[CRIU] [PATCH 1/5] mount: save the result of mnt_is_overmounted

[Pavel Tikhomirov]

On 09/26/2018 11:35 PM, Andrey Vagin wrote:
> On Mon, Sep 17, 2018 at 02:47:53PM +0300, Pavel Tikhomirov wrote:
>> On restore we change mounts tree topology and paths in find_remap_mounts
>> thus mns_is_overmounted does not account remaped overmounts. So to know
>> which mounts will be actually overmounted after restore we need two much
>> effort, better prepare these info in advance.
>>
>> That also should improve performance of mnt_is_overmounted on dump,
>> as we reuse calculations from previous calls.
>>
>> Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
>> ---
>>   criu/include/mount.h |  2 ++
>>   criu/mount.c         | 36 ++++++++++++++++++++++++++++++------
>>   2 files changed, 32 insertions(+), 6 deletions(-)
>>
>> diff --git a/criu/include/mount.h b/criu/include/mount.h
>> index ca17b059a..e7d026264 100644
>> --- a/criu/include/mount.h
>> +++ b/criu/include/mount.h
>> @@ -70,6 +70,8 @@ struct mount_info {
>>   
>>   	struct list_head	postpone;
>>   
>> +	int			is_overmounted;
>> +
>>   	void			*private;	/* associated filesystem data */
>>   };
>>   
>> diff --git a/criu/mount.c b/criu/mount.c
>> index bdc39b530..ba202f0c9 100644
>> --- a/criu/mount.c
>> +++ b/criu/mount.c
>> @@ -1152,17 +1152,29 @@ static int get_clean_fd(struct mount_info *mi)
>>    * root of our mount namespace as it is covered by other mount.
>>    * mnt_is_overmounted() checks if mount is not visible.
>>    */
>> -static bool mnt_is_overmounted(struct mount_info *mi)
>> +static int mnt_is_overmounted(struct mount_info *mi)
> 
> Why do you change a type?

Leftover, It seem I changed these at some early stage of preparing the 
patch, sorry =)

> 
>>   {
>>   	struct mount_info *t, *c, *m = mi;
>>   
>> +	if (mi->is_overmounted != -1)
>> +		goto exit;
>> +
>> +	mi->is_overmounted = 0;
>> +
>>   	while (m->parent) {
>> +		if (mi->parent->is_overmounted == 1) {
>> +			mi->is_overmounted = 1;
>> +			goto exit;
>> +		}
>> +
>>   		/* Check there is no sibling-overmount */
>>   		list_for_each_entry(t, &m->parent->children, siblings) {
>>   			if (m == t)
>>   				continue;
>> -			if (issubpath(m->mountpoint, t->mountpoint))
>> -				return true;
>> +			if (issubpath(m->mountpoint, t->mountpoint)) {
>> +				mi->is_overmounted = 1;
>> +				goto exit;
>> +			}
>>   		}
>>   
>>   		/*
>> @@ -1175,10 +1187,19 @@ static bool mnt_is_overmounted(struct mount_info *mi)
>>   
>>   	/* Check there is no children-overmount */
>>   	list_for_each_entry(c, &mi->children, siblings)
>> -		if (!strcmp(c->mountpoint, mi->mountpoint))
>> -			return true;
>> +		if (!strcmp(c->mountpoint, mi->mountpoint)) {
>> +			mi->is_overmounted = 1;
>> +			goto exit;
>> +		}
>>   
>> -	return false;
>> +exit:
>> +	return mi->is_overmounted;
>> +}
>> +
>> +static int set_is_overmounted(struct mount_info *mi)
>> +{
>> +	mnt_is_overmounted(mi);
>> +	return 0;
>>   }
>>   
>>   /*
>> @@ -2723,6 +2744,7 @@ struct mount_info *mnt_entry_alloc()
>>   	new = xzalloc(sizeof(struct mount_info));
>>   	if (new) {
>>   		new->fd = -1;
>> +		new->is_overmounted = -1;
>>   		INIT_LIST_HEAD(&new->children);
>>   		INIT_LIST_HEAD(&new->siblings);
>>   		INIT_LIST_HEAD(&new->mnt_slave_list);
>> @@ -3160,6 +3182,8 @@ static int populate_mnt_ns(void)
>>   	if (validate_mounts(mntinfo, false))
>>   		return -1;
>>   
>> +	mnt_tree_for_each(pms, set_is_overmounted);
>> +
>>   	if (find_remap_mounts(pms))
>>   		return -1;
>>   
>> -- 
>> 2.17.1
>>

-- 
Best regards, Tikhomirov Pavel
Software Developer, Virtuozzo.