From a0b9b0f1433c845bda708753db32befef78e0f1f Mon Sep 17 00:00:00 2001 From: Alice Ryhl Date: Wed, 18 Feb 2026 15:13:23 +0000 Subject: [PATCH] rust_binder: use lock_vma_under_rcu() in use_page_slow() There's no reason to lock the whole mm when we are doing operations on the vma if we can help it, so to reduce contention, use the lock_vma_under_rcu() abstraction. Signed-off-by: Alice Ryhl Reviewed-by: Jann Horn Reviewed-by: Liam R. Howlett Link: https://patch.msgid.link/20260218-binder-vma-rcu-v1-1-8bd45b2b1183@google.com Signed-off-by: Greg Kroah-Hartman --- drivers/android/binder/page_range.rs | 37 ++++++++++++++-------------- 1 file changed, 19 insertions(+), 18 deletions(-) diff --git a/drivers/android/binder/page_range.rs b/drivers/android/binder/page_range.rs index 67aae783e8b8..9dfc154e5dd4 100644 --- a/drivers/android/binder/page_range.rs +++ b/drivers/android/binder/page_range.rs @@ -435,24 +435,25 @@ impl ShrinkablePageRange { // // Using `mmput_async` avoids this, because then the `mm` cleanup is instead queued to a // workqueue. - check_vma( - MmWithUser::into_mmput_async(self.mm.mmget_not_zero().ok_or(ESRCH)?) - .mmap_read_lock() - .vma_lookup(vma_addr) - .ok_or(ESRCH)?, - self, - ) - .ok_or(ESRCH)? - .vm_insert_page(user_page_addr, &new_page) - .inspect_err(|err| { - pr_warn!( - "Failed to vm_insert_page({}): vma_addr:{} i:{} err:{:?}", - user_page_addr, - vma_addr, - i, - err - ) - })?; + let mm = MmWithUser::into_mmput_async(self.mm.mmget_not_zero().ok_or(ESRCH)?); + { + let vma_read; + let mmap_read; + let vma = if let Some(ret) = mm.lock_vma_under_rcu(vma_addr) { + vma_read = ret; + check_vma(&vma_read, self) + } else { + mmap_read = mm.mmap_read_lock(); + mmap_read + .vma_lookup(vma_addr) + .and_then(|vma| check_vma(vma, self)) + }; + + match vma { + Some(vma) => vma.vm_insert_page(user_page_addr, &new_page)?, + None => return Err(ESRCH), + } + } let inner = self.lock.lock();