[PATCH 4.19 09/16] bdi: add a ->dev_name field to struct backing_dev_info

Greg Kroah-Hartman
2021-08-06T08:19:57Z

From: Christoph Hellwig <hch@lst.de>

[ 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@huawei.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/linux/backing-dev-defs.h | 1 +
mm/backing-dev.c | 5 +++--
2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h
index 07e02d6df5ad..65d47522413c 100644
--- a/include/linux/backing-dev-defs.h
+++ b/include/linux/backing-dev-defs.h
@@ -197,6 +197,7 @@ 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 8501b033bca8..1d37c80d023a 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -880,7 +880,8 @@ 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);

@@ -980,7 +981,7 @@ 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);

--
2.30.2