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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
parent
5669ef3644
commit
d379d44255
33
Makefile.am
33
Makefile.am
@ -1327,7 +1327,8 @@ systemd_SOURCES = \
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systemd_CFLAGS = \
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$(AM_CFLAGS) \
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$(SECCOMP_CFLAGS)
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$(SECCOMP_CFLAGS) \
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$(MOUNT_CFLAGS)
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systemd_LDADD = \
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libcore.la
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@ -1532,7 +1533,8 @@ test_engine_SOURCES = \
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test_engine_CFLAGS = \
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$(AM_CFLAGS) \
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$(SECCOMP_CFLAGS)
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$(SECCOMP_CFLAGS) \
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$(MOUNT_CFLAGS)
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test_engine_LDADD = \
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libcore.la
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@ -1542,7 +1544,8 @@ test_job_type_SOURCES = \
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test_job_type_CFLAGS = \
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$(AM_CFLAGS) \
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$(SECCOMP_CFLAGS)
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$(SECCOMP_CFLAGS) \
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$(MOUNT_CFLAGS)
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test_job_type_LDADD = \
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libcore.la
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@ -1592,7 +1595,8 @@ test_unit_name_SOURCES = \
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test_unit_name_CFLAGS = \
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$(AM_CFLAGS) \
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$(SECCOMP_CFLAGS)
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$(SECCOMP_CFLAGS) \
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$(MOUNT_CFLAGS)
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test_unit_name_LDADD = \
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libcore.la
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@ -1602,7 +1606,8 @@ test_unit_file_SOURCES = \
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test_unit_file_CFLAGS = \
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$(AM_CFLAGS) \
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$(SECCOMP_CFLAGS)
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$(SECCOMP_CFLAGS) \
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$(MOUNT_CFLAGS)
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test_unit_file_LDADD = \
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libcore.la
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@ -1811,7 +1816,8 @@ test_tables_CPPFLAGS = \
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test_tables_CFLAGS = \
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$(AM_CFLAGS) \
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$(SECCOMP_CFLAGS)
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$(SECCOMP_CFLAGS) \
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$(MOUNT_CFLAGS)
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test_tables_LDADD = \
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libjournal-core.la \
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@ -1937,7 +1943,8 @@ test_cgroup_mask_SOURCES = \
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src/test/test-cgroup-mask.c
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test_cgroup_mask_CPPFLAGS = \
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$(AM_CPPFLAGS)
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$(AM_CPPFLAGS) \
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$(MOUNT_CFLAGS)
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test_cgroup_mask_CFLAGS = \
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$(AM_CFLAGS) \
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@ -1980,7 +1987,8 @@ test_path_SOURCES = \
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src/test/test-path.c
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test_path_CFLAGS = \
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$(AM_CFLAGS)
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$(AM_CFLAGS) \
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$(MOUNT_CFLAGS)
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test_path_LDADD = \
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libcore.la
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@ -1989,7 +1997,8 @@ test_execute_SOURCES = \
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src/test/test-execute.c
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test_execute_CFLAGS = \
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$(AM_CFLAGS)
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$(AM_CFLAGS) \
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$(MOUNT_CFLAGS)
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test_execute_LDADD = \
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libcore.la
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@ -2016,7 +2025,8 @@ test_sched_prio_SOURCES = \
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src/test/test-sched-prio.c
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test_sched_prio_CPPFLAGS = \
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$(AM_CPPFLAGS)
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$(AM_CPPFLAGS) \
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$(MOUNT_CFLAGS)
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test_sched_prio_CFLAGS = \
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$(AM_CFLAGS) \
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@ -2103,7 +2113,8 @@ systemd_analyze_SOURCES = \
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systemd_analyze_CFLAGS = \
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$(AM_CFLAGS) \
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$(SECCOMP_CFLAGS)
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$(SECCOMP_CFLAGS) \
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$(MOUNT_CFLAGS)
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systemd_analyze_LDADD = \
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libcore.la
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4
README
4
README
@ -122,7 +122,7 @@ REQUIREMENTS:
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glibc >= 2.16
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libcap
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libmount >= 2.20 (from util-linux)
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libmount >= 2.27 (from util-linux)
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libseccomp >= 1.0.0 (optional)
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libblkid >= 2.24 (from util-linux) (optional)
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libkmod >= 15 (optional)
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@ -144,7 +144,7 @@ REQUIREMENTS:
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During runtime, you need the following additional
