Re: [PATCH V2 2/4] Btrfs: don't get the lock when adding a csum into a ordered extent

[Miao Xie <miaox@cn.fujitsu.com>]

On 	tue, 28 Jan 2014 11:00:54 -0500, Josef Bacik wrote:
> 
> On 01/14/2014 07:31 AM, Miao Xie wrote:
>> We are sure that:
>> - one ordered extent just has one csum calculation worker, and no one
>>    access the csum list during the csum calculation except the worker.
>> - we don't change the list and free the csum until no one reference
>>    to the ordered extent
>> So it is safe to add csum without the lock.
>>
>> Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
>> ---
>>   fs/btrfs/ordered-data.c |    5 -----
>>   1 files changed, 0 insertions(+), 5 deletions(-)
>>
>> diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c
>> index e4c3d56..396c6d1 100644
>> --- a/fs/btrfs/ordered-data.c
>> +++ b/fs/btrfs/ordered-data.c
>> @@ -280,16 +280,11 @@ void btrfs_add_ordered_sum(struct inode *inode,
>>                  struct btrfs_ordered_extent *entry,
>>                  struct btrfs_ordered_sum *sum)
>>   {
>> -    struct btrfs_ordered_inode_tree *tree;
>> -
>> -    tree = &BTRFS_I(inode)->ordered_tree;
>> -    spin_lock_irq(&tree->lock);
>>       list_add_tail(&sum->list, &entry->list);
>>       WARN_ON(entry->csum_bytes_left < sum->len);
>>       entry->csum_bytes_left -= sum->len;
>>       if (entry->csum_bytes_left == 0)
>>           wake_up(&entry->wait);
>> -    spin_unlock_irq(&tree->lock);
>>   }
>>     /*
> This blew up in xfstests so one of your assumptions is incorrect. Thanks,

I think it is because there is a bug in the other place. Please tell me
the case that can reproduce the problem.

Thanks
Miao

> 
> Josef
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