[PATCH] block: kmemleak: Track the page allocations for struct request

[Catalin Marinas]

The pages allocated for struct request contain pointers to other slab
allocations (via ops->init_request). Since kmemleak does not track/scan
page allocations, the slab objects will be reported as leaks (false
positives). This patch adds kmemleak callbacks to allow tracking of such
pages.

Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Reported-by: Bart Van Assche <bart.vanassche@xxxxxxxxxxx>
Tested-by: Bart Van Assche<bart.vanassche@xxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
---

Jens,

I just realised that no-one has picked this patch up for -rc1. It was
discussed here previously:

http://lkml.kernel.org/r/20150803104309.GB4033@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Since it touches the block layer, are you fine with merging it?

Thanks,

Catalin

 block/blk-mq.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index f2d67b4047a0..2077f0d2f95f 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -9,6 +9,7 @@
 #include <linux/backing-dev.h>
 #include <linux/bio.h>
 #include <linux/blkdev.h>
+#include <linux/kmemleak.h>
 #include <linux/mm.h>
 #include <linux/init.h>
 #include <linux/slab.h>
@@ -1438,6 +1439,11 @@ static void blk_mq_free_rq_map(struct blk_mq_tag_set *set,
 	while (!list_empty(&tags->page_list)) {
 		page = list_first_entry(&tags->page_list, struct page, lru);
 		list_del_init(&page->lru);
+		/*
+		 * Remove kmemleak object previously allocated in
+		 * blk_mq_init_rq_map().
+		 */
+		kmemleak_free(page_address(page));
 		__free_pages(page, page->private);
 	}
 
@@ -1510,6 +1516,11 @@ static struct blk_mq_tags *blk_mq_init_rq_map(struct blk_mq_tag_set *set,
 		list_add_tail(&page->lru, &tags->page_list);
 
 		p = page_address(page);
+		/*
+		 * Allow kmemleak to scan these pages as they contain pointers
+		 * to additional allocations like via ops->init_request().
+		 */
+		kmemleak_alloc(p, order_to_size(this_order), 1, GFP_KERNEL);
 		entries_per_page = order_to_size(this_order) / rq_size;
 		to_do = min(entries_per_page, set->queue_depth - i);
 		left -= to_do * rq_size;
--
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