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Date:   Tue, 1 Aug 2023 19:18:38 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Pintu Agarwal <pintu.ping@gmail.com>
Cc:     Christoph Hellwig <hch@lst.de>,
        Pintu Kumar <quic_pintu@quicinc.com>,
        linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
        linux-mm@kvack.org, m.szyprowski@samsung.com, robin.murphy@arm.com,
        iommu@lists.linux.dev, Sumit Semwal <sumit.semwal@linaro.org>,
        Benjamin Gaignard <benjamin.gaignard@collabora.com>,
        Liam Mark <lmark@codeaurora.org>,
        Laura Abbott <labbott@redhat.com>,
        Brian Starkey <Brian.Starkey@arm.com>,
        John Stultz <jstultz@google.com>,
        Christian =?iso-8859-1?Q?K=F6nig?= <christian.koenig@amd.com>,
        linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org,
        linaro-mm-sig@lists.linaro.org
Subject: Re: [PATCH v2] dma-contiguous: define proper name for global cma
 region
Message-ID: <20230801171838.GA14599@lst.de>
References: <1690598115-26287-1-git-send-email-quic_pintu@quicinc.com> <20230731112155.GA3662@lst.de> <CAOuPNLjnfq1JefngtNrg0Q+JdMTSRz+eEqxGQJFfx9+af+k9WA@mail.gmail.com>
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On Tue, Aug 01, 2023 at 10:42:42PM +0530, Pintu Agarwal wrote:
> > I agree that reserved is not a very useful name.  Unfortuately the
> > name of the region leaks to userspace through cma_heap.
> >
> > So I think we need prep patches to hardcode "reserved" in
> > add_default_cma_heap first, and then remove the cma_get_name
> > first.
> 
> Sorry, but I could not fully understand your comments.
> Can you please elaborate a little more what changes are required in
> cma_heap if we change "reserved" to "global-cma-region" ?

Step 1:

Instead of setting exp_info.name to cma_get_name(cma);
in __add_cma_heap just set it to "reserved", probably by passing a name
argument.  You can also remove the unused data argument to __add_cma_heap
and/or just fold that function into the only caller while you're at it.

Step 2:

Remove cma_get_name, as it is unused now.

Step 3:

The patch your previously sent.

> You mean to say there are userspace tools that rely on this "reserved"
> naming for global cma ?

Yes.