From: Liam R. Howlett Liam.Howlett@oracle.com
commit 58c5d0d6d522112577c7eeb71d382ea642ed7be4 upstream.
The maple tree limits the gap returned to a window that specifically fits what was asked. This may not be optimal in the case of switching search directions or a gap that does not satisfy the requested space for other reasons. Fix the search by retrying the operation and limiting the search window in the rare occasion that a conflict occurs.
Link: https://lkml.kernel.org/r/20230414185919.4175572-1-Liam.Howlett@oracle.com Fixes: 3499a13168da ("mm/mmap: use maple tree for unmapped_area{_topdown}") Signed-off-by: Liam R. Howlett Liam.Howlett@oracle.com Reported-by: Rick Edgecombe rick.p.edgecombe@intel.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/mmap.c | 48 +++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 43 insertions(+), 5 deletions(-)
--- a/mm/mmap.c +++ b/mm/mmap.c @@ -1565,7 +1565,8 @@ static inline int accountable_mapping(st */ static unsigned long unmapped_area(struct vm_unmapped_area_info *info) { - unsigned long length, gap; + unsigned long length, gap, low_limit; + struct vm_area_struct *tmp;
MA_STATE(mas, ¤t->mm->mm_mt, 0, 0);
@@ -1574,12 +1575,29 @@ static unsigned long unmapped_area(struc if (length < info->length) return -ENOMEM;
- if (mas_empty_area(&mas, info->low_limit, info->high_limit - 1, - length)) + low_limit = info->low_limit; +retry: + if (mas_empty_area(&mas, low_limit, info->high_limit - 1, length)) return -ENOMEM;
gap = mas.index; gap += (info->align_offset - gap) & info->align_mask; + tmp = mas_next(&mas, ULONG_MAX); + if (tmp && (tmp->vm_flags & VM_GROWSDOWN)) { /* Avoid prev check if possible */ + if (vm_start_gap(tmp) < gap + length - 1) { + low_limit = tmp->vm_end; + mas_reset(&mas); + goto retry; + } + } else { + tmp = mas_prev(&mas, 0); + if (tmp && vm_end_gap(tmp) > gap) { + low_limit = vm_end_gap(tmp); + mas_reset(&mas); + goto retry; + } + } + return gap; }
@@ -1595,7 +1613,8 @@ static unsigned long unmapped_area(struc */ static unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info) { - unsigned long length, gap; + unsigned long length, gap, high_limit, gap_end; + struct vm_area_struct *tmp;
MA_STATE(mas, ¤t->mm->mm_mt, 0, 0); /* Adjust search length to account for worst case alignment overhead */ @@ -1603,12 +1622,31 @@ static unsigned long unmapped_area_topdo if (length < info->length) return -ENOMEM;
- if (mas_empty_area_rev(&mas, info->low_limit, info->high_limit - 1, + high_limit = info->high_limit; +retry: + if (mas_empty_area_rev(&mas, info->low_limit, high_limit - 1, length)) return -ENOMEM;
gap = mas.last + 1 - info->length; gap -= (gap - info->align_offset) & info->align_mask; + gap_end = mas.last; + tmp = mas_next(&mas, ULONG_MAX); + if (tmp && (tmp->vm_flags & VM_GROWSDOWN)) { /* Avoid prev check if possible */ + if (vm_start_gap(tmp) <= gap_end) { + high_limit = vm_start_gap(tmp); + mas_reset(&mas); + goto retry; + } + } else { + tmp = mas_prev(&mas, 0); + if (tmp && vm_end_gap(tmp) > gap) { + high_limit = tmp->vm_start; + mas_reset(&mas); + goto retry; + } + } + return gap; }