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

[Kirill Tkhai]

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?

>> +			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",
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;
>>  
>>
>> _______________________________________________
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>> CRIU at openvz.org
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>> .
>>
>