block: Dynamically allocate and refcount backing_dev_info

Instead of storing backing_dev_info inside struct request_queue,
allocate it dynamically, reference count it, and free it when the last
reference is dropped. Currently only request_queue holds the reference
but in the following patch we add other users referencing
backing_dev_info.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 33 insertions, 1 deletions

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 3bfed5ab2475..28ce6cf7b2ff 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -237,6 +237,7 @@ static __init int bdi_class_init(void)
 
         bdi_class->dev_groups = bdi_dev_groups;
         bdi_debug_init();
+
         return 0;
 }
 postcore_initcall(bdi_class_init);
@@ -776,6 +777,7 @@ int bdi_init(struct backing_dev_info *bdi)
 
         bdi->dev = NULL;
 
+        kref_init(&bdi->refcnt);
         bdi->min_ratio = 0;
         bdi->max_ratio = 100;
         bdi->max_prop_frac = FPROP_FRAC_BASE;
@@ -791,6 +793,22 @@ int bdi_init(struct backing_dev_info *bdi)
 }
 EXPORT_SYMBOL(bdi_init);
 
+struct backing_dev_info *bdi_alloc_node(gfp_t gfp_mask, int node_id)
+{
+        struct backing_dev_info *bdi;
+
+        bdi = kmalloc_node(sizeof(struct backing_dev_info),
+                           gfp_mask | __GFP_ZERO, node_id);
+        if (!bdi)
+                return NULL;
+
+        if (bdi_init(bdi)) {
+                kfree(bdi);
+                return NULL;
+        }
+        return bdi;
+}
+
 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
                 const char *fmt, ...)
 {
@@ -871,12 +889,26 @@ void bdi_unregister(struct backing_dev_info *bdi)
         }
 }
 
-void bdi_exit(struct backing_dev_info *bdi)
+static void bdi_exit(struct backing_dev_info *bdi)
 {
         WARN_ON_ONCE(bdi->dev);
         wb_exit(&bdi->wb);
 }
 
+static void release_bdi(struct kref *ref)
+{
+        struct backing_dev_info *bdi =
+                        container_of(ref, struct backing_dev_info, refcnt);
+
+        bdi_exit(bdi);
+        kfree(bdi);
+}
+
+void bdi_put(struct backing_dev_info *bdi)
+{
+        kref_put(&bdi->refcnt, release_bdi);
+}
+
 void bdi_destroy(struct backing_dev_info *bdi)
 {
         bdi_unregister(bdi);