On Wed, 30 Nov 2016, wangyijing wrote:

在 2016/11/30 4:49, Eric Wheeler 写道:

quoted

On Fri, 25 Nov 2016, Yijing Wang wrote:

quoted

set_capacity() has been called in bcache_device_init(),
remove the redundant one.

Signed-off-by: Yijing Wang <redacted>
---
 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.

I want to make sure that the set_capacity call that happens on cache 
attachment is not necessary when a backing device is attached without 
its dirty writeback cache since bcache0 is not presented until the cache 
attaches in that case.

Can you also unregister the volume, attach the backing device first, and 
then the cache while the cache is dirty to make sure that the size is set 
correctly?

--
Eric Wheeler

quoted

-Eric

quoted

 	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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