Re: [PATCH 1/2] btrfs-progs: Add missing devices check for mounted btrfs.

[Qu Wenruo <quwenruo@cn.fujitsu.com>]

On Fri, 07 Feb 2014 17:34:46 +0800, Anand Jain wrote:
>
>
>  IMO btrfs-progs shouldn't add its intelligence to know if disk
>  is missing. If btrfs-kernel doesn't know when disk is missing
>  that's a bug to fix in btrfs-kernel. yes that indeed true as
>  of now in btrfs-kernel. btrfs kernel has no idea when disk
>  goes missing, just -EIO doesn't tell btrfs that. I am trying
>  to fix this first.
>
>  But the problem is there isn't good way with in btrfs/FS
>  to know when disk goes missing. did I miss anything ?
Yes, kernel detection is the best way.
But since it has no better way to detect missing device, I think the 
btrfs-progs way fix is good enough for now.

Since btrfs fi show with "-d" options will scan the /dev to find fs and 
check missing disks,
I think adds some user-land check even using the ioctl way is still 
somewhat reasonable.

Thanks
Qu
>
>
> Thanks, Anand
>
>
> On 02/07/2014 02:45 PM, Qu Wenruo wrote:
>> In btrfs/003 of xfstest, it will check whether btrfs fi show can find
>> missing devices.
>>
>> But before the patch, btrfs-progs will not check whether device missing
>> if given a mounted btrfs mountpoint/block device.
>> This patch fixes the bug and will pass btrfs/003.
>>
>> Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
>> Cc: Anand Jain <anand.jain@oracle.com>
>> ---
>>   cmds-filesystem.c | 12 ++++++++++++
>>   1 file changed, 12 insertions(+)
>>
>> diff --git a/cmds-filesystem.c b/cmds-filesystem.c
>> index 384d1b9..4c9933d 100644
>> --- a/cmds-filesystem.c
>> +++ b/cmds-filesystem.c
>> @@ -363,6 +363,8 @@ static int print_one_fs(struct 
>> btrfs_ioctl_fs_info_args *fs_info,
>>           char *label, char *path)
>>   {
>>       int i;
>> +    int fd;
>> +    int missing;
>>       char uuidbuf[BTRFS_UUID_UNPARSED_SIZE];
>>       struct btrfs_ioctl_dev_info_args *tmp_dev_info;
>>       int ret;
>> @@ -385,6 +387,14 @@ static int print_one_fs(struct 
>> btrfs_ioctl_fs_info_args *fs_info,
>>
>>       for (i = 0; i < fs_info->num_devices; i++) {
>>           tmp_dev_info = (struct btrfs_ioctl_dev_info_args 
>> *)&dev_info[i];
>> +
>> +        /* Add check for missing devices even mounted */
>> +        fd = open((char *)tmp_dev_info->path, O_RDONLY);
>> +        if (fd < 0) {
>> +            missing = 1;
>> +            continue;
>> +        }
>> +        close(fd);
>>           printf("\tdevid %4llu size %s used %s path %s\n",
>>               tmp_dev_info->devid,
>>               pretty_size(tmp_dev_info->total_bytes),
>> @@ -392,6 +402,8 @@ static int print_one_fs(struct 
>> btrfs_ioctl_fs_info_args *fs_info,
>>               tmp_dev_info->path);
>>       }
>>
>> +    if (missing)
>> +        printf("\t*** Some devices missing\n");
>>       printf("\n");
>>       return 0;
>>   }
>>
>