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Date:   Thu, 27 Apr 2023 04:58:36 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Ming Lei <ming.lei@redhat.com>
Cc:     Theodore Ts'o <tytso@mit.edu>, linux-ext4@vger.kernel.org,
        Andreas Dilger <adilger.kernel@dilger.ca>,
        linux-block@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
        Dave Chinner <dchinner@redhat.com>,
        Eric Sandeen <sandeen@redhat.com>,
        Christoph Hellwig <hch@lst.de>, Zhang Yi <yi.zhang@redhat.com>
Subject: Re: [ext4 io hang] buffered write io hang in balance_dirty_pages
Message-ID: <ZEny7Izr8iOc/23B@casper.infradead.org>
References: <ZEnb7KuOWmu5P+V9@ovpn-8-24.pek2.redhat.com>
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On Thu, Apr 27, 2023 at 10:20:28AM +0800, Ming Lei wrote:
> Hello Guys,
> 
> I got one report in which buffered write IO hangs in balance_dirty_pages,
> after one nvme block device is unplugged physically, then umount can't
> succeed.

That's a feature, not a bug ... the dd should continue indefinitely?

balance_dirty_pages() is sleeping in KILLABLE state, so kill -9 of
the dd process should succeed.