bcache: store disk name in struct cache and struct cached_dev
Current code uses bdevname() or bio_devname() to reference gendisk disk name when bcache needs to display the disk names in kernel message. It was safe before bcache device failure handling patch set merged in, because when devices are failed, there was deadlock to prevent bcache printing error messages with gendisk disk name. But after the failure handling patch set merged, the deadlock is fixed, so it is possible that the gendisk structure bdev->hd_disk is released when bdevname() is called to reference bdev->bd_disk->disk_name[]. This is why I receive bug report of NULL pointers deference panic. This patch stores gendisk disk name in a buffer inside struct cache and struct cached_dev, then print out the offline device name won't reference bdev->hd_disk anymore. And this patch also avoids extra function calls of bdevname() and bio_devnmae(). Changelog: v3, add Reviewed-by from Hannes. v2, call bdevname() earlier in register_bdev() v1, first version with segguestion from Junhui Tang. Fixes: c7b7bd07 ("bcache: add io_disable to struct cached_dev") Fixes: 5138ac67 ("bcache: fix misleading error message in bch_count_io_errors()") Signed-off-by: NColy Li <colyli@suse.de> Reviewed-by: NHannes Reinecke <hare@suse.com> Signed-off-by: NJens Axboe <axboe@kernel.dk>
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