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authorJakub Matěna <matenajakub@gmail.com>2022-06-03 16:57:18 +0200
committerAndrew Morton <akpm@linux-foundation.org>2022-09-26 19:46:27 -0700
commiteef199440df950942b3c7ef2e2de507fd6ced031 (patch)
tree416b154f63b2c8657be4b538e0e066cb9fe40b9d /mm/mmap.c
parentb3541d912a84dc40cabb516f2deeac9ae6fa30da (diff)
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mm: refactor of vma_merge()
Patch series "Refactor of vma_merge and new merge call", v4. I am currently working on my master's thesis trying to increase number of merges of VMAs currently failing because of page offset incompatibility and difference in their anon_vmas. The following refactor and added merge call included in this series is just two smaller upgrades I created along the way. This patch (of 2): Refactor vma_merge() to make it shorter and more understandable. Main change is the elimination of code duplicity in the case of merge next check. This is done by first doing checks and caching the results before executing the merge itself. The variable 'area' is divided into 'mid' and 'res' as previously it was used for two purposes, as the middle VMA between prev and next and also as the result of the merge itself. Exit paths are also unified. Link: https://lkml.kernel.org/r/20220603145719.1012094-1-matenajakub@gmail.com Link: https://lkml.kernel.org/r/20220603145719.1012094-2-matenajakub@gmail.com Signed-off-by: Jakub Matěna <matenajakub@gmail.com> Reviewed-by: Vlastimil Babka <vbabka@suse.cz> Cc: Michal Hocko <mhocko@kernel.org> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Matthew Wilcox <willy@infradead.org> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Hugh Dickins <hughd@google.com> Cc: "Kirill A . Shutemov" <kirill@shutemov.name> Cc: Rik van Riel <riel@surriel.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/mmap.c')
-rw-r--r--mm/mmap.c87
1 files changed, 37 insertions, 50 deletions
diff --git a/mm/mmap.c b/mm/mmap.c
index 2a62d589d3c2..6e447544f07d 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1005,8 +1005,10 @@ struct vm_area_struct *vma_merge(struct mm_struct *mm,
struct anon_vma_name *anon_name)
{
pgoff_t pglen = (end - addr) >> PAGE_SHIFT;
- struct vm_area_struct *area, *next;
- int err;
+ struct vm_area_struct *mid, *next, *res;
+ int err = -1;
+ bool merge_prev = false;
+ bool merge_next = false;
/*
* We later require that vma->vm_flags == vm_flags,
@@ -1016,75 +1018,60 @@ struct vm_area_struct *vma_merge(struct mm_struct *mm,
return NULL;
next = find_vma(mm, prev ? prev->vm_end : 0);
- area = next;
- if (area && area->vm_end == end) /* cases 6, 7, 8 */
+ mid = next;
+ if (next && next->vm_end == end) /* cases 6, 7, 8 */
next = find_vma(mm, next->vm_end);
/* verify some invariant that must be enforced by the caller */
VM_WARN_ON(prev && addr <= prev->vm_start);
- VM_WARN_ON(area && end > area->vm_end);
+ VM_WARN_ON(mid && end > mid->vm_end);
VM_WARN_ON(addr >= end);
- /*
- * Can it merge with the predecessor?
- */
+ /* Can we merge the predecessor? */
if (prev && prev->vm_end == addr &&
mpol_equal(vma_policy(prev), policy) &&
can_vma_merge_after(prev, vm_flags,
anon_vma, file, pgoff,
vm_userfaultfd_ctx, anon_name)) {
- /*
- * OK, it can. Can we now merge in the successor as well?
- */
- if (next && end == next->vm_start &&
- mpol_equal(policy, vma_policy(next)) &&
- can_vma_merge_before(next, vm_flags,
- anon_vma, file,
- pgoff+pglen,
- vm_userfaultfd_ctx, anon_name) &&
- is_mergeable_anon_vma(prev->anon_vma,
- next->anon_vma, NULL)) {
- /* cases 1, 6 */
- err = __vma_adjust(prev, prev->vm_start,
- next->vm_end, prev->vm_pgoff, NULL,
- prev);
- } else /* cases 2, 5, 7 */
- err = __vma_adjust(prev, prev->vm_start,
- end, prev->vm_pgoff, NULL, prev);
- if (err)
- return NULL;
- khugepaged_enter_vma(prev, vm_flags);
- return prev;
+ merge_prev = true;
}
-
- /*
- * Can this new request be merged in front of next?
- */
+ /* Can we merge the successor? */
if (next && end == next->vm_start &&
mpol_equal(policy, vma_policy(next)) &&
can_vma_merge_before(next, vm_flags,
anon_vma, file, pgoff+pglen,
vm_userfaultfd_ctx, anon_name)) {
+ merge_next = true;
+ }
+ /* Can we merge both the predecessor and the successor? */
+ if (merge_prev && merge_next &&
+ is_mergeable_anon_vma(prev->anon_vma,
+ next->anon_vma, NULL)) { /* cases 1, 6 */
+ err = __vma_adjust(prev, prev->vm_start,
+ next->vm_end, prev->vm_pgoff, NULL,
+ prev);
+ res = prev;
+ } else if (merge_prev) { /* cases 2, 5, 7 */
+ err = __vma_adjust(prev, prev->vm_start,
+ end, prev->vm_pgoff, NULL, prev);
+ res = prev;
+ } else if (merge_next) {
if (prev && addr < prev->vm_end) /* case 4 */
err = __vma_adjust(prev, prev->vm_start,
- addr, prev->vm_pgoff, NULL, next);
- else { /* cases 3, 8 */
- err = __vma_adjust(area, addr, next->vm_end,
- next->vm_pgoff - pglen, NULL, next);
- /*
- * In case 3 area is already equal to next and
- * this is a noop, but in case 8 "area" has
- * been removed and next was expanded over it.
- */
- area = next;
- }
- if (err)
- return NULL;
- khugepaged_enter_vma(area, vm_flags);
- return area;
+ addr, prev->vm_pgoff, NULL, next);
+ else /* cases 3, 8 */
+ err = __vma_adjust(mid, addr, next->vm_end,
+ next->vm_pgoff - pglen, NULL, next);
+ res = next;
}
- return NULL;
+ /*
+ * Cannot merge with predecessor or successor or error in __vma_adjust?
+ */
+ if (err)
+ return NULL;
+ khugepaged_enter_vma(res, vm_flags);
+ return res;
}
/*