From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932328AbdJZRV7 (ORCPT ); Thu, 26 Oct 2017 13:21:59 -0400 Received: from mail-yw0-f193.google.com ([209.85.161.193]:47583 "EHLO mail-yw0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932127AbdJZRV4 (ORCPT ); Thu, 26 Oct 2017 13:21:56 -0400 X-Google-Smtp-Source: ABhQp+TT8GeKfMG1d9FE5Jpp3bYx64kaVcov+wcVDiklXu45ywyzX2SSw32u+7FhxYQcHXF1F2e28A== Message-ID: <1509038513.29077.31.camel@redhat.com> Subject: Re: [PATCH 07/14] VFS: Add a sample program for fsopen/fsmount [ver #6] From: Jeff Layton To: David Howells , viro@ZenIV.linux.org.uk Cc: linux-fsdevel@vger.kernel.org, mszeredi@redhat.com, linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org Date: Thu, 26 Oct 2017 13:21:53 -0400 In-Reply-To: <150730500019.6182.15975727444128962384.stgit@warthog.procyon.org.uk> References: <150730494491.6182.5139368907374172391.stgit@warthog.procyon.org.uk> <150730500019.6182.15975727444128962384.stgit@warthog.procyon.org.uk> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.24.6 (3.24.6-1.fc26) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2017-10-06 at 16:50 +0100, David Howells wrote: > Add a sample program for driving fsopen/fsmount. > > Signed-off-by: David Howells > --- > > samples/fsmount/test-fsmount.c | 94 ++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 94 insertions(+) > create mode 100644 samples/fsmount/test-fsmount.c > > diff --git a/samples/fsmount/test-fsmount.c b/samples/fsmount/test-fsmount.c > new file mode 100644 > index 000000000000..75f91d272a19 > --- /dev/null > +++ b/samples/fsmount/test-fsmount.c > @@ -0,0 +1,94 @@ > +/* fd-based mount test. > + * > + * Copyright (C) 2017 Red Hat, Inc. All Rights Reserved. > + * Written by David Howells (dhowells@redhat.com) > + * > + * This program is free software; you can redistribute it and/or > + * modify it under the terms of the GNU General Public Licence > + * as published by the Free Software Foundation; either version > + * 2 of the Licence, or (at your option) any later version. > + */ > + > +#include > +#include > +#include > +#include > +#include > +#include > +#include > + > +#define PR_ERRMSG_ENABLE 48 > +#define PR_ERRMSG_READ 49 > + > +#define E(x) do { if ((x) == -1) { perror(#x); exit(1); } } while(0) > + > +static __attribute__((noreturn)) > +void mount_error(int fd, const char *s) > +{ > + char buf[4096]; > + int err, n, perr; > + > + do { > + err = errno; > + errno = 0; > + n = prctl(PR_ERRMSG_READ, buf, sizeof(buf)); > + perr = errno; > + errno = err; > + if (n > 0) { > + fprintf(stderr, "Error: '%s': %*.*s: %m\n", s, n, n, buf); > + } else { > + fprintf(stderr, "%s: %m\n", s); > + } > + } while (perr == 0); > + exit(1); > +} > + > +#define E_write(fd, s) \ > + do { \ > + if (write(fd, s, sizeof(s) - 1) == -1) \ > + mount_error(fd, s); \ > + } while (0) > + > +static inline int fsopen(const char *fs_name, int flags, > + void *reserved3, void *reserved4, void *reserved5); > + > +{ > + return syscall(333, fs_name, flags, reserved3, reserved4, reserved5); > +} > + > +static inline int fsmount(int fsfd, int dfd, const char *path, > + unsigned int at_flags, unsigned int flags) > +{ > + return syscall(334, fsfd, dfd, path, at_flags, flags); > +} > + > +int main() > +{ > + int mfd; > + > + if (prctl(PR_ERRMSG_ENABLE, 1) < 0) { > + perror("prctl/en"); > + exit(1); > + } > + > + /* Mount an NFS filesystem */ > + mfd = fsopen("nfs4", 0, NULL, NULL, NULL); > + if (mfd == -1) { > + perror("fsopen"); > + exit(1); > + } > + > + E_write(mfd, "s warthog:/data"); > + E_write(mfd, "o fsc"); > + E_write(mfd, "o sync"); > + E_write(mfd, "o intr"); > + E_write(mfd, "o vers=4.2"); > + E_write(mfd, "o addr=90.155.74.18"); > + E_write(mfd, "o clientaddr=90.155.74.21"); > + E_write(mfd, "x create"); > + if (fsmount(mfd, AT_FDCWD, "/mnt", 0, 0) < 0) > + mount_error(mfd, "fsmount"); > + E(close(mfd)); > + > + exit(0); > +} > So to make sure I understand.... Suppose I want to do a bind mount with the new API. Would I do something like this? mfd = fsopen("???"); write(mfd, "s /path/to/old/mount"); write(mfd, "o bind"); fsmount(mfd, ...); That seems a bit klunkier than before as I now need to pay attention to the fstype. I guess I'd have to scrape /proc/mounts for that info? -- Jeff Layton