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[13/30,for,5.4] dma-pool: fix too large DMA pools on medium memory size systems

Message ID 20200925161916.204667-14-pgonda@google.com
State New
Headers show
Series Backport unencrypted non-blocking DMA allocations | expand

Commit Message

Peter Gonda Sept. 25, 2020, 4:18 p.m. UTC 
From: Geert Uytterhoeven <geert@linux-m68k.org>

upstream 3ee06a6d532f75f20528ff4d2c473cda36c484fe commit.

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.  Invert the order of the min/max operations, to keep on
calculating in pages until the last step, which aids readability.

Fixes: 1d659236fb43c4d2 ("dma-pool: scale the default DMA coherent pool size with memory capacity")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Peter Gonda <pgonda@google.com>
---
 kernel/dma/pool.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)
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Patch

diff --git a/kernel/dma/pool.c b/kernel/dma/pool.c
index 35bb51c31fff..8cfa01243ed2 100644
--- a/kernel/dma/pool.c
+++ b/kernel/dma/pool.c
@@ -175,10 +175,9 @@  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;
-		atomic_pool_size = min_t(size_t, atomic_pool_size,
-					 1 << (PAGE_SHIFT + MAX_ORDER-1));
+		unsigned long pages = totalram_pages() / (SZ_1G / SZ_128K);
+		pages = min_t(unsigned long, pages, MAX_ORDER_NR_PAGES);
+		atomic_pool_size = max_t(size_t, pages << PAGE_SHIFT, SZ_128K);
 	}
 	INIT_WORK(&atomic_pool_work, atomic_pool_work_fn);