[CRIU] [PATCH v5 4/5] mount: Forced mount unmounted binfmt_misc to do not lost its content
Kirill Tkhai
ktkhai at virtuozzo.com
Mon Aug 15 01:44:22 PDT 2016
On 05.08.2016 18:38, Pavel Emelyanov wrote:
> On 08/04/2016 04:49 PM, Kirill Tkhai wrote:
>> Umount does not remove binfmt_misc content. If it's mounted once again,
>> the same entries remain registered.
>>
>> Criu does not dump content of umounted binfmt_misc. So, after C/R we
>> lose it at all.
>>
>> This patch forces mounting of unmounted binfmt_misc after we collected
>> mountpoints. If it's unmounted, we mount it back and add this mount
>> to the tree of collected mounted mountpoints. Further, binfmt_misc
>> content is dumped in usual way with the only difference, that mount
>> point itself is not dumped.
>>
>> v2: Print error in case of umount() fail.
>> Move add_forced_mount() to another patch.
>> v3: Close binfmt_misc dir before its umount().
>> v4: Do not dump forced mounted mountpoint.
>> v5: Do not search for binfmt_misc mounted: use opts.has_binfmt_misc.
>> Do not count number of entries in binfmt_misc directory.
>>
>> Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
>> ---
>> criu/cr-dump.c | 1
>> criu/include/mount.h | 1
>> criu/mount.c | 128 ++++++++++++++++++++++++++++++++++++++++++++++++++
>> 3 files changed, 130 insertions(+)
>>
>> diff --git a/criu/cr-dump.c b/criu/cr-dump.c
>> index 06ff2d7..5761c14 100644
>> --- a/criu/cr-dump.c
>> +++ b/criu/cr-dump.c
>> @@ -1643,6 +1643,7 @@ static int cr_dump_finish(int ret)
>> if (ret || post_dump_ret || opts.final_state == TASK_ALIVE) {
>> network_unlock();
>> delete_link_remaps();
>> + clean_cr_time_mounts();
>> }
>>
>> if (opts.lazy_pages)
>> diff --git a/criu/include/mount.h b/criu/include/mount.h
>> index d3f472d..3332c53 100644
>> --- a/criu/include/mount.h
>> +++ b/criu/include/mount.h
>> @@ -127,5 +127,6 @@ extern int ext_mount_add(char *key, char *val);
>> extern int mntns_maybe_create_roots(void);
>> extern int read_mnt_ns_img(void);
>> extern void cleanup_mnt_ns(void);
>> +extern void clean_cr_time_mounts(void);
>>
>> #endif /* __CR_MOUNT_H__ */
>> diff --git a/criu/mount.c b/criu/mount.c
>> index 43ea96b..926817a 100644
>> --- a/criu/mount.c
>> +++ b/criu/mount.c
>> @@ -41,6 +41,7 @@
>> #undef LOG_PREFIX
>> #define LOG_PREFIX "mnt: "
>>
>> +#define BINFMT_MISC_HOME "/proc/sys/fs/binfmt_misc"
>> static struct fstype fstypes[];
>>
>> int ext_mount_add(char *key, char *val)
>> @@ -1136,6 +1137,53 @@ static int attach_option(struct mount_info *pm, char *opt)
>> return pm->options ? 0 : -1;
>> }
>>
>> +static int add_cr_time_mount(struct mount_info *root, char *fsname, const char *path, unsigned int s_dev)
>> +{
>> + struct mount_info *mi, *t, *parent;
>> +
>> + mi = mnt_entry_alloc();
>> + if (!mi)
>> + return -1;
>> + mi->mountpoint = xmalloc(strlen(path) + 2);
>> + if (!mi->mountpoint)
>> + return -1;
>> + mi->ns_mountpoint = mi->mountpoint;
>> + sprintf(mi->mountpoint, ".%s", path);
>> + mi->mnt_id = mi->flags = mi->sb_flags = 0;
>> + mi->root = xstrdup("/");
>> + mi->fsname = xstrdup(fsname);
>> + mi->source = xstrdup(fsname);
>> + mi->options = xstrdup("");
>> + if (!mi->root || !mi->fsname || !mi->source || !mi->options)
>> + return -1;
>> + mi->fstype = find_fstype_by_name(fsname);
>> +
>> + mi->s_dev = mi->s_dev_rt = s_dev;
>> +
>> + parent = root;
>> + while (1) {
>> + list_for_each_entry(t, &parent->children, siblings) {
>> + if (strstartswith(mi->mountpoint, t->mountpoint)) {
>> + parent = t;
>> + break;
>> + }
>> + }
>> + if (&t->siblings == &parent->children)
>> + break;
>> + }
>> +
>> + mi->nsid = parent->nsid;
>> + mi->parent = parent;
>> + mi->parent_mnt_id = parent->mnt_id;
>> + mi->next = parent->next;
>> + parent->next = mi;
>> + list_add(&mi->siblings, &parent->children);
>> + pr_info("Add cr-time mountpoint %s with parent %s(%u)\n",
>> + mi->mountpoint, parent->mountpoint, parent->mnt_id);
>> + return 0;
>> +}
>> +
>> +
>> /* Is it mounted w or w/o the newinstance option */
>> static int devpts_parse(struct mount_info *pm)
>> {
>> @@ -1281,6 +1329,46 @@ static int binfmt_misc_parse(struct mount_info *pm)
>>
>> }
>>
>> +static int try_mount_binfmt_misc(struct ns_id *ns, unsigned int *s_dev)
>> +{
>
> What's here in this function that deserves _binfmt_ in its name?
