* [PATCH v1] mm: initialize struct page for reserved pages in ZONE_DEVICE @ 2018-06-22 6:08 Naoya Horiguchi 2018-06-22 6:12 ` Dan Williams 0 siblings, 1 reply; 5+ messages in thread From: Naoya Horiguchi @ 2018-06-22 6:08 UTC (permalink / raw) To: linux-mm Cc: linux-kernel, Andrew Morton, Michal Hocko, Dan Williams, Thomas Gleixner, Ingo Molnar, H. Peter Anvin, Dave Hansen Reading /proc/kpageflags for pfns allocated by pmem namespace triggers kernel panic with a message like "BUG: unable to handle kernel paging request at fffffffffffffffe". The first few pages (controlled by altmap passed to memmap_init_zone()) in the ZONE_DEVICE can skip struct page initialization, which causes the reported issue. This patch simply adds some initialization code for them. Fixes: 4b94ffdc4163 ("x86, mm: introduce vmem_altmap to augment vmemmap_populate()") Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> --- mm/page_alloc.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git v4.17-mmotm-2018-06-07-16-59/mm/page_alloc.c v4.17-mmotm-2018-06-07-16-59_patched/mm/page_alloc.c index 1772513..0b36afe 100644 --- v4.17-mmotm-2018-06-07-16-59/mm/page_alloc.c +++ v4.17-mmotm-2018-06-07-16-59_patched/mm/page_alloc.c @@ -5574,8 +5574,16 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone, * Honor reservation requested by the driver for this ZONE_DEVICE * memory */ - if (altmap && start_pfn == altmap->base_pfn) + if (altmap && start_pfn == altmap->base_pfn) { + unsigned long i; + + for (i = 0; i < altmap->reserve; i++) { + page = pfn_to_page(start_pfn + i); + __init_single_page(page, start_pfn + i, zone, nid); + SetPageReserved(page); + } start_pfn += altmap->reserve; + } for (pfn = start_pfn; pfn < end_pfn; pfn++) { /* -- 2.7.0 ^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH v1] mm: initialize struct page for reserved pages in ZONE_DEVICE 2018-06-22 6:08 [PATCH v1] mm: initialize struct page for reserved pages in ZONE_DEVICE Naoya Horiguchi @ 2018-06-22 6:12 ` Dan Williams 2018-06-22 6:13 ` Dan Williams 2018-06-22 6:55 ` Naoya Horiguchi 0 siblings, 2 replies; 5+ messages in thread From: Dan Williams @ 2018-06-22 6:12 UTC (permalink / raw) To: Naoya Horiguchi Cc: Linux MM, Linux Kernel Mailing List, Andrew Morton, Michal Hocko, Thomas Gleixner, Ingo Molnar, H. Peter Anvin, Dave Hansen On Thu, Jun 21, 2018 at 11:08 PM, Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> wrote: > Reading /proc/kpageflags for pfns allocated by pmem namespace triggers > kernel panic with a message like "BUG: unable to handle kernel paging > request at fffffffffffffffe". > > The first few pages (controlled by altmap passed to memmap_init_zone()) > in the ZONE_DEVICE can skip struct page initialization, which causes > the reported issue. > > This patch simply adds some initialization code for them. > > Fixes: 4b94ffdc4163 ("x86, mm: introduce vmem_altmap to augment vmemmap_populate()") > Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> > --- > mm/page_alloc.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git v4.17-mmotm-2018-06-07-16-59/mm/page_alloc.c v4.17-mmotm-2018-06-07-16-59_patched/mm/page_alloc.c > index 1772513..0b36afe 100644 > --- v4.17-mmotm-2018-06-07-16-59/mm/page_alloc.c > +++ v4.17-mmotm-2018-06-07-16-59_patched/mm/page_alloc.c > @@ -5574,8 +5574,16 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone, > * Honor reservation requested by the driver for this ZONE_DEVICE > * memory > */ > - if (altmap && start_pfn == altmap->base_pfn) > + if (altmap && start_pfn == altmap->base_pfn) { > + unsigned long i; > + > + for (i = 0; i < altmap->reserve; i++) { > + page = pfn_to_page(start_pfn + i); > + __init_single_page(page, start_pfn + i, zone, nid); > + SetPageReserved(page); > + } > start_pfn += altmap->reserve; > + } No, unfortunately this will clobber metadata that lives in that reserved area, see __nvdimm_setup_pfn(). ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v1] mm: initialize struct page for reserved pages in ZONE_DEVICE 2018-06-22 6:12 ` Dan Williams @ 2018-06-22 6:13 ` Dan Williams 2018-06-22 6:55 ` Naoya Horiguchi 1 sibling, 0 replies; 5+ messages in thread From: Dan Williams @ 2018-06-22 6:13 UTC (permalink / raw) To: Naoya Horiguchi Cc: Linux MM, Linux Kernel Mailing List, Andrew Morton, Michal Hocko, Thomas Gleixner, Ingo Molnar, H. Peter Anvin, Dave Hansen On Thu, Jun 21, 2018 at 11:12 PM, Dan Williams <dan.j.williams@intel.com> wrote: > On Thu, Jun 21, 2018 at 11:08 PM, Naoya Horiguchi > <n-horiguchi@ah.jp.nec.com> wrote: >> Reading /proc/kpageflags for pfns allocated by pmem namespace triggers >> kernel panic with a message like "BUG: unable to handle kernel paging >> request at fffffffffffffffe". >> >> The first few pages (controlled by altmap passed to memmap_init_zone()) >> in the ZONE_DEVICE can skip struct page initialization, which causes >> the reported issue. >> >> This patch simply adds some initialization code for them. >> >> Fixes: 4b94ffdc4163 ("x86, mm: introduce vmem_altmap to augment vmemmap_populate()") >> Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> >> --- >> mm/page_alloc.c | 10 +++++++++- >> 1 file changed, 9 insertions(+), 1 deletion(-) >> >> diff --git v4.17-mmotm-2018-06-07-16-59/mm/page_alloc.c v4.17-mmotm-2018-06-07-16-59_patched/mm/page_alloc.c >> index 1772513..0b36afe 100644 >> --- v4.17-mmotm-2018-06-07-16-59/mm/page_alloc.c >> +++ v4.17-mmotm-2018-06-07-16-59_patched/mm/page_alloc.c >> @@ -5574,8 +5574,16 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone, >> * Honor reservation requested by the driver for this ZONE_DEVICE >> * memory >> */ >> - if (altmap && start_pfn == altmap->base_pfn) >> + if (altmap && start_pfn == altmap->base_pfn) { >> + unsigned long i; >> + >> + for (i = 0; i < altmap->reserve; i++) { >> + page = pfn_to_page(start_pfn + i); >> + __init_single_page(page, start_pfn + i, zone, nid); >> + SetPageReserved(page); >> + } >> start_pfn += altmap->reserve; >> + } > > No, unfortunately this will clobber metadata that lives in that > reserved area, see __nvdimm_setup_pfn(). I think the kpageflags code needs to lookup the dev_pagemap in the ZONE_DEVICE case and honor the altmap. ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v1] mm: initialize struct page for reserved pages in ZONE_DEVICE 2018-06-22 6:12 ` Dan Williams 2018-06-22 6:13 ` Dan Williams @ 2018-06-22 6:55 ` Naoya Horiguchi 2018-06-22 7:30 ` Dan Williams 1 sibling, 1 reply; 5+ messages in thread From: Naoya Horiguchi @ 2018-06-22 6:55 UTC (permalink / raw) To: Dan Williams Cc: Linux MM, Linux Kernel Mailing List, Andrew Morton, Michal Hocko, Thomas Gleixner, Ingo Molnar, H. Peter Anvin, Dave Hansen On Thu, Jun 21, 2018 at 11:12:01PM -0700, Dan Williams wrote: > On Thu, Jun 21, 2018 at 11:08 PM, Naoya Horiguchi > <n-horiguchi@ah.jp.nec.com> wrote: > > Reading /proc/kpageflags for pfns allocated by pmem namespace triggers > > kernel panic with a message like "BUG: unable to handle kernel paging > > request at fffffffffffffffe". > > > > The first few pages (controlled by altmap passed to memmap_init_zone()) > > in the ZONE_DEVICE can skip struct page initialization, which causes > > the reported issue. > > > > This patch simply adds some initialization code for them. > > > > Fixes: 4b94ffdc4163 ("x86, mm: introduce vmem_altmap to augment vmemmap_populate()") > > Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> > > --- > > mm/page_alloc.c | 10 +++++++++- > > 1 file changed, 9 insertions(+), 1 deletion(-) > > > > diff --git v4.17-mmotm-2018-06-07-16-59/mm/page_alloc.c v4.17-mmotm-2018-06-07-16-59_patched/mm/page_alloc.c > > index 1772513..0b36afe 100644 > > --- v4.17-mmotm-2018-06-07-16-59/mm/page_alloc.c > > +++ v4.17-mmotm-2018-06-07-16-59_patched/mm/page_alloc.c > > @@ -5574,8 +5574,16 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone, > > * Honor reservation requested by the driver for this ZONE_DEVICE > > * memory > > */ > > - if (altmap && start_pfn == altmap->base_pfn) > > + if (altmap && start_pfn == altmap->base_pfn) { > > + unsigned long i; > > + > > + for (i = 0; i < altmap->reserve; i++) { > > + page = pfn_to_page(start_pfn + i); > > + __init_single_page(page, start_pfn + i, zone, nid); > > + SetPageReserved(page); > > + } > > start_pfn += altmap->reserve; > > + } > > No, unfortunately this will clobber metadata that lives in that > reserved area, see __nvdimm_setup_pfn(). Hi Dan, This patch doesn't touch the reserved region itself, but only struct pages on the region. I'm still not sure why it's necessary to leave these struct pages uninitialized for pmem operation? My another related concern is about memory_failure_dev_pagemap(). If a memory error happens on the reserved pfn range, this function seems to try to access to the uninitialized struct page and maybe trigger oops. So do we need something to prevent this? Thanks, Naoya Horiguchi ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v1] mm: initialize struct page for reserved pages in ZONE_DEVICE 2018-06-22 6:55 ` Naoya Horiguchi @ 2018-06-22 7:30 ` Dan Williams 0 siblings, 0 replies; 5+ messages in thread From: Dan Williams @ 2018-06-22 7:30 UTC (permalink / raw) To: Naoya Horiguchi Cc: Linux MM, Linux Kernel Mailing List, Andrew Morton, Michal Hocko, Thomas Gleixner, Ingo Molnar, H. Peter Anvin, Dave Hansen On Thu, Jun 21, 2018 at 11:55 PM, Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> wrote: > On Thu, Jun 21, 2018 at 11:12:01PM -0700, Dan Williams wrote: >> On Thu, Jun 21, 2018 at 11:08 PM, Naoya Horiguchi >> <n-horiguchi@ah.jp.nec.com> wrote: >> > Reading /proc/kpageflags for pfns allocated by pmem namespace triggers >> > kernel panic with a message like "BUG: unable to handle kernel paging >> > request at fffffffffffffffe". >> > >> > The first few pages (controlled by altmap passed to memmap_init_zone()) >> > in the ZONE_DEVICE can skip struct page initialization, which causes >> > the reported issue. >> > >> > This patch simply adds some initialization code for them. >> > >> > Fixes: 4b94ffdc4163 ("x86, mm: introduce vmem_altmap to augment vmemmap_populate()") >> > Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> >> > --- >> > mm/page_alloc.c | 10 +++++++++- >> > 1 file changed, 9 insertions(+), 1 deletion(-) >> > >> > diff --git v4.17-mmotm-2018-06-07-16-59/mm/page_alloc.c v4.17-mmotm-2018-06-07-16-59_patched/mm/page_alloc.c >> > index 1772513..0b36afe 100644 >> > --- v4.17-mmotm-2018-06-07-16-59/mm/page_alloc.c >> > +++ v4.17-mmotm-2018-06-07-16-59_patched/mm/page_alloc.c >> > @@ -5574,8 +5574,16 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone, >> > * Honor reservation requested by the driver for this ZONE_DEVICE >> > * memory >> > */ >> > - if (altmap && start_pfn == altmap->base_pfn) >> > + if (altmap && start_pfn == altmap->base_pfn) { >> > + unsigned long i; >> > + >> > + for (i = 0; i < altmap->reserve; i++) { >> > + page = pfn_to_page(start_pfn + i); >> > + __init_single_page(page, start_pfn + i, zone, nid); >> > + SetPageReserved(page); >> > + } >> > start_pfn += altmap->reserve; >> > + } >> >> No, unfortunately this will clobber metadata that lives in that >> reserved area, see __nvdimm_setup_pfn(). > > Hi Dan, > > This patch doesn't touch the reserved region itself, but only > struct pages on the region. I'm still not sure why it's necessary > to leave these struct pages uninitialized for pmem operation? > > My another related concern is about memory_failure_dev_pagemap(). > If a memory error happens on the reserved pfn range, this function > seems to try to access to the uninitialized struct page and maybe > trigger oops. So do we need something to prevent this? Those pages are never mapped to userspace, so there is no opportunity to consume the media error in that space. I'm still not sure it is safe to initialize the pfns in the reserved range, I'll take a closer look tomorrow. Otherwise, why not just delete the entire check and let the main loop initialize the pages? ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2018-06-22 7:30 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2018-06-22 6:08 [PATCH v1] mm: initialize struct page for reserved pages in ZONE_DEVICE Naoya Horiguchi 2018-06-22 6:12 ` Dan Williams 2018-06-22 6:13 ` Dan Williams 2018-06-22 6:55 ` Naoya Horiguchi 2018-06-22 7:30 ` Dan Williams
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