Re: [PATCH 11/51] memcg: implement mem_cgroup_css_from_page()

[Tejun Heo]

Hello,

On Fri, May 22, 2015 at 07:28:31PM -0400, Johannes Weiner wrote:
> replace_page_cache() can clear page->mem_cgroup even when the page
> still has references, so unfortunately you must hold the page lock
> when calling this function.
> 
> I haven't checked how you use this - chances are you always have the
> page locked anyways - but it probably needs a comment.

Hmmm... as replace_page_cache_page() is used only by fuse and fuse's
bdi doesn't go through the usual writeback accounting which is
necessary for cgroup writeback support anyway, so I don't think this
presents an actual problem.  I'll add a warning in
replace_page_cache_page() which triggers when it's used on a bdi which
has cgroup writeback enabled and add comments explaining what's going
on.

Thanks.

-- 
tejun
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