Hm... Mount device type, doesn't it?
> Why not move all this code into add_cr_time_mount() and let is
> just call switch_ns() and mount(fstype->name, path, ...) ?
Because add_cr_time_mount() is used on restore too (patch 5), and it's not necessary
to "try mount" it there.
>> + int mnt_fd, ret, exit_code = -1;
>> + struct stat st;
>> +
>> + ret = switch_ns(ns->ns_pid, &mnt_ns_desc, &mnt_fd);
>> + if (ret < 0) {
>> + pr_err("Can't switch mnt_ns\n");
>> + goto out;
>> + }
>> +
>> + ret = mount("binfmt_misc", BINFMT_MISC_HOME, "binfmt_misc", 0, NULL);
>> + if (ret < 0) {
>> + if (errno == EPERM) {
>> + pr_info("Can't mount binfmt_misc: EPERM. Running in user_ns?\n");
>> + exit_code = 0;
>> + goto restore_ns;
>> + }
>> + if (errno != EBUSY && errno != ENODEV && errno != ENOENT) {
>> + pr_perror("Can't mount binfmt_misc");
>> + goto restore_ns;
>> + }
>> + pr_info("Prepare binfmt_misc: skipping(%d)\n", errno);
>> + } else {
>> + if (stat(BINFMT_MISC_HOME, &st) < 0)
>> + pr_perror("Can't stat on binfmt_misc path\n");
>> + else {
>> + *s_dev = st.st_dev;
>> + exit_code = 1;
>> + }
>> + goto restore_ns;
>> + }
>> +
>> + exit_code = 0;
>> +restore_ns:
>> + ret = restore_ns(mnt_fd, &mnt_ns_desc);
>> +out:
>> + return ret ? -1 : exit_code;
>> +}
>> +
>> static int binfmt_misc_virtual(struct mount_info *pm)
>> {
>> return kerndat_fs_virtualized(KERNDAT_FS_STAT_BINFMT_MISC, pm->s_dev);
>> @@ -1907,6 +1995,11 @@ static int dump_one_mountpoint(struct mount_info *pm, struct cr_img *img)
>> if (!pm->dumped && dump_one_fs(pm))
>> return -1;
>>
>> + if (pm->mnt_id == 0) {
>> + pr_info("Skip dumping cr-time mountpoint: %s\n", pm->mountpoint);
>> + return 0;
>> + }
>> +
>> me.mnt_id = pm->mnt_id;
>> me.root_dev = pm->s_dev;
>> me.parent_mnt_id = pm->parent_mnt_id;
>> @@ -1966,6 +2059,7 @@ static void free_mntinfo(struct mount_info *pms)
>> struct mount_info *collect_mntinfo(struct ns_id *ns, bool for_dump)
>> {
>> struct mount_info *pm;
>> + int ret;
>>
>> pm = parse_mountinfo(ns->ns_pid, ns, for_dump);
>> if (!pm) {
>> @@ -1977,6 +2071,16 @@ struct mount_info *collect_mntinfo(struct ns_id *ns, bool for_dump)
>> if (ns->mnt.mntinfo_tree == NULL)
>> goto err;
>>
>> + if (for_dump && ns->type == NS_ROOT && !opts.has_binfmt_misc) {
>> + unsigned int s_dev = 0;
>> + ret = try_mount_binfmt_misc(ns, &s_dev);
>> + if (ret < 0)
>> + return NULL;
>> + if (ret > 0 && add_cr_time_mount(ns->mnt.mntinfo_tree, "binfmt_misc",
>> + BINFMT_MISC_HOME, s_dev) < 0)
>> + return NULL;
>> + }
>> +
>> ns->mnt.mntinfo_list = pm;
>> return pm;
>> err:
>> @@ -3786,4 +3890,28 @@ int dump_mnt_namespaces(void)
>> return 0;
>> }
>>
>> +void clean_cr_time_mounts(void)
>> +{
>> + struct mount_info *mi;
>> + int mnt_fd, ret;
>> +
>> + for (mi = mntinfo; mi; mi = mi->next) {
>> + if (mi->mnt_id)
>> + continue;
>> + ret = switch_ns(mi->nsid->ns_pid, &mnt_ns_desc, &mnt_fd);
>> + if (ret) {
>> + pr_err("Can't switch to pid's %u mnt_ns\n", mi->nsid->ns_pid);
>> + continue;
>> + }
>> +
>> + if (umount(mi->mountpoint) < 0)
>> + pr_perror("Can't umount forced mount %s\n", mi->mountpoint);
>> +
>> + if (restore_ns(mnt_fd, &mnt_ns_desc)) {
>> + pr_err("cleanup_forced_mounts exiting with wrong mnt_ns\n");
>> + return;
>> + }
>> + }
>> +}
>> +
>> struct ns_desc mnt_ns_desc = NS_DESC_ENTRY(CLONE_NEWNS, "mnt");
>>
>> _______________________________________________
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>> CRIU at openvz.org
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>> .
>>
>
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