From: Dave Kleikamp <dave.kleikamp@oracle•com>
To: Mel Gorman <mgorman@suse•de>,
Linus Torvalds <torvalds@linux-foundation•org>
Cc: Richard Yao <ryao@gentoo•org>,
Andrew Morton <akpm@linux-foundation•org>,
Rik van Riel <riel@redhat•com>,
Eric Van Hensbergen <ericvh@gmail•com>,
Ron Minnich <rminnich@sandia•gov>,
Latchesar Ionkov <lucho@ionkov•net>,
"David S. Miller" <davem@davemloft•net>,
V9FS Develooper Mailing List
<v9fs-developer@lists•sourceforge.net>,
Linux Netdev Mailing List <netdev@vger•kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger•kernel.org>,
"Aneesh Kumar K.V" <aneesh.kumar@linux•vnet.ibm.com>,
Will Deacon <will.deacon@arm•com>,
Christopher Covington <cov@codeaurora•org>,
Matthew Thode <mthode@mthode•org>,
Al Viro <viro@ZenIV•linux.org.uk>
Subject: Re: [PATCH 1/2] mm/vmalloc: export is_vmalloc_or_module_addr
Date: Mon, 10 Feb 2014 08:40:48 -0600 [thread overview]
Message-ID: <52F8E4F0.5010903@oracle.com> (raw)
In-Reply-To: <20140210121020.GC6732@suse.de>
On 02/10/2014 06:10 AM, Mel Gorman wrote:
> On Sat, Feb 08, 2014 at 11:45:53AM -0800, Linus Torvalds wrote:
>> On Sat, Feb 8, 2014 at 11:12 AM, Richard Yao <ryao@gentoo•org> wrote:
>>> 9p-virtio needs is_vmalloc_or_module_addr exported before a patch can be
>>> merged to prevent the virtio zero-copy routines from triggering a
>>> hypervisor page fault when loading kernel modules:
>>>
>>> https://groups.google.com/forum/#!topic/linux.kernel/eRR7AyLE29Y
>>>
>>> Without this export, the kernel build breaks with that patch applied and
>>> CONFIG_NET_9P_VIRTIO=m. With this export in place, all is well.
>>
>> I absolutely *detest* this patch.
>>
>> Not so much because is_vmalloc_or_module_addr() should never be used,
>> but because the particular use in question is pure and utter garbage.
>>
>> There are valid reasons to use "is_vmalloc_or_module_addr()", but
>> those are along the lines of drivers/char/mem.c, which says "return
>> -ENXIO for this crap".
>>
>> And btw, that horrid crap called "kmap_to_page()" needs to die too.
>> When is it *ever* valid to use a kmap'ed page for IO? Here's a clue:
>> never.
>>
>> <SNIP>
>>
>> Those *disgusting* get_kernel_page[s]() functions came with a
>> commentary about "The initial user is expected to be NFS.." and that
>> is still the *only* user. The fact that *everybody* else has been able
>> to avoid that crap should tell us something.
>
> kmap_to_page, get_kernel_page and the NFS user for it are already scheduled
> for death. Dave Kleikamp has been working on a series "Issue O_DIRECT aio
> using bio_vec" that replaces what NFS currently does with something far
> more sane. The series does not remove the helpers on top, probably because
> of the 9P use of it, but if that was changed then the helpers would finally
> die. I'm not sure why Dave's series never got merged so added him to the
> cc to find out.
The patchset I submitted was too ugly to live. Linus and Al Viro both
had numerous issues with the implementation, but not the overall concept.
Al has the same idea for a io-vector container that can hold either an
iovec or a kernel vector and is starting to work on his own
implementation. Once he settles on the particulars of new
aio_write/aio_read methods, I should be able to get the rest of my
patchset to fall into line with it.
http://www.spinics.net/lists/linux-fsdevel/msg71938.html
Shaggy
next prev parent reply other threads:[~2014-02-10 14:40 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-08 19:12 [PATCH 0/2] Attention by Linus Torvalds needed to export symbol he wrote Richard Yao
2014-02-08 19:12 ` [PATCH 1/2] mm/vmalloc: export is_vmalloc_or_module_addr Richard Yao
2014-02-08 19:45 ` Linus Torvalds
2014-02-08 19:58 ` Richard Yao
2014-02-08 20:06 ` Linus Torvalds
2014-02-08 20:44 ` Richard Yao
2014-02-08 22:24 ` Linus Torvalds
2014-02-08 23:39 ` Richard Yao
2014-02-10 19:33 ` Andy Lutomirski
2014-02-10 19:43 ` Linus Torvalds
2014-02-10 12:10 ` Mel Gorman
2014-02-10 14:40 ` Dave Kleikamp [this message]
2014-02-08 19:12 ` [PATCH 2/2] 9p/trans_virtio.c: Fix broken zero-copy on vmalloc() buffers Richard Yao
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