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

[Guoqing Jiang <gqjiang@xxxxxxxx>]

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@xxxxxxxx>
> > Signed-off-by: Guoqing Jiang <gqjiang@xxxxxxxx>
> > ---
> >   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);

Thanks,
Guoqing
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