| Message ID | 20081224233536.b067c9da.akpm@linux-foundation.org (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
Andrew Morton writes: > On Wed, 24 Dec 2008 13:25:49 +0530 Chandru <chandru@in.ibm.com> wrote: > > > On a ppc machine booting linux-2.6.28-rc9 with crashkernel=256M@32M boot > > parameter causes the kernel to panic while booting. __Following are the console > > messages... > > - Please put [patch] in the Subject: line of patches > > - Please choose a suitable title, as per > Documentation/SubmittingPatches, section 15. > > - Please cc suitable mailing lists and maintainers on bug reports and > on patches. Dave Hansen was working on this code recently, and this looks a bit similar to some changes he was making. Dave, what's your opinion on this patch? Paul. > From: Chandru <chandru@in.ibm.com> > > When booted with crashkernel=224M@32M or any memory size less than this, > the system boots properly. The following was the observation.. The > system comes up with two nodes (0-256M and 256M-4GB). _The crashkernel > memory reservation spans across these two nodes. _The > mark_reserved_regions_for_nid() in arch/powerpc/mm/numa.c resizes the > reserved part of the memory within it as: > > _ _ _ _ _ _ if (end_pfn > node_ar.end_pfn) > _ _ _ _ _ _ _ _ reserve_size = (node_ar.end_pfn << PAGE_SHIFT) > _ _ _ _ _ _ _ _ _ _ - (start_pfn << PAGE_SHIFT); > > > but the reserve_bootmem_node() in mm/bootmem.c raises the pfn value of end > > _ _ end = PFN_UP(physaddr + size); > > This causes end to get a value past the last page in the 0-256M node. > _Again when reserve_bootmem_node() returns, > _mark_reserved_regions_for_nid() loops around to set the rest of the > crashkernel memory in the next node as reserved. _ It references > NODE_DATA(node_ar.nid) and this causes another 'Oops: kernel access of bad > area' problem. The following changes made the system to boot with any > amount of crashkernel memory size. > > Signed-off-by: Chandru S <chandru@linux.vnet.ibm.com> > Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> > Cc: Paul Mackerras <paulus@samba.org> > Signed-off-by: Andrew Morton <akpm@linux-foundation.org> > --- > > arch/powerpc/mm/numa.c | 7 ++++--- > mm/bootmem.c | 4 ++++ > 2 files changed, 8 insertions(+), 3 deletions(-) > > diff -puN arch/powerpc/mm/numa.c~2628-rc9-panics-with-crashkernel=256m-while-booting arch/powerpc/mm/numa.c > --- a/arch/powerpc/mm/numa.c~2628-rc9-panics-with-crashkernel=256m-while-booting > +++ a/arch/powerpc/mm/numa.c > @@ -995,10 +995,11 @@ void __init do_init_bootmem(void) > start_pfn, end_pfn); > > free_bootmem_with_active_regions(nid, end_pfn); > + } > + > + for_each_online_node(nid) { > /* > - * Be very careful about moving this around. Future > - * calls to careful_allocation() depend on this getting > - * done correctly. > + * Be very careful about moving this around. > */ > mark_reserved_regions_for_nid(nid); > sparse_memory_present_with_active_regions(nid); > diff -puN mm/bootmem.c~2628-rc9-panics-with-crashkernel=256m-while-booting mm/bootmem.c > --- a/mm/bootmem.c~2628-rc9-panics-with-crashkernel=256m-while-booting > +++ a/mm/bootmem.c > @@ -375,10 +375,14 @@ int __init reserve_bootmem_node(pg_data_ > unsigned long size, int flags) > { > unsigned long start, end; > + bootmem_data_t *bdata = pgdat->bdata; > > start = PFN_DOWN(physaddr); > end = PFN_UP(physaddr + size); > > + if (end > bdata->node_low_pfn) > + end = bdata->node_low_pfn; > + > return mark_bootmem_node(pgdat->bdata, start, end, 1, flags); > } > > _
On Fri, 2008-12-26 at 11:59 +1100, Paul Mackerras wrote: > > > diff -puN arch/powerpc/mm/numa.c~2628-rc9-panics-with-crashkernel=256m-while-booting arch/powerpc/mm/numa.c > > --- a/arch/powerpc/mm/numa.c~2628-rc9-panics-with-crashkernel=256m-while-booting > > +++ a/arch/powerpc/mm/numa.c > > @@ -995,10 +995,11 @@ void __init do_init_bootmem(void) > > start_pfn, end_pfn); > > > > free_bootmem_with_active_regions(nid, end_pfn); > > + } > > + > > + for_each_online_node(nid) { > > /* > > - * Be very careful about moving this around. Future > > - * calls to careful_allocation() depend on this getting > > - * done correctly. > > + * Be very careful about moving this around. > > */ > > mark_reserved_regions_for_nid(nid); > > sparse_memory_present_with_active_regions(nid); I think this reintroduces one of the bugs that I squashed. You *have* to call mark_reserved_regions_for_nid() right after you do free_bootmem_with_active_regions(). Otherwise, someone else can bootmem_alloc() a reserved region from that node. Perhaps I need to make that comment a bit more forceful. :) /* * Don't break this loop out. Period. Never. Ever. * No, seriously. Don't do it. I mean it. Really! */ -- Dave
diff -puN arch/powerpc/mm/numa.c~2628-rc9-panics-with-crashkernel=256m-while-booting arch/powerpc/mm/numa.c --- a/arch/powerpc/mm/numa.c~2628-rc9-panics-with-crashkernel=256m-while-booting +++ a/arch/powerpc/mm/numa.c @@ -995,10 +995,11 @@ void __init do_init_bootmem(void) start_pfn, end_pfn); free_bootmem_with_active_regions(nid, end_pfn); + } + + for_each_online_node(nid) { /* - * Be very careful about moving this around. Future - * calls to careful_allocation() depend on this getting - * done correctly. + * Be very careful about moving this around. */ mark_reserved_regions_for_nid(nid); sparse_memory_present_with_active_regions(nid); diff -puN mm/bootmem.c~2628-rc9-panics-with-crashkernel=256m-while-booting mm/bootmem.c --- a/mm/bootmem.c~2628-rc9-panics-with-crashkernel=256m-while-booting +++ a/mm/bootmem.c @@ -375,10 +375,14 @@ int __init reserve_bootmem_node(pg_data_ unsigned long size, int flags) { unsigned long start, end; + bootmem_data_t *bdata = pgdat->bdata; start = PFN_DOWN(physaddr); end = PFN_UP(physaddr + size); + if (end > bdata->node_low_pfn) + end = bdata->node_low_pfn; + return mark_bootmem_node(pgdat->bdata, start, end, 1, flags); }