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dependencies:
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util-linux >= v2.26 required
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util-linux >= v2.27 required
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dbus >= 1.4.0 (strictly speaking optional, but recommended)
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dracut (optional)
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PolicyKit (optional)
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@ -427,7 +427,7 @@ AM_CONDITIONAL(HAVE_BLKID, [test "$have_blkid" = "yes"])
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# ------------------------------------------------------------------------------
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have_libmount=no
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PKG_CHECK_MODULES(MOUNT, [ mount >= 2.20 ],
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PKG_CHECK_MODULES(MOUNT, [ mount >= 2.27 ],
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[AC_DEFINE(HAVE_LIBMOUNT, 1, [Define if libmount is available]) have_libmount=yes], have_libmount=no)
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if test "x$have_libmount" = xno; then
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AC_MSG_ERROR([*** libmount support required but libraries not found])
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@ -571,8 +571,8 @@ int manager_new(ManagerRunningAs running_as, bool test_run, Manager **_m) {
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m->idle_pipe[0] = m->idle_pipe[1] = m->idle_pipe[2] = m->idle_pipe[3] = -1;
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m->pin_cgroupfs_fd = m->notify_fd = m->signal_fd = m->time_change_fd =
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m->dev_autofs_fd = m->private_listen_fd = m->kdbus_fd = m->utab_inotify_fd =
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m->cgroup_inotify_fd = -1;
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m->dev_autofs_fd = m->private_listen_fd = m->kdbus_fd = m->cgroup_inotify_fd = -1;
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m->current_job_id = 1; /* start as id #1, so that we can leave #0 around as "null-like" value */
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m->ask_password_inotify_fd = -1;
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@ -23,6 +23,7 @@
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#include <stdbool.h>
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#include <stdio.h>
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#include <libmount.h>
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#include "sd-bus.h"
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#include "sd-event.h"
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@ -176,10 +177,8 @@ struct Manager {
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Hashmap *devices_by_sysfs;
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/* Data specific to the mount subsystem */
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FILE *proc_self_mountinfo;
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struct libmnt_monitor *mount_monitor;
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sd_event_source *mount_event_source;
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int utab_inotify_fd;
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sd_event_source *mount_utab_event_source;
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/* Data specific to the swap filesystem */
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FILE *proc_swaps;
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118
src/core/mount.c
118
src/core/mount.c
@ -23,8 +23,6 @@
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#include <stdio.h>
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#include <sys/epoll.h>
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#include <signal.h>
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#include <libmount.h>
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#include <sys/inotify.h>
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#include "manager.h"
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#include "unit.h"
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@ -1535,13 +1533,13 @@ static int mount_load_proc_self_mountinfo(Manager *m, bool set_flags) {
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}
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static void mount_shutdown(Manager *m) {
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assert(m);
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m->mount_event_source = sd_event_source_unref(m->mount_event_source);
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m->mount_utab_event_source = sd_event_source_unref(m->mount_utab_event_source);
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m->proc_self_mountinfo = safe_fclose(m->proc_self_mountinfo);
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m->utab_inotify_fd = safe_close(m->utab_inotify_fd);
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mnt_unref_monitor(m->mount_monitor);
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m->mount_monitor = NULL;
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}
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static int mount_get_timeout(Unit *u, uint64_t *timeout) {
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@ -1560,53 +1558,41 @@ static int mount_get_timeout(Unit *u, uint64_t *timeout) {
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static int mount_enumerate(Manager *m) {
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int r;
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assert(m);
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mnt_init_debug(0);
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if (!m->proc_self_mountinfo) {
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m->proc_self_mountinfo = fopen("/proc/self/mountinfo", "re");
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if (!m->proc_self_mountinfo)
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return -errno;
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if (!m->mount_monitor) {
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int fd;
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r = sd_event_add_io(m->event, &m->mount_event_source, fileno(m->proc_self_mountinfo), EPOLLPRI, mount_dispatch_io, m);
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m->mount_monitor = mnt_new_monitor();
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if (!m->mount_monitor) {
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r = -ENOMEM;
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goto fail;
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}
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r = mnt_monitor_enable_kernel(m->mount_monitor, 1);
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if (r < 0)
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goto fail;
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r = mnt_monitor_enable_userspace(m->mount_monitor, 1, NULL);
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if (r < 0)
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goto fail;
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/* mnt_unref_monitor() will close the fd */
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fd = r = mnt_monitor_get_fd(m->mount_monitor);
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if (r < 0)
