From: lipeifeng <lipeifeng@xxxxxxxx> when we found a suitable gap_end(> info->high_limit), gap_end must be set to info->high_limit. And we will get the gap_end after computing highest gap address at the desired alignment. 2096 found: 2097 if (gap_end > info->high_limit) 2098 gap_end = info->high_limit; 2099 2100 found_highest: 2101 gap_end -= info->length; 2102 gap_end -= (gap_end - info->align_offset) & info->align_mask; 2103 2104 VM_BUG_ON(gap_end < info->low_limit); 2105 VM_BUG_ON(gap_end < gap_start); 2106 return gap_end; so we must promise: info->high_limit - info->low_limit >= info->length + info->align_mask. Or in rare cases(info->high_limit - info->low_limit < info->length + info->align_mask) we will get the addr in align-error if found suitable gap_end(> info->high_limit). Signed-off-by: lipeifeng <lipeifeng@xxxxxxxx> --- mm/mmap.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/mmap.c b/mm/mmap.c index 30e33d3..a28ea5c 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2009,7 +2009,6 @@ static unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info) if (length < info->length) return -ENOMEM; - length = info->length; /* * Adjust search limits by the desired length. * See implementation comment at top of unmapped_area(). @@ -2021,6 +2020,8 @@ static unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info) if (info->low_limit > high_limit) return -ENOMEM; + + length = info->length; low_limit = info->low_limit + length; /* Check highest gap, which does not precede any rbtree node */ -- 2.7.4
