[CRIU] [PATCH v5 5/5] mount: Restore binfmt_misc content in case of missing mount

[Kirill Tkhai]

On 05.08.2016 18:43, Pavel Emelyanov wrote:
> On 08/04/2016 04:49 PM, Kirill Tkhai wrote:
>> In case of mount image is not containing binfmt_misc mountpoint,
>> add temporary mountpoint to mount tree and try to restore
>> binfmt_misc content in ordinary way. Then, umount temporary mountpoint.
>>
>> v4: New
>> v5: Check for opts.has_binfmt_misc to determine if image presents
>>
>> Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
>> ---
>>  criu/mount.c |   19 ++++++++++++++++++-
>>  1 file changed, 18 insertions(+), 1 deletion(-)
>>
>> diff --git a/criu/mount.c b/criu/mount.c
>> index 926817a..964dbbc 100644
>> --- a/criu/mount.c
>> +++ b/criu/mount.c
>> @@ -2451,6 +2451,15 @@ 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) {
>> +			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");
>> @@ -2470,7 +2479,7 @@ 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;
>> @@ -3339,6 +3348,7 @@ static int populate_mnt_ns(void)
>>  	struct mount_info *pms;
>>  	struct ns_id *nsid;
>>  	struct mount_info *roots_mp = NULL;
>> +	struct stat st;
>>  	int ret;
>>  
>>  	if (mnt_roots) {
>> @@ -3355,6 +3365,13 @@ static int populate_mnt_ns(void)
>>  	if (!pms)
>>  		return -1;
>>  
>> +	if (!opts.has_binfmt_misc && stat_image(CR_FD_BINFMT_MISC, &st, 0) == 0) {
> 
> This should be the other way. In cr-restore.c we have an array of so called cinfos -- these
> are images that should be pre-loaded during restore. So it's better to add new-style binfmt
> cinfo and read_mnt_ns_img should check cinfo->flags for COLLECT_HAPPENED (not 100% sure it
> handles empty images correctly, plz, check) and add cr-time mount if it had.

You had suggested to dump any binfmt_misc content (belonging to a mount point or not)
to the file of the same name. So, the new suggestion doesn't work.

The code, I did, populates opts.has_binfmt_misc in dependence of belonging mountpoint exists or not.
Your new suggestion isn't able to handle this.
 
> -- Pavel
> 
>> +		/* Add to mount tree. Generic code will mount it later */
>> +		ret = add_cr_time_mount(pms, "binfmt_misc", BINFMT_MISC_HOME, 0);
>> +		if (ret)
>> +			return -1;
>> +	}
>> +
>>  	if (resolve_shared_mounts(mntinfo, pms->master_id))
>>  		return -1;
>>  
>>
>> _______________________________________________
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>> CRIU at openvz.org
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>> .
>>
>