linux-kernel - Re: [PATCH] dmapool: push new blocks in ascending order

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Message-ID: <Y/UIZC+plt9Y0nr1@kbusch-mbp>
Date:   Tue, 21 Feb 2023 11:07:32 -0700
From:   Keith Busch <kbusch@...nel.org>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Keith Busch <kbusch@...a.com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Bryan O'Donoghue <bryan.odonoghue@...aro.org>
Subject: Re: [PATCH] dmapool: push new blocks in ascending order

On Tue, Feb 21, 2023 at 10:02:34AM -0800, Christoph Hellwig wrote:
> On Tue, Feb 21, 2023 at 08:54:00AM -0800, Keith Busch wrote:
> > From: Keith Busch <kbusch@...nel.org>
> > 
> > Some users of the dmapool need their allocations to happen in ascending
> > order. The recent optimizations pushed the blocks in reverse order, so
> > restore the previous behavior by linking the next available block from
> > low-to-high.
> 
> Who are those users?
> 
> Also should we document this behavior somewhere so that it isn't
> accidentally changed again some time in the future?

usb/chipidea/udc.c qh_pool called "ci_hw_qh". My initial thought was dmapool
isn't the right API if you need a specific order when allocating from it, but I
can't readily test any changes to that driver. Restoring the previous behavior
is easy enough.