[PATCH] dma-pool: Do not allocate pool memory from CMA

Nicolas Saenz Julienne
2020-07-08T16:55:35Z

There is no guarantee to CMA's placement, so allocating a zone specific
atomic pool from CMA might return memory from a completely different
memory zone. So stop using it.

Fixes: c84dc6e68a1d ("dma-pool: add additional coherent pools to map to gfp mask")
Reported-by: Jeremy Linton <jeremy.linton@arm.com>
Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
---

An more costly alternative would be adding an option to
dma_alloc_from_contiguous() so it fails when the allocation doesn't fall
in a specific zone.

kernel/dma/pool.c | 11 ++---------
1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/kernel/dma/pool.c b/kernel/dma/pool.c
index 8cfa01243ed2..4bc1c46ae6ef 100644
--- a/kernel/dma/pool.c
+++ b/kernel/dma/pool.c
@@ -6,7 +6,6 @@
#include <linux/debugfs.h>
#include <linux/dma-direct.h>
#include <linux/dma-noncoherent.h>
-#include <linux/dma-contiguous.h>
#include <linux/init.h>
#include <linux/genalloc.h>
#include <linux/set_memory.h>
@@ -69,12 +68,7 @@ static int atomic_pool_expand(struct gen_pool *pool, size_t pool_size,

do {
pool_size = 1 << (PAGE_SHIFT + order);
-
- if (dev_get_cma_area(NULL))
- page = dma_alloc_from_contiguous(NULL, 1 << order,
- order, false);
- else
- page = alloc_pages(gfp, order);
+ page = alloc_pages(gfp, order);
} while (!page && order-- > 0);
if (!page)
goto out;
@@ -118,8 +112,7 @@ static int atomic_pool_expand(struct gen_pool *pool, size_t pool_size,
dma_common_free_remap(addr, pool_size);
#endif
free_page: __maybe_unused
- if (!dma_release_from_contiguous(NULL, page, 1 << order))
- __free_pages(page, order);
+ __free_pages(page, order);
out:
return ret;
}
--
2.27.0