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mount: use libmount to monitor mountinfo & utab 

The current implementation directly monitor /proc/self/mountinfo and
/run/mount/utab files. It's really not optimal because utab file is
private libmount stuff without any official guaranteed semantic.

The libmount since v2.26 provides API to monitor mount kernel &
userspace changes and since v2.27 the monitor is usable for
non-root users too.

This patch replaces the current implementation with libmount based
solution.

Signed-off-by: Karel Zak <kzak@redhat.com>
This commit is contained in:
Karel Zak 2015-06-01 13:48:01 +02:00
parent 5669ef3644
commit d379d44255
6 changed files with 72 additions and 94 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

33
Makefile.am
View File

@ -1327,7 +1327,8 @@ systemd_SOURCES = \
systemd_CFLAGS = \
$(AM_CFLAGS) \
$(SECCOMP_CFLAGS)
$(SECCOMP_CFLAGS) \
$(MOUNT_CFLAGS)
systemd_LDADD = \
libcore.la
@ -1532,7 +1533,8 @@ test_engine_SOURCES = \
test_engine_CFLAGS = \
$(AM_CFLAGS) \
$(SECCOMP_CFLAGS)
$(SECCOMP_CFLAGS) \
$(MOUNT_CFLAGS)
test_engine_LDADD = \
libcore.la
@ -1542,7 +1544,8 @@ test_job_type_SOURCES = \
test_job_type_CFLAGS = \
$(AM_CFLAGS) \
$(SECCOMP_CFLAGS)
$(SECCOMP_CFLAGS) \
$(MOUNT_CFLAGS)
test_job_type_LDADD = \
libcore.la
@ -1592,7 +1595,8 @@ test_unit_name_SOURCES = \
test_unit_name_CFLAGS = \
$(AM_CFLAGS) \
$(SECCOMP_CFLAGS)
$(SECCOMP_CFLAGS) \
$(MOUNT_CFLAGS)
test_unit_name_LDADD = \
libcore.la
@ -1602,7 +1606,8 @@ test_unit_file_SOURCES = \
test_unit_file_CFLAGS = \
$(AM_CFLAGS) \
$(SECCOMP_CFLAGS)
$(SECCOMP_CFLAGS) \
$(MOUNT_CFLAGS)
test_unit_file_LDADD = \
libcore.la
@ -1811,7 +1816,8 @@ test_tables_CPPFLAGS = \
test_tables_CFLAGS = \
$(AM_CFLAGS) \
$(SECCOMP_CFLAGS)
$(SECCOMP_CFLAGS) \
$(MOUNT_CFLAGS)
test_tables_LDADD = \
libjournal-core.la \
@ -1937,7 +1943,8 @@ test_cgroup_mask_SOURCES = \
src/test/test-cgroup-mask.c
test_cgroup_mask_CPPFLAGS = \
$(AM_CPPFLAGS)
$(AM_CPPFLAGS) \
$(MOUNT_CFLAGS)
test_cgroup_mask_CFLAGS = \
$(AM_CFLAGS) \
@ -1980,7 +1987,8 @@ test_path_SOURCES = \
src/test/test-path.c
test_path_CFLAGS = \
$(AM_CFLAGS)
$(AM_CFLAGS) \
$(MOUNT_CFLAGS)
test_path_LDADD = \
libcore.la
@ -1989,7 +1997,8 @@ test_execute_SOURCES = \
src/test/test-execute.c
test_execute_CFLAGS = \
$(AM_CFLAGS)
$(AM_CFLAGS) \
$(MOUNT_CFLAGS)
test_execute_LDADD = \
libcore.la
@ -2016,7 +2025,8 @@ test_sched_prio_SOURCES = \
src/test/test-sched-prio.c
test_sched_prio_CPPFLAGS = \
$(AM_CPPFLAGS)
$(AM_CPPFLAGS) \
$(MOUNT_CFLAGS)
test_sched_prio_CFLAGS = \
$(AM_CFLAGS) \
@ -2103,7 +2113,8 @@ systemd_analyze_SOURCES = \
systemd_analyze_CFLAGS = \
$(AM_CFLAGS) \
$(SECCOMP_CFLAGS)
$(SECCOMP_CFLAGS) \
$(MOUNT_CFLAGS)
systemd_analyze_LDADD = \
libcore.la

