Re: alternative take on the same page merging leak fix v2

[Ming Lei <ming.lei@redhat.com>]

On Thu, Jun 13, 2019 at 04:04:03AM -0600, Jens Axboe wrote:
> On 6/13/19 3:55 AM, Christoph Hellwig wrote:
> > Hi Jens, hi Ming,
> > 
> > this is the tested and split version of what I think is the better
> > fix for the get_user_pages page leak, as it leaves the intelligence
> > in the callers instead of in bio_try_to_merge_page.
> > 
> > Changes since v1:
> >   - drop patches not required for 5.2
> >   - added Reviewed-by tags
> 
> Applied for 5.2, thanks.

Hi Jens & Christoph,

Looks the following change is missed in patch 1, otherwise kernel oops
is triggered during kernel booting:

diff --git a/block/bio.c b/block/bio.c
index 35b3c568a48f..9ccf07c666f7 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -706,6 +706,8 @@ static int __bio_add_pc_page(struct request_queue *q, struct bio *bio,
 		return 0;
 
 	if (bio->bi_vcnt > 0) {
+		bool same_page;
+
 		bvec = &bio->bi_io_vec[bio->bi_vcnt - 1];
 
 		if (page == bvec->bv_page &&
@@ -723,7 +725,7 @@ static int __bio_add_pc_page(struct request_queue *q, struct bio *bio,
 		if (bvec_gap_to_prev(q, bvec, offset))
 			return 0;
 
-		if (page_is_mergeable(bvec, page, len, offset, false) &&
+		if (page_is_mergeable(bvec, page, len, offset, &same_page) &&
 		    can_add_page_to_seg(q, bvec, page, len, offset)) {
 			bvec->bv_len += len;
 			goto done;

Thanks,
Ming