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From:   Petr Tesarik <petrtesarik@huaweicloud.com>
To:     Stefano Stabellini <sstabellini@kernel.org>,
        Russell King <linux@armlinux.org.uk>,
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Cc:     Roberto Sassu <roberto.sassu@huaweicloud.com>, petr@tesarici.cz
Subject: [PATCH v5 1/9] swiotlb: bail out of swiotlb_init_late() if swiotlb is already allocated
Date:   Mon, 24 Jul 2023 14:12:37 +0200
Message-Id: <437209bd783fa3febc3a207acb7799a0ff5cf1f3.1690200598.git.petr.tesarik.ext@huawei.com>
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From: Petr Tesarik <petr.tesarik.ext@huawei.com>

If swiotlb is allocated, immediately return 0, so callers do not have to
check io_tlb_default_mem.nslabs explicitly.

Signed-off-by: Petr Tesarik <petr.tesarik.ext@huawei.com>
---
 arch/arm/xen/mm.c         | 10 ++++------
 arch/x86/kernel/pci-dma.c | 12 ++++++------
 kernel/dma/swiotlb.c      |  3 +++
 3 files changed, 13 insertions(+), 12 deletions(-)

diff --git a/arch/arm/xen/mm.c b/arch/arm/xen/mm.c
index 3d826c0b5fee..882cd70c7a2f 100644
--- a/arch/arm/xen/mm.c
+++ b/arch/arm/xen/mm.c
@@ -125,12 +125,10 @@ static int __init xen_mm_init(void)
 		return 0;
 
 	/* we can work with the default swiotlb */
-	if (!io_tlb_default_mem.nslabs) {
-		rc = swiotlb_init_late(swiotlb_size_or_default(),
-				       xen_swiotlb_gfp(), NULL);
-		if (rc < 0)
-			return rc;
-	}
+	rc = swiotlb_init_late(swiotlb_size_or_default(),
+			       xen_swiotlb_gfp(), NULL);
+	if (rc < 0)
+		return rc;
 
 	cflush.op = 0;
 	cflush.a.dev_bus_addr = 0;
diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index de6be0a3965e..08988b0a1c91 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -86,16 +86,16 @@ static void __init pci_xen_swiotlb_init(void)
 
 int pci_xen_swiotlb_init_late(void)
 {
+	int rc;
+
 	if (dma_ops == &xen_swiotlb_dma_ops)
 		return 0;
 
 	/* we can work with the default swiotlb */
-	if (!io_tlb_default_mem.nslabs) {
-		int rc = swiotlb_init_late(swiotlb_size_or_default(),
-					   GFP_KERNEL, xen_swiotlb_fixup);
-		if (rc < 0)
-			return rc;
-	}
+	rc = swiotlb_init_late(swiotlb_size_or_default(),
+			       GFP_KERNEL, xen_swiotlb_fixup);
+	if (rc < 0)
+		return rc;
 
 	/* XXX: this switches the dma ops under live devices! */
 	dma_ops = &xen_swiotlb_dma_ops;
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 2b83e3ad9dca..66fc8ec9ae45 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -384,6 +384,9 @@ int swiotlb_init_late(size_t size, gfp_t gfp_mask,
 	bool retried = false;
 	int rc = 0;
 
+	if (io_tlb_default_mem.nslabs)
+		return 0;
+
 	if (swiotlb_force_disable)
 		return 0;
 
-- 
2.25.1