The quilt patch titled
Subject: mm: move vma locking out of vma_prepare and dup_anon_vma
has been removed from the -mm tree. Its filename was
mm-move-vma-locking-out-of-vma_prepare-and-dup_anon_vma.patch
This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Subject: mm: move vma locking out of vma_prepare and dup_anon_vma
Date: Fri, 4 Aug 2023 08:27:24 -0700
vma_prepare() is currently the central place where vmas are being locked
before vma_complete() applies changes to them. While this is convenient,
it also obscures vma locking and makes it harder to follow the locking
rules. Move vma locking out of vma_prepare() and take vma locks
explicitly at the locations where vmas are being modified. Move vma
locking and replace it with an assertion inside dup_anon_vma() to further
clarify the locking pattern inside vma_merge().
Link: https://lkml.kernel.org/r/20230804152724.3090321-7-surenb@xxxxxxxxxx
Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxx>
Suggested-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/mmap.c | 30 +++++++++++++++++++-----------
1 file changed, 19 insertions(+), 11 deletions(-)
--- a/mm/mmap.c~mm-move-vma-locking-out-of-vma_prepare-and-dup_anon_vma
+++ a/mm/mmap.c
@@ -462,16 +462,6 @@ static inline void init_vma_prep(struct
*/
static inline void vma_prepare(struct vma_prepare *vp)
{
- vma_start_write(vp->vma);
- if (vp->adj_next)
- vma_start_write(vp->adj_next);
- if (vp->insert)
- vma_start_write(vp->insert);
- if (vp->remove)
- vma_start_write(vp->remove);
- if (vp->remove2)
- vma_start_write(vp->remove2);
-
if (vp->file) {
uprobe_munmap(vp->vma, vp->vma->vm_start, vp->vma->vm_end);
@@ -605,7 +595,7 @@ static inline int dup_anon_vma(struct vm
* anon pages imported.
*/
if (src->anon_vma && !dst->anon_vma) {
- vma_start_write(dst);
+ vma_assert_write_locked(dst);
dst->anon_vma = src->anon_vma;
return anon_vma_clone(dst, src);
}
@@ -637,10 +627,12 @@ int vma_expand(struct vma_iterator *vmi,
bool remove_next = false;
struct vma_prepare vp;
+ vma_start_write(vma);
if (next && (vma != next) && (end == next->vm_end)) {
int ret;
remove_next = true;
+ vma_start_write(next);
ret = dup_anon_vma(vma, next);
if (ret)
return ret;
@@ -696,6 +688,8 @@ int vma_shrink(struct vma_iterator *vmi,
if (vma_iter_prealloc(vmi, NULL))
return -ENOMEM;
+ vma_start_write(vma);
+
init_vma_prep(&vp, vma);
vma_prepare(&vp);
vma_adjust_trans_huge(vma, start, end, 0);
@@ -921,16 +915,21 @@ struct vm_area_struct *vma_merge(struct
if (!merge_prev && !merge_next)
return NULL; /* Not mergeable. */
+ if (merge_prev)
+ vma_start_write(prev);
+
res = vma = prev;
remove = remove2 = adjust = NULL;
/* 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)) {
+ vma_start_write(next);
remove = next; /* case 1 */
vma_end = next->vm_end;
err = dup_anon_vma(prev, next);
if (curr) { /* case 6 */
+ vma_start_write(curr);
remove = curr;
remove2 = next;
if (!next->anon_vma)
@@ -938,6 +937,7 @@ struct vm_area_struct *vma_merge(struct
}
} else if (merge_prev) { /* case 2 */
if (curr) {
+ vma_start_write(curr);
err = dup_anon_vma(prev, curr);
if (end == curr->vm_end) { /* case 7 */
remove = curr;
@@ -947,8 +947,10 @@ struct vm_area_struct *vma_merge(struct
}
}
} else { /* merge_next */
+ vma_start_write(next);
res = next;
if (prev && addr < prev->vm_end) { /* case 4 */
+ vma_start_write(prev);
vma_end = addr;
adjust = next;
adj_start = -(prev->vm_end - addr);
@@ -964,6 +966,7 @@ struct vm_area_struct *vma_merge(struct
vma_pgoff = next->vm_pgoff - pglen;
if (curr) { /* case 8 */
vma_pgoff = curr->vm_pgoff;
+ vma_start_write(curr);
remove = curr;
err = dup_anon_vma(next, curr);
}
@@ -2366,6 +2369,9 @@ int __split_vma(struct vma_iterator *vmi
if (new->vm_ops && new->vm_ops->open)
new->vm_ops->open(new);
+ vma_start_write(vma);
+ vma_start_write(new);
+
init_vma_prep(&vp, vma);
vp.insert = new;
vma_prepare(&vp);
@@ -3071,6 +3077,8 @@ static int do_brk_flags(struct vma_itera
if (vma_iter_prealloc(vmi, vma))
goto unacct_fail;
+ vma_start_write(vma);
+
init_vma_prep(&vp, vma);
vma_prepare(&vp);
vma_adjust_trans_huge(vma, vma->vm_start, addr + len, 0);
_
Patches currently in -mm which might be from surenb@xxxxxxxxxx are
swap-remove-remnants-of-polling-from-read_swap_cache_async.patch
mm-add-missing-vm_fault_result_trace-name-for-vm_fault_completed.patch
mm-drop-per-vma-lock-when-returning-vm_fault_retry-or-vm_fault_completed.patch
mm-change-folio_lock_or_retry-to-use-vm_fault-directly.patch
mm-handle-swap-page-faults-under-per-vma-lock.patch
mm-handle-userfaults-under-vma-lock.patch
mm-handle-userfaults-under-vma-lock-fix.patch
