linux-kernel - [PATCH] Supports to use the default CMA when the device-specified CMA memory is not enough.

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Date: Wed, 12 Jun 2024 10:38:31 +0800
From: "zhai.he" <zhai.he@....com>
To: akpm@...ux-foundation.org
Cc: sboyd@...nel.org,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	stable@...r.kernel.org,
	zhipeng.wang_1@....com,
	jindong.yue@....com
Subject: [PATCH] Supports to use the default CMA when the device-specified CMA memory is not enough.

From: He Zhai <zhai.he@....com>

In the current code logic, if the device-specified CMA memory
allocation fails, memory will not be allocated from the default CMA area.
This patch will use the default cma region when the device's
specified CMA is not enough.

Signed-off-by: He Zhai <zhai.he@....com>
---
 kernel/dma/contiguous.c | 11 +++++++++--
 mm/cma.c                |  2 +-
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c
index 055da410ac71..e45cfb24500f 100644
--- a/kernel/dma/contiguous.c
+++ b/kernel/dma/contiguous.c
@@ -357,8 +357,13 @@ struct page *dma_alloc_contiguous(struct device *dev, size_t size, gfp_t gfp)
 	/* CMA can be used only in the context which permits sleeping */
 	if (!gfpflags_allow_blocking(gfp))
 		return NULL;
-	if (dev->cma_area)
-		return cma_alloc_aligned(dev->cma_area, size, gfp);
+	if (dev->cma_area) {
+		struct page *page = NULL;
+
+		page = cma_alloc_aligned(dev->cma_area, size, gfp);
+		if (page)
+			return page;
+	}
 	if (size <= PAGE_SIZE)
 		return NULL;
 
@@ -406,6 +411,8 @@ void dma_free_contiguous(struct device *dev, struct page *page, size_t size)
 	if (dev->cma_area) {
 		if (cma_release(dev->cma_area, page, count))
 			return;
+		if (cma_release(dma_contiguous_default_area, page, count))
+			return;
 	} else {
 		/*
 		 * otherwise, page is from either per-numa cma or default cma
diff --git a/mm/cma.c b/mm/cma.c
index 3e9724716bad..f225b3f65bd2 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -495,7 +495,7 @@ struct page *cma_alloc(struct cma *cma, unsigned long count,
 	}
 
 	if (ret && !no_warn) {
-		pr_err_ratelimited("%s: %s: alloc failed, req-size: %lu pages, ret: %d\n",
+		pr_debug("%s: %s: alloc failed, req-size: %lu pages, ret: %d, try to use default cma\n",
 				   __func__, cma->name, count, ret);
 		cma_debug_show_areas(cma);
 	}
-- 
2.34.1