Re: [RFC PATCH 1/2] btrfs: Add missing device check in dev_info/rm_dev ioctl

From: Anand Jain <Anand.Jain@oracle.com>
To: Qu Wenruo <quwenruo@cn.fujitsu.com>
Cc: linux-btrfs@vger.kernel.org
Subject: Re: [RFC PATCH 1/2] btrfs: Add missing device check in dev_info/rm_dev ioctl
Date: Wed, 21 May 2014 11:54:07 +0800	[thread overview]
Message-ID: <537C235F.5030303@oracle.com> (raw)
In-Reply-To: <537C19B9.8080203@cn.fujitsu.com>

Hi Qu,

  Thanks for checking with me. sorry for the delay. The
  preliminary RFC patch which was sent and mentioned in
  the other emails took time more than expected.

  Further on top of your check_missing patch I am writing
  code to to handle disk reappear. I should be sending them
  all soon.

Thanks, Anand

On 21/05/14 11:12, Qu Wenruo wrote:
>
> I'm sorry to bother your but it has been about 2 weeks after your last
> reply.
>
> Is there any problem?
>
> Thanks,
> Qu
> -------- Original Message --------
> Subject: Re: [RFC PATCH 1/2] btrfs: Add missing device check in
> dev_info/rm_dev ioctl
> From: Anand Jain <Anand.Jain@oracle.com>
> To: Qu Wenruo <quwenruo@cn.fujitsu.com>
> Date: 2014年05月07日 16:00
>>
>>
>> Thanks for working on this.
>> I am running some tests will let you know.
>>
>> Anand
>>
>>
>> On 05/06/2014 02:33 PM, Qu Wenruo wrote:
>>> Old btrfs can't find a missing btrfs device since there is no
>>> mechanism for block layer to inform fs layer.
>>>
>>> But we can use a workaround that only check status(by using
>>> request_queue->queue_flags) of every device in a btrfs
>>> filesystem when calling dev_info/rm_dev ioctl, since other ioctls
>>> do not really cares about missing device.
>>>
>>> Cc: Anand Jain <Anand.Jain@oracle.com>
>>> Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
>>> ---
>>>   fs/btrfs/ioctl.c   |  1 +
>>>   fs/btrfs/volumes.c | 25 ++++++++++++++++++++++++-
>>>   fs/btrfs/volumes.h |  2 ++
>>>   3 files changed, 27 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
>>> index 0401397..7680a40 100644
>>> --- a/fs/btrfs/ioctl.c
>>> +++ b/fs/btrfs/ioctl.c
>>> @@ -2606,6 +2606,7 @@ static long btrfs_ioctl_dev_info(struct
>>> btrfs_root *root, void __user *arg)
>>>           goto out;
>>>       }
>>>
>>> +    btrfs_check_dev_missing(root, dev, 1);
>>>       di_args->devid = dev->devid;
>>>       di_args->bytes_used = dev->bytes_used;
>>>       di_args->total_bytes = dev->total_bytes;
>>> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
>>> index d241130a..c7d7908 100644
>>> --- a/fs/btrfs/volumes.c
>>> +++ b/fs/btrfs/volumes.c
>>> @@ -1548,9 +1548,10 @@ int btrfs_rm_device(struct btrfs_root *root,
>>> char *device_path)
>>>            * is held.
>>>            */
>>>           list_for_each_entry(tmp, devices, dev_list) {
>>> +            btrfs_check_dev_missing(root, tmp, 0);
>>>               if (tmp->in_fs_metadata &&
>>>                   !tmp->is_tgtdev_for_dev_replace &&
>>> -                !tmp->bdev) {
>>> +                (!tmp->bdev || tmp->missing)) {
>>>                   device = tmp;
>>>                   break;
>>>               }
>>> @@ -6300,3 +6301,25 @@ int btrfs_scratch_superblock(struct
>>> btrfs_device *device)
>>>
>>>       return 0;
>>>   }
>>> +
>>> +/* If need_lock is set, uuid_mutex will be used */
>>> +int btrfs_check_dev_missing(struct btrfs_root *root, struct
>>> btrfs_device *dev,
>>> +                int need_lock)
>>> +{
>>> +    struct request_queue *q;
>>> +
>>> +    if (unlikely(!dev || !dev->bdev || !dev->bdev->bd_queue))
>>> +        return -ENOENT;
>>> +    q = dev->bdev->bd_queue;
>>> +
>>> +    if (need_lock)
>>> +        mutex_lock(&uuid_mutex);
>>> +    if (test_bit(QUEUE_FLAG_DEAD, &q->queue_flags) ||
>>> +        test_bit(QUEUE_FLAG_DYING, &q->queue_flags)) {
>>> +        dev->missing = 1;
>>> +        root->fs_info->fs_devices->missing_devices++;
>>> +    }
>>> +    if (need_lock)
>>> +        mutex_unlock(&uuid_mutex);
>>> +    return 0;
>>> +}
>>> diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
>>> index 80754f9..47a44af 100644
>>> --- a/fs/btrfs/volumes.h
>>> +++ b/fs/btrfs/volumes.h
>>> @@ -356,6 +356,8 @@ unsigned long btrfs_full_stripe_len(struct
>>> btrfs_root *root,
>>>   int btrfs_finish_chunk_alloc(struct btrfs_trans_handle *trans,
>>>                   struct btrfs_root *extent_root,
>>>                   u64 chunk_offset, u64 chunk_size);
>>> +int btrfs_check_dev_missing(struct btrfs_root *root, struct
>>> btrfs_device *dev,
>>> +                int need_lock);
>>>   static inline void btrfs_dev_stat_inc(struct btrfs_device *dev,
>>>                         int index)
>>>   {
>>>
>
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