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Date: Wed, 19 Nov 2025 08:58:00 +0100
From: Christoph Hellwig <hch@lst.de>
To: Bart Van Assche <bvanassche@acm.org>
Cc: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
	Damien Le Moal <dlemoal@kernel.org>,
	Mike Snitzer <snitzer@kernel.org>,
	Mikulas Patocka <mpatocka@redhat.com>, linux-block@vger.kernel.org,
	dm-devel@lists.linux.dev
Subject: Re: add a flag to allow underordered zoned writes
Message-ID: <20251119075800.GA23083@lst.de>
References: <20251118070321.2367097-1-hch@lst.de> <f385de59-5bef-4ddf-b363-edf76f88d855@acm.org>
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On Tue, Nov 18, 2025 at 10:10:33PM -0800, Bart Van Assche wrote:
> Is the following deadlock inherent to this approach?
> - Several bios are present on zwplug->bio_list and these bios cannot be
>   submitted because their starting offset is past the write pointer.
> - No new bios can be allocated because all memory is in use.
> - A deadlock occurs because none of the queued bios can be submitted
>   and no new bio can be allocated.

This can if the number of in-flight bios is larger than bio mempool
reserve.  Which is real, but we also have this in various other
submitters that hold bios to submit in a list.  This suggests it is
mostly theoretical, but I'd still love to address it for all these
cases.