From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1FDFF26FD9B for ; Fri, 8 May 2026 17:29:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778261373; cv=none; b=WUO154EpcldUBgxJIuBxGOUTlw8Oknr+v/Rx05/a5XTZakjxlPe7F1vemf1bge7CgaInLHtGLHkhyOHwm6TPwuTiS9NZp5IgliLKDQom5cwr3BfC+htNqn4yHkysgcnOi5LrAMklblLD8Ssxa1CVGuLT8oaXvc9V74ztJ21PSWU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778261373; c=relaxed/simple; bh=6SVrO0LmOjWH4obgCokBnZqfrETPZpR+dj9JHY4awYU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=N5S9NLkgQw7aEOp42sJClkk2pVjiyHRM/G7p5FVwCK9KT2ZcKHUS3qhToPLy+PdF0sW8wMirY8esBxvdBW8oKhgKDpV3KnMTFxWY5UfGAa2AaNIGmJbJ4Q0l506gnBf5RK3om2LhNWIKrzpnAxzYCk68VaGCgG3Q3ree7pSmX00= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DkubKOtD; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="DkubKOtD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B8921C2BCB0; Fri, 8 May 2026 17:29:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778261372; bh=6SVrO0LmOjWH4obgCokBnZqfrETPZpR+dj9JHY4awYU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=DkubKOtDiUcZwfo4FOCvSQ2G/fDHpJgYZc9S9NhkYt6NS0BD5CXbcJcY3v/LpR6R0 yOsPdGBnv2+X+vMyyTX2SL3lLQ/q1TlVzLyqSoTJ3l0EkAQgKUJvAS+/hLCQ/SAdhq 8jwtQBZZyUFTRLLNUiAsF7n04TPU/brw7uXifZZAEhnZRDhXmCSeIrkVXbSn7c78nT 7ePqU+4QdYVg1cSOhVdNvYsVGS/+1JASfp2loVGoBwkiJmQ66idhGc0Jy1SaWTU8cJ 6J3muLhBqGy3y03DqAcTviRpK5VAmdoC4VclNmYqkeaNh/YZy7ZdTMnYrYc5XLJXrh x9Mu7i9IG91sA== Date: Fri, 8 May 2026 18:29:26 +0100 From: Lorenzo Stoakes To: Dave Hansen Cc: linux-kernel@vger.kernel.org, Andrew Morton , "Liam R. Howlett" , linux-mm@kvack.org, Shakeel Butt , Suren Baghdasaryan , Vlastimil Babka Subject: Re: [PATCH 4/6] binder: Remove mmap_lock fallback Message-ID: References: <20260429181954.F50224AE@davehans-spike.ostc.intel.com> <20260429182000.93887DFB@davehans-spike.ostc.intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260429182000.93887DFB@davehans-spike.ostc.intel.com> On Wed, Apr 29, 2026 at 11:20:00AM -0700, Dave Hansen wrote: > > From: Dave Hansen > > Previously, the per-VMA locking could fail in the face of writers > which necessitate a fallback to mmap_lock. The new > lock_vma_under_rcu_wait() will wait for writers instead of failing. > > Use the new helper. Wait for writers. Remove the fallback to mmap_lock. > > Signed-off-by: Dave Hansen LGTM in principal, though again not a binder dev so just an A-b :) Acked-by: Lorenzo Stoakes > Cc: Suren Baghdasaryan > Cc: Andrew Morton > Cc: "Liam R. Howlett" > Cc: Lorenzo Stoakes > Cc: Vlastimil Babka > Cc: Shakeel Butt > Cc: linux-mm@kvack.org > --- > > b/drivers/android/binder_alloc.c | 17 +++++------------ > 1 file changed, 5 insertions(+), 12 deletions(-) > > diff -puN drivers/android/binder_alloc.c~binder-vma-waiter drivers/android/binder_alloc.c > --- a/drivers/android/binder_alloc.c~binder-vma-waiter 2026-04-29 11:18:51.307654829 -0700 > +++ b/drivers/android/binder_alloc.c 2026-04-29 11:18:51.310654944 -0700 > @@ -259,21 +259,14 @@ static int binder_page_insert(struct bin > struct vm_area_struct *vma; > int ret = -ESRCH; > > - /* attempt per-vma lock first */ > - vma = lock_vma_under_rcu(mm, addr); > - if (vma) { > - if (binder_alloc_is_mapped(alloc)) > - ret = vm_insert_page(vma, addr, page); > - vma_end_read(vma); > + vma = lock_vma_under_rcu_wait(mm, addr); Yeah this name is definitely iffy haha! > + if (!vma) > return ret; > - } > > - /* fall back to mmap_lock */ > - mmap_read_lock(mm); > - vma = vma_lookup(mm, addr); > - if (vma && binder_alloc_is_mapped(alloc)) > + if (binder_alloc_is_mapped(alloc)) > ret = vm_insert_page(vma, addr, page); > - mmap_read_unlock(mm); > + > + vma_end_read(vma); > > return ret; > } > _