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In a 32-bit program, running on arm64 architecture. When the address space below mmap base is completely exhausted, shmat() for huge pages will return ENOMEM, but shmat() for normal pages can still success on no-legacy mode. This seems not fair. For normal pages, the calling trace of get_unmapped_area() is: => mm->get_unmapped_area() if on legacy mode, => arch_get_unmapped_area() => vm_unmapped_area() if on no-legacy mode, => arch_get_unmapped_area_topdown() => vm_unmapped_area() For huge pages, the calling trace of get_unmapped_area() is: => file->f_op->get_unmapped_area() => hugetlb_get_unmapped_area() => vm_unmapped_area() To solve this issue, we only need to make hugetlb_get_unmapped_area() take the same way as mm->get_unmapped_area(). Add *bottomup() and *topdown() for hugetlbfs, and check current mm->get_unmapped_area() to decide which one to use. If mm->get_unmapped_area is equal to arch_get_unmapped_area_topdown(), hugetlb_get_unmapped_area() calls topdown routine, otherwise calls bottomup routine. Reported-by: kbuild test robot <lkp@intel.com> Signed-off-by: Shijie Hu <hushijie3@huawei.com> Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: Will Deacon <will@kernel.org> Cc: Xiaoming Ni <nixiaoming@huawei.com> Cc: Kefeng Wang <wangkefeng.wang@huawei.com> Cc: yangerkun <yangerkun@huawei.com> Cc: ChenGang <cg.chen@huawei.com> Cc: Chen Jie <chenjie6@huawei.com> Link: http://lkml.kernel.org/r/20200518065338.113664-1-hushijie3@huawei.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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