Re: [PATCH 1/5] Btrfs: wake up the tasks that wait for the io earlier

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

On Fri, 22 Nov 2013 12:30:40 +0800, Liu Bo wrote:
> On Thu, Nov 21, 2013 at 09:43:14PM +0800, Miao Xie wrote:
>> The tasks that wait for the IO_DONE flag just care about the io of the dirty
>> pages, so it is better to wake up them immediately after all the pages are
>> written, not the whole process of the io completes.
> 
> This doesn't seem to make sense, the waiters still go to wait and schedule since
> IO_DONE is not set there yet.

I can not understand what you said. We wake up the waiters after IO_DONE is set,
the waiters who wait for IO_DONE flag will not go to wait.

Miao

> 
> -liubo
> 
>>
>> Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
>> ---
>>  fs/btrfs/ordered-data.c | 14 ++++++++++----
>>  1 file changed, 10 insertions(+), 4 deletions(-)
>>
>> diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c
>> index eb5bac4..1bd7002 100644
>> --- a/fs/btrfs/ordered-data.c
>> +++ b/fs/btrfs/ordered-data.c
>> @@ -348,10 +348,13 @@ int btrfs_dec_test_first_ordered_pending(struct inode *inode,
>>  	if (!uptodate)
>>  		set_bit(BTRFS_ORDERED_IOERR, &entry->flags);
>>  
>> -	if (entry->bytes_left == 0)
>> +	if (entry->bytes_left == 0) {
>>  		ret = test_and_set_bit(BTRFS_ORDERED_IO_DONE, &entry->flags);
>> -	else
>> +		if (waitqueue_active(&entry->wait))
>> +			wake_up(&entry->wait);
>> +	} else {
>>  		ret = 1;
>> +	}
>>  out:
>>  	if (!ret && cached && entry) {
>>  		*cached = entry;
>> @@ -408,10 +411,13 @@ have_entry:
>>  	if (!uptodate)
>>  		set_bit(BTRFS_ORDERED_IOERR, &entry->flags);
>>  
>> -	if (entry->bytes_left == 0)
>> +	if (entry->bytes_left == 0) {
>>  		ret = test_and_set_bit(BTRFS_ORDERED_IO_DONE, &entry->flags);
>> -	else
>> +		if (waitqueue_active(&entry->wait))
>> +			wake_up(&entry->wait);
>> +	} else {
>>  		ret = 1;
>> +	}
>>  out:
>>  	if (!ret && cached && entry) {
>>  		*cached = entry;
>> -- 
>> 1.8.3.1
>>
>> --
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>