Messages in this thread | | | Date | Mon, 30 Nov 2015 14:08:53 -0800 | Subject | Re: [PATCH] mm: Fix mmap MAP_POPULATE for DAX pmd mapping | From | Dan Williams <> |
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On Mon, Nov 23, 2015 at 12:04 PM, Toshi Kani <toshi.kani@hpe.com> wrote: > The following oops was observed when mmap() with MAP_POPULATE > pre-faulted pmd mappings of a DAX file. follow_trans_huge_pmd() > expects that a target address has a struct page. > > BUG: unable to handle kernel paging request at ffffea0012220000 > follow_trans_huge_pmd+0xba/0x390 > follow_page_mask+0x33d/0x420 > __get_user_pages+0xdc/0x800 > populate_vma_page_range+0xb5/0xe0 > __mm_populate+0xc5/0x150 > vm_mmap_pgoff+0xd5/0xe0 > SyS_mmap_pgoff+0x1c1/0x290 > SyS_mmap+0x1b/0x30 > > Fix it by making the PMD pre-fault handling consistent with PTE. > After pre-faulted in faultin_page(), follow_page_mask() calls > follow_trans_huge_pmd(), which is changed to call follow_pfn_pmd() > for VM_PFNMAP or VM_MIXEDMAP. follow_pfn_pmd() handles FOLL_TOUCH > and returns with -EEXIST. > > Reported-by: Mauricio Porto <mauricio.porto@hpe.com> > Signed-off-by: Toshi Kani <toshi.kani@hpe.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > Cc: Matthew Wilcox <willy@linux.intel.com> > Cc: Dan Williams <dan.j.williams@intel.com> > Cc: Ross Zwisler <ross.zwisler@linux.intel.com> > ---
Hey Toshi,
I ended up fixing this differently with follow_pmd_devmap() introduced in this series:
https://lists.01.org/pipermail/linux-nvdimm/2015-November/003033.html
Does the latest libnvdimm-pending branch [1] pass your test case?
[1]: git://git.kernel.org/pub/scm/linux/kernel/git/djbw/nvdimm libnvdimm-pending
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