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Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH 33/33] vfs: Add a sample program for the new mount API [ver #11] From: David Howells To: viro@zeniv.linux.org.uk Cc: torvalds@linux-foundation.org, dhowells@redhat.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Date: Wed, 01 Aug 2018 16:27:49 +0100 Message-ID: <153313726964.13253.5202020232694227661.stgit@warthog.procyon.org.uk> In-Reply-To: <153313703562.13253.5766498657900728120.stgit@warthog.procyon.org.uk> References: <153313703562.13253.5766498657900728120.stgit@warthog.procyon.org.uk> User-Agent: StGit/unknown-version MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.78 on 10.11.54.3 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.7]); Wed, 01 Aug 2018 15:27:50 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.7]); Wed, 01 Aug 2018 15:27:50 +0000 (UTC) for IP:'10.11.54.3' DOMAIN:'int-mx03.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'dhowells@redhat.com' RCPT:'' Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Add a sample program to demonstrate fsopen/fsmount/move_mount to mount something. Signed-off-by: David Howells --- samples/Kconfig | 6 ++ samples/Makefile | 2 - samples/mount_api/Makefile | 7 ++ samples/mount_api/test-fsmount.c | 118 ++++++++++++++++++++++++++++++++++++++ 4 files changed, 132 insertions(+), 1 deletion(-) create mode 100644 samples/mount_api/Makefile create mode 100644 samples/mount_api/test-fsmount.c diff --git a/samples/Kconfig b/samples/Kconfig index bd133efc1a56..daa17e9f3197 100644 --- a/samples/Kconfig +++ b/samples/Kconfig @@ -152,4 +152,10 @@ config SAMPLE_STATX help Build example userspace program to use the new extended-stat syscall. +config SAMPLE_MOUNT_API + bool "Build example code using the new mount API" + depends on BROKEN + help + Build example userspace program(s) that use the new mount API. + endif # SAMPLES diff --git a/samples/Makefile b/samples/Makefile index bd601c038b86..31d08cc71a5c 100644 --- a/samples/Makefile +++ b/samples/Makefile @@ -3,4 +3,4 @@ obj-$(CONFIG_SAMPLES) += kobject/ kprobes/ trace_events/ livepatch/ \ hw_breakpoint/ kfifo/ kdb/ hidraw/ rpmsg/ seccomp/ \ configfs/ connector/ v4l/ trace_printk/ \ - vfio-mdev/ statx/ qmi/ + vfio-mdev/ statx/ qmi/ mount_api/ diff --git a/samples/mount_api/Makefile b/samples/mount_api/Makefile new file mode 100644 index 000000000000..6856df236dbf --- /dev/null +++ b/samples/mount_api/Makefile @@ -0,0 +1,7 @@ +# List of programs to build +hostprogs-$(CONFIG_SAMPLE_MOUNT_API) := test-fsmount + +# Tell kbuild to always build the programs +always := $(hostprogs-y) + +HOSTCFLAGS_test-fsmount.o += -I$(objtree)/usr/include diff --git a/samples/mount_api/test-fsmount.c b/samples/mount_api/test-fsmount.c new file mode 100644 index 000000000000..74124025ade0 --- /dev/null +++ b/samples/mount_api/test-fsmount.c @@ -0,0 +1,118 @@ +/* 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 +#include +#include + +#define E(x) do { if ((x) == -1) { perror(#x); exit(1); } } while(0) + +static void check_messages(int fd) +{ + char buf[4096]; + int err, n; + + err = errno; + + for (;;) { + n = read(fd, buf, sizeof(buf)); + if (n < 0) + break; + n -= 2; + + switch (buf[0]) { + case 'e': + fprintf(stderr, "Error: %*.*s\n", n, n, buf + 2); + break; + case 'w': + fprintf(stderr, "Warning: %*.*s\n", n, n, buf + 2); + break; + case 'i': + fprintf(stderr, "Info: %*.*s\n", n, n, buf + 2); + break; + } + } + + errno = err; +} + +static __attribute__((noreturn)) +void mount_error(int fd, const char *s) +{ + check_messages(fd); + fprintf(stderr, "%s: %m\n", s); + exit(1); +} + +static inline int fsopen(const char *fs_name, unsigned int flags) +{ + return syscall(__NR_fsopen, fs_name, flags); +} + +static inline int fsmount(int fsfd, unsigned int flags, unsigned int ms_flags) +{ + return syscall(__NR_fsmount, fsfd, flags, ms_flags); +} + +static inline int fsconfig(int fsfd, unsigned int cmd, + const char *key, const void *val, int aux) +{ + return syscall(__NR_fsconfig, fsfd, cmd, key, val, aux); +} + +static inline int move_mount(int from_dfd, const char *from_pathname, + int to_dfd, const char *to_pathname, + unsigned int flags) +{ + return syscall(__NR_move_mount, + from_dfd, from_pathname, + to_dfd, to_pathname, flags); +} + +#define E_fsconfig(fd, cmd, key, val, aux) \ + do { \ + if (fsconfig(fd, cmd, key, val, aux) == -1) \ + mount_error(fd, key ?: "create"); \ + } while (0) + +int main(int argc, char *argv[]) +{ + int fsfd, mfd; + + /* Mount a publically available AFS filesystem */ + fsfd = fsopen("afs", 0); + if (fsfd == -1) { + perror("fsopen"); + exit(1); + } + + E_fsconfig(fsfd, FSCONFIG_SET_STRING, "source", "#grand.central.org:root.cell.", 0); + E_fsconfig(fsfd, FSCONFIG_CMD_CREATE, NULL, NULL, 0); + + mfd = fsmount(fsfd, 0, MS_RDONLY); + if (mfd < 0) + mount_error(fsfd, "fsmount"); + E(close(fsfd)); + + if (move_mount(mfd, "", AT_FDCWD, "/mnt", MOVE_MOUNT_F_EMPTY_PATH) < 0) { + perror("move_mount"); + exit(1); + } + + E(close(mfd)); + exit(0); +}