[PATCH] dma-pool: Fix too large DMA pools on medium systems

From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Christoph Hellwig <hch@lst.de>,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	Robin Murphy <robin.murphy@arm.com>,
	David Rientjes <rientjes@google.com>
Cc: iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
	Geert Uytterhoeven <geert@linux-m68k.org>
Subject: [PATCH] dma-pool: Fix too large DMA pools on medium systems
Date: Mon,  8 Jun 2020 10:52:31 +0200	[thread overview]
Message-ID: <20200608085231.8924-1-geert@linux-m68k.org> (raw)

On systems with at least 32 MiB, but less than 32 GiB of RAM, the DMA
memory pools are much larger than intended (e.g. 2 MiB instead of 128
KiB on a 256 MiB system).

Fix this by correcting the calculation of the number of GiBs of RAM in
the system.

Fixes: 1d659236fb43c4d2 ("dma-pool: scale the default DMA coherent pool size with memory capacity")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
---
 kernel/dma/pool.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/dma/pool.c b/kernel/dma/pool.c
index 35bb51c31fff370f..1c7eab2cc0498003 100644
--- a/kernel/dma/pool.c
+++ b/kernel/dma/pool.c
@@ -175,8 +175,8 @@ static int __init dma_atomic_pool_init(void)
 	 * sizes to 128KB per 1GB of memory, min 128KB, max MAX_ORDER-1.
 	 */
 	if (!atomic_pool_size) {
-		atomic_pool_size = max(totalram_pages() >> PAGE_SHIFT, 1UL) *
-					SZ_128K;
+		unsigned long gigs = totalram_pages() >> (30 - PAGE_SHIFT);
+		atomic_pool_size = max(gigs, 1UL) * SZ_128K;
 		atomic_pool_size = min_t(size_t, atomic_pool_size,
 					 1 << (PAGE_SHIFT + MAX_ORDER-1));
 	}
-- 
2.17.1

