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

[Kirill Tkhai]

On 02.08.2016 16:39, Pavel Emelyanov wrote:
> 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?

Introduce a new type of objects, "dump images". And collect names of images,
like we do for other object types.

As I understand right, you want so.

 
>>>
>>>> +		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;
>>>>  
>>>>
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>>>> .
>>>>
>>>
>> .
>>
>