linux-kernel - [PATCH 1/3] dma-pool: factor out a calculate_pool

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Message-Id: <20220817060647.1032426-2-hch@lst.de>
Date:   Wed, 17 Aug 2022 08:06:45 +0200
From:   Christoph Hellwig <hch@....de>
To:     iommu@...ts.linux.dev, Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>
Cc:     Michal Hocko <mhocko@...e.com>,
        David Rientjes <rientjes@...gle.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] dma-pool: factor out a calculate_pool_size helper

Add a helper to calculate the pool size from dma_atomic_pool_init,
and fix up the last max_t to use the proper type.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 kernel/dma/pool.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/kernel/dma/pool.c b/kernel/dma/pool.c
index 4d40dcce7604b..56f96678934bf 100644
--- a/kernel/dma/pool.c
+++ b/kernel/dma/pool.c
@@ -184,6 +184,15 @@ static __init struct gen_pool *__dma_atomic_pool_init(size_t pool_size,
 	return pool;
 }
 
+static unsigned long calculate_pool_size(unsigned long zone_pages)
+{
+	unsigned long nr_pages = min_t(unsigned long,
+				       zone_pages / (SZ_1G / SZ_128K),
+				       MAX_ORDER_NR_PAGES);
+
+	return max_t(unsigned long, nr_pages << PAGE_SHIFT, SZ_128K);
+}
+
 static int __init dma_atomic_pool_init(void)
 {
 	int ret = 0;
@@ -192,11 +201,9 @@ static int __init dma_atomic_pool_init(void)
 	 * If coherent_pool was not used on the command line, default the pool
 	 * sizes to 128KB per 1GB of memory, min 128KB, max MAX_ORDER-1.
 	 */
-	if (!atomic_pool_size) {
-		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);
-	}
+	if (!atomic_pool_size)
+		atomic_pool_size = calculate_pool_size(totalram_pages());
+
 	INIT_WORK(&atomic_pool_work, atomic_pool_work_fn);
 
 	atomic_pool_kernel = __dma_atomic_pool_init(atomic_pool_size,
-- 
2.30.2