linux-kernel - Re: [PATCH 1/2] bcache: Remove redundant set

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Date:   Wed, 30 Nov 2016 10:00:14 +0800
From:   wangyijing <wangyijing@...wei.com>
To:     Eric Wheeler <bcache@...ts.ewheeler.net>
CC:     <axboe@...com>, <kent.overstreet@...il.com>,
        <git@...ux.ewheeler.net>, <colyli@...e.de>,
        <linux-bcache@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] bcache: Remove redundant set_capacity



在 2016/11/30 4:49, Eric Wheeler 写道:
> On Fri, 25 Nov 2016, Yijing Wang wrote:
> 
>> set_capacity() has been called in bcache_device_init(),
>> remove the redundant one.
>>
>> Signed-off-by: Yijing Wang <wangyijing@...wei.com>
>> ---
>>  drivers/md/bcache/super.c | 3 ---
>>  1 file changed, 3 deletions(-)
>>
>> diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
>> index 849ad44..b638a16 100644
>> --- a/drivers/md/bcache/super.c
>> +++ b/drivers/md/bcache/super.c
>> @@ -1126,9 +1126,6 @@ static int cached_dev_init(struct cached_dev *dc, unsigned block_size)
>>  	if (ret)
>>  		return ret;
>>  
>> -	set_capacity(dc->disk.disk,
>> -		     dc->bdev->bd_part->nr_sects - dc->sb.data_offset);
>> -
> 
> It probably is a duplicate set_capacity, but has anyone tested bringing on 
> a writeback volume, and late-attaching the cache volume with this patch 
> applied?
> 
> Otherwise stated, is it possible to get the backing device attached 
> without setting the capacity?

Hi Eric, I tested this case in following steps, the result is fine, the capability is setted.

[root@38 sys]# make-bcache -B /dev/nvme1n1
UUID:			6758bd42-c226-4de9-a6d5-fb003af63f9f
Set UUID:		2661eadd-79b4-4c56-a2fb-9f8b505aa9fd
version:		1
block_size:		1
data_offset:		16
[root@38 sys]# ls /dev/bcache
bcache/  bcache0
[root@38 sys]# fdisk -l
Disk /dev/nvme1n1: 1.8 TiB, 2000398934016 bytes, 3907029168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
....
Disk /dev/bcache0: 1.8 TiB, 2000398925824 bytes, 3907029152 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
....
[root@38 sys]# make-bcache -C /dev/ram0
UUID:			b64a4425-b9c1-4650-9cab-3856410c9566
Set UUID:		a0a31965-a89d-43b6-a5d6-968897abeb7a
version:		0
nbuckets:		1024
block_size:		1
bucket_size:		1024
nr_in_set:		1
nr_this_dev:		0
first_bucket:		1
[root@38 sys]# echo a0a31965-a89d-43b6-a5d6-968897abeb7a > /sys/block/bcache0/bcache/attach
[root@38 sys]# echo writeback > /sys/block/bcache0/bcache/cache_mode
[root@38 sys]# mount /dev/bcache0 /tmp
[root@38 sys]# cd /tmp/
[root@38 tmp]# fio ~/fio_write.sh
file1: (g=0): rw=randwrite, bs=4K-4K/4K-4K/4K-4K, ioengine=psync, iodepth=1
fio-2.2.8
Starting 1 thread
file1: Laying out IO file(s) (1 file(s) / 128MB)
Jobs: 1 (f=1): [w(1)] [0.0% done] [0KB/177.2MB/0KB /s] [0/45.4K/0 iops] [eta 05h:33m:13s]

Thanks!
Yijing.

> 
> -Eric
> 
>>  	dc->disk.disk->queue->backing_dev_info.ra_pages =
>>  		max(dc->disk.disk->queue->backing_dev_info.ra_pages,
>>  		    q->backing_dev_info.ra_pages);
>> -- 
>> 2.5.0
>>
>> --
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>>
> 
> .
>