From: Wu Fengguang <fengguang.wu@intel.com>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
Michal Hocko <mhocko@suse.cz>, Mel Gorman <mel@csn.ul.ie>
Subject: Re: [BUGFIX][PATCH] fix is_mem_section_removable() page_order BUG_ON check.
Date: Mon, 25 Oct 2010 15:49:33 +0800 [thread overview]
Message-ID: <20101025074933.GB5452@localhost> (raw)
In-Reply-To: <20101025153726.2ae9baec.kamezawa.hiroyu@jp.fujitsu.com>
On Mon, Oct 25, 2010 at 02:37:26PM +0800, KAMEZAWA Hiroyuki wrote:
> I wonder this should be for stable tree...but want to hear opinions before.
> ==
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
>
> page_order() is called by memory hotplug's user interface to check
> the section is removable or not. (is_mem_section_removable())
>
> It calls page_order() withoug holding zone->lock.
> So, even if the caller does
>
> if (PageBuddy(page))
> ret = page_order(page) ...
> The caller may hit BUG_ON().
>
> For fixing this, there are 2 choices.
> 1. add zone->lock.
> 2. remove BUG_ON().
One more alternative might be to introduce a private
maybe_page_order() for is_mem_section_removable(). Not a big deal.
> is_mem_section_removable() is used for some "advice" and doesn't need
> to be 100% accurate. This is_removable() can be called via user program..
> We don't want to take this important lock for long by user's request.
> So, this patch removes BUG_ON().
Acked-by: Wu Fengguang <fengguang.wu@intel.com>
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next prev parent reply other threads:[~2010-10-25 7:49 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-25 6:37 [BUGFIX][PATCH] fix is_mem_section_removable() page_order BUG_ON check KAMEZAWA Hiroyuki
2010-10-25 7:49 ` Wu Fengguang [this message]
2010-10-25 13:10 ` Michal Hocko
2010-10-25 13:16 ` Wu Fengguang
2010-10-25 21:24 ` Andrew Morton
2010-10-25 17:03 ` Mel Gorman
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