Messages in this thread | | | Subject | Re: [RFC] some page can't be migrated | From | Shaohua Li <> | Date | Mon, 28 Jan 2008 09:48:28 +0800 |
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On Mon, 2008-01-28 at 12:43 +1100, Nick Piggin wrote: > On Sunday 27 January 2008 17:03, Andrew Morton wrote: > > > On Fri, 25 Jan 2008 14:03:25 +0800 Shaohua Li <shaohua.li@intel.com> > > > wrote: > > > > > > - if (!page->mapping) > > > + if (!page->mapping) { > > > + if (!PageAnon(page) && PagePrivate(page)) > > > + try_to_release_page(page, GFP_KERNEL); > > > goto rcu_unlock; > > > + } > > > > We call something(GFP_KERNEL) under rcu_read_lock()? I've lost track of > > the myriad flavours of rcu which we purport to support, but I don't think > > they'll all like us blocking under rcu_read_lock(). > > > > We _won't_ block, because try_to_release_page() will see the NULL ->mapping > > and will call the non-blocking try_to_free_buffers(). But still, it looks > > bad, and will cause problems if someone decides to add a might_sleep_if() > > to try_to_release_page(). > > > > So... I'd suggest that it would be better to add an apologetic comment and > > call direct into try_to_free_buffers(). > > You're right, but can't we just rcu_read_unlock() before try_to_release_page? or we could move the code above before doing rcu_read_lock()?
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