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umount: Provide the same mount flags too when remounting read-only

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This most likely amounts to no real benefits and is just here for
completeness sake.
This commit is contained in:
Jan Janssen 2018-03-08 18:37:21 +01:00
parent 1d62d22d94
commit 3bc341bee9
1 changed files with 35 additions and 22 deletions
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57
src/core/umount.c
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@ -48,7 +48,8 @@
typedef struct MountPoint {
char *path;
char *options;
char *remount_options;
unsigned long remount_flags;
bool try_remount_ro;
dev_t devnum;
LIST_FIELDS(struct MountPoint, mount_point);
@ -61,7 +62,7 @@ static void mount_point_free(MountPoint **head, MountPoint *m) {
LIST_REMOVE(mount_point, *head, m);
free(m->path);
free(m->options);
free(m->remount_options);
free(m);
}
@ -84,7 +85,7 @@ static int mount_points_list_get(MountPoint **head) {
return -errno;
for (i = 1;; i++) {
_cleanup_free_ char *path = NULL, *options = NULL, *type = NULL, *p = NULL;
_cleanup_free_ char *path = NULL, *options = NULL, *flags = NULL, *type = NULL, *p = NULL;
MountPoint *m;
int k;
@ -94,15 +95,15 @@ static int mount_points_list_get(MountPoint **head) {
"%*s " /* (3) major:minor */
"%*s " /* (4) root */
"%ms " /* (5) mount point */
"%*s" /* (6) mount flags */
"%ms" /* (6) mount flags */
"%*[^-]" /* (7) optional fields */
"- " /* (8) separator */
"%ms " /* (9) file system type */
"%*s" /* (10) mount source */
"%ms" /* (11) mount options */
"%*[^\n]", /* some rubbish at the end */
&path, &type, &options);
if (k != 3) {
&path, &flags, &type, &options);
if (k != 4) {
if (k == EOF)
break;
@ -132,6 +133,8 @@ static int mount_points_list_get(MountPoint **head) {
if (!m)
return -ENOMEM;
free_and_replace(m->path, p);
/* If we are in a container, don't attempt to
* read-only mount anything as that brings no real
* benefits, but might confuse the host, as we remount
@ -146,8 +149,28 @@ static int mount_points_list_get(MountPoint **head) {
!fstype_is_network(type) &&
!fstab_test_yes_no_option(options, "ro\0rw\0");
free_and_replace(m->path, p);
free_and_replace(m->options, options);
if (m->try_remount_ro) {
_cleanup_free_ char *unknown_flags = NULL;
/* mount(2) states that mount flags and options need to be exactly the same
* as they were when the filesystem was mounted, except for the desired
* changes. So we reconstruct both here and adjust them for the later
* remount call too. */
r = mount_option_mangle(flags, 0, &m->remount_flags, &unknown_flags);
if (r < 0)
return r;
if (!isempty(unknown_flags))
log_warning("Ignoring unknown mount flags '%s'.", unknown_flags);
r = mount_option_mangle(options, m->remount_flags, &m->remount_flags, &m->remount_options);
if (r < 0)
return r;
/* MS_BIND is special. If it is provided it will only make the mount-point
* read-only. If left out, the super block itself is remounted, which we want. */
m->remount_flags = (m->remount_flags|MS_REMOUNT|MS_RDONLY) & ~MS_BIND;
}
LIST_PREPEND(mount_point, *head, m);
}
@ -389,14 +412,13 @@ static bool nonunmountable_path(const char *path) {
|| path_startswith(path, "/run/initramfs");
}
static int remount_with_timeout(MountPoint *m, char *options) {
static int remount_with_timeout(MountPoint *m) {
pid_t pid;
int r;
BLOCK_SIGNALS(SIGCHLD);
assert(m);
assert(options);
/* Due to the possiblity of a remount operation hanging, we
* fork a child process and set a timeout. If the timeout
@ -406,10 +428,10 @@ static int remount_with_timeout(MountPoint *m, char *options) {
if (r < 0)
return r;
if (r == 0) {
log_info("Remounting '%s' read-only in with options '%s'.", m->path, options);
log_info("Remounting '%s' read-only in with options '%s'.", m->path, m->remount_options);
/* Start the mount operation here in the child */
r = mount(NULL, m->path, NULL, MS_REMOUNT|MS_RDONLY, options);
r = mount(NULL, m->path, NULL, m->remount_flags, m->remount_options);
if (r < 0)
log_error_errno(errno, "Failed to remount '%s' read-only: %m", m->path);
@ -474,7 +496,6 @@ static int umount_with_timeout(MountPoint *m) {
/* This includes remounting readonly, which changes the kernel mount options.
* Therefore the list passed to this function is invalidated, and should not be reused. */
static int mount_points_list_umount(MountPoint **head, bool *changed) {
MountPoint *m;
int n_failed = 0;
@ -484,14 +505,6 @@ static int mount_points_list_umount(MountPoint **head, bool *changed) {
LIST_FOREACH(mount_point, m, *head) {
if (m->try_remount_ro) {
_cleanup_free_ char *options = NULL;
/* MS_REMOUNT requires that the data parameter
* should be the same from the original mount
* except for the desired changes. Since we want
* to remount read-only, we should filter out
* rw (and ro too, because it confuses the kernel) */
(void) fstab_filter_options(m->options, "rw\0ro\0", NULL, NULL, &options);
/* We always try to remount directories
* read-only first, before we go on and umount
* them.
@ -512,7 +525,7 @@ static int mount_points_list_umount(MountPoint **head, bool *changed) {
* Since the remount can hang in the instance of
* remote filesystems, we remount asynchronously
* and skip the subsequent umount if it fails */
if (remount_with_timeout(m, options) < 0) {
if (remount_with_timeout(m) < 0) {
if (nonunmountable_path(m->path))
n_failed++;
continue;