Re: [PATCH 2/2] btrfs: Remove unneeded missing device number check

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

Thanks for pointing this out.

Although previous patch is small enough, but for remount case, we need 
to iterate all the existing chunk cache.

So fix for remount will take a little more time.

Thanks for reviewing.
Qu

在 2015年09月17日 17:43, Anand Jain 写道:
>
>
> On 09/16/2015 11:43 AM, Qu Wenruo wrote:
>> As we do per-chunk missing device number check at read_one_chunk() time,
>> it's not needed to do global missing device number check.
>>
>> Just remove it.
>
> However the missing device count, what we have during the remount is not
> fine grained per chunk.
> -----------
> btrfs_remount
> ::
>                   if (fs_info->fs_devices->missing_devices >
>                       fs_info->num_tolerated_disk_barrier_failures &&
>                      !(*flags & MS_RDONLY ||
>                          btrfs_test_opt(root, DEGRADED))) {
>                          btrfs_warn(fs_info,
>                                  "too many missing devices, writeable
> remount is not allowed");
>                          ret = -EACCES;
>                          goto restore;
>                  }
> ---------
>
> Thanks, Anand
>
>
>> Now btrfs can handle the following case:
>>   # mkfs.btrfs -f -m raid1 -d single /dev/sdb /dev/sdc
>>
>>   Data chunk will be located in sdb, so we should be safe to wipe sdc
>>   # wipefs -a /dev/sdc
>>
>>   # mount /dev/sdb /mnt/btrfs -o degraded
>>
>> Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
>> ---
>>   fs/btrfs/disk-io.c | 8 --------
>>   1 file changed, 8 deletions(-)
>>
>> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
>> index 0b658d0..ac640ea 100644
>> --- a/fs/btrfs/disk-io.c
>> +++ b/fs/btrfs/disk-io.c
>> @@ -2947,14 +2947,6 @@ retry_root_backup:
>>       }
>>       fs_info->num_tolerated_disk_barrier_failures =
>>           btrfs_calc_num_tolerated_disk_barrier_failures(fs_info);
>> -    if (fs_info->fs_devices->missing_devices >
>> -         fs_info->num_tolerated_disk_barrier_failures &&
>> -        !(sb->s_flags & MS_RDONLY)) {
>> -        pr_warn("BTRFS: missing devices(%llu) exceeds the limit(%d),
>> writeable mount is not allowed\n",
>> -            fs_info->fs_devices->missing_devices,
>> -            fs_info->num_tolerated_disk_barrier_failures);
>> -        goto fail_sysfs;
>> -    }
>>
>>       fs_info->cleaner_kthread = kthread_run(cleaner_kthread, tree_root,
>>                              "btrfs-cleaner");
>>
> --
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