Messages in this thread Patch in this message | | | From | "Chen, Kenneth W" <> | Subject | RE: Hugepage regression | Date | Tue, 10 Oct 2006 16:34:40 -0700 |
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Hugh Dickins wrote on Tuesday, October 10, 2006 12:18 PM > Yes, I'd expect your i_mmap_lock to solve the problem: and since > you're headed in that direction anyway, it makes most sense to use > that solution rather than get into defining arrays, or sacrificing > the lazy flush, or risking page_count races. > > So please extract the __unmap_hugepage_range mods from your shared > pagetable patch, and use that to fix the bug.
OK, here is a bug fix patch fixing earlier "bug fix" patch :-(
[patch] hugetlb: fix linked list corruption in unmap_hugepage_range
commit fe1668ae5bf0145014c71797febd9ad5670d5d05 causes kernel to oops with libhugetlbfs test suite. The problem is that hugetlb pages can be shared by multiple mappings. Multiple threads can fight over page->lru in the unmap path and bad things happen. We now serialize __unmap_hugepage_range to void concurrent linked list manipulation. Such serialization is also needed for shared page table page on hugetlb area. This patch will fixed the bug and also serve as a prepatch for shared page table.
Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
--- ./fs/hugetlbfs/inode.c.orig 2006-10-05 10:25:20.000000000 -0700 +++ ./fs/hugetlbfs/inode.c 2006-10-10 14:27:48.000000000 -0700 @@ -293,7 +293,7 @@ hugetlb_vmtruncate_list(struct prio_tree if (h_vm_pgoff >= h_pgoff) v_offset = 0; - unmap_hugepage_range(vma, + __unmap_hugepage_range(vma, vma->vm_start + v_offset, vma->vm_end); } } --- ./mm/hugetlb.c.orig 2006-10-05 10:25:21.000000000 -0700 +++ ./mm/hugetlb.c 2006-10-10 14:27:48.000000000 -0700 @@ -356,8 +356,8 @@ nomem: return -ENOMEM; } -void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start, - unsigned long end) +void __unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start, + unsigned long end) { struct mm_struct *mm = vma->vm_mm; unsigned long address; @@ -398,6 +398,24 @@ void unmap_hugepage_range(struct vm_area } } +void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start, + unsigned long end) +{ + /* + * It is undesirable to test vma->vm_file as it should be non-null + * for valid hugetlb area. However, vm_file will be NULL in the error + * cleanup path of do_mmap_pgoff. When hugetlbfs ->mmap method fails, + * do_mmap_pgoff() nullifies vma->vm_file before calling this function + * to clean up. Since no pte has actually been setup, it is safe to + * do nothing in this case. + */ + if (vma->vm_file) { + spin_lock(&vma->vm_file->f_mapping->i_mmap_lock); + __unmap_hugepage_range(vma, start, end); + spin_unlock(&vma->vm_file->f_mapping->i_mmap_lock); + } +} + static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, pte_t *ptep, pte_t pte) { --- ./include/linux/hugetlb.h.orig 2006-10-05 10:25:21.000000000 -0700 +++ ./include/linux/hugetlb.h 2006-10-10 13:08:48.000000000 -0700 @@ -17,6 +17,7 @@ int hugetlb_sysctl_handler(struct ctl_ta int copy_hugetlb_page_range(struct mm_struct *, struct mm_struct *, struct vm_area_struct *); int follow_hugetlb_page(struct mm_struct *, struct vm_area_struct *, struct page **, struct vm_area_struct **, unsigned long *, int *, int); void unmap_hugepage_range(struct vm_area_struct *, unsigned long, unsigned long); +void __unmap_hugepage_range(struct vm_area_struct *, unsigned long, unsigned long); int hugetlb_prefault(struct address_space *, struct vm_area_struct *); int hugetlb_report_meminfo(char *); int hugetlb_report_node_meminfo(int, char *);
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