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authorLiam R. Howlett <Liam.Howlett@oracle.com>2023-04-14 21:59:19 +0300
committerAndrew Morton <akpm@linux-foundation.org>2023-04-19 00:22:14 +0300
commit58c5d0d6d522112577c7eeb71d382ea642ed7be4 (patch)
tree18e74dcce2826b651093634757906c6b9b55e6a1 /mm
parent06e8fd999334bcd76b4d72d7b9206d4aea89764e (diff)
downloadlinux-58c5d0d6d522112577c7eeb71d382ea642ed7be4.tar.xz
mm/mmap: regression fix for unmapped_area{_topdown}
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>
Diffstat (limited to 'mm')
-rw-r--r--mm/mmap.c48
1 files changed, 43 insertions, 5 deletions
diff --git a/mm/mmap.c b/mm/mmap.c
index ff68a67a2a7c..d5475fbf5729 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1518,7 +1518,8 @@ static inline int accountable_mapping(struct file *file, vm_flags_t vm_flags)
*/
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, &current->mm->mm_mt, 0, 0);
@@ -1527,12 +1528,29 @@ static unsigned long unmapped_area(struct vm_unmapped_area_info *info)
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;
}
@@ -1548,7 +1566,8 @@ static unsigned long unmapped_area(struct vm_unmapped_area_info *info)
*/
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, &current->mm->mm_mt, 0, 0);
/* Adjust search length to account for worst case alignment overhead */
@@ -1556,12 +1575,31 @@ static unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info)
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;
}