Re: [PATCH 09/13] md-cluster: always setup in-memory bitmap

[Shaohua Li <shli@kernel.org>]

On Thu, Apr 21, 2016 at 01:58:10PM +0800, Guoqing Jiang wrote:
> The in-memory bitmap for raid is allocated on demand,
> then for cluster scenario, it is possible that slave
> node which received RESYNCING message doesn't have the
> in-memory bitmap when master node is perform resyncing,
> so we can't make bitmap is match up well among each
> nodes.
> 
> So for cluster scenario, we need always preserve the
> bitmap, and ensure the page will not be freed. And a
> no_hijack flag is introduced to both bitmap_checkpage
> and bitmap_get_counter, which makes cluster raid returns
> fail once allocate failed.
> 
> And the next patch is relied on this change since it
> keeps sync bitmap among each nodes during resyncing
> stage.
> 
> Reviewed-by: NeilBrown <neilb@suse.com>
> Signed-off-by: Guoqing Jiang <gqjiang@suse.com>
> ---
>  drivers/md/bitmap.c | 59 +++++++++++++++++++++++++++++++++++++++++------------
>  1 file changed, 46 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
> index 7df6b4f..00cf1c1 100644
> --- a/drivers/md/bitmap.c
> +++ b/drivers/md/bitmap.c
> @@ -46,7 +46,7 @@ static inline char *bmname(struct bitmap *bitmap)
>   * allocated while we're using it
>   */
>  static int bitmap_checkpage(struct bitmap_counts *bitmap,
> -			    unsigned long page, int create)
> +			    unsigned long page, int create, int no_hijack)
>  __releases(bitmap->lock)
>  __acquires(bitmap->lock)
>  {
> @@ -90,6 +90,9 @@ __acquires(bitmap->lock)
>  
>  	if (mappage == NULL) {
>  		pr_debug("md/bitmap: map page allocation failed, hijacking\n");
> +		/* We don't support hijack for cluster raid */
> +		if (no_hijack)
> +			return -ENOMEM;
>  		/* failed - set the hijacked flag so that we can use the
>  		 * pointer as a counter */
>  		if (!bitmap->bp[page].map)
> @@ -1177,7 +1180,7 @@ static void bitmap_set_pending(struct bitmap_counts *bitmap, sector_t offset)
>  
>  static bitmap_counter_t *bitmap_get_counter(struct bitmap_counts *bitmap,
>  					    sector_t offset, sector_t *blocks,
> -					    int create);
> +					    int create, int no_hijack);
>  
>  /*
>   * bitmap daemon -- periodically wakes up to clean bits and flush pages
> @@ -1257,7 +1260,7 @@ void bitmap_daemon_work(struct mddev *mddev)
>  		}
>  		bmc = bitmap_get_counter(counts,
>  					 block,
> -					 &blocks, 0);
> +					 &blocks, 0, 0);
>  
>  		if (!bmc) {
>  			j |= PAGE_COUNTER_MASK;
> @@ -1307,7 +1310,7 @@ void bitmap_daemon_work(struct mddev *mddev)
>  
>  static bitmap_counter_t *bitmap_get_counter(struct bitmap_counts *bitmap,
>  					    sector_t offset, sector_t *blocks,
> -					    int create)
> +					    int create, int no_hijack)
>  __releases(bitmap->lock)
>  __acquires(bitmap->lock)
>  {
> @@ -1321,7 +1324,7 @@ __acquires(bitmap->lock)
>  	sector_t csize;
>  	int err;
>  
> -	err = bitmap_checkpage(bitmap, page, create);
> +	err = bitmap_checkpage(bitmap, page, create, 0);
>  
>  	if (bitmap->bp[page].hijacked ||
>  	    bitmap->bp[page].map == NULL)

bitmap_get_counter doesn't use the new no_hijack parameter. And you always pass
0 to this function. so looks this change isn't required.