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Date: Mon, 9 Dec 2024 09:21:24 +0100
From: Christoph Hellwig <hch@lst.de>
To: Damien Le Moal <dlemoal@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>, linux-block@vger.kernel.org,
	Jens Axboe <axboe@kernel.dk>, Mike Snitzer <snitzer@kernel.org>,
	Mikulas Patocka <mpatocka@redhat.com>, dm-devel@lists.linux.dev,
	Bart Van Assche <bvanassche@acm.org>
Subject: Re: [PATCH v2 3/4] block: Prevent potential deadlocks in zone
 write plug error recovery
Message-ID: <20241209082124.GA25530@lst.de>
References: <20241208225758.219228-1-dlemoal@kernel.org> <20241208225758.219228-4-dlemoal@kernel.org> <20241209075743.GD24323@lst.de> <3496570f-d434-42e9-b06f-51a1305f0555@kernel.org>
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On Mon, Dec 09, 2024 at 05:18:00PM +0900, Damien Le Moal wrote:
> 
> Yep. But even that one is actually coded in scsi to return a -EIO instead of
> ENOTSUPP. We can patch that (return ENOTSUPP for an invalid opcode error), but I
> am not sure if that is safe to do given that this has been like this for ages.
> 
> This is all to say that we cannot even reliably distinguish special/valid error
> cases that can be recovered from actual medium/hard errors.

I think we can't change the return value, as the whole thing is messy.
I just meant EOPNOTSUP-like.  The exact error should not matter for
the handling anyway, just reasoning about use cases.

> I have test cases for zonefs already. That is because zonefs has the
> "recover-error" mount option which forces a recovery of a file size (== write
> pointer position) if a write fails or is torn. The default even for zonefs is to
> go read-only since there is indeed not much we can do about failed writes.

Yes, that іs the sensible way to handle errors as far as I'm conerned.