From: Christoph Hellwig <hch@lst.de>
To: Christian Brauner <brauner@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>, 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: Tue, 16 Jun 2026 14:34:43 +0200 [thread overview]
Message-ID: <20260616123443.GA21024@lst.de> (raw)
In-Reply-To: <20260602-work-super-bdev_holder_global-v1-2-bb0fd82f3861@kernel.org>
On Tue, Jun 02, 2026 at 12:10:08PM +0200, Christian Brauner wrote:
> fs_holder_ops recovers the owning superblock from bdev->bd_holder, which
> forces the holder to be exactly one superblock and prevents several
> superblocks from sharing one block device. That's what erofs is doing.
>
> Introduce a global dev_t-keyed rhltable mapping each block device to the
> superblock(s) using it. The holder argument becomes purely the block
> layer's exclusivity token (a superblock, or a file_system_type for
> shared devices) and is no longer needed by the fs specific callbacks.
Err, no. block devices need to have a specific owner. If erofs wants
to share a device between superblock it needs to come up with an entity
that owns the block devices which is not a superblock.
IMHO sharing devices between superblocks is a bad idea, but that ship
has sailed, but please keep it contained inside of erofs.
next prev parent reply other threads:[~2026-06-16 12:40 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 [this message]
2026-06-16 14:59 ` Christian Brauner
2026-06-16 15:19 ` Christian Brauner
2026-06-16 16:35 ` Gao Xiang
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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