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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id DD605C433F5 for ; Mon, 7 Feb 2022 22:56:44 +0000 (UTC) Received: from localhost ([::1]:37680 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nHCw7-0001RJ-Rk for qemu-devel@archiver.kernel.org; Mon, 07 Feb 2022 17:56:43 -0500 Received: from eggs.gnu.org ([209.51.188.92]:34474) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nHCoD-0000Ht-A6 for qemu-devel@nongnu.org; Mon, 07 Feb 2022 17:48:34 -0500 Received: from kylie.crudebyte.com ([5.189.157.229]:34043) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nHCnl-0006jn-MY for qemu-devel@nongnu.org; Mon, 07 Feb 2022 17:48:08 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=crudebyte.com; s=kylie; h=Content-Type:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Content-ID:Content-Description; bh=mPo/BlFt4qzVG3ctYcDDuTb11xRQOjuuKKzqRWP/i7s=; b=a6+BRiN/R6lOk69PAmLLjatRVW xGoScRSmpLqYXHStL244lgkvq8YX6FAGqLb6n7cn+siZ19gy6B1NdA/m+gb2yp4iqzbeFcPrravKY 4oCvYTTJm/tfWeuqhIF32pybvFH0Y46MM9eOAtGIt/3EL72y6PL30Ul4cg1A51cA+YjEJbcmwK4BA Xs/MlbVl6fFIHSHIEIZQ2Pe9TH9x358TCIjYvC+LjbcafmOLpbSXKT4G+xpKoPtCVbbK1Rsol7akK KWeERlK6j398oqwQeJ0lyWmCjulcNRAYmVEvOiCEeJTX8mgtqvRQiBZBnp3vC5jHpCyipK9eUVU72 Hd202AOeWrtlZGjQe0GlVolnAL/hNWFQ79c786d3dOa8LZXwb/2OOqXE50FBq7+5+GxYJ9eHo7/nz XWSO33i3abs/bSPrz9LMYFZBB97QydZfHv4fMYuK/qpwYd/GGybiHJtsQzKbYwglROypWdaG/O3Q6 7xfkdgb8JhV29ZNCugQHCng9iL2IdE7DnJ2LzrVazfLl3qRc835LzjtdxwntVA3d0sjIzBSGDNbH3 gOvj61dnRT4IaBLJFNvkwL8+R/CypO+/Cfhs3Z6XFSNiusL641MyVsMQT1oTdYKRSXJ2odEUrjk/L KaJ0rmqMF+7bS1ZCVCiT/s4L7epmlRdfNf2tnmEjg=; From: Christian Schoenebeck To: Will Cohen Cc: "Dr. David Alan Gilbert" , Greg Kurz , Philippe =?ISO-8859-1?Q?Mathieu=2DDaud=E9?= , qemu-devel@nongnu.org, Laurent Vivier , Thomas Huth , hi@alyssa.is, Michael Roitzsch , Paolo Bonzini , Keno Fischer , Vivek Subject: Re: [PATCH v4 09/11] 9p: darwin: Implement compatibility for mknodat Date: Mon, 07 Feb 2022 23:47:58 +0100 Message-ID: <8937604.n9ZydULHvW@silver> In-Reply-To: References: <20220206200719.74464-1-wwcohen@gmail.com> <5204641.elYuxvqpol@silver> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="iso-8859-1" Received-SPF: pass client-ip=5.189.157.229; envelope-from=qemu_oss@crudebyte.com; helo=kylie.crudebyte.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Montag, 7. Februar 2022 22:07:34 CET Will Cohen wrote: > On Mon, Feb 7, 2022 at 9:21 AM Christian Schoenebeck > > wrote: > > On Montag, 7. Februar 2022 11:57:25 CET Dr. David Alan Gilbert wrote: > > > * Greg Kurz (groug@kaod.org) wrote: > > > > On Mon, 7 Feb 2022 11:30:18 +0100 > > > >=20 > > > > Philippe Mathieu-Daud=E9 wrote: > > > > > On 7/2/22 09:47, Greg Kurz wrote: > > > > > > On Sun, 6 Feb 2022 20:10:23 -0500 > > > > > >=20 > > > > > > Will Cohen wrote: > > > > > >> This patch set currently places it in 9p-util only because 9p = is > >=20 > > the > >=20 > > > > > >> only > > > > > >> place where this issue seems to have come up so far and we were > >=20 > > wary > >=20 > > > > > >> of > > > > > >> editing files too far afield, but I have no attachment to its > > > > > >> specific > > > > > >> location! > > > > > >=20 > > > > > > Inline comments are preferred on qemu-devel. Please don't top p= ost > >=20 > > ! > >=20 > > > > > > This complicates the review a lot. > > > > > >=20 > > > > > > This is indeed a good candidate for osdep. This being said, unl= ess > > > > > > there's > > > > > > some other user in the QEMU code base, it is acceptable to leave > > > > > > it > > > > > > under > > > > > > 9pfs. > > > > >=20 > > > > > virtiofsd could eventually use it. > > > >=20 > > > > Indeed but virtiofsd is for linux hosts only AFAICT and I'm not awa= re > >=20 > > of > >=20 > > > > any work to support any other host OS. > > > >=20 > > > > Cc'ing virtio-fs people for inputs on this topic. > > >=20 > > > Indeeed, there's a lot of Linux specific code in the virtiofsd - I kn= ow > > > people are interested in other platforms, but I'm not sure that's the > > > right starting point. > > >=20 > > > Dave > >=20 > > Agreeing with Greg here: i.e. I would have placed this into osdep, but I > > would > > not insist on it either. > >=20 > > Best regards, > > Christian Schoenebeck >=20 > This makes sense. A revised version of this patch, moving qemu_mknodat fr= om > 9p-util to osdep and