On Tue, Aug 27, 2013 at 04:05:23PM +0800, Wanpeng Li wrote: > Date: Tue, 27 Aug 2013 16:05:23 +0800 > From: Wanpeng Li <[email protected]> > To: Chen Gong <[email protected]> > Cc: Naoya Horiguchi <[email protected]>, Andrew Morton > <[email protected]>, Andi Kleen <[email protected]>, Fengguang > Wu <[email protected]>, Tony Luck <[email protected]>, > [email protected], [email protected] > Subject: Re: [PATCH v2 3/3] mm/hwpoison: fix return value of > madvise_hwpoison > User-Agent: Mutt/1.5.21 (2010-09-15) > > Hi Chen, > On Tue, Aug 27, 2013 at 03:37:01AM -0400, Chen Gong wrote: > >On Mon, Aug 26, 2013 at 11:41:36PM -0400, Naoya Horiguchi wrote: > >> Date: Mon, 26 Aug 2013 23:41:36 -0400 > >> From: Naoya Horiguchi <[email protected]> > >> To: Wanpeng Li <[email protected]> > >> Cc: Andrew Morton <[email protected]>, Andi Kleen > >> <[email protected]>, Fengguang Wu <[email protected]>, Tony Luck > >> <[email protected]>, [email protected], [email protected], > >> [email protected] > >> Subject: Re: [PATCH v2 3/3] mm/hwpoison: fix return value of > >> madvise_hwpoison > >> User-Agent: Mutt 1.5.21 (2010-09-15) > >> > >> On Tue, Aug 27, 2013 at 11:38:27AM +0800, Wanpeng Li wrote: > >> > Hi Naoya, > >> > On Mon, Aug 26, 2013 at 11:28:16PM -0400, Naoya Horiguchi wrote: > >> > >On Tue, Aug 27, 2013 at 10:39:31AM +0800, Wanpeng Li wrote: > >> > >> The return value outside for loop is always zero which means > >> > >> madvise_hwpoison > >> > >> return success, however, this is not truth for soft_offline_page w/ > >> > >> failure > >> > >> return value. > >> > > > >> > >I don't understand what you want to do for what reason. Could you > >> > >clarify > >> > >those? > >> > > >> > int ret is defined in two place in madvise_hwpoison. One is out of for > >> > loop and its value is always zero(zero means success for madvise), the > >> > other one is in for loop. The soft_offline_page function maybe return > >> > -EBUSY and break, however, the ret out of for loop is return which means > >> > madvise_hwpoison success. > >> > >> Oh, I see. Thanks. > >> > >I don't think such change is a good idea. The original code is obviously > >easy to confuse people. Why not removing redundant local variable? > > > > I think the trick here is get_user_pages_fast will return the number of > pages pinned. It is always 1 in madvise_hwpoison, the return value of > memory_failure is ignored. Therefore we still need to reset ret to 0 > before return madvise_hwpoison. > > Regards, > Wanpeng Li > It looks like the original author wrote in that way deliberately but botching it. FWIW, I just think its harmness is more than good.
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