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Date: Fri, 31 Oct 2025 10:09:25 +0100
From: Christoph Hellwig <hch@lst.de>
To: Gao Xiang <hsiangkao@linux.alibaba.com>
Cc: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
	Jan Kara <jack@suse.cz>, Christian Brauner <brauner@kernel.org>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	Jason Wang <jasowang@redhat.com>,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	Luis Chamberlain <mcgrof@kernel.org>, linux-block@vger.kernel.org,
	Joseph Qi <joseph.qi@linux.alibaba.com>,
	guanghuifeng@linux.alibaba.com, zongyong.wzy@alibaba-inc.com,
	zyfjeff@linux.alibaba.com
Subject: Re: question about bd_inode hashing against device_add() // Re:
 [PATCH 03/11] block: call bdev_add later in device_add_disk
Message-ID: <20251031090925.GA9379@lst.de>
References: <20210818144542.19305-1-hch@lst.de> <20210818144542.19305-4-hch@lst.de> <43375218-2a80-4a7a-b8bb-465f6419b595@linux.alibaba.com>
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On Fri, Oct 31, 2025 at 03:46:02PM +0800, Gao Xiang wrote:
> From my understanding, before this commit, bdev_add() will
> be called prior to device_add() so insert_inode_hash()
> in bdev_add() will be called before users can see blkdev
> in the devtmpfs.
>
> But after this change, blkdev can be seen before
> insert_inode_hash(), which opens a race (although I'm not
> sure if it's an expected behavior) blkdev_get_no_open() will
> find nothing (e.g. mounting) even blkdev in devtmpfs is
> there.

We're not supposed to see the uevent notification before the
block device is ready.  Do you see that earlier, or do you have
code busy polling for a node?