Commit a0b9b0f1 authored by Alice Ryhl's avatar Alice Ryhl Committed by Greg Kroah-Hartman
Browse files

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: default avatarAlice Ryhl <aliceryhl@google.com>
Reviewed-by: default avatarJann Horn <jannh@google.com>
Reviewed-by: default avatarLiam R. Howlett <Liam.Howlett@oracle.com>
Link: https://patch.msgid.link/20260218-binder-vma-rcu-v1-1-8bd45b2b1183@google.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 2e303f0f

drivers/android/binder/page_range.rs

+19 −18
Original line number Diff line number Diff line
@@ -435,24 +435,25 @@ unsafe fn use_page_slow(&self, i: usize) -> Result<()> { 
        //

        // 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()

        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)

                .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

            )

        })?;

                    .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();