4
README
View File

@ -122,7 +122,7 @@ REQUIREMENTS:
glibc >= 2.16
libcap
libmount >= 2.20 (from util-linux)
libmount >= 2.27 (from util-linux)
libseccomp >= 1.0.0 (optional)
libblkid >= 2.24 (from util-linux) (optional)
libkmod >= 15 (optional)
@ -144,7 +144,7 @@ REQUIREMENTS:
During runtime, you need the following additional
dependencies:
util-linux >= v2.26 required
util-linux >= v2.27 required
dbus >= 1.4.0 (strictly speaking optional, but recommended)
dracut (optional)
PolicyKit (optional)

2
configure.ac
View File

@ -427,7 +427,7 @@ AM_CONDITIONAL(HAVE_BLKID, [test "$have_blkid" = "yes"])
# ------------------------------------------------------------------------------
have_libmount=no
PKG_CHECK_MODULES(MOUNT, [ mount >= 2.20 ],
PKG_CHECK_MODULES(MOUNT, [ mount >= 2.27 ],
[AC_DEFINE(HAVE_LIBMOUNT, 1, [Define if libmount is available]) have_libmount=yes], have_libmount=no)
if test "x$have_libmount" = xno; then
AC_MSG_ERROR([*** libmount support required but libraries not found])

4
src/core/manager.c
View File

@ -571,8 +571,8 @@ int manager_new(ManagerRunningAs running_as, bool test_run, Manager **_m) {
m->idle_pipe[0] = m->idle_pipe[1] = m->idle_pipe[2] = m->idle_pipe[3] = -1;
m->pin_cgroupfs_fd = m->notify_fd = m->signal_fd = m->time_change_fd =
m->dev_autofs_fd = m->private_listen_fd = m->kdbus_fd = m->utab_inotify_fd =
m->cgroup_inotify_fd = -1;
m->dev_autofs_fd = m->private_listen_fd = m->kdbus_fd = m->cgroup_inotify_fd = -1;
m->current_job_id = 1; /* start as id #1, so that we can leave #0 around as "null-like" value */
m->ask_password_inotify_fd = -1;

5
src/core/manager.h
View File

@ -23,6 +23,7 @@
#include <stdbool.h>
#include <stdio.h>
#include <libmount.h>
#include "sd-bus.h"
#include "sd-event.h"
@ -176,10 +177,8 @@ struct Manager {
Hashmap *devices_by_sysfs;
/* Data specific to the mount subsystem */
FILE *proc_self_mountinfo;
struct libmnt_monitor *mount_monitor;
sd_event_source *mount_event_source;
int utab_inotify_fd;
sd_event_source *mount_utab_event_source;
/* Data specific to the swap filesystem */
FILE *proc_swaps;

