Linux block layer
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From: Gao Xiang <hsiangkao@linux.alibaba.com>
To: Christoph Hellwig <hch@lst.de>, Christian Brauner <brauner@kernel.org>
Cc: Jan Kara <jack@suse.cz>, Jens Axboe <axboe@kernel.dk>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, Carlos Maiolino <cem@kernel.org>,
	linux-xfs@vger.kernel.org, Chris Mason <clm@fb.com>,
	David Sterba <dsterba@suse.com>,
	linux-btrfs@vger.kernel.org, Theodore Ts'o <tytso@mit.edu>,
	linux-ext4@vger.kernel.org, Gao Xiang <xiang@kernel.org>,
	linux-erofs@lists.ozlabs.org
Subject: Re: [PATCH RFC 2/8] fs: add a global device to super block hash table
Date: Wed, 17 Jun 2026 00:35:48 +0800	[thread overview]
Message-ID: <8f1c032b-b951-4d0d-93fa-229248993f2c@linux.alibaba.com> (raw)
In-Reply-To: <20260616123443.GA21024@lst.de>



On 2026/6/16 20:34, Christoph Hellwig wrote:

> IMHO sharing devices between superblocks is a bad idea, but that ship
> has sailed, but please keep it contained inside of erofs.

I'm not sure why it's a bad idea, for example,
the immutable layer model is already applied to layered virtual
block formats (such as qcow2) and layered fs like overlayfs.

and I think device mappers may have some similar immutable
approaches as shared layers but works in a slight different
way.

The principle is that each instance uses shared blobs in a
read-only way, and that is almost a simple and safest way
to share data among filesystem instances.

Yet I don't want to argue with that since it's pretty common
for years and I've seen no practical risk using this model.

Thanks,
Gao Xiang

  parent reply	other threads:[~2026-06-16 16:36 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-06-02 10:10 [PATCH RFC 0/8] fs: support freeze/thaw/mark_dead/sync with shared devices Christian Brauner
2026-06-02 10:10 ` [PATCH RFC 1/8] fs, block: move blk_mode_t and fop_flags_t into <linux/types.h> Christian Brauner
2026-06-08  9:57   ` Jan Kara
2026-06-02 10:10 ` [PATCH RFC 2/8] fs: add a global device to super block hash table Christian Brauner
2026-06-08 10:14   ` Jan Kara
2026-06-16 12:34   ` Christoph Hellwig
2026-06-16 14:59     ` Christian Brauner
2026-06-16 15:19       ` Christian Brauner
2026-06-16 16:35     ` Gao Xiang [this message]
2026-06-02 10:10 ` [PATCH RFC 3/8] fs: refuse to claim any frozen block device Christian Brauner
2026-06-08 10:01   ` Jan Kara
2026-06-02 10:10 ` [PATCH RFC 4/8] xfs: port to fs_bdev_file_open_by_path() Christian Brauner
2026-06-08 10:15   ` Jan Kara
2026-06-02 10:10 ` [PATCH RFC 5/8] btrfs: open via dedicated fs bdev helpers Christian Brauner
2026-06-02 10:10 ` [PATCH RFC 6/8] ext4: " Christian Brauner
2026-06-08 10:18   ` Jan Kara
2026-06-02 10:10 ` [PATCH RFC 7/8] erofs: " Christian Brauner
2026-06-02 16:25   ` Gao Xiang
2026-06-03 13:42     ` Christian Brauner
2026-06-10  6:55       ` Gao Xiang
2026-06-02 10:10 ` [PATCH RFC 8/8] super: make fs_holder_ops private Christian Brauner
2026-06-08 10:18   ` Jan Kara
2026-06-02 16:12 ` [PATCH RFC 0/8] fs: support freeze/thaw/mark_dead/sync with shared devices Gao Xiang
2026-06-03  6:43 ` [syzbot ci] " syzbot ci

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