linux-kernel - Re: [PATCH 10/28] mm: only allow page table mappings for built-in zsmalloc

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Message-ID: <20200409165030.GG20713@hirez.programming.kicks-ass.net>
Date:   Thu, 9 Apr 2020 18:50:30 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Minchan Kim <minchan@...nel.org>
Cc:     Christoph Hellwig <hch@....de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>, x86@...nel.org,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Laura Abbott <labbott@...hat.com>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Nitin Gupta <ngupta@...are.org>,
        Robin Murphy <robin.murphy@....com>,
        Christophe Leroy <christophe.leroy@....fr>,
        linuxppc-dev@...ts.ozlabs.org, linux-hyperv@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org,
        linux-arch@...r.kernel.org, linux-mm@...ck.org,
        iommu@...ts.linux-foundation.org,
        linux-arm-kernel@...ts.infradead.org, linux-s390@...r.kernel.org,
        bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
        sergey.senozhatsky@...il.com
Subject: Re: [PATCH 10/28] mm: only allow page table mappings for built-in
 zsmalloc

On Thu, Apr 09, 2020 at 09:08:26AM -0700, Minchan Kim wrote:
> On Wed, Apr 08, 2020 at 01:59:08PM +0200, Christoph Hellwig wrote:
> > This allows to unexport map_vm_area and unmap_kernel_range, which are
> > rather deep internal and should not be available to modules.
> 
> Even though I don't know how many usecase we have using zsmalloc as
> module(I heard only once by dumb reason), it could affect existing
> users. Thus, please include concrete explanation in the patch to
> justify when the complain occurs.

The justification is 'we can unexport functions that have no sane reason
of being exported in the first place'.

The Changelog pretty much says that.