linux-kernel - Re: [PATCH v2] mm/hmm/test: use xa_for_each

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Date:   Tue, 19 May 2020 16:50:40 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Ralph Campbell <rcampbell@...dia.com>
Cc:     linux-rdma@...r.kernel.org, linux-mm@...ck.org,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jerome Glisse <jglisse@...hat.com>,
        John Hubbard <jhubbard@...dia.com>,
        Christoph Hellwig <hch@....de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Shuah Khan <shuah@...nel.org>
Subject: Re: [PATCH v2] mm/hmm/test: use xa_for_each_range instead of looping

On Fri, May 15, 2020 at 06:04:24PM -0700, Ralph Campbell wrote:
> The test driver uses an xa_array to store virtual to physical address
> translations for a simulated hardware device. The MMU notifier
> invalidation callback is used to keep the table consistent with the CPU
> page table and is frequently called only for a page or two. However, if
> the test process exits unexpectedly or is killed, the range can be
> [0..ULONG_MAX] in which case calling xa_erase() for every possible PFN
> results in CPU timeouts.
> Use xa_for_each_range() to efficiently erase entries in the range.
> 
> Signed-off-by: Ralph Campbell <rcampbell@...dia.com>
> ---
> 
> This patch is based on Jason Gunthorpe's hmm tree and should be folded
> into the ("mm/hmm/test: add selftest driver for HMM") patch once this
> patch is reviewed, etc.
> 
> v1 -> v2:
> Use xa_for_each_range() instead of special casing [0..ULONG_MAX].
> 
>  lib/test_hmm.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)

I squashed this in

Thanks,
Jason