> -----Original Message----- > From: Naoya Horiguchi [mailto:n-horigu...@ah.jp.nec.com] > Sent: Friday, January 30, 2015 4:24 PM > To: Wang, Yalin > Cc: 'a...@linux-foundation.org'; 'kirill.shute...@linux.intel.com'; > 'o...@redhat.com'; 'gorcu...@openvz.org'; 'pfei...@google.com'; > 'aqu...@redhat.com'; 'linux-kernel@vger.kernel.org' > Subject: Re: [RFC V2] mm:change smaps/pagemap_read calculation behavior > > On Fri, Jan 30, 2015 at 03:47:54PM +0800, Wang, Yalin wrote: > > This patch change smaps/pagemap_read pagetable walk behavior, to make > > sure not skip VM_PFNMAP pagetables, > > so that we can calculate COW pages of VM_PFNMAP as normal pages. > > > > Signed-off-by: Yalin Wang <yalin.w...@sonymobile.com> > > Hi Yalin, > > The original motivation of the VM_PFNMAP code in pagewalk.c comes from the > following patch: > > commit a9ff785e4437c83d2179161e012f5bdfbd6381f0 > Author: Cliff Wickman <c...@sgi.com> > Date: Fri May 24 15:55:36 2013 -0700 > > mm/pagewalk.c: walk_page_range should avoid VM_PFNMAP areas > > , where Cliff stated that some kind of vma(VM_PFNMAP) caused kernel panic > when walk_page_range() was called over it. So I don't think that re- > enabling > to walk over every vma(VM_PFNMAP) unexceptionally is a good idea. > > If you really want to get some information from a vma(VM_PFNMAP) via these > interfaces, I recommend you to implement proper judging code which returns > 0 for your vma(VM_PFNMAP) and returns 1 for Cliff's vma(VM_PFNMAP). > I see, but I am curious that why kernel panic when I just access process pagetables in page_table_walk()? Is it caused by hardware problem?
The reason that I want to enable it is to see some drivers map some COW pages With VM_PFNMAP, so that user space can get correct page allocation info for These COW special pages with VM_PFNMAP flag. Thanks -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
