[CRIU] [PATCH v5 2/5] mount: Create binfmt_misc image w/o device suffix

[Pavel Emelyanov]

On 08/15/2016 11:39 AM, Kirill Tkhai wrote:
> On 05.08.2016 18:34, Pavel Emelyanov wrote:
>> On 08/04/2016 04:49 PM, Kirill Tkhai wrote:
>>> Use name binfmt_misc-0.img for any mounted binfmt_misc.
>>> Note, that newly created binfmt_misc images won't restore
>>> on old criu.
>>>
>>> Also, because of above, let's change a behaviour of dump and now
>>> we do not create binfmt_misc images if there is no registered
>>> binfmt_misc entries.
>>>
>>> v5: New
>>> Suggested-by: Pavel Emelyanov <xemul at virtuozzo.com>
>>> Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
>>> ---
>>>  criu/mount.c |   40 ++++++++++++++++++++++++++++++++--------
>>>  1 file changed, 32 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/criu/mount.c b/criu/mount.c
>>> index f90ec69..c5533de 100644
>>> --- a/criu/mount.c
>>> +++ b/criu/mount.c
>>> @@ -1361,7 +1361,7 @@ static int dump_binfmt_misc_entry(int dfd, char *name, struct cr_img *img)
>>>  
>>>  static int binfmt_misc_dump(struct mount_info *pm)
>>>  {
>>> -	struct cr_img *img;
>>> +	struct cr_img *img = NULL;
>>>  	struct dirent *de;
>>>  	DIR *fdir = NULL;
>>>  	int fd, ret;
>>> @@ -1381,10 +1381,6 @@ static int binfmt_misc_dump(struct mount_info *pm)
>>>  	}
>>>  
>>>  	ret = -1;
>>> -	img = open_image(CR_FD_BINFMT_MISC, O_DUMP, pm->s_dev);
>>> -	if (!img)
>>> -		goto out;
>>> -
>>>  	while ((de = readdir(fdir))) {
>>>  		if (dir_dots(de))
>>>  			continue;
>>> @@ -1393,6 +1389,13 @@ static int binfmt_misc_dump(struct mount_info *pm)
>>>  		if (!strcmp(de->d_name, "status"))
>>>  			continue;
>>>  
>>> +		if (!img) {
>>> +			/* Create image only if an extry exists, i.e. here */
>>> +			img = open_image(CR_FD_BINFMT_MISC, O_DUMP, 0);
>>
>> Let's change the name format and remove 0 from it.
> 
> It requires to add a new image type. Is it ok?

Yes.

>>> +			if (!img)
>>> +				goto out;
>>> +		}
>>> +
>>>  		if (dump_binfmt_misc_entry(fd, de->d_name, img))
>>>  			goto out;
>>>  	}
>>> @@ -1487,20 +1490,41 @@ static int make_bfmtm_magic_str(char *buf, BinfmtMiscEntry *bme)
>>>  
>>>  static int binfmt_misc_restore(struct mount_info *mi)
>>>  {
>>> +	unsigned int suffix;
>>>  	struct cr_img *img;
>>> +	struct stat st;
>>>  	char *buf;
>>> -	int ret = -1;
>>> +	int ret;
>>>  
>>>  	buf = xmalloc(BINFMT_MISC_STR);
>>>  	if (!buf)
>>>  		return -1;
>>>  
>>> -	img = open_image(CR_FD_BINFMT_MISC, O_RSTR, mi->s_dev);
>>> +	suffix = 0;
>>> +	ret = stat_image(CR_FD_BINFMT_MISC, &st, suffix);
>>
>> There's no need to stat the image. Just do it like we did before -- try
>> to open image by legacy name and, if it's empty_image(), try to open
>> by new name.
> 
> Why so? open_image() does not make difference between "no image" and "wrong permittions",

It does. Please, show me the bug if you see it.

> for example. We may lose existing binfmt_misc if some problem exists, doesn't it?
>  
>>> +	if (ret < 0) {
>>> +		if (ret == -ENOENT) {
>>> +			suffix = mi->s_dev;
>>> +			ret = stat_image(CR_FD_BINFMT_MISC, &st, suffix);
>>> +			if (ret == -ENOENT) {
>>> +				ret = 0;
>>> +				pr_info("No binfmt image found\n");
>>> +				goto free_buf;
>>> +			}
>>> +		}
>>> +		else if (ret) {
>>> +			pr_err("Can't stat binfmt_misc image: %s\n", strerror(ret));
>>> +			goto free_buf;
>>> +		}
>>> +	}
>>> +
>>> +	img = open_image(CR_FD_BINFMT_MISC, O_RSTR, suffix);
>>>  	if (!img) {
>>> +		pr_err("Can't open binfmt_misc image\n");
>>> +		ret = -1;
>>>  		goto free_buf;
>>>  	}
>>>  
>>> -	ret = 0;
>>>  	while (ret == 0) {
>>>  		BinfmtMiscEntry *bme;
>>>  
>>>
>>> _______________________________________________
>>> CRIU mailing list
>>> CRIU at openvz.org
>>> https://lists.openvz.org/mailman/listinfo/criu
>>> .
>>>
>>
> .
>