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mm/mmap/vma_merge: init cleanup, be explicit about the non-mergeable case
Rather than setting err = -1 and only resetting if we hit merge cases, explicitly check the non-mergeable case to make it abundantly clear that we only proceed with the rest if something is mergeable, default err to 0 and only update if an error might occur. Move the merge_prev, merge_next cases closer to the logic determining curr, next and reorder initial variables so they are more logically grouped. This has no functional impact. Link: https://lkml.kernel.org/r/99259fbc6403e80e270e1cc4612abbc8620b121b.1679516210.git.lstoakes@gmail.com Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com> Reviewed-by: Vlastimil Babka <vbabka@suse.cz> Cc: David Hildenbrand <david@redhat.com> Cc: Liam R. Howlett <Liam.Howlett@oracle.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Vernon Yang <vernon2gm@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
parent
b0729ae0ae
commit
0173db4f7f
49
mm/mmap.c
49
mm/mmap.c
@ -896,18 +896,18 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
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struct vm_userfaultfd_ctx vm_userfaultfd_ctx,
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struct vm_userfaultfd_ctx vm_userfaultfd_ctx,
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struct anon_vma_name *anon_name)
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struct anon_vma_name *anon_name)
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{
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{
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pgoff_t pglen = (end - addr) >> PAGE_SHIFT;
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pgoff_t vma_pgoff;
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struct vm_area_struct *curr, *next, *res;
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struct vm_area_struct *curr, *next, *res;
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struct vm_area_struct *vma, *adjust, *remove, *remove2;
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struct vm_area_struct *vma, *adjust, *remove, *remove2;
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int err = -1;
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struct vma_prepare vp;
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pgoff_t vma_pgoff;
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int err = 0;
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bool merge_prev = false;
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bool merge_prev = false;
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bool merge_next = false;
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bool merge_next = false;
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bool vma_expanded = false;
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bool vma_expanded = false;
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struct vma_prepare vp;
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unsigned long vma_end = end;
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long adj_start = 0;
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unsigned long vma_start = addr;
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unsigned long vma_start = addr;
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unsigned long vma_end = end;
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pgoff_t pglen = (end - addr) >> PAGE_SHIFT;
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long adj_start = 0;
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validate_mm(mm);
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validate_mm(mm);
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/*
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/*
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@ -926,24 +926,14 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
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else
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else
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next = NULL; /* case 5 */
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next = NULL; /* case 5 */
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/*
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* By default, we return prev. Cases 3, 4, 8 will instead return next
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* and cases 3, 8 will also update vma to point at next.
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*/
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res = vma = prev;
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/* Verify some invariant that must be enforced by the caller. */
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VM_WARN_ON(prev && addr <= prev->vm_start);
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VM_WARN_ON(curr && (addr != curr->vm_start || end > curr->vm_end));
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VM_WARN_ON(addr >= end);
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if (prev) {
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if (prev) {
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vma_start = prev->vm_start;
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vma_start = prev->vm_start;
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vma_pgoff = prev->vm_pgoff;
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vma_pgoff = prev->vm_pgoff;
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/* Can we merge the predecessor? */
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/* Can we merge the predecessor? */
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if (prev->vm_end == addr && mpol_equal(vma_policy(prev), policy)
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if (addr == prev->vm_end && mpol_equal(vma_policy(prev), policy)
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&& can_vma_merge_after(prev, vm_flags, anon_vma, file,
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&& can_vma_merge_after(prev, vm_flags, anon_vma, file,
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pgoff, vm_userfaultfd_ctx, anon_name)) {
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pgoff, vm_userfaultfd_ctx, anon_name)) {
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merge_prev = true;
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merge_prev = true;
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vma_prev(vmi);
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vma_prev(vmi);
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}
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}
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@ -951,13 +941,22 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
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/* Can we merge the successor? */
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/* Can we merge the successor? */
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if (next && mpol_equal(policy, vma_policy(next)) &&
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if (next && mpol_equal(policy, vma_policy(next)) &&
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can_vma_merge_before(next, vm_flags,
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can_vma_merge_before(next, vm_flags, anon_vma, file, pgoff+pglen,
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anon_vma, file, pgoff+pglen,
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vm_userfaultfd_ctx, anon_name)) {
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vm_userfaultfd_ctx, anon_name)) {
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merge_next = true;
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merge_next = true;
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}
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}
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if (!merge_prev && !merge_next)
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return NULL; /* Not mergeable. */
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res = vma = prev;
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remove = remove2 = adjust = NULL;
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remove = remove2 = adjust = NULL;
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/* Verify some invariant that must be enforced by the caller. */
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VM_WARN_ON(prev && addr <= prev->vm_start);
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VM_WARN_ON(curr && (addr != curr->vm_start || end > curr->vm_end));
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VM_WARN_ON(addr >= end);
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/* Can we merge both the predecessor and the successor? */
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/* Can we merge both the predecessor and the successor? */
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if (merge_prev && merge_next &&
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if (merge_prev && merge_next &&
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is_mergeable_anon_vma(prev->anon_vma, next->anon_vma, NULL)) {
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is_mergeable_anon_vma(prev->anon_vma, next->anon_vma, NULL)) {
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@ -970,8 +969,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
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if (!next->anon_vma)
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if (!next->anon_vma)
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err = dup_anon_vma(prev, curr);
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err = dup_anon_vma(prev, curr);
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}
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}
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} else if (merge_prev) {
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} else if (merge_prev) { /* case 2 */
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err = 0; /* case 2 */
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if (curr) {
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if (curr) {
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err = dup_anon_vma(prev, curr);
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err = dup_anon_vma(prev, curr);
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if (end == curr->vm_end) { /* case 7 */
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if (end == curr->vm_end) { /* case 7 */
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@ -981,7 +979,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
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adj_start = (end - curr->vm_start);
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adj_start = (end - curr->vm_start);
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}
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}
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}
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}
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} else if (merge_next) {
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} else { /* merge_next */
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res = next;
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res = next;
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if (prev && addr < prev->vm_end) { /* case 4 */
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if (prev && addr < prev->vm_end) { /* case 4 */
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vma_end = addr;
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vma_end = addr;
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@ -997,7 +995,6 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
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vma_start = addr;
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vma_start = addr;
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vma_end = next->vm_end;
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vma_end = next->vm_end;
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vma_pgoff = next->vm_pgoff;
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vma_pgoff = next->vm_pgoff;
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err = 0;
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if (curr) { /* case 8 */
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if (curr) { /* case 8 */
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vma_pgoff = curr->vm_pgoff;
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vma_pgoff = curr->vm_pgoff;
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remove = curr;
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remove = curr;
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@ -1006,7 +1003,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
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}
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}
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}
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}
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/* Cannot merge or error in anon_vma clone */
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/* Error in anon_vma clone. */
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if (err)
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if (err)
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return NULL;
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return NULL;
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