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Message-ID: <52F929A6.8040209@mit.edu> Date: Mon, 10 Feb 2014 11:33:58 -0800 From: Andy Lutomirski <luto@...capital.net> To: Linus Torvalds <torvalds@...ux-foundation.org>, Richard Yao <ryao@...too.org> CC: Mel Gorman <mgorman@...e.de>, Andrew Morton <akpm@...ux-foundation.org>, Rik van Riel <riel@...hat.com>, Eric Van Hensbergen <ericvh@...il.com>, Ron Minnich <rminnich@...dia.gov>, Latchesar Ionkov <lucho@...kov.net>, "David S. Miller" <davem@...emloft.net>, V9FS Develooper Mailing List <v9fs-developer@...ts.sourceforge.net>, Linux Netdev Mailing List <netdev@...r.kernel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>, Will Deacon <will.deacon@....com>, Christopher Covington <cov@...eaurora.org>, Matthew Thode <mthode@...ode.org> Subject: Re: [PATCH 1/2] mm/vmalloc: export is_vmalloc_or_module_addr On 02/08/2014 02:24 PM, Linus Torvalds wrote: > On Sat, Feb 8, 2014 at 12:44 PM, Richard Yao <ryao@...too.org> wrote: >> >> However, is_vmalloc_addr() only applies to the vmalloc region. While all >> architectures load kernel modules into virtual memory (to my knowledge), >> some architectures do not load them into the vmalloc region. > > So? > > People shouldn't do IO to module data, so who cares if something is a > module address or not? > > The thing is, even module *loading* doesn't do IO to the magic module > addresses - it loads the module data into regular vmalloc space, and > then copies it into the final location separately. > > And no module should ever do any IO on random static data (and > certainly not on code). > > So there is _zero_ reason for a driver or a filesystem to use > is_vmalloc_or_module_addr(). It's just not a valid question to ask. > > If somebody uses module data/code addresses, we're *better* off with a > oops or other nasty behavior than to try to make it "work". I agree that reading to module space is awful, but is it obviously terrible for a module to do this: static const char header[] = {...}; kernel_write(file, header, sizeof(header), 0); The current nasty behavior is doing the I/O to the wrong place if the appropriate CONFIG_DEBUG option isn't set. That IMO sucks. --Andy -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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