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

[Mikulas Patocka]

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

> 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
> 
> 
>