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core: dont't remount /sys/fs/cgroup for relabel if not needed #8595

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merged 1 commit into from Mar 28, 2018
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core: dont't remount /sys/fs/cgroup for relabel if not needed #8595

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42 changes: 33 additions & 9 deletions src/core/mount-setup.c
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Expand Up @@ -22,6 +22,7 @@
#include <ftw.h>
#include <stdlib.h>
#include <sys/mount.h>
#include <sys/statvfs.h>
#include <unistd.h>

#include "alloc-util.h"
Expand Down Expand Up @@ -385,6 +386,35 @@ static int nftw_cb(

return FTW_CONTINUE;
};

static int relabel_cgroup_filesystems(void) {
int r;
struct statfs st;

r = cg_all_unified();
if (r == 0) {
/* Temporarily remount the root cgroup filesystem to give it a proper label. Do this
only when the filesystem has been already populated by a previous instance of systemd
running from initrd. Otherwise don't remount anything and leave the filesystem read-write
for the cgroup filesystems to be mounted inside. */
r = statfs("/sys/fs/cgroup", &st);
if (r < 0) {
return log_error_errno(errno, "Failed to determine mount flags for /sys/fs/cgroup: %m");
}
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nitpick: no {} around single-line if blocks, please.


if (st.f_flags & ST_RDONLY)
(void) mount(NULL, "/sys/fs/cgroup", NULL, MS_REMOUNT, NULL);

(void) label_fix("/sys/fs/cgroup", 0);
nftw("/sys/fs/cgroup", nftw_cb, 64, FTW_MOUNT|FTW_PHYS|FTW_ACTIONRETVAL);

if (st.f_flags & ST_RDONLY)
(void) mount(NULL, "/sys/fs/cgroup", NULL, MS_REMOUNT|MS_RDONLY, NULL);
} else if (r < 0)
return log_error_errno(r, "Failed to determine whether we are in all unified mode: %m");

return 0;
}
#endif

int mount_setup(bool loaded_policy) {
Expand All @@ -409,15 +439,9 @@ int mount_setup(bool loaded_policy) {
nftw("/dev/shm", nftw_cb, 64, FTW_MOUNT|FTW_PHYS|FTW_ACTIONRETVAL);
nftw("/run", nftw_cb, 64, FTW_MOUNT|FTW_PHYS|FTW_ACTIONRETVAL);

/* Temporarily remount the root cgroup filesystem to give it a proper label. */
r = cg_all_unified();
if (r == 0) {
(void) mount(NULL, "/sys/fs/cgroup", NULL, MS_REMOUNT, NULL);
(void) label_fix("/sys/fs/cgroup", 0);
nftw("/sys/fs/cgroup", nftw_cb, 64, FTW_MOUNT|FTW_PHYS|FTW_ACTIONRETVAL);
(void) mount(NULL, "/sys/fs/cgroup", NULL, MS_REMOUNT|MS_RDONLY, NULL);
} else if (r < 0)
return log_error_errno(r, "Failed to determine whether we are in all unified mode: %m");
r = relabel_cgroup_filesystems();
if (r < 0)
return r;

after_relabel = now(CLOCK_MONOTONIC);

Expand Down