Messages in this thread Patch in this message | | | Subject | Hugetlb page bug fix for i386 in PAE mode | Date | Wed, 16 Jun 2004 15:07:35 -0700 | From | "Chen, Kenneth W" <> |
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Hit a bug check when unmap a hugetlb vma in PAE mode on i386 (and x86-64).
Bad page state at free_hot_cold_page (in process 'a.out', page c165cc40) flags:0x20000000 mapping:f75e1d00 mapped:0 count:0 Backtrace: Call Trace: [<c0133e0d>] bad_page+0x79/0x9e [<c0134550>] free_hot_cold_page+0x71/0xfa [<c0115d60>] unmap_hugepage_range+0xa3/0xbf [<c013d375>] unmap_vmas+0xac/0x252 [<c0117691>] default_wake_function+0x0/0xc [<c0140bea>] unmap_region+0xd8/0x145 [<c0140f2d>] do_munmap+0xfc/0x14d [<c01b8a56>] sys_shmdt+0xa5/0x126 [<c010a2ad>] sys_ipc+0x23c/0x27f [<c014a85e>] sys_write+0x38/0x59 [<c0103e1b>] syscall_call+0x7/0xb
It turns out there is a bug in hugetlb_prefault(): with 3 level page table, huge_pte_alloc() might return a pmd that points to a PTE page. It happens if the virtual address for hugetlb mmap is recycled from previously used normal page mmap. free_pgtables() might not scrub the pmd entry on munmap and hugetlb_prefault skips on any pmd presence regardless what type it is. Patch to fix the bug.
Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
diff -Nurp linux-2.6.7/arch/i386/mm/hugetlbpage.c linux-2.6.7.htlb/arch/i386/mm/hugetlbpage.c --- linux-2.6.7/arch/i386/mm/hugetlbpage.c 2004-06-16 18:32:30.000000000 -0700 +++ linux-2.6.7.htlb/arch/i386/mm/hugetlbpage.c 2004-06-16 18:34:32.000000000 -0700 @@ -244,8 +244,15 @@ int hugetlb_prefault(struct address_spac ret = -ENOMEM; goto out; } - if (!pte_none(*pte)) - continue; + + if (!pte_none(*pte)) { + pmd_t *pmd = (pmd_t *) pte; + + page = pmd_page(*pmd); + pmd_clear(pmd); + dec_page_state(nr_page_table_pages); + page_cache_release(page); + } idx = ((addr - vma->vm_start) >> HPAGE_SHIFT) + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT)); - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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