[CRIU] [PATCH 07/37] mounts: create a temporary directory for restoring non-root mntns (v2)
Andrey Vagin
avagin at openvz.org
Fri Apr 18 07:42:45 PDT 2014
All non-root namespaces will be restored as sub-trees of the root tree.
This patch adds helpers to create a temporary directory and mount tmpfs
in it, then create directories for each non-root mount namespace.
tmpfs is quite useful here to simplify destroying this construction,
we don't need to unmount each namespace separately.
v2: add a comment why MNT_DETACH is not dangerous here
Signed-off-by: Andrey Vagin <avagin at openvz.org>
---
cr-restore.c | 22 +++++++----
include/mount.h | 2 +
mount.c | 120 +++++++++++++++++++++++++++++++++++++++++++++++++++++---
3 files changed, 132 insertions(+), 12 deletions(-)
diff --git a/cr-restore.c b/cr-restore.c
index 584e1dc..e8db73f 100644
--- a/cr-restore.c
+++ b/cr-restore.c
@@ -1258,7 +1258,7 @@ static int restore_task_with_children(void *_arg)
* Thus -- mount proc at custom location for any new namespace
*/
if (mount_proc())
- exit(1);
+ goto err;
if (close_old_fds(current))
exit(1);
@@ -1267,7 +1267,7 @@ static int restore_task_with_children(void *_arg)
exit(1);
if (root_prepare_shared())
- exit(1);
+ goto err;
}
/*
@@ -1280,27 +1280,35 @@ static int restore_task_with_children(void *_arg)
ret = sigprocmask(SIG_BLOCK, &blockmask, NULL);
if (ret) {
pr_perror("%d: Can't block signals", current->pid.virt);
- exit(1);
+ goto err;
}
if (prepare_mappings(pid))
- exit(1);
+ goto err;
if (create_children_and_session())
- exit(1);
+ goto err;
if (unmap_guard_pages())
- exit(1);
+ goto err;
restore_pgid();
if (restore_finish_stage(CR_STATE_FORKING) < 0)
- exit(1);
+ goto err;
+
+ if (current->parent == NULL && fini_mnt_ns())
+ exit (1);
if (current->state == TASK_HELPER)
return 0;
return restore_one_task(current->pid.virt, ca->core);
+err:
+ if (current->parent == NULL)
+ fini_mnt_ns();
+
+ exit(1);
}
static inline int stage_participants(int next_stage)
diff --git a/include/mount.h b/include/mount.h
index a2bc17d..4fd10e3 100644
--- a/include/mount.h
+++ b/include/mount.h
@@ -24,4 +24,6 @@ extern struct ns_desc mnt_ns_desc;
extern dev_t phys_stat_resolve_dev(dev_t st_dev, const char *path);
extern bool phys_stat_dev_match(dev_t st_dev, dev_t phys_dev, const char *path);
+extern int fini_mnt_ns(void);
+
#endif /* __CR_MOUNT_H__ */
diff --git a/mount.c b/mount.c
index bf20e98..46c8c48 100644
--- a/mount.c
+++ b/mount.c
@@ -1369,6 +1369,37 @@ static void free_mounts(void)
}
}
+/*
+ * mnt_roots is a temporary directory for restoring sub-trees of
+ * non-root namespaces.
+ */
+static char *mnt_roots;
+
+static int create_mnt_roots()
+{
+ if (mnt_roots)
+ return 0;
+
+ if (chdir(opts.root ? : "/")) {
+ pr_perror("Unable to change working directory on %s", opts.root);
+ return -1;
+ }
+
+ mnt_roots = strdup(".criu.mntns.XXXXXX");
+ if (mnt_roots == NULL) {
+ pr_perror("Can't allocate memory");
+ return -1;
+ }
+
+ if (mkdtemp(mnt_roots) == NULL) {
+ pr_perror("Unable to create a temporary directory");
+ mnt_roots = NULL;
+ return -1;
+ }
+
+ return 0;
+}
+
static int collect_mnt_from_image(struct mount_info **pms, struct ns_id *nsid)
{
MntEntry *me = NULL;
@@ -1382,7 +1413,8 @@ static int collect_mnt_from_image(struct mount_info **pms, struct ns_id *nsid)
while (1) {
struct mount_info *pm;
- int len;
+ char root[PATH_MAX] = ".";
+ int len, root_len = 1;
ret = pb_read_one_eof(img, &me, PB_MNT);
if (ret <= 0)
@@ -1412,8 +1444,10 @@ static int collect_mnt_from_image(struct mount_info **pms, struct ns_id *nsid)
if (!pm->root)
goto err;
- pr_debug("\t\tGetting mpt for %d:%s\n", pm->mnt_id, me->mountpoint);
- len = strlen(me->mountpoint) + 2;
+ if (nsid->id != root_item->ids->mnt_ns_id)
+ root_len = snprintf(root, sizeof(root), "%s/%d/",
+ mnt_roots, nsid->id);
+ len = strlen(me->mountpoint) + root_len + 1;
pm->mountpoint = xmalloc(len);
if (!pm->mountpoint)
goto err;
@@ -1424,8 +1458,10 @@ static int collect_mnt_from_image(struct mount_info **pms, struct ns_id *nsid)
* that.
