| Message ID | 20230711202047.3818697-3-willy@infradead.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Avoid the mmap lock for fault-around | expand |
On Tue, Jul 11, 2023 at 1:21 PM Matthew Wilcox (Oracle) <willy@infradead.org> wrote: > > The fault path will immediately fail in handle_mm_fault(), so this > is the minimal step which allows the per-VMA lock to be taken on > file-backed VMAs. There may be a small performance reduction as a > little unnecessary work will be done on each page fault. See later > patches for the improvement. > > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Reviewed-by: Suren Baghdasaryan <surenb@google.com> > --- > mm/memory.c | 11 ++++++----- > 1 file changed, 6 insertions(+), 5 deletions(-) > > diff --git a/mm/memory.c b/mm/memory.c > index 2c7967632866..f2dcc695f54e 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -5247,6 +5247,11 @@ vm_fault_t handle_mm_fault(struct vm_area_struct *vma, unsigned long address, > goto out; > } > > + if ((flags & FAULT_FLAG_VMA_LOCK) && !vma_is_anonymous(vma)) { > + vma_end_read(vma); > + return VM_FAULT_RETRY; > + } > + > /* > * Enable the memcg OOM handling for faults triggered in user > * space. Kernel faults are handled more gracefully. > @@ -5418,12 +5423,8 @@ struct vm_area_struct *lock_vma_under_rcu(struct mm_struct *mm, > if (!vma) > goto inval; > > - /* Only anonymous vmas are supported for now */ > - if (!vma_is_anonymous(vma)) > - goto inval; > - > /* find_mergeable_anon_vma uses adjacent vmas which are not locked */ > - if (!vma->anon_vma) > + if (vma_is_anonymous(vma) && !vma->anon_vma) > goto inval; > > if (!vma_start_read(vma)) > -- > 2.39.2 >
diff --git a/mm/memory.c b/mm/memory.c index 2c7967632866..f2dcc695f54e 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -5247,6 +5247,11 @@ vm_fault_t handle_mm_fault(struct vm_area_struct *vma, unsigned long address, goto out; } + if ((flags & FAULT_FLAG_VMA_LOCK) && !vma_is_anonymous(vma)) { + vma_end_read(vma); + return VM_FAULT_RETRY; + } + /* * Enable the memcg OOM handling for faults triggered in user * space. Kernel faults are handled more gracefully. @@ -5418,12 +5423,8 @@ struct vm_area_struct *lock_vma_under_rcu(struct mm_struct *mm, if (!vma) goto inval; - /* Only anonymous vmas are supported for now */ - if (!vma_is_anonymous(vma)) - goto inval; - /* find_mergeable_anon_vma uses adjacent vmas which are not locked */ - if (!vma->anon_vma) + if (vma_is_anonymous(vma) && !vma->anon_vma) goto inval; if (!vma_start_read(vma))
The fault path will immediately fail in handle_mm_fault(), so this is the minimal step which allows the per-VMA lock to be taken on file-backed VMAs. There may be a small performance reduction as a little unnecessary work will be done on each page fault. See later patches for the improvement. Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> --- mm/memory.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-)