[PATCH v2 2/2] Revert "Revert "iommu/dma: Fix race condition during iova_domain initialization""

[Janusz Krzysztofik]

This reverts commit bc79ef6d5a223ea59acf874f0493b79c835b17d4.
---
 drivers/iommu/dma-iommu.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 9616b473e4c7e..17dd683b2fcea 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -65,6 +65,7 @@ struct iommu_dma_cookie {
 
 	/* Domain for flush queue callback; NULL if flush queue not in use */
 	struct iommu_domain		*fq_domain;
+	struct mutex			mutex;
 };
 
 static DEFINE_STATIC_KEY_FALSE(iommu_deferred_attach_enabled);
@@ -311,6 +312,7 @@ int iommu_get_dma_cookie(struct iommu_domain *domain)
 	if (!domain->iova_cookie)
 		return -ENOMEM;
 
+	mutex_init(&domain->iova_cookie->mutex);
 	return 0;
 }
 
@@ -561,26 +563,33 @@ static int iommu_dma_init_domain(struct iommu_domain *domain, dma_addr_t base,
 	}
 
 	/* start_pfn is always nonzero for an already-initialised domain */
+	mutex_lock(&cookie->mutex);
 	if (iovad->start_pfn) {
 		if (1UL << order != iovad->granule ||
 		    base_pfn != iovad->start_pfn) {
 			pr_warn("Incompatible range for DMA domain\n");
-			return -EFAULT;
+			ret = -EFAULT;
+			goto done_unlock;
 		}
 
-		return 0;
+		ret = 0;
+		goto done_unlock;
 	}
 
 	init_iova_domain(iovad, 1UL << order, base_pfn);
 	ret = iova_domain_init_rcaches(iovad);
 	if (ret)
-		return ret;
+		goto done_unlock;
 
 	/* If the FQ fails we can simply fall back to strict mode */
 	if (domain->type == IOMMU_DOMAIN_DMA_FQ && iommu_dma_init_fq(domain))
 		domain->type = IOMMU_DOMAIN_DMA;
 
-	return iova_reserve_iommu_regions(dev, domain);
+	ret = iova_reserve_iommu_regions(dev, domain);
+
+done_unlock:
+	mutex_unlock(&cookie->mutex);
+	return ret;
 }
 
 /**
-- 
2.25.1