Patch "bdi: add a ->dev_name field to struct backing_dev_info" has been added to the 5.6-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    bdi: add a ->dev_name field to struct backing_dev_info

to the 5.6-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     bdi-add-a-dev_name-field-to-struct-backing_dev_info.patch
and it can be found in the queue-5.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit e598a50997574ec269cb929840825a615c9fdf9b
Author: Christoph Hellwig <hch@xxxxxx>
Date:   Mon May 4 14:47:56 2020 +0200

    bdi: add a ->dev_name field to struct backing_dev_info
    
    [ Upstream commit 6bd87eec23cbc9ed222bed0f5b5b02bf300e9a8d ]
    
    Cache a copy of the name for the life time of the backing_dev_info
    structure so that we can reference it even after unregistering.
    
    Fixes: 68f23b89067f ("memcg: fix a crash in wb_workfn when a device disappears")
    Reported-by: Yufen Yu <yuyufen@xxxxxxxxxx>
    Signed-off-by: Christoph Hellwig <hch@xxxxxx>
    Reviewed-by: Jan Kara <jack@xxxxxxx>
    Reviewed-by: Bart Van Assche <bvanassche@xxxxxxx>
    Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h
index 4fc87dee005ab..2849bdbb3acbe 100644
--- a/include/linux/backing-dev-defs.h
+++ b/include/linux/backing-dev-defs.h
@@ -220,6 +220,7 @@ struct backing_dev_info {
 	wait_queue_head_t wb_waitq;
 
 	struct device *dev;
+	char dev_name[64];
 	struct device *owner;
 
 	struct timer_list laptop_mode_wb_timer;
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 680e5028d0fc5..3f2480e4c5af3 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -938,7 +938,8 @@ int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args)
 	if (bdi->dev)	/* The driver needs to use separate queues per device */
 		return 0;
 
-	dev = device_create_vargs(bdi_class, NULL, MKDEV(0, 0), bdi, fmt, args);
+	vsnprintf(bdi->dev_name, sizeof(bdi->dev_name), fmt, args);
+	dev = device_create(bdi_class, NULL, MKDEV(0, 0), bdi, bdi->dev_name);
 	if (IS_ERR(dev))
 		return PTR_ERR(dev);
 
@@ -1047,7 +1048,7 @@ const char *bdi_dev_name(struct backing_dev_info *bdi)
 {
 	if (!bdi || !bdi->dev)
 		return bdi_unknown_name;
-	return dev_name(bdi->dev);
+	return bdi->dev_name;
 }
 EXPORT_SYMBOL_GPL(bdi_dev_name);