*/
- pm->mountpoint[0] = '.';
- strcpy(pm->mountpoint + 1, me->mountpoint);
+ strcpy(pm->mountpoint, root);
+ strcpy(pm->mountpoint + root_len, me->mountpoint);
+
+ pr_debug("\t\tGetting mpt for %d %s\n", pm->mnt_id, pm->mountpoint);
pr_debug("\t\tGetting source for %d\n", pm->mnt_id);
pm->source = xstrdup(me->source);
@@ -1463,6 +1499,10 @@ static struct mount_info *read_mnt_ns_img()
continue;
}
+ if (nsid->id != root_item->ids->mnt_ns_id)
+ if (create_mnt_roots(true))
+ return NULL;
+
if (collect_mnt_from_image(&pms, nsid))
goto err;
@@ -1473,6 +1513,44 @@ err:
return NULL;
}
+/*
+ * All nested mount namespaces are restore as sub-trees of the root namespace.
+ */
+static int prepare_temporary_roots()
+{
+ char path[PATH_MAX];
+ struct ns_id *nsid;
+
+ if (mnt_roots == NULL)
+ return 0;
+
+ if (mount("none", mnt_roots, "tmpfs", 0, NULL)) {
+ pr_perror("Unable to mount tmpfs in %s", mnt_roots);
+ return -1;
+ }
+ if (mount("none", mnt_roots, NULL, MS_PRIVATE, NULL))
+ return -1;
+
+ nsid = ns_ids;
+ while (nsid) {
+ if (nsid->nd != &mnt_ns_desc) {
+ nsid = nsid->next;
+ continue;
+ }
+
+ snprintf(path, sizeof(path), "%s/%d",
+ mnt_roots, nsid->id);
+
+ if (mkdir(path, 0600)) {
+ pr_perror("Unable to create %s", path);
+ return -1;
+ }
+ nsid = nsid->next;
+ }
+
+ return 0;
+}
+
static int populate_mnt_ns(int ns_pid, struct mount_info *mis)
{
struct mount_info *pms;
@@ -1480,6 +1558,9 @@ static int populate_mnt_ns(int ns_pid, struct mount_info *mis)
mntinfo_tree = NULL;
mntinfo = mis;
+ if (prepare_temporary_roots())
+ return -1;
+
pms = mnt_build_tree(mntinfo);
if (!pms)
return -1;
@@ -1491,6 +1572,35 @@ static int populate_mnt_ns(int ns_pid, struct mount_info *mis)
return mnt_tree_for_each(pms, do_mount_one);
}
+int fini_mnt_ns()
+{
+ int ret = 0;
+
+ if (mnt_roots == NULL)
+ return 0;
+
+ if (mount("none", mnt_roots, "none", MS_REC|MS_PRIVATE, NULL)) {
+ pr_perror("Can't remount root with MS_PRIVATE");
+ ret = 1;
+ }
+ /*
+ * Don't exit after a first error, becuase this function
+ * can be used to rollback in a error case.
+ * Don't worry about MNT_DETACH, because files are restored after this
+ * and nobody will not be restored from a wrong mount namespace.
+ */
+ if (umount2(mnt_roots, MNT_DETACH)) {
+ pr_perror("Can't unmount %s", mnt_roots);
+ ret = 1;
+ }
+ if (rmdir(mnt_roots)) {
+ pr_perror("Can't remove the directory %s", mnt_roots);
+ ret = 1;
+ }
+
+ return ret;
+}
+
int prepare_mnt_ns(int ns_pid)
{
int ret = -1;
--
1.8.5.3
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