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Date:   Wed, 18 Oct 2023 08:46:46 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Ming Lei <ming.lei@redhat.com>
Cc:     Christoph Hellwig <hch@lst.de>,
        Christian Brauner <brauner@kernel.org>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Jens Axboe <axboe@kernel.dk>, Jan Kara <jack@suse.cz>,
        Denis Efremov <efremov@linux.com>, linux-block@vger.kernel.org,
        linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 3/5] block: move bdev_mark_dead out of
 disk_check_media_change
Message-ID: <20231018064646.GA18710@lst.de>
References: <20231017184823.1383356-1-hch@lst.de> <20231017184823.1383356-4-hch@lst.de> <ZS9ODABLaRVcI5iy@fedora>
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On Wed, Oct 18, 2023 at 11:16:28AM +0800, Ming Lei wrote:
> On Tue, Oct 17, 2023 at 08:48:21PM +0200, Christoph Hellwig wrote:
> > disk_check_media_change is mostly called from ->open where it makes
> > little sense to mark the file system on the device as dead, as we
> > are just opening it.  So instead of calling bdev_mark_dead from
> > disk_check_media_change move it into the few callers that are not
> > in an open instance.  This avoid calling into bdev_mark_dead and
> > thus taking s_umount with open_mutex held.
> 
> ->open() is called when opening bdev every times, and there can be
> existed openers, so not sure if it makes little sense here.

Yes. It has to be a non-exclusive open, though, and how is that going
to help us with any general use case?  If we really want to make the
media change notifications any useful we'd better just do the work
straight from the workqueue that polls for it.