linux-kernel - [PATCH v3 1/3] iommu/iova: Tidy up iova_cache

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Message-Id: <ae4a3bda2d6a9b738221553c838d30473bd624e7.1707144953.git.robin.murphy@arm.com>
Date: Mon,  5 Feb 2024 15:32:39 +0000
From: Robin Murphy <robin.murphy@....com>
To: joro@...tes.org
Cc: will@...nel.org,
	pasha.tatashin@...een.com,
	iommu@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	rientjes@...gle.com,
	yosryahmed@...gle.com,
	john.g.garry@...cle.com
Subject: [PATCH v3 1/3] iommu/iova: Tidy up iova_cache_get() failure

Failure handling in iova_cache_get() is a little messy, and we'd like
to add some more to it, so let's tidy up a bit first. By leaving the
hotplug handler until last we can take advantage of kmem_cache_destroy()
being NULL-safe to have a single cleanup label. We can also improve the
error reporting, noting that kmem_cache_create() already screams if it
fails, so that one is redundant.

Signed-off-by: Robin Murphy <robin.murphy@....com>
---
 drivers/iommu/iova.c | 33 ++++++++++++++++-----------------
 1 file changed, 16 insertions(+), 17 deletions(-)

diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index d30e453d0fb4..cf95001d85c0 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -254,26 +254,20 @@ static void free_iova_mem(struct iova *iova)
 
 int iova_cache_get(void)
 {
+	int err = -ENOMEM;
+
 	mutex_lock(&iova_cache_mutex);
 	if (!iova_cache_users) {
-		int ret;
+		iova_cache = kmem_cache_create("iommu_iova", sizeof(struct iova), 0,
+					       SLAB_HWCACHE_ALIGN, NULL);
+		if (!iova_cache)
+			goto out_err;
 
-		ret = cpuhp_setup_state_multi(CPUHP_IOMMU_IOVA_DEAD, "iommu/iova:dead", NULL,
-					iova_cpuhp_dead);
-		if (ret) {
-			mutex_unlock(&iova_cache_mutex);
-			pr_err("Couldn't register cpuhp handler\n");
-			return ret;
-		}
-
-		iova_cache = kmem_cache_create(
-			"iommu_iova", sizeof(struct iova), 0,
-			SLAB_HWCACHE_ALIGN, NULL);
-		if (!iova_cache) {
-			cpuhp_remove_multi_state(CPUHP_IOMMU_IOVA_DEAD);
-			mutex_unlock(&iova_cache_mutex);
-			pr_err("Couldn't create iova cache\n");
-			return -ENOMEM;
+		err = cpuhp_setup_state_multi(CPUHP_IOMMU_IOVA_DEAD, "iommu/iova:dead",
+					      NULL, iova_cpuhp_dead);
+		if (err) {
+			pr_err("IOVA: Couldn't register cpuhp handler: %pe\n", ERR_PTR(err));
+			goto out_err;
 		}
 	}
 
@@ -281,6 +275,11 @@ int iova_cache_get(void)
 	mutex_unlock(&iova_cache_mutex);
 
 	return 0;
+
+out_err:
+	kmem_cache_destroy(iova_cache);
+	mutex_unlock(&iova_cache_mutex);
+	return err;
 }
 EXPORT_SYMBOL_GPL(iova_cache_get);
 
-- 
2.39.2.101.g768bb238c484.dirty