| Message ID | 20220901173516.702122-12-surenb@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | per-VMA locks proposal | expand |
Le 01/09/2022 à 19:34, Suren Baghdasaryan a écrit : > 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) That looks good to me, the new VMA allocated by vm_area_dup(vma) is inheriting the locked state from vma. Reviewed-by: Laurent Dufour <laurent.dufour@fr.ibm.com>
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)
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(-)