The patch titled
Subject: mm/mmap/vma_merge: be explicit about the non-mergeable case
has been added to the -mm mm-unstable branch. Its filename is
mm-mmap-vma_merge-be-explicit-about-the-non-mergeable-case.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-mmap-vma_merge-be-explicit-about-the-non-mergeable-case.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
Subject: mm/mmap/vma_merge: be explicit about the non-mergeable case
Date: Sat, 18 Mar 2023 11:13:21 +0000
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.
Additionally set merge_next directly as there is no need for an if() {}
statement assigning a boolean.
This has no functional impact.
Link: https://lkml.kernel.org/r/d5fae254dc394e96860f41327f24b6ffd20cdf22.1679137163.git.lstoakes@xxxxxxxxx
Signed-off-by: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/mm/mmap.c~mm-mmap-vma_merge-be-explicit-about-the-non-mergeable-case
+++ a/mm/mmap.c
@@ -913,7 +913,7 @@ struct vm_area_struct *vma_merge(struct
pgoff_t vma_pgoff;
struct vm_area_struct *curr, *next, *res;
struct vm_area_struct *vma, *adjust, *remove, *remove2;
- int err = -1;
+ int err = 0;
bool merge_prev = false;
bool merge_next = false;
bool vma_expanded = false;
@@ -1002,12 +1002,15 @@ struct vm_area_struct *vma_merge(struct
}
/* Can we merge the successor? */
- if (next && 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;
- }
+ merge_next = next &&
+ mpol_equal(policy, vma_policy(next)) &&
+ can_vma_merge_before(next, vm_flags,
+ anon_vma, file, pgoff+pglen,
+ vm_userfaultfd_ctx, anon_name);
+
+ /* Not mergeable. */
+ if (!merge_prev && !merge_next)
+ return NULL;
remove = remove2 = adjust = NULL;
/* Can we merge both the predecessor and the successor? */
@@ -1023,7 +1026,7 @@ struct vm_area_struct *vma_merge(struct
err = dup_anon_vma(prev, curr);
}
} else if (merge_prev) {
- err = 0; /* case 2 */
+ /* case 2 */
if (curr) {
err = dup_anon_vma(prev, curr);
if (end == curr->vm_end) { /* case 7 */
@@ -1033,7 +1036,7 @@ struct vm_area_struct *vma_merge(struct
adj_start = (end - curr->vm_start);
}
}
- } else if (merge_next) {
+ } else { /* merge_next */
res = next;
if (prev && addr < prev->vm_end) { /* case 4 */
vma_end = addr;
@@ -1049,7 +1052,7 @@ struct vm_area_struct *vma_merge(struct
vma_start = addr;
vma_end = next->vm_end;
vma_pgoff = next->vm_pgoff;
- err = 0;
+
if (curr) { /* case 8 */
vma_pgoff = curr->vm_pgoff;
remove = curr;
@@ -1058,7 +1061,7 @@ struct vm_area_struct *vma_merge(struct
}
}
- /* Cannot merge or error in anon_vma clone */
+ /* Error in anon_vma clone. */
if (err)
return NULL;
_
Patches currently in -mm which might be from lstoakes@xxxxxxxxx are
mm-remove-unused-vmf_insert_mixed_prot.patch
mm-remove-vmf_insert_pfn_xxx_prot-for-huge-page-table-entries.patch
drm-ttm-remove-comment-referencing-now-removed-vmf_insert_mixed_prot.patch
mm-prefer-xxx_page-alloc-free-functions-for-order-0-pages.patch
mm-refactor-do_fault_around.patch
mm-pefer-fault_around_pages-to-fault_around_bytes.patch
mm-mmap-vma_merge-further-improve-prev-next-vma-naming.patch
mm-mmap-vma_merge-set-next-to-null-if-not-applicable.patch
mm-mmap-vma_merge-extend-invariants-avoid-invalid-res-vma.patch
mm-mmap-vma_merge-be-explicit-about-the-non-mergeable-case.patch
fs-proc-kcore-avoid-bounce-buffer-for-ktext-data.patch
mm-vmalloc-use-rwsem-mutex-for-vmap_area_lock-and-vmap_block-lock.patch
fs-proc-kcore-convert-read_kcore-to-read_kcore_iter.patch
mm-vmalloc-convert-vread-to-vread_iter.patch
