[CRIU] [PATCH v4 3/3] mount: Restore binfmt_misc content in case of missing mount

[Pavel Emelyanov]

On 08/02/2016 04:29 PM, Kirill Tkhai wrote:
> 
> 
> On 02.08.2016 16:03, Pavel Emelyanov wrote:
>> On 07/20/2016 01:13 PM, Kirill Tkhai wrote:
>>> In case of mount image is not containing binfmt_misc mountpoint,
>>> scan image directory for binfmt_misc content file (binfmt-misc-xxx).
>>> If a file is found, add temporary mountpoint to mount tree and
>>> restore the content in ordinary way. Then, umount temporary mountpoint.
>>>
>>> v4: New
>>>
>>> Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
>>> ---
>>>  criu/mount.c |   61 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++--
>>>  1 file changed, 59 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/criu/mount.c b/criu/mount.c
>>> index d583429..8657c36 100644
>>> --- a/criu/mount.c
>>> +++ b/criu/mount.c
>>> @@ -1379,6 +1379,39 @@ static int try_mount_binfmt_misc(struct ns_id *ns, unsigned int *s_dev)
>>>  	return ret ? -1 : exit_code;
>>>  }
>>>  
>>> +static int find_binfmt_misc_img(unsigned int *s_dev)
>>> +{
>>> +	struct dirent *de;
>>> +	int dfd, ret;
>>> +	DIR *dir;
>>> +
>>> +	*s_dev = 0;
>>> +	dfd = dup(get_service_fd(IMG_FD_OFF));
>>> +	dir = fdopendir(dfd);
>>> +	if (!dir) {
>>> +		close(dfd);
>>> +		pr_perror("Can't open img dir\n");
>>> +		return -1;
>>> +	}
>>> +	rewinddir(dir);
>>> +
>>> +	errno = 0;
>>> +	while ((de = readdir(dir)) != NULL) {
>>
>> Scanning the images dir doesn't look valid. Instead, there should be a proper
>> collection of this image (like we do with fdinfo-s, sockets and others). Then,
>> when reading the mountpoint images, the binfmt_misc collected data should be
>> looked up and orphan data should add the cr-time mountpoints.
> 
> So, for every type you want to make array of images, don't you?

What do you mean?

>>
>>> +		if (strncmp(de->d_name, "binfmt-misc-", 12) == 0) {
>>> +			*s_dev = (unsigned int)strtoul(de->d_name + 12, NULL, 10);
>>> +			break;
>>> +		}
>>> +	}
>>> +	ret = errno;
>>> +	if (ret)
>>> +		pr_perror("Can't read dir\n");
>>> +	else if (*s_dev)
>>> +		pr_info("Found binfmt_misc img for dev=%u\n", *s_dev);
>>> +	closedir(dir);
>>> +
>>> +	return ret ? -1 : (*s_dev != 0);
>>> +}
>>> +
>>>  static int binfmt_misc_virtual(struct mount_info *pm)
>>>  {
>>>  	return kerndat_fs_virtualized(KERNDAT_FS_STAT_BINFMT_MISC, pm->s_dev);
>>> @@ -2442,6 +2475,15 @@ static int do_new_mount(struct mount_info *mi)
>>>  	if (tp->restore && tp->restore(mi))
>>>  		return -1;
>>>  
>>> +	if (!mi->mnt_id) {
>>> +		/* C-r time mountpoint, umount it */
>>> +		if (umount(mi->mountpoint) < 0) {
>>
>> I don't see the corresponding mount() callback. Where is it?
> 
> Generic code does this after mount_info is created in add_cr_time_mount().

Ah! OK, we need a code comment saying this explicitly.

>>> +			pr_perror("Can't umount %s\n", mi->mountpoint);
>>> +			return -1;
>>> +		}
>>> +		goto out;
>>> +	}
>>> +
>>>  	if (remount_ro && mount(NULL, mi->mountpoint, tp->name,
>>>  				     MS_REMOUNT | MS_RDONLY, NULL)) {
>>>  		pr_perror("Unable to apply mount options");
>>> @@ -2461,7 +2503,7 @@ static int do_new_mount(struct mount_info *mi)
>>>  	BUG_ON(mi->master_id);
>>>  	if (restore_shared_options(mi, !mi->shared_id, mi->shared_id, 0))
>>>  		return -1;
>>> -
>>> +out:
>>>  	mi->mounted = true;
>>>  
>>>  	return 0;
>>> @@ -3324,7 +3366,7 @@ static int populate_roots_yard(void)
>>>  
>>>  static int populate_mnt_ns(void)
>>>  {
>>> -	struct mount_info *pms;
>>> +	struct mount_info *pms, *mi;
>>>  	struct ns_id *nsid;
>>>  	struct mount_info *roots_mp = NULL;
>>>  	int ret;
>>> @@ -3343,6 +3385,21 @@ static int populate_mnt_ns(void)
>>>  	if (!pms)
>>>  		return -1;
>>>  
>>> +	for (mi = mntinfo; mi != NULL; mi = mi->next) {
>>> +		if (strcmp(mi->fstype->name, "binfmt_misc") == 0)
>>> +			break;
>>> +	}
>>> +
>>> +	if (!mi) {
>>> +		unsigned int s_dev;
>>> +
>>> +		ret = find_binfmt_misc_img(&s_dev);
>>> +		if (ret > 0)
>>> +			ret = add_cr_time_mount(pms, "binfmt_misc", BINFMT_MISC_HOME, s_dev);
>>> +		if (ret < 0)
>>> +			return -1;
>>> +	}
>>> +
>>>  	if (resolve_shared_mounts(mntinfo, pms->master_id))
>>>  		return -1;
>>>  
>>>
>>> _______________________________________________
>>> CRIU mailing list
>>> CRIU at openvz.org
>>> https://lists.openvz.org/mailman/listinfo/criu
>>> .
>>>
>>
> .
>