The patch titled
Subject: mm/mmap/vma_merge: init cleanup, be explicit about the non-mergeable case
has been added to the -mm mm-unstable branch. Its filename is
mm-mmap-vma_merge-init-cleanup-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-init-cleanup-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: init cleanup, be explicit about the non-mergeable case
Date: Tue, 21 Mar 2023 20:45:58 +0000
Reorder the initial variables sensibly and set vma_start and vm_pgoff
there rather than later so all initial values are set at the same time
meaning we don't have to set these later.
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.
This has no functional impact.
Link: https://lkml.kernel.org/r/f5e27d1bb9259b7ef7a45099a838e47fbaaad3ab.1679431180.git.lstoakes@xxxxxxxxx
Signed-off-by: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Liam Howlett <liam.howlett@xxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Vernon Yang <vernon2gm@xxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/mmap.c | 55 ++++++++++++++++++++++++----------------------------
1 file changed, 26 insertions(+), 29 deletions(-)
--- a/mm/mmap.c~mm-mmap-vma_merge-init-cleanup-be-explicit-about-the-non-mergeable-case
+++ a/mm/mmap.c
@@ -909,18 +909,18 @@ struct vm_area_struct *vma_merge(struct
struct vm_userfaultfd_ctx vm_userfaultfd_ctx,
struct anon_vma_name *anon_name)
{
- pgoff_t pglen = (end - addr) >> PAGE_SHIFT;
- pgoff_t vma_pgoff;
struct vm_area_struct *curr, *next, *res;
struct vm_area_struct *vma, *adjust, *remove, *remove2;
- int err = -1;
+ struct vma_prepare vp;
+ int err = 0;
bool merge_prev = false;
bool merge_next = false;
bool vma_expanded = false;
- struct vma_prepare vp;
+ unsigned long vma_start = prev ? prev->vm_start : addr;
unsigned long vma_end = end;
+ pgoff_t vma_pgoff = prev ? prev->vm_pgoff : 0;
+ pgoff_t pglen = (end - addr) >> PAGE_SHIFT;
long adj_start = 0;
- unsigned long vma_start = addr;
validate_mm(mm);
/*
@@ -940,6 +940,23 @@ struct vm_area_struct *vma_merge(struct
/* Is there a VMA next to a hole (case 1 - 3) or prev (4)? */
next = vma_lookup(mm, end);
+ /* Can we merge the predecessor? */
+ if (prev && addr == prev->vm_end && mpol_equal(vma_policy(prev), policy)
+ && can_vma_merge_after(prev, vm_flags, anon_vma, file,
+ pgoff, vm_userfaultfd_ctx, anon_name)) {
+ merge_prev = true;
+ vma_prev(vmi);
+ }
+
+ /* Can we merge the successor? */
+ 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);
+
+ if (!merge_prev && !merge_next)
+ return NULL; /* Not mergeable. */
+
/*
* By default, we return prev. Cases 3, 4, 8 will instead return next
* and cases 3, 8 will also update vma to point at next.
@@ -951,26 +968,6 @@ struct vm_area_struct *vma_merge(struct
VM_WARN_ON(curr && (addr != curr->vm_start || end > curr->vm_end));
VM_WARN_ON(addr >= end);
- if (prev) {
- vma_start = prev->vm_start;
- vma_pgoff = prev->vm_pgoff;
- /* Can we merge the predecessor? */
- if (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)) {
- merge_prev = true;
- vma_prev(vmi);
- }
- }
-
- /* 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;
- }
-
remove = remove2 = adjust = NULL;
/* Can we merge both the predecessor and the successor? */
if (merge_prev && merge_next &&
@@ -985,7 +982,7 @@ 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 */
@@ -995,7 +992,7 @@ 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;
@@ -1011,7 +1008,7 @@ 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;
@@ -1020,7 +1017,7 @@ 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-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
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
maintainers-add-myself-as-vmalloc-reviewer.patch
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-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-init-cleanup-be-explicit-about-the-non-mergeable-case.patch
