From: Matthew Wilcox <willy@infradead.org>
To: Russell King - ARM Linux <linux@armlinux.org.uk>
Cc: Souptick Joarder <jrdr.linux@gmail.com>,
miguel.ojeda.sandonis@gmail.com, robin@protonic.nl,
stefanr@s5r6.in-berlin.de, hjc@rock-chips.com, heiko@sntech.de,
airlied@linux.ie, robin.murphy@arm.com, iamjoonsoo.kim@lge.com,
akpm@linux-foundation.org, m.szyprowski@samsung.com,
keescook@chromium.org, treding@nvidia.com, mhocko@suse.com,
dan.j.williams@intel.com, kirill.shutemov@linux.intel.com,
mark.rutland@arm.com, aryabinin@virtuozzo.com,
dvyukov@google.com, kstewart@linuxfoundation.org,
tchibo@google.com, riel@redhat.com, minchan@kernel.org,
peterz@infradead.org, ying.huang@intel.com, ak@linux.intel.com,
rppt@linux.vnet.ibm.com, linux@dominikbrodowski.net,
arnd@arndb.de, cpandya@codeaurora.org, hannes@cmpxchg.org,
joe@perches.com, mcgrof@kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org,
linux1394-devel@lists.sourceforge.net,
dri-devel@lists.freedesktop.org,
linux-rockchip@lists.infradead.org, linux-mm@kvack.org
Subject: Re: [PATCH v2] mm: Introduce new function vm_insert_kmem_page
Date: Wed, 3 Oct 2018 17:39:56 -0700 [thread overview]
Message-ID: <20181004003956.GA31522@bombadil.infradead.org> (raw)
In-Reply-To: <20181003221444.GZ30658@n2100.armlinux.org.uk>
On Wed, Oct 03, 2018 at 11:14:45PM +0100, Russell King - ARM Linux wrote:
> On Wed, Oct 03, 2018 at 01:00:03PM -0700, Matthew Wilcox wrote:
> > On Thu, Oct 04, 2018 at 12:28:54AM +0530, Souptick Joarder wrote:
> > > These are the approaches which could have been taken to handle
> > > this scenario -
> > >
> > > * Replace vm_insert_page with vmf_insert_page and then write few
> > > extra lines of code to convert VM_FAULT_CODE to errno which
> > > makes driver users more complex ( also the reverse mapping errno to
> > > VM_FAULT_CODE have been cleaned up as part of vm_fault_t migration ,
> > > not preferred to introduce anything similar again)
> > >
> > > * Maintain both vm_insert_page and vmf_insert_page and use it in
> > > respective places. But it won't gurantee that vm_insert_page will
> > > never be used in #PF context.
> > >
> > > * Introduce a similar API like vm_insert_page, convert all non #PF
> > > consumer to use it and finally remove vm_insert_page by converting
> > > it to vmf_insert_page.
> > >
> > > And the 3rd approach was taken by introducing vm_insert_kmem_page().
> > >
> > > In short, vmf_insert_page will be used in page fault handlers
> > > context and vm_insert_kmem_page will be used to map kernel
> > > memory to user vma outside page fault handlers context.
> >
> > As far as I can tell, vm_insert_kmem_page() is line-for-line identical
> > with vm_insert_page(). Seriously, here's a diff I just did:
[...]
> > What on earth are you trying to do?
>
> Reading the commit log, it seems that the intention is to split out
> vm_insert_page() used outside of page-fault handling with the use
> within page-fault handling, so that different return codes can be
> used.
Right, but we already did that. We now have vmf_insert_page() which
returns a VM_FAULT_* code and vm_insert_page() which returns an errno.
next prev parent reply other threads:[~2018-10-04 0:40 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-03 18:58 [PATCH v2] mm: Introduce new function vm_insert_kmem_page Souptick Joarder
2018-10-03 19:58 ` Miguel Ojeda
2018-10-04 11:56 ` Souptick Joarder
2018-10-03 20:00 ` Matthew Wilcox
2018-10-03 22:14 ` Russell King - ARM Linux
2018-10-04 0:39 ` Matthew Wilcox [this message]
2018-10-04 12:15 ` Souptick Joarder
2018-10-04 12:34 ` Russell King - ARM Linux
2018-10-04 18:12 ` Souptick Joarder
2018-10-04 18:17 ` Matthew Wilcox
2018-10-04 18:53 ` Souptick Joarder
2018-10-04 19:46 ` Miguel Ojeda
2018-10-05 5:50 ` Souptick Joarder
2018-10-05 8:52 ` Miguel Ojeda
2018-10-05 10:01 ` Souptick Joarder
2018-10-05 10:49 ` Miguel Ojeda
2018-10-05 12:11 ` Souptick Joarder
2018-10-05 18:09 ` Miguel Ojeda
2018-10-06 5:14 ` Souptick Joarder
2018-10-06 10:49 ` Miguel Ojeda
2018-10-23 12:14 ` Souptick Joarder
2018-10-23 12:24 ` Matthew Wilcox
2018-10-23 12:33 ` Souptick Joarder
2018-10-23 12:59 ` Matthew Wilcox
2018-10-23 13:15 ` Souptick Joarder
2018-10-04 18:21 ` Souptick Joarder
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