Re: [PATCH 23/24] mdrestore: Add support for passing log device as an argument

[Chandan Babu R <chandan.babu@oracle.com>]

On Tue, May 23, 2023 at 11:09:59 AM -0700, Darrick J. Wong wrote:
> On Tue, May 23, 2023 at 02:30:49PM +0530, Chandan Babu R wrote:
>> metadump v2 format allows dumping metadata from external log devices. This
>> commit allows passing the device file to which log data must be restored from
>> the corresponding metadump file.
>> 
>> Signed-off-by: Chandan Babu R <chandan.babu@oracle.com>
>> ---
>>  mdrestore/xfs_mdrestore.c | 10 ++++++++--
>>  1 file changed, 8 insertions(+), 2 deletions(-)
>> 
>> diff --git a/mdrestore/xfs_mdrestore.c b/mdrestore/xfs_mdrestore.c
>> index 9e06d37dc..f5eff62ef 100644
>> --- a/mdrestore/xfs_mdrestore.c
>> +++ b/mdrestore/xfs_mdrestore.c
>> @@ -427,7 +427,8 @@ static struct mdrestore_ops mdrestore_ops_v2 = {
>>  static void
>>  usage(void)
>>  {
>> -	fprintf(stderr, "Usage: %s [-V] [-g] [-i] source target\n", progname);
>> +	fprintf(stderr, "Usage: %s [-V] [-g] [-i] [-l logdev] source target\n",
>> +		progname);
>>  	exit(1);
>>  }
>>  
>> @@ -453,7 +454,7 @@ main(
>>  
>>  	progname = basename(argv[0]);
>>  
>> -	while ((c = getopt(argc, argv, "giV")) != EOF) {
>> +	while ((c = getopt(argc, argv, "gil:V")) != EOF) {
>>  		switch (c) {
>>  			case 'g':
>>  				mdrestore.show_progress = 1;
>> @@ -461,6 +462,9 @@ main(
>>  			case 'i':
>>  				mdrestore.show_info = 1;
>>  				break;
>> +			case 'l':
>> +				logdev = optarg;
>> +				break;
>>  			case 'V':
>>  				printf("%s version %s\n", progname, VERSION);
>>  				exit(0);
>> @@ -493,6 +497,8 @@ main(
>>  	}
>>  
>>  	if (mdrestore_ops_v1.read_header(&mb, src_f) == 0) {
>> +		if (logdev != NULL)
>> +			usage();
>>  		mdrestore.mdrops = &mdrestore_ops_v1;
>>  		header = &mb;
>>  	} else if (mdrestore_ops_v2.read_header(&xmh, src_f) == 0) {
>
> What if we have a v2 with XME_ADDR_LOG_DEVICE meta_extents but the
> caller doesn't specify -l?  Do we proceed with the metadump, only to
> fail midway through the restore?

restore_v2() has the following statement just after reading in the superblock,

	if (sb.sb_logstart == 0 && log_fd == -1)
                fatal("External Log device is required\n");

Hence, In the case of a missing log device argument, the program exits before
any metadata is written to the target device.

-- 
chandan