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Date: Mon, 20 May 2024 18:03:11 -0400
From: Mike Snitzer <snitzer@kernel.org>
To: Christoph Hellwig <hch@lst.de>, Theodore Ts'o <tytso@mit.edu>
Cc: dm-devel@lists.linux.dev, fstests@vger.kernel.org,
	linux-ext4@vger.kernel.org, regressions@lists.linux.dev,
	linux-block@vger.kernel.org
Subject: Re: dm: use queue_limits_set
Message-ID: <ZkvIn73jAqz94LjI@kernel.org>
References: <20240518022646.GA450709@mit.edu>
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 <20240520201237.GA6235@lst.de>
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In-Reply-To: <20240520201237.GA6235@lst.de>

On Mon, May 20, 2024 at 10:12:37PM +0200, Christoph Hellwig wrote:
> On Mon, May 20, 2024 at 01:17:46PM -0400, Mike Snitzer wrote:
> > Doubt there was anything in fstests setting max discard user limit
> > (max_user_discard_sectors) in Ted's case. blk_set_stacking_limits()
> > sets max_user_discard_sectors to UINT_MAX, so given the use of
> > min(lim->max_hw_discard_sectors, lim->max_user_discard_sectors) I
> > suspect blk_stack_limits() stacks up max_discard_sectors to match the
> > underlying storage's max_hw_discard_sectors.
> > 
> > And max_hw_discard_sectors exceeds BIO_PRISON_MAX_RANGE, resulting in
> > dm_cell_key_has_valid_range() triggering on:
> > WARN_ON_ONCE(key->block_end - key->block_begin > BIO_PRISON_MAX_RANGE)
> 
> Oh, that makes more sense.
> 
> I think you just want to set the max_hw_discard_sectors limit before
> stacking in the lower device limits so that they can only lower it.
> 
> (and in the long run we should just stop stacking the limits except
> for request based dm which really needs it)

This is what I staged, I cannot send a patch out right now.. 

Ted if you need the patch in email (rather than from linux-dm.git) I
can send it later tonight.  Please see:

https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-6.10&id=825d8bbd2f32cb229c3b6653bd454832c3c20acb