linux-kernel - [PATCH v2 2/2] dma-buf: system_heap: account for system heap allocation in memcg

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Message-Id: <20260113-dmabuf-heap-system-memcg-v2-2-e85722cc2f24@redhat.com>
Date: Tue, 13 Jan 2026 16:32:45 -0500
From: Eric Chanudet <echanude@...hat.com>
To: Sumit Semwal <sumit.semwal@...aro.org>, 
 Benjamin Gaignard <benjamin.gaignard@...labora.com>, 
 Brian Starkey <Brian.Starkey@....com>, John Stultz <jstultz@...gle.com>, 
 "T.J. Mercier" <tjmercier@...gle.com>, 
 Christian König <christian.koenig@....com>, 
 Maxime Ripard <mripard@...hat.com>
Cc: linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
 linaro-mm-sig@...ts.linaro.org, linux-kernel@...r.kernel.org, 
 Eric Chanudet <echanude@...hat.com>
Subject: [PATCH v2 2/2] dma-buf: system_heap: account for system heap
 allocation in memcg

The system dma-buf heap lets userspace allocate buffers from the page
allocator. However, these allocations are not accounted for in memcg,
allowing processes to escape limits that may be configured.

Pass __GFP_ACCOUNT for system heap allocations, based on the
dma_heap.mem_accounting parameter, to use memcg and account for them.

Signed-off-by: Eric Chanudet <echanude@...hat.com>
---
 drivers/dma-buf/heaps/system_heap.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c
index 4c782fe33fd497a74eb5065797259576f9b651b6..139b50df64ed4c4a6fdd69f25fe48324fbe2c481 100644
--- a/drivers/dma-buf/heaps/system_heap.c
+++ b/drivers/dma-buf/heaps/system_heap.c
@@ -52,6 +52,8 @@ static gfp_t order_flags[] = {HIGH_ORDER_GFP, HIGH_ORDER_GFP, LOW_ORDER_GFP};
 static const unsigned int orders[] = {8, 4, 0};
 #define NUM_ORDERS ARRAY_SIZE(orders)

+extern bool mem_accounting;
+
 static int dup_sg_table(struct sg_table *from, struct sg_table *to)
 {
 	struct scatterlist *sg, *new_sg;
@@ -320,14 +322,17 @@ static struct page *alloc_largest_available(unsigned long size,
 {
 	struct page *page;
 	int i;
+	gfp_t flags;

 	for (i = 0; i < NUM_ORDERS; i++) {
 		if (size <  (PAGE_SIZE << orders[i]))
 			continue;
 		if (max_order < orders[i])
 			continue;
-
-		page = alloc_pages(order_flags[i], orders[i]);
+		flags = order_flags[i];
+		if (mem_accounting)
+			flags |= __GFP_ACCOUNT;
+		page = alloc_pages(flags, orders[i]);
 		if (!page)
 			continue;
 		return page;

-- 
2.52.0