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path: root/drivers/vhost/vhost.c
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Diffstat (limited to 'drivers/vhost/vhost.c')
-rw-r--r--drivers/vhost/vhost.c42
1 files changed, 34 insertions, 8 deletions
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 80da9d9662f2..a40d16bdebb5 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -541,6 +541,36 @@ bool vhost_dev_has_owner(struct vhost_dev *dev)
}
EXPORT_SYMBOL_GPL(vhost_dev_has_owner);
+static void vhost_attach_mm(struct vhost_dev *dev)
+{
+ /* No owner, become one */
+ if (dev->use_worker) {
+ dev->mm = get_task_mm(current);
+ } else {
+ /* vDPA device does not use worker thead, so there's
+ * no need to hold the address space for mm. This help
+ * to avoid deadlock in the case of mmap() which may
+ * held the refcnt of the file and depends on release
+ * method to remove vma.
+ */
+ dev->mm = current->mm;
+ mmgrab(dev->mm);
+ }
+}
+
+static void vhost_detach_mm(struct vhost_dev *dev)
+{
+ if (!dev->mm)
+ return;
+
+ if (dev->use_worker)
+ mmput(dev->mm);
+ else
+ mmdrop(dev->mm);
+
+ dev->mm = NULL;
+}
+
/* Caller should have device mutex */
long vhost_dev_set_owner(struct vhost_dev *dev)
{
@@ -553,8 +583,8 @@ long vhost_dev_set_owner(struct vhost_dev *dev)
goto err_mm;
}
- /* No owner, become one */
- dev->mm = get_task_mm(current);
+ vhost_attach_mm(dev);
+
dev->kcov_handle = kcov_common_handle();
if (dev->use_worker) {
worker = kthread_create(vhost_worker, dev,
@@ -583,9 +613,7 @@ err_cgroup:
dev->worker = NULL;
}
err_worker:
- if (dev->mm)
- mmput(dev->mm);
- dev->mm = NULL;
+ vhost_detach_mm(dev);
dev->kcov_handle = 0;
err_mm:
return err;
@@ -682,9 +710,7 @@ void vhost_dev_cleanup(struct vhost_dev *dev)
dev->worker = NULL;
dev->kcov_handle = 0;
}
- if (dev->mm)
- mmput(dev->mm);
- dev->mm = NULL;
+ vhost_detach_mm(dev);
}
EXPORT_SYMBOL_GPL(vhost_dev_cleanup);