Re: [PATCH] proc: pagemap: Hold mmap_sem during page walk
From: Matt Mackall
Date: Thu Apr 01 2010 - 03:09:43 EST
On Thu, 2010-04-01 at 15:34 +0900, KAMEZAWA Hiroyuki wrote:
> On Thu, 1 Apr 2010 15:09:56 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:
> > + pm.pos = 0;
> > + start_vaddr += PAGEMAP_WALK_SIZE;
> > + end = start_vaddr + PAGEMAP_WALK_SIZE;
> Sigh...this is bad..
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> In initial design, walk_page_range() was designed just for walking page table and
> it didn't require mmap_sem. Now, find_vma() etc.. are used in walk_page_range()
> and we need mmap_sem around it.
This looks pretty reasonable. However, it also looks very similar to my
first version of pagemap (which started with double-buffering). It's
going to need re-testing to make sure it hasn't reintroduced any
wrapping, alignment, or off-by-one bugs that have already been ironed
out once or twice.
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