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

[Shaohua Li <shli@kernel.org>]

On Tue, Apr 26, 2016 at 11:22:37AM +0800, Guoqing Jiang wrote:
> 
> 
> On 04/26/2016 01:45 AM, Shaohua Li wrote:
> >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.
> >
> 
> The below part of this patch pass 1 to bitmap_checkpage, so it is needed.
> 
> +	/* For cluster raid, need to pre-allocate bitmap */
> +	if (mddev_is_clustered(bitmap->mddev)) {
> +		unsigned long page;
> +		for (page = 0; page < pages; page++) {
> +			ret = bitmap_checkpage(&bitmap->counts, page, 1, 1);

I mean bitmap_get_counter(). You add no_hijack parameter, but not use it