[dm-devel] [PATCH] dm writecache: flush metadata in single commit in init_memory

[shenghui]

On 10/24/2018 10:38 PM, Mikulas Patocka wrote:
> 
> 
> On Wed, 24 Oct 2018, Shenghui Wang wrote:
> 
>> Do not flush sb ->magic in second commit.
> 
> This is intentional. The magic is written last, so that if the machine 
> crashes while formatting the device, the incomplete superblock won't be 
> misidentified as already formatted.
> 
> Mikulas

Got it. Thanks,

-
shenghui

> 
>> Signed-off-by: Shenghui Wang <shhuiw at foxmail.com>
>> ---
>>  drivers/md/dm-writecache.c | 5 ++---
>>  1 file changed, 2 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/md/dm-writecache.c b/drivers/md/dm-writecache.c
>> index d656bd1799ae..8e9e96a22f68 100644
>> --- a/drivers/md/dm-writecache.c
>> +++ b/drivers/md/dm-writecache.c
>> @@ -1749,6 +1749,8 @@ static int init_memory(struct dm_writecache *wc)
>>  
>>  	for (b = 0; b < ARRAY_SIZE(sb(wc)->padding); b++)
>>  		pmem_assign(sb(wc)->padding[b], cpu_to_le64(0));
>> +
>> +	pmem_assign(sb(wc)->magic, cpu_to_le32(MEMORY_SUPERBLOCK_MAGIC));
>>  	pmem_assign(sb(wc)->version, cpu_to_le32(MEMORY_SUPERBLOCK_VERSION));
>>  	pmem_assign(sb(wc)->block_size, cpu_to_le32(wc->block_size));
>>  	pmem_assign(sb(wc)->n_blocks, cpu_to_le64(wc->n_blocks));
>> @@ -1759,9 +1761,6 @@ static int init_memory(struct dm_writecache *wc)
>>  
>>  	writecache_flush_all_metadata(wc);
>>  	writecache_commit_flushed(wc);
>> -	pmem_assign(sb(wc)->magic, cpu_to_le32(MEMORY_SUPERBLOCK_MAGIC));
>> -	writecache_flush_region(wc, &sb(wc)->magic, sizeof sb(wc)->magic);
>> -	writecache_commit_flushed(wc);
>>  
>>  	return 0;
>>  }
>> -- 
>> 2.18.0
>>
>>
>>
> 
>