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

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Message-Id: <20200608085231.8924-1-geert@linux-m68k.org>
Date:   Mon,  8 Jun 2020 10:52:31 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>,
        David Rientjes <rientjes@...gle.com>
Cc:     iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: [PATCH] dma-pool: Fix too large DMA pools on medium systems

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@...ux-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