lkml.org 
[lkml]   [2022]   [Aug]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
Subject[RFC PATCH 11/28] mm/mmap: mark VMAs as locked before merging or splitting them
From
Decisions about whether VMAs can be merged or split must be made while
VMAs are protected from the changes which can affect that decision.
For example, merge_vma uses vma->anon_vma in its decision whether the
VMA can be merged. Meanwhile, page fault handler changes vma->anon_vma
during COW operation.
Mark all VMAs which might be affected by a merge or split operation as
locked before making decision how such operations should be performed.

Signed-off-by: Suren Baghdasaryan <surenb@google.com>
---
mm/mmap.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index ed58cf0689b2..ade3909c89b4 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1147,10 +1147,17 @@ struct vm_area_struct *vma_merge(struct mm_struct *mm,
if (vm_flags & VM_SPECIAL)
return NULL;

+ if (prev)
+ vma_mark_locked(prev);
next = vma_next(mm, prev);
area = next;
- if (area && area->vm_end == end) /* cases 6, 7, 8 */
+ if (area)
+ vma_mark_locked(area);
+ if (area && area->vm_end == end) { /* cases 6, 7, 8 */
next = next->vm_next;
+ if (next)
+ vma_mark_locked(next);
+ }

/* verify some invariant that must be enforced by the caller */
VM_WARN_ON(prev && addr <= prev->vm_start);
@@ -2687,6 +2694,7 @@ int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
struct vm_area_struct *new;
int err;

+ vma_mark_locked(vma);
if (vma->vm_ops && vma->vm_ops->may_split) {
err = vma->vm_ops->may_split(vma, addr);
if (err)
--
2.37.2.672.g94769d06f0-goog
\
 
 \ /
  Last update: 2022-08-29 23:27    [W:0.100 / U:0.368 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site