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chenjietorvalds
chenjie
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mm/madvise.c: fix madvise() infinite loop under special circumstances
MADVISE_WILLNEED has always been a noop for DAX (formerly XIP) mappings. Unfortunately madvise_willneed() doesn't communicate this information properly to the generic madvise syscall implementation. The calling convention is quite subtle there. madvise_vma() is supposed to either return an error or update &prev otherwise the main loop will never advance to the next vma and it will keep looping for ever without a way to get out of the kernel. It seems this has been broken since introduction. Nobody has noticed because nobody seems to be using MADVISE_WILLNEED on these DAX mappings. [mhocko@suse.com: rewrite changelog] Link: http://lkml.kernel.org/r/20171127115318.911-1-guoxuenan@huawei.com Fixes: fe77ba6 ("[PATCH] xip: madvice/fadvice: execute in place") Signed-off-by: chenjie <chenjie6@huawei.com> Signed-off-by: guoxuenan <guoxuenan@huawei.com> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Minchan Kim <minchan@kernel.org> Cc: zhangyi (F) <yi.zhang@huawei.com> Cc: Miao Xie <miaoxie@huawei.com> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Shaohua Li <shli@fb.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: David Rientjes <rientjes@google.com> Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com> Cc: Rik van Riel <riel@redhat.com> Cc: Carsten Otte <cotte@de.ibm.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Diff for: mm/madvise.c

+1-3
Original file line numberDiff line numberDiff line change
@@ -276,15 +276,14 @@ static long madvise_willneed(struct vm_area_struct *vma,
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{
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struct file *file = vma->vm_file;
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*prev = vma;
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#ifdef CONFIG_SWAP
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if (!file) {
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*prev = vma;
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force_swapin_readahead(vma, start, end);
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return 0;
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}
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if (shmem_mapping(file->f_mapping)) {
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*prev = vma;
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force_shm_swapin_readahead(vma, start, end,
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file->f_mapping);
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return 0;
@@ -299,7 +298,6 @@ static long madvise_willneed(struct vm_area_struct *vma,
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return 0;
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}
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*prev = vma;
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start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
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if (end > vma->vm_end)
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end = vma->vm_end;

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