On Thu, Nov 28, 2013 at 05:48:02PM +0900, HATAYAMA Daisuke wrote: > Hello Vivek, > > Here is a patch set for mmap failure for /proc/vmcore. > Could you try to use this on the problematic system? > > This patch doesn't copy partial pages to the 2nd kernel, only prepares > vmcore objects for respective partial pages to invoke remap_pfn_range() > for individual partial pages. Hi Hatayama, Thanks for the patch. Ok, I see that partial pages will be put in a separate call to remap_oldmem_pfn_range() and this time it should succeed. I am wondering what do you think about your old approach of copying only relevant old memory to a new kernel page in new kernel. I kind of feel little uncomfortable with the idea of rounding down start and roudning up end to page size boundaries and then accessing the full page using oldmem interface. A safer approach might be to allocate page in new kernel, read *only* those bytes as reported by elf header and fill rest of the page with zeros. Thanks Vivek > > >From c83dddd23be2a2972dcb3f252598c39abfa23078 Mon Sep 17 00:00:00 2001 > From: HATAYAMA Daisuke <d.hatayama at jp.fujitsu.com> > Date: Thu, 28 Nov 2013 14:51:22 +0900 > Subject: [PATCH] vmcore: call remap_pfn_range() separately for respective > partial pages > > Acording to the report by Vivek in > https://lkml.org/lkml/2013/11/13/439, on some specific systems, some > of the System RAM ranges don't end at page boundary and the later part > of the same page is used for some kind of ACPI data. As a result, > remap_pfn_range() to the partial page failed if mapping range covers a > boundary of the System RAM part and the ACPI data part in the partial > page, due to the detection of different cache types in > track_pfn_remap(). > > To resolve the issue, call remap_pfn_range() separately for respective > partial pages, not for multiple consequtive pages that don't either > start or end at page boundary, by creating vmcore objects for > respective partial pages. > > This patch never changes shape of /proc/vmcore visible from user-land. > > Reported-by: Vivek Goyal <vgoyal at redhat.com> > Signed-off-by: HATAYAMA Daisuke <d.hatayama at jp.fujitsu.com> > --- > fs/proc/vmcore.c | 108 ++++++++++++++++++++++++++++++++++++++++++------------- > 1 file changed, 84 insertions(+), 24 deletions(-) > > diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c > index 9100d69..e396a1d 100644 > --- a/fs/proc/vmcore.c > +++ b/fs/proc/vmcore.c > @@ -816,26 +816,56 @@ static int __init process_ptload_program_headers_elf64(char *elfptr, > vmcore_off = elfsz + elfnotes_sz; > > for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) { > - u64 paddr, start, end, size; > + u64 start, end, size, rest; > + u64 start_up, start_down, end_up, end_down; > > if (phdr_ptr->p_type != PT_LOAD) > continue; > > - paddr = phdr_ptr->p_offset; > - start = rounddown(paddr, PAGE_SIZE); > - end = roundup(paddr + phdr_ptr->p_memsz, PAGE_SIZE); > - size = end - start; > + start = phdr_ptr->p_offset; > + start_up = roundup(start, PAGE_SIZE); > + start_down = rounddown(start, PAGE_SIZE); > + end = phdr_ptr->p_offset + phdr_ptr->p_memsz; > + end_up = roundup(end, PAGE_SIZE); > + end_down = rounddown(end, PAGE_SIZE); > + size = end_up - start_down; > + rest = phdr_ptr->p_memsz; > + > + if (!PAGE_ALIGNED(start)) { > + new = get_new_element(); > + if (!new) > + return -ENOMEM; > + new->paddr = start_down; > + new->size = PAGE_SIZE; > + list_add_tail(&new->list, vc_list); > + rest -= min(start_up, end) - start; > + } > > /* Add this contiguous chunk of memory to vmcore list.*/ > - new = get_new_element(); > - if (!new) > - return -ENOMEM; > - new->paddr = start; > - new->size = size; > - list_add_tail(&new->list, vc_list); > + if (rest > 0 && start_up < end_down) { > + new = get_new_element(); > + if (!new) > + return -ENOMEM; > + new->paddr = start_up; > + new->size = end_down - start_up; > + list_add_tail(&new->list, vc_list); > + rest -= end_down - start_up; > + } > + > + if (rest > 0) { > + new = get_new_element(); > + if (!new) > + return -ENOMEM; > + new->paddr = end_down; > + new->size = PAGE_SIZE; > + list_add_tail(&new->list, vc_list); > + rest -= end - end_down; > + } > + > + WARN_ON(rest > 0); > > /* Update the program header offset. */ > - phdr_ptr->p_offset = vmcore_off + (paddr - start); > + phdr_ptr->p_offset = vmcore_off + (start - start_down); > vmcore_off = vmcore_off + size; > } > return 0; > @@ -859,26 +889,56 @@ static int __init process_ptload_program_headers_elf32(char *elfptr, > vmcore_off = elfsz + elfnotes_sz; > > for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) { > - u64 paddr, start, end, size; > + u64 start, end, size, rest; > + u64 start_up, start_down, end_up, end_down; > > if (phdr_ptr->p_type != PT_LOAD) > continue; > > - paddr = phdr_ptr->p_offset; > - start = rounddown(paddr, PAGE_SIZE); > - end = roundup(paddr + phdr_ptr->p_memsz, PAGE_SIZE); > - size = end - start; > + start = phdr_ptr->p_offset; > + start_up = roundup(start, PAGE_SIZE); > + start_down = rounddown(start, PAGE_SIZE); > + end = phdr_ptr->p_offset + phdr_ptr->p_memsz; > + end_up = roundup(end, PAGE_SIZE); > + end_down = rounddown(end, PAGE_SIZE); > + rest = phdr_ptr->p_memsz; > + size = end_up - start_down; > + > + if (!PAGE_ALIGNED(start)) { > + new = get_new_element(); > + if (!new) > + return -ENOMEM; > + new->paddr = start_down; > + new->size = PAGE_SIZE; > + list_add_tail(&new->list, vc_list); > + rest -= min(start_up, end) - start; > + } > > /* Add this contiguous chunk of memory to vmcore list.*/ > - new = get_new_element(); > - if (!new) > - return -ENOMEM; > - new->paddr = start; > - new->size = size; > - list_add_tail(&new->list, vc_list); > + if (rest > 0 && start_up < end_down) { > + new = get_new_element(); > + if (!new) > + return -ENOMEM; > + new->paddr = start_up; > + new->size = end_down - start_up; > + list_add_tail(&new->list, vc_list); > + rest -= end_down - start_up; > + } > + > + if (rest > 0) { > + new = get_new_element(); > + if (!new) > + return -ENOMEM; > + new->paddr = end_down; > + new->size = PAGE_SIZE; > + list_add_tail(&new->list, vc_list); > + rest -= end - end_down; > + } > + > + WARN_ON(rest > 0); > > /* Update the program header offset */ > - phdr_ptr->p_offset = vmcore_off + (paddr - start); > + phdr_ptr->p_offset = vmcore_off + (start - start_down); > vmcore_off = vmcore_off + size; > } > return 0; > -- > 1.8.3.1 > > -- > Thanks. > HATAYAMA, Daisuke
