From: Michal Hocko <mhocko@kernel.org>
To: Logan Gunthorpe <logang@deltatee.com>
Cc: David Hildenbrand <david@redhat.com>,
Dan Williams <dan.j.williams@intel.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
linux-ia64@vger.kernel.org,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
linux-s390 <linux-s390@vger.kernel.org>,
Linux-sh <linux-sh@vger.kernel.org>,
platform-driver-x86@vger.kernel.org,
Linux MM <linux-mm@kvack.org>, Christoph Hellwig <hch@lst.de>,
Andrew Morton <akpm@linux-foundation.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH 5/6] mm, memory_hotplug: Provide argument for the pgprot_t in arch_add_memory()
Date: Wed, 11 Dec 2019 09:37:45 +0100 [thread overview]
Message-ID: <20191211083745.GA14655@dhcp22.suse.cz> (raw)
In-Reply-To: <297b7cc0-c5bc-a4c6-83eb-afc008395234@deltatee.com>
On Tue 10-12-19 16:52:31, Logan Gunthorpe wrote:
[...]
> In my opinion, having a coder and reviewer see PAGE_KERNEL and ask if
> that makes sense is a benefit. Having it hidden because we don't want
> people to think about it is worse, harder to understand and results in
> bugs that are more difficult to spot.
My experience would disagree here. We have several examples in the MM
where an overly complex and versatile APIs led to suble bugs, a lot of
copy&pasting and cargo cult programing (just look at the page allocator
as a shiny example - e.g. gfp_flags). So I am always trying to be
carefull here.
> Though, we may be overthinking this: arch_add_memory() is a low level
> non-exported API that's currently used in exactly two places.
This is a fair argument. Most users are and should be using
add_memory().
> I don't
> think there's going to be many, if any, valid new use cases coming up
> for it in the future. That's more what memremap_pages() is for.
OK, fair enough. If this is indeed the simplest way forward then I will
not stand in the way.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2019-12-11 8:37 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-09 19:13 [PATCH 0/6] Allow setting caching mode in arch_add_memory() for P2PDMA Logan Gunthorpe
2019-12-09 19:13 ` [PATCH 1/6] x86/mm: Thread pgprot_t through init_memory_mapping() Logan Gunthorpe
2019-12-09 19:13 ` [PATCH 2/6] x86/mm: Introduce _set_memory_prot() Logan Gunthorpe
2019-12-09 19:13 ` [PATCH 3/6] powerpc/mm: Thread pgprot_t through create_section_mapping() Logan Gunthorpe
2019-12-09 19:13 ` [PATCH 4/6] s390/mm: Thread pgprot_t through vmem_add_mapping() Logan Gunthorpe
2019-12-09 19:13 ` [PATCH 5/6] mm, memory_hotplug: Provide argument for the pgprot_t in arch_add_memory() Logan Gunthorpe
2019-12-09 19:23 ` David Hildenbrand
2019-12-09 20:24 ` Logan Gunthorpe
2019-12-09 20:41 ` Michal Hocko
2019-12-09 21:00 ` Dan Williams
2019-12-09 21:27 ` Logan Gunthorpe
2019-12-09 21:24 ` Logan Gunthorpe
2019-12-10 9:56 ` Michal Hocko
2019-12-09 20:43 ` Dan Williams
2019-12-09 20:52 ` David Hildenbrand
2019-12-10 10:04 ` Michal Hocko
2019-12-10 10:09 ` David Hildenbrand
2019-12-10 10:34 ` Michal Hocko
2019-12-10 11:25 ` David Hildenbrand
2019-12-10 23:52 ` Logan Gunthorpe
2019-12-11 8:37 ` Michal Hocko [this message]
2019-12-09 19:13 ` [PATCH 6/6] mm/memremap: Set caching mode for PCI P2PDMA memory to WC Logan Gunthorpe
2019-12-09 20:43 ` [PATCH 0/6] Allow setting caching mode in arch_add_memory() for P2PDMA Christoph Hellwig
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