Re: [PATCH v4] btrfs-progs: add 'btrfs device ignore' cli

[Anand Jain <anand.jain@oracle.com>]

On 12/06/2017 03:11 AM, David Sterba wrote:
> On Tue, Dec 05, 2017 at 04:52:57PM +0800, Anand Jain wrote:
>> This patch adds
>>    btrfs device ignode <dev>
>> so that a device can be ignored/missed during mount if the device is
>> already been scanned. Basically, this command will undo the effect
>> of the command
>>    btrfs device scan <dev>
> 
> As it logicall belongs to scan, I'd rather make it an option, like
> 
>    $ btrfs scan --unregister
> 
> or
> 
>    $ btrfs scan --forget
>
> The meaning of 'ignore' in this context is not clear to me, we can
> ignore errors on the device.

  Do you mean to say..

      $btrfs dev scan --unregister
   or
      $btrfs dev scan --forget

  further, as there is a suggestion to have an option to purge all
  unmounted devices, in view of adding further options, how
  about..

     $btrfs dev <sub-sub-cmd> [ <--all> | <dev-path> ]

  all:       purge all unmounted devices
  dev-path:  purge one given device

  and name choices for <sub-sub-cmd>  are:
     unscan
     unregister
     forget
     purge

  I am fine with any, will go by suggested.

Thanks, Anand

>> This change is compatible with older kernel without the ioctl
>> BTRFS_IOC_IGNORE_DEV which is added here. At which it shall
>> report 'Inappropriate ioctl for device'. And will report
>> 'Operation not permitted' on mounted device.
>>
>> Signed-off-by: Anand Jain <anand.jain@oracle.com>
>> ---
>> v1-4: No change.
>>
>>   cmds-device.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>>   ioctl.h       |  2 ++
>>   2 files changed, 56 insertions(+)
>>
>> diff --git a/cmds-device.c b/cmds-device.c
>> index f4cdb39f64ac..31b1945d3339 100644
>> --- a/cmds-device.c
>> +++ b/cmds-device.c
>> @@ -329,6 +329,59 @@ out:
>>   	return !!ret;
>>   }
>>   
>> +static const char * const cmd_device_ignore_usage[] = {
>> +	"btrfs device ignore [<device>]",
>> +	"Ignore a device in the btrfs kernel module.",
>> +	NULL
>> +};
>> +
>> +static int btrfs_ignore_one_device(char *path)
>> +{
>> +	struct btrfs_ioctl_vol_args args;
>> +	int fd;
>> +	int ret;
>> +
>> +	fd = open("/dev/btrfs-control", O_RDWR);
>> +	if (fd < 0)
>> +		return -errno;
>> +
>> +	memset(&args, 0, sizeof(args));
>> +	strncpy_null(args.name, path);
>> +	ret = ioctl(fd, BTRFS_IOC_IGNORE_DEV, &args);
>> +	if (ret)
>> +		ret = -errno;
>> +	close(fd);
>> +	return ret;
>> +}
>> +
>> +static int cmd_device_ignore(int argc, char **argv)
>> +{
>> +	int ret = 0;
>> +	char *path;
>> +
>> +	if (check_argc_max(argc - optind, 1))
>> +		usage(cmd_device_ignore_usage);
>> +
>> +	if (is_block_device(argv[1]) != 1) {
>> +		error("Not a block device: %s", argv[1]);
>> +		return -ENOENT;
>> +	}
>> +
>> +	path = canonicalize_path(argv[1]);
>> +	if (!path) {
>> +		error("Could not canonicalize path '%s': %s",
>> +					argv[1], strerror(errno));
>> +		return -ENOENT;
>> +	}
>> +
>> +	ret  = btrfs_ignore_one_device(path);
>> +	if (ret)
>> +		error("Can't ignore %s: %s", path, strerror(-ret));
>> +
>> +	free(path);
>> +	return ret;
>> +}
>> +
>>   static const char * const cmd_device_ready_usage[] = {
>>   	"btrfs device ready <device>",
>>   	"Check device to see if it has all of its devices in cache for mounting",
>> @@ -604,6 +657,7 @@ const struct cmd_group device_cmd_group = {
>>   			CMD_ALIAS },
>>   		{ "remove", cmd_device_remove, cmd_device_remove_usage, NULL, 0 },
>>   		{ "scan", cmd_device_scan, cmd_device_scan_usage, NULL, 0 },
>> +		{ "ignore", cmd_device_ignore, cmd_device_ignore_usage, NULL, 0 },
>>   		{ "ready", cmd_device_ready, cmd_device_ready_usage, NULL, 0 },
>>   		{ "stats", cmd_device_stats, cmd_device_stats_usage, NULL, 0 },
>>   		{ "usage", cmd_device_usage,
>> diff --git a/ioctl.h b/ioctl.h
>> index 709e996f401c..bef8508119aa 100644
>> --- a/ioctl.h
>> +++ b/ioctl.h
>> @@ -721,6 +721,8 @@ static inline char *btrfs_err_str(enum btrfs_err_code err_code)
>>   				   struct btrfs_ioctl_vol_args)
>>   #define BTRFS_IOC_SCAN_DEV _IOW(BTRFS_IOCTL_MAGIC, 4, \
>>   				   struct btrfs_ioctl_vol_args)
>> +#define BTRFS_IOC_IGNORE_DEV _IOW(BTRFS_IOCTL_MAGIC, 5, \
>> +				   struct btrfs_ioctl_vol_args)
>>   /* trans start and trans end are dangerous, and only for
>>    * use by applications that know how to avoid the
>>    * resulting deadlocks
>> -- 
>> 2.7.0
>>
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