os-posix, is attached below. I'd appreciate any > feedback from those looped in here, so that the context isn't lost before > resubmitting as a v5 patch, especially since this is starting to touch > files outside of 9p. >=20 > From c9713c87163da7c96b5357d0d85ac318ae3d3051 Mon Sep 17 00:00:00 2001 > From: Keno Fischer > Date: Sat, 16 Jun 2018 20:56:55 -0400 > Subject: [PATCH] 9p: darwin: Implement compatibility for mknodat >=20 > Darwin does not support mknodat. However, to avoid race conditions > with later setting the permissions, we must avoid using mknod on > the full path instead. We could try to fchdir, but that would cause > problems if multiple threads try to call mknodat at the same time. > However, luckily there is a solution: Darwin includes a function > that sets the cwd for the current thread only. > This should suffice to use mknod safely. >=20 > This function (pthread_fchdir_np) is protected by a check in > meson in a patch later in tihs series. >=20 > Signed-off-by: Keno Fischer > Signed-off-by: Michael Roitzsch > [Will Cohen: - Adjust coding style > - Replace clang references with gcc > - Note radar filed with Apple for missing syscall > - Replace direct syscall with pthread_fchdir_np and > adjust patch notes accordingly > - Move qemu_mknodat from 9p-util to osdep and os-posix] > Signed-off-by: Will Cohen > --- > hw/9pfs/9p-local.c | 4 ++-- > include/qemu/osdep.h | 10 ++++++++++ > os-posix.c | 34 ++++++++++++++++++++++++++++++++++ > 3 files changed, 46 insertions(+), 2 deletions(-) >=20 > diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c > index a0d08e5216..d42ce6d8b8 100644 > --- a/hw/9pfs/9p-local.c > +++ b/hw/9pfs/9p-local.c > @@ -682,7 +682,7 @@ static int local_mknod(FsContext *fs_ctx, V9fsPath > *dir_path, >=20 > if (fs_ctx->export_flags & V9FS_SM_MAPPED || > fs_ctx->export_flags & V9FS_SM_MAPPED_FILE) { > - err =3D mknodat(dirfd, name, fs_ctx->fmode | S_IFREG, 0); > + err =3D qemu_mknodat(dirfd, name, fs_ctx->fmode | S_IFREG, 0); > if (err =3D=3D -1) { > goto out; > } > @@ -697,7 +697,7 @@ static int local_mknod(FsContext *fs_ctx, V9fsPath > *dir_path, > } > } else if (fs_ctx->export_flags & V9FS_SM_PASSTHROUGH || > fs_ctx->export_flags & V9FS_SM_NONE) { > - err =3D mknodat(dirfd, name, credp->fc_mode, credp->fc_rdev); > + err =3D qemu_mknodat(dirfd, name, credp->fc_mode, credp->fc_rdev= ); > if (err =3D=3D -1) { > goto out; > } > diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h > index d1660d67fa..f3a8367ece 100644 > --- a/include/qemu/osdep.h > +++ b/include/qemu/osdep.h > @@ -810,3 +810,13 @@ static inline int > platform_does_not_support_system(const char *command) > #endif >=20 > #endif > + > +/* > + * As long as mknodat is not available on macOS, this workaround > + * using pthread_fchdir_np is needed. qemu_mknodat is defined in > + * os-posix.c > + */ > +#ifdef CONFIG_DARWIN > +int pthread_fchdir_np(int fd); > +#endif I would make that: #ifdef CONFIG_DARWIN int pthread_fchdir_np(int fd) API_AVAILABLE(macosx(10.12)); #endif here and ... > +int qemu_mknodat(int dirfd, const char *filename, mode_t mode, dev_t dev= ); > diff --git a/os-posix.c b/os-posix.c > index ae6c9f2a5e..95c1607065 100644 > --- a/os-posix.c > +++ b/os-posix.c > @@ -24,6 +24,7 @@ > */ >=20 > #include "qemu/osdep.h" > +#include > #include > #include > #include > @@ -332,3 +333,36 @@ int os_mlock(void) > return -ENOSYS; > #endif > } > + > +/* > + * As long as mknodat is not available on macOS, this workaround > + * using pthread_fchdir_np is needed. > + * > + * Radar filed with Apple for implementing mknodat: > + * rdar://FB9862426 (https://openradar.appspot.com/FB9862426) > + */ > +#ifdef CONFIG_DARWIN > + > +int pthread_fchdir_np(int fd) API_AVAILABLE(macosx(10.12)); =2E.. drop the duplicate declaration of pthread_fchdir_np() here. > + > +int qemu_mknodat(int dirfd, const char *filename, mode_t mode, dev_t dev) > +{ > + int preserved_errno, err; > + if (pthread_fchdir_np(dirfd) < 0) { > + return -1; > + } > + err =3D mknod(filename, mode, dev); > + preserved_errno =3D errno; > + /* Stop using the thread-local cwd */ > + pthread_fchdir_np(-1); > + if (err < 0) { > + errno =3D preserved_errno; > + } > + return err; > +} > +#else > +int qemu_mknodat(int dirfd, const char *filename, mode_t mode, dev_t dev) > +{ > + return mknodat(dirfd, filename, mode, dev); > +} > +#endif