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

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Message-ID: <ZLjQ0YfH7JyQyMyJ@infradead.org>
Date:   Wed, 19 Jul 2023 23:14:41 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Yu Kuai <yukuai1@...weicloud.com>
Cc:     Sergei Shtepa <sergei.shtepa@...am.com>, axboe@...nel.dk,
        hch@...radead.org, corbet@....net, snitzer@...nel.org,
        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 Tue, Jul 18, 2023 at 09:37:33AM +0800, Yu Kuai wrote:
> I haven't review blksnap code yet, but this sounds like a problem.
> 
> possible solutions I have in mind:
> 
> 1. Store blkfilter for each partition from bdev_disk_changed() before
> delete_partition(), and add blkfilter back after add_partition().
> 
> 2. Store blkfilter from gendisk as a xarray, and protect it by
> 'open_mutex' like 'part_tbl', block_device can keep the pointer to
> reference blkfilter so that performance from fast path is ok, and the
> lifetime of blkfiter can be managed separately.

The whole point of bdev_disk_changed is that the partitions might not
be the same ones as before..