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goto fail;
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r = sd_event_add_io(m->event, &m->mount_event_source, fd, EPOLLIN, mount_dispatch_io, m);
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if (r < 0)
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goto fail;
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/* Dispatch this before we dispatch SIGCHLD, so that
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* we always get the events from /proc/self/mountinfo
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* before the SIGCHLD of /usr/bin/mount. */
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r = sd_event_source_set_priority(m->mount_event_source, -10);
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if (r < 0)
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goto fail;
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(void) sd_event_source_set_description(m->mount_event_source, "mount-mountinfo-dispatch");
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}
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if (m->utab_inotify_fd < 0) {
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m->utab_inotify_fd = inotify_init1(IN_NONBLOCK|IN_CLOEXEC);
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if (m->utab_inotify_fd < 0) {
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r = -errno;
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goto fail;
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}
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(void) mkdir_p_label("/run/mount", 0755);
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r = inotify_add_watch(m->utab_inotify_fd, "/run/mount", IN_MOVED_TO);
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if (r < 0) {
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r = -errno;
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goto fail;
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}
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r = sd_event_add_io(m->event, &m->mount_utab_event_source, m->utab_inotify_fd, EPOLLIN, mount_dispatch_io, m);
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if (r < 0)
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goto fail;
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r = sd_event_source_set_priority(m->mount_utab_event_source, -10);
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if (r < 0)
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goto fail;
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(void) sd_event_source_set_description(m->mount_utab_event_source, "mount-utab-dispatch");
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(void) sd_event_source_set_description(m->mount_event_source, "mount-monitor-dispatch");
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}
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r = mount_load_proc_self_mountinfo(m, false);
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@ -1629,45 +1615,27 @@ static int mount_dispatch_io(sd_event_source *source, int fd, uint32_t revents,
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int r;
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assert(m);
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assert(revents & (EPOLLPRI | EPOLLIN));
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assert(revents & EPOLLIN);
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/* The manager calls this for every fd event happening on the
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* /proc/self/mountinfo file, which informs us about mounting
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* table changes, and for /run/mount events which we watch
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* for mount options. */
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if (fd == m->utab_inotify_fd) {
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if (fd == mnt_monitor_get_fd(m->mount_monitor)) {
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bool rescan = false;
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/* FIXME: We *really* need to replace this with
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* libmount's own API for this, we should not hardcode
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* internal behaviour of libmount here. */
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for (;;) {
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union inotify_event_buffer buffer;
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struct inotify_event *e;
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ssize_t l;
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l = read(fd, &buffer, sizeof(buffer));
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if (l < 0) {
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if (errno == EAGAIN || errno == EINTR)
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break;
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log_error_errno(errno, "Failed to read utab inotify: %m");
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break;
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}
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FOREACH_INOTIFY_EVENT(e, buffer, l) {
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/* Only care about changes to utab,
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* but we have to monitor the
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* directory to reliably get
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* notifications about when utab is
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* replaced using rename(2) */
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if ((e->mask & IN_Q_OVERFLOW) || streq(e->name, "utab"))
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rescan = true;
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}
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}
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/* Drain all events and verify that the event is valid.
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*
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* Note that libmount also monitors /run/mount mkdir if the
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* directory does not exist yet. The mkdir may generate event
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* which is irrelevant for us.
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*
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* error: r < 0; valid: r == 0, false positive: rc == 1 */
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do {
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r = mnt_monitor_next_change(m->mount_monitor, NULL, NULL);
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if (r == 0)
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rescan = true;
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else if (r < 0)
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return log_error_errno(r, "Failed to drain libmount events");
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} while (r == 0);
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log_debug("libmount event [rescan: %s]", yes_no(rescan));
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if (!rescan)
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return 0;
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}
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