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Date: Wed, 5 Aug 2009 10:39:38 +0900 From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> To: Andrew Morton <akpm@...ux-foundation.org> Cc: scgtrp@...il.com, bugzilla-daemon@...zilla.kernel.org, bugme-daemon@...zilla.kernel.org, xiyou.wangcong@...il.com, linux-kernel@...r.kernel.org Subject: Re: [BUGFIX][PATCH 2/3] kcore: fix vread/vwrite to be aware of holes. On Tue, 4 Aug 2009 18:24:57 -0700 Andrew Morton <akpm@...ux-foundation.org> wrote: > On Wed, 5 Aug 2009 10:08:43 +0900 KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote: > > > > > + /* > > > > + * To do safe access to this _mapped_ area, we need > > > > + * lock. But adding lock here means that we need to add > > > > + * overhead of vmalloc()/vfree() calles for this _debug_ > > > > + * interface, rarely used. Instead of that, we'll use > > > > + * kmap() and get small overhead in this access function. > > > > + */ > > > > + if (p) { > > > > + /* we can expect USR1 is not used */ > > > > > > It would be nice if the comment were to explain _why_ KM_USER1 is known > > > to be free here. > > > > > ok, will do. Hmm, but KM_USR0 is better ? > > I'm not sure difference between KM_USR0/KM_USR1... > > KM_USER0 is conventionally the first one to use. We only use KM_USER1 > if it is known that KM_USER0 is already used. > Hmm, It sounds better to update this to use KM_USER0 when I applying Amerigo's comment. Thanks, -Kame > > > > > > > > > > > + void *map = kmap_atomic(p, KM_USER1); > > > > + memcpy(buf, map + offset, length); > > > > + kunmap_atomic(map, KM_USER1); > > > > > > Can use clear_highpage(). > > > > > ah, "buf" is expected to be kmalloc'ed buffer. I'll explain it in Usage > > or adds comment. > > > > argh, memcpy != memset. I knew that ;) > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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