linux-kernel - [PATCH v11 4/7] iommufd: Use iommufd_access_change_ioas in iommufd_access_destroy

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Message-ID: <f9fbeca2cde7f8515da18d689b3e02a6a40a5e14.1690523699.git.nicolinc@nvidia.com>
Date:   Thu, 27 Jul 2023 23:33:26 -0700
From:   Nicolin Chen <nicolinc@...dia.com>
To:     <jgg@...dia.com>, <kevin.tian@...el.com>
CC:     <yi.l.liu@...el.com>, <joro@...tes.org>, <will@...nel.org>,
        <robin.murphy@....com>, <alex.williamson@...hat.com>,
        <shuah@...nel.org>, <linux-kernel@...r.kernel.org>,
        <iommu@...ts.linux.dev>, <kvm@...r.kernel.org>,
        <linux-kselftest@...r.kernel.org>, <mjrosato@...ux.ibm.com>,
        <farman@...ux.ibm.com>
Subject: [PATCH v11 4/7] iommufd: Use iommufd_access_change_ioas in iommufd_access_destroy_object

Update the unprotect routine in iommufd_access_destroy_object() to calling
the new iommufd_access_change_ioas() helper. This will reduce some risk of
race condition with another concurrent iommufd_access_replace/detach call.

Note that the behavior of this function call is changed: a WARN_ON will be
triggered by a -EBUSY return code if there is another ongoing detach.

Reviewed-by: Kevin Tian <kevin.tian@...el.com>
Signed-off-by: Nicolin Chen <nicolinc@...dia.com>
---
 drivers/iommu/iommufd/device.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
index e5c408415e95..c0b9cd97ec58 100644
--- a/drivers/iommu/iommufd/device.c
+++ b/drivers/iommu/iommufd/device.c
@@ -753,12 +753,10 @@ void iommufd_access_destroy_object(struct iommufd_object *obj)
 	struct iommufd_access *access =
 		container_of(obj, struct iommufd_access, obj);
 
-	if (access->ioas) {
-		iopt_remove_access(&access->ioas->iopt, access,
-				   access->iopt_access_list_id);
-		refcount_dec(&access->ioas->obj.users);
-		access->ioas = NULL;
-	}
+	mutex_lock(&access->ioas_lock);
+	if (access->ioas)
+		WARN_ON(iommufd_access_change_ioas(access, NULL));
+	mutex_unlock(&access->ioas_lock);
 	iommufd_ctx_put(access->ictx);
 }
 
-- 
2.41.0