linux-kernel - Re: [PATCH v5 77/78] irqdomain: Convert to XArray

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Date:   Sat, 16 Dec 2017 10:51:05 +0000
From:   Marc Zyngier <marc.zyngier@....com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     linux-kernel@...r.kernel.org,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        Ross Zwisler <ross.zwisler@...ux.intel.com>,
        David Howells <dhowells@...hat.com>,
        Shaohua Li <shli@...nel.org>, Jens Axboe <axboe@...nel.dk>,
        Rehas Sachdeva <aquannie@...il.com>, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-nilfs@...r.kernel.org, linux-btrfs@...r.kernel.org,
        linux-xfs@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-raid@...r.kernel.org
Subject: Re: [PATCH v5 77/78] irqdomain: Convert to XArray

On Fri, 15 Dec 2017 22:04:49 +0000,
Matthew Wilcox wrote:
> 
> From: Matthew Wilcox <mawilcox@...rosoft.com>
> 
> In a non-critical path, irqdomain wants to know how many entries are
> stored in the xarray, so add xa_count().  This is a pretty straightforward
> conversion; mostly just removing now-redundant locking.  The only thing
> of note is just how much simpler irq_domain_fix_revmap() becomes.
> 
> Signed-off-by: Matthew Wilcox <mawilcox@...rosoft.com>
> ---
>  include/linux/irqdomain.h | 10 ++++------
>  include/linux/xarray.h    |  1 +
>  kernel/irq/irqdomain.c    | 39 ++++++++++-----------------------------
>  lib/xarray.c              | 25 +++++++++++++++++++++++++
>  4 files changed, 40 insertions(+), 35 deletions(-)

I certainly welcome the simplification this provides.

As for xa_count(), I'm trying to convince myself that the code under
CONFIG_IRQ_DOMAIN_DEBUG is now completely superseded by
CONFIG_GENERIC_IRQ_DEBUGFS, and that there would be more value in
getting rid of it rather than keeping it on life support.

Until then, the 1:1 replacement is good enough.

Acked-by: Marc Zyngier <marc.zyngier@....com>

	M.