > > +++ b/mm/memory.c > > > @@ -2144,7 +2144,7 @@ static vm_fault_t do_page_mkwrite(struct > > > vm_fault *vmf) > > > ret =3D vmf->vma->vm_ops->page_mkwrite(vmf); > > > /* Restore original flags so that caller is not surprised > > > */ > > > vmf->flags =3D old_flags; > > > - if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE))) > > > + if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_RETRY | > > > VM_FAULT_NOPAGE))) > > > > With this patch there will multiple instances of (VM_FAULT_ERROR | > > VM_FAULT_RETRY | VM_FAULT_NOPAGE) > > in mm/memory.c. Does it make sense to wrap it in a macro and use it ? > > Even though the code will look neater, it might be trickier to follow a > particular error path. Could we perhaps postpone to a follow-up patch? Sure. follow-up-patch is fine. > > Thomas > > > > > > > > return ret; > > > if (unlikely(!(ret & VM_FAULT_LOCKED))) { > > > lock_page(page); > > > @@ -2419,7 +2419,7 @@ static vm_fault_t wp_pfn_shared(struct > > > vm_fault *vmf) > > > pte_unmap_unlock(vmf->pte, vmf->ptl); > > > vmf->flags |=3D FAULT_FLAG_MKWRITE; > > > ret =3D vma->vm_ops->pfn_mkwrite(vmf); > > > - if (ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)) > > > + if (ret & (VM_FAULT_ERROR | VM_FAULT_RETRY | > > > VM_FAULT_NOPAGE)) > > > return ret; > > > return finish_mkwrite_fault(vmf); > > > } > > > @@ -2440,7 +2440,8 @@ static vm_fault_t wp_page_shared(struct > > > vm_fault *vmf) > > > pte_unmap_unlock(vmf->pte, vmf->ptl); > > > tmp =3D do_page_mkwrite(vmf); > > > if (unlikely(!tmp || (tmp & > > > - (VM_FAULT_ERROR | > > > VM_FAULT_NOPAGE)))) { > > > + (VM_FAULT_ERROR | > > > VM_FAULT_RETRY | > > > + VM_FAULT_NOPAGE)))) { > > > put_page(vmf->page); > > > return tmp; > > > } > > > @@ -3494,7 +3495,8 @@ static vm_fault_t do_shared_fault(struct > > > vm_fault *vmf) > > > unlock_page(vmf->page); > > > tmp =3D do_page_mkwrite(vmf); > > > if (unlikely(!tmp || > > > - (tmp & (VM_FAULT_ERROR | > > > VM_FAULT_NOPAGE)))) { > > > + (tmp & (VM_FAULT_ERROR | > > > VM_FAULT_RETRY | > > > + VM_FAULT_NOPAGE)))) { > > > put_page(vmf->page); > > > return tmp; > > > } > > > -- > > > 2.20.1 > > > 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 X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A5AD4C282DA for ; Wed, 17 Apr 2019 13:00:58 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 519832173C for ; 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[209.85.220.65]) by mx.google.com with SMTPS id 16sor2607663lfr.9.2019.04.17.06.00.55 for (Google Transport Security); Wed, 17 Apr 2019 06:00:55 -0700 (PDT) Received-SPF: pass (google.com: domain of jrdr.linux@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=BjZsvhO3; spf=pass (google.com: domain of jrdr.linux@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=jrdr.linux@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=nD5N/gZK0Hc9/leGn/iw1G+jz11LpAQc97DIEWLBEH0=; b=BjZsvhO3f2TtZdypKM0jxF9FMvsBQgKsjOjoxn88+v7JSDK6dBNSiffPm+ktPRILcE HmWGSWZxWZHKnDwj5FtEyQyi0yj7N3sx12LtX22qusLXABFr0uNQaTgY4ME5c+GsOW5/ cdEURgaDBigSxdcG2kpRozIdV+yh2dtTvlQyqrQdcX1l+FHwwNxp3WKEhssRK+Dtj5ML bol8BNRZ/nTq/h9U2713ozFZCt/zN6G1HMOANjAJqqVeRne08HkFoDLPlb2H/asmksvu e57LwlEC/XyHZJILatdvhwGcZTcgiOGrP3JA0IsDCg6RlFrY0cwU1y9ZqEANl9d65w8L IoVA== X-Google-Smtp-Source: APXvYqzYJsHEPZUdZi7dgUmK7iczzP/OpZWI0kCGkirNZhXZR65KeukbkI/1y7q+0vV1rRiXwgEe0vywbPgmOrs7Vcs= X-Received: by 2002:a19:3f09:: with SMTP id m9mr14983716lfa.36.1555506054907; Wed, 17 Apr 2019 06:00:54 -0700 (PDT) MIME-Version: 1.0 References: <20190412160338.64994-1-thellstrom@vmware.com> <20190412160338.64994-2-thellstrom@vmware.com> In-Reply-To: From: Souptick Joarder Date: Wed, 17 Apr 2019 18:30:43 +0530 Message-ID: Subject: Re: [PATCH 1/9] mm: Allow the [page|pfn]_mkwrite callbacks to drop the mmap_sem To: Thomas Hellstrom Cc: "linux-kernel@vger.kernel.org" , "peterz@infradead.org" , "willy@infradead.org" , "linux-mm@kvack.org" , "akpm@linux-foundation.org" , "minchan@kernel.org" , "jglisse@redhat.com" , "dri-devel@lists.freedesktop.org" , "will.deacon@arm.com" , Linux-graphics-maintainer , "mhocko@suse.com" , "ying.huang@intel.com" , "riel@surriel.com" Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable 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 Wed, Apr 17, 2019 at 4:28 PM Thomas Hellstrom wr= ote: > > Hi, Souptick, > > On Sat, 2019-04-13 at 20:41 +0530, Souptick Joarder wrote: > > On Fri, Apr 12, 2019 at 9:34 PM Thomas Hellstrom < > > thellstrom@vmware.com> wrote: > > > Driver fault callbacks are allowed to drop the mmap_sem when > > > expecting > > > long hardware waits to avoid blocking other mm users. Allow the > > > mkwrite > > > callbacks to do the same by returning early on VM_FAULT_RETRY. > > > > > > In particular we want to be able to drop the mmap_sem when waiting > > > for > > > a reservation object lock on a GPU buffer object. These locks may > > > be > > > held while waiting for the GPU. > > > > > > Cc: Andrew Morton > > > Cc: Matthew Wilcox > > > Cc: Will Deacon > > > Cc: Peter Zijlstra > > > Cc: Rik van Riel > > > Cc: Minchan Kim > > > Cc: Michal Hocko > > > Cc: Huang Ying > > > Cc: Souptick Joarder > > > Cc: "J=C3=A9r=C3=B4me Glisse" > > > Cc: linux-mm@kvack.org > > > Cc: linux-kernel@vger.kernel.org > > > > > > Signed-off-by: Thomas Hellstrom > > > --- > > > mm/memory.c | 10 ++++++---- > > > 1 file changed, 6 insertions(+), 4 deletions(-) > > > > > > diff --git a/mm/memory.c b/mm/memory.c > > > index e11ca9dd823f..a95b4a3b1ae2 100644 > > > --- a/mm/memory.c > > > +++ b/mm/memory.c > > > @@ -2144,7 +2144,7 @@ static vm_fault_t do_page_mkwrite(struct > > > vm_fault *vmf) > > > ret =3D vmf->vma->vm_ops->page_mkwrite(vmf); > > > /* Restore original flags so that caller is not surprised > > > */ > > > vmf->flags =3D old_flags; > > > - if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE))) > > > + if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_RETRY | > > > VM_FAULT_NOPAGE))) > > > > With this patch there will multiple instances of (VM_FAULT_ERROR | > > VM_FAULT_RETRY | VM_FAULT_NOPAGE) > > in mm/memory.c. Does it make sense to wrap it in a macro and use it ? > > Even though the code will look neater, it might be trickier to follow a > particular error path. Could we perhaps postpone to a follow-up patch? Sure. follow-up-patch is fine. > > Thomas > > > > > > > > return ret; > > > if (unlikely(!(ret & VM_FAULT_LOCKED))) { > > > lock_page(page); > > > @@ -2419,7 +2419,7 @@ static vm_fault_t wp_pfn_shared(struct > > > vm_fault *vmf) > > > pte_unmap_unlock(vmf->pte, vmf->ptl); > > > vmf->flags |=3D FAULT_FLAG_MKWRITE; > > > ret =3D vma->vm_ops->pfn_mkwrite(vmf); > > > - if (ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)) > > > + if (ret & (VM_FAULT_ERROR | VM_FAULT_RETRY | > > > VM_FAULT_NOPAGE)) > > > return ret; > > > return finish_mkwrite_fault(vmf); > > > } > > > @@ -2440,7 +2440,8 @@ static vm_fault_t wp_page_shared(struct > > > vm_fault *vmf) > > > pte_unmap_unlock(vmf->pte, vmf->ptl); > > > tmp =3D do_page_mkwrite(vmf); > > > if (unlikely(!tmp || (tmp & > > > - (VM_FAULT_ERROR | > > > VM_FAULT_NOPAGE)))) { > > > + (VM_FAULT_ERROR | > > > VM_FAULT_RETRY | > > > + VM_FAULT_NOPAGE)))) { > > > put_page(vmf->page); > > > return tmp; > > > } > > > @@ -3494,7 +3495,8 @@ static vm_fault_t do_shared_fault(struct > > > vm_fault *vmf) > > > unlock_page(vmf->page); > > > tmp =3D do_page_mkwrite(vmf); > > > if (unlikely(!tmp || > > > - (tmp & (VM_FAULT_ERROR | > > > VM_FAULT_NOPAGE)))) { > > > + (tmp & (VM_FAULT_ERROR | > > > VM_FAULT_RETRY | > > > + VM_FAULT_NOPAGE)))) { > > > put_page(vmf->page); > > > return tmp; > > > } > > > -- > > > 2.20.1 > > >