bdi: add a ->dev_name field to struct backing_dev_info

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: 68f23b8 ("memcg: fix a crash in wb_workfn when a device disappears") Reported-by: Yufen Yu <[email protected]> Signed-off-by: Christoph Hellwig <[email protected]> Reviewed-by: Jan Kara <[email protected]> Reviewed-by: Bart Van Assche <[email protected]> Signed-off-by: Jens Axboe <[email protected]>
josf · May 9, 2020 · 6bd87ee · 6bd87ee
1 parent d51cfc5
commit 6bd87ee
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Showing 2 changed files with 4 additions and 2 deletions.
diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h
@@ -219,6 +219,7 @@ 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
@@ -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);