linux-kernel - Re: [PATCH v5 02/11] block: Block Device Filtering Mechanism

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Message-ID: <90f79cf3-86a2-02c0-1887-d3490f9848bb@veeam.com>
Date:   Mon, 17 Jul 2023 16:39:52 +0200
From:   Sergei Shtepa <sergei.shtepa@...am.com>
To:     Yu Kuai <yukuai1@...weicloud.com>, <axboe@...nel.dk>,
        <hch@...radead.org>, <corbet@....net>, <snitzer@...nel.org>
CC:     <viro@...iv.linux.org.uk>, <brauner@...nel.org>,
        <dchinner@...hat.com>, <willy@...radead.org>, <dlemoal@...nel.org>,
        <linux@...ssschuh.net>, <jack@...e.cz>, <ming.lei@...hat.com>,
        <linux-block@...r.kernel.org>, <linux-doc@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>,
        Donald Buczek <buczek@...gen.mpg.de>,
        "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH v5 02/11] block: Block Device Filtering Mechanism

On 7/11/23 04:02, Yu Kuai wrote:
> bdev_disk_changed() is not handled, where delete_partition() and
> add_partition() will be called, this means blkfilter for partiton will
> be removed after partition rescan. Am I missing something?

Yes, when the bdev_disk_changed() is called, all disk block devices
are deleted and new ones are re-created. Therefore, the information
about the attached filters will be lost. This is equivalent to
removing the disk and adding it back.

For the blksnap module, partition rescan will mean the loss of the
change trackers data. If a snapshot was created, then such
a partition rescan will cause the snapshot to be corrupted.

There was an idea to do filtering at the disk level,
but I abandoned it.