118
src/core/mount.c
View File

@ -23,8 +23,6 @@
#include <stdio.h>
#include <sys/epoll.h>
#include <signal.h>
#include <libmount.h>
#include <sys/inotify.h>
#include "manager.h"
#include "unit.h"
@ -1535,13 +1533,13 @@ static int mount_load_proc_self_mountinfo(Manager *m, bool set_flags) {
}
static void mount_shutdown(Manager *m) {
assert(m);
m->mount_event_source = sd_event_source_unref(m->mount_event_source);
m->mount_utab_event_source = sd_event_source_unref(m->mount_utab_event_source);
m->proc_self_mountinfo = safe_fclose(m->proc_self_mountinfo);
m->utab_inotify_fd = safe_close(m->utab_inotify_fd);
mnt_unref_monitor(m->mount_monitor);
m->mount_monitor = NULL;
}
static int mount_get_timeout(Unit *u, uint64_t *timeout) {
@ -1560,53 +1558,41 @@ static int mount_get_timeout(Unit *u, uint64_t *timeout) {
static int mount_enumerate(Manager *m) {
int r;
assert(m);
mnt_init_debug(0);
if (!m->proc_self_mountinfo) {
m->proc_self_mountinfo = fopen("/proc/self/mountinfo", "re");
if (!m->proc_self_mountinfo)
return -errno;
if (!m->mount_monitor) {
int fd;
r = sd_event_add_io(m->event, &m->mount_event_source, fileno(m->proc_self_mountinfo), EPOLLPRI, mount_dispatch_io, m);
m->mount_monitor = mnt_new_monitor();
if (!m->mount_monitor) {
r = -ENOMEM;
goto fail;
}
r = mnt_monitor_enable_kernel(m->mount_monitor, 1);
if (r < 0)
goto fail;
r = mnt_monitor_enable_userspace(m->mount_monitor, 1, NULL);
if (r < 0)
goto fail;
/* mnt_unref_monitor() will close the fd */
fd = r = mnt_monitor_get_fd(m->mount_monitor);
if (r < 0)
goto fail;
r = sd_event_add_io(m->event, &m->mount_event_source, fd, EPOLLIN, mount_dispatch_io, m);
if (r < 0)
goto fail;
/* Dispatch this before we dispatch SIGCHLD, so that
* we always get the events from /proc/self/mountinfo
* before the SIGCHLD of /usr/bin/mount. */
r = sd_event_source_set_priority(m->mount_event_source, -10);
if (r < 0)
goto fail;
(void) sd_event_source_set_description(m->mount_event_source, "mount-mountinfo-dispatch");
}
if (m->utab_inotify_fd < 0) {
m->utab_inotify_fd = inotify_init1(IN_NONBLOCK|IN_CLOEXEC);
if (m->utab_inotify_fd < 0) {
r = -errno;
goto fail;
}
(void) mkdir_p_label("/run/mount", 0755);
r = inotify_add_watch(m->utab_inotify_fd, "/run/mount", IN_MOVED_TO);
if (r < 0) {
r = -errno;
goto fail;
}
r = sd_event_add_io(m->event, &m->mount_utab_event_source, m->utab_inotify_fd, EPOLLIN, mount_dispatch_io, m);
if (r < 0)
goto fail;
r = sd_event_source_set_priority(m->mount_utab_event_source, -10);
if (r < 0)
goto fail;
(void) sd_event_source_set_description(m->mount_utab_event_source, "mount-utab-dispatch");
(void) sd_event_source_set_description(m->mount_event_source, "mount-monitor-dispatch");
}
r = mount_load_proc_self_mountinfo(m, false);
@ -1629,45 +1615,27 @@ static int mount_dispatch_io(sd_event_source *source, int fd, uint32_t revents,
int r;
assert(m);
assert(revents & (EPOLLPRI | EPOLLIN));
assert(revents & EPOLLIN);
/* The manager calls this for every fd event happening on the
* /proc/self/mountinfo file, which informs us about mounting
* table changes, and for /run/mount events which we watch
* for mount options. */
if (fd == m->utab_inotify_fd) {
if (fd == mnt_monitor_get_fd(m->mount_monitor)) {
bool rescan = false;
/* FIXME: We *really* need to replace this with
* libmount's own API for this, we should not hardcode
* internal behaviour of libmount here. */
for (;;) {
union inotify_event_buffer buffer;
struct inotify_event *e;
ssize_t l;
l = read(fd, &buffer, sizeof(buffer));
if (l < 0) {
if (errno == EAGAIN || errno == EINTR)
break;
log_error_errno(errno, "Failed to read utab inotify: %m");
break;
}
FOREACH_INOTIFY_EVENT(e, buffer, l) {
/* Only care about changes to utab,
* but we have to monitor the
* directory to reliably get
* notifications about when utab is
* replaced using rename(2) */
if ((e->mask & IN_Q_OVERFLOW) || streq(e->name, "utab"))
rescan = true;
}
}
/* Drain all events and verify that the event is valid.
*
* Note that libmount also monitors /run/mount mkdir if the
* directory does not exist yet. The mkdir may generate event
* which is irrelevant for us.
*
* error: r < 0; valid: r == 0, false positive: rc == 1 */
do {
r = mnt_monitor_next_change(m->mount_monitor, NULL, NULL);
if (r == 0)
rescan = true;
else if (r < 0)
return log_error_errno(r, "Failed to drain libmount events");
} while (r == 0);
log_debug("libmount event [rescan: %s]", yes_no(rescan));
if (!rescan)
return 0;
}