From nobody Fri Dec 19 08:07:14 2025 Received: from mail-pj1-f74.google.com (mail-pj1-f74.google.com [209.85.216.74]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 34F6120A5FA for ; Tue, 3 Dec 2024 21:55:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.74 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733262920; cv=none; b=EqC/ugYefbVgzB5dJEguZUofkyD6y3GSdk0VP8SdP3A/t+wnfdZ6Yk5dclnY4jNEt5425SYBkek54v0zcoycZyybcW5HaL7Y/eAjN7MYE5LriFQ2JOWGySh96tAprBxbF0WVTYThAMWx0vo7UatNEsZ1JXGf92WbmNZJyllJ+Pk= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733262920; c=relaxed/simple; bh=feto92b180sVitSUi6WA4dfzTO6KX//Xofn2Sv0b/xs=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=sVnf7matonMmwq3x18Mu+YVj2LzoAvpDmYMaEtrFtrV62ONqtWTIBXjWNEZqVkfzGccvsOxqLx8cxVxJfcetCCBcphDPJbbC5twJhrMyLR0PdFUNuYvYUzp4+0hh84sspAnN28ErngF4GeQyUhNhUXJBAe7eiDcwfLWvpq799sg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--cmllamas.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=B+l91Jci; arc=none smtp.client-ip=209.85.216.74 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--cmllamas.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="B+l91Jci" Received: by mail-pj1-f74.google.com with SMTP id 98e67ed59e1d1-2ee5f6fa3feso6000283a91.0 for ; Tue, 03 Dec 2024 13:55:18 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1733262918; x=1733867718; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=ybt3W/utb4idptlSsffJBzP4pVTicA4UuTKY+AOtES8=; b=B+l91JciG+VKXvQYWhKEFn8Q1sTPTT6R/q6Y/t54yTMZhYaETWRO0crPalU/q6JbsC dJYjghmOYTzeCbEQ0GIVaZ16RKx3cByk1p5LTN7p6Mm7TotUDWoCHp+7TiTo0amOTKs6 ZtBz863UzmWgEoo9BawfOjArCmPnE1E7Exok+wPiAn9GVJitqvq4rbNyLI5ld82rzZLl CojRASfl3K3AcRUDRBYTJugUlHroH5dv8lILEvHyxfTCIDucpAkWZayxRDKPAd1UGV40 c0f0XdHyvR+XaiDqGB6xwrpW3us58ekJDllLN5p9HA7oqDXA0JWHUR5kYXgpYyNNQRnk PGvA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1733262918; x=1733867718; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=ybt3W/utb4idptlSsffJBzP4pVTicA4UuTKY+AOtES8=; b=Ob2I6M1rK0PsJmvjOnCNV272QAUeCWKlofOvLSxYwJGnlYr0No7dEZlrGwgPnB26pr 76CIL1iCBLWa5aPRgp4jNyfc5Lljzyq8J18X9OJ2CXMJ+miq26XZbGSvpwdQYlM2wO4E cgnYdfMDMgad6n/8guWXQtYNrO9xj2xZs1WU0s+M+wAqILdlJGorVKeyJNYf8vJ4uKc5 6bZtNdhSxVj643yiZoGsRhEJG2Fmsp614Uz0tPULXfnNEb081Uh2iMYJCj8cKqp70jMF DvTBQyFlRGiEngS/HD3yMsI6sjQdfvyPz3i5Sml36Fsu64R+PxH/uRIc+kNyUP6KiwUS hWLA== X-Gm-Message-State: AOJu0YzUEPy59xwUYWDvKxTazmmet7kuKHpf2Ma6zW8xjgCrlOCjLe3g pLlZG2JRHoYog/F2/lrNp6Dp2m2k+D4IPgCdLmZgrjWZUdM2L5nFIDFDpsmAmlMPajTIGBMqm1m mwfrH4uRvZQ== X-Google-Smtp-Source: AGHT+IG6LOHr8nv/5OQkg2nS8yTZbbXLg7Kko7qvE20Jg+aPBhyBNIWSEjDB4gfRA/S7rXb1WX7MD+b7L5OsTw== X-Received: from pjur6.prod.google.com ([2002:a17:90a:d406:b0:2ee:4b69:50e1]) (user=cmllamas job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:2547:b0:2ee:fa3f:4740 with SMTP id 98e67ed59e1d1-2ef012759b6mr6171548a91.35.1733262918471; Tue, 03 Dec 2024 13:55:18 -0800 (PST) Date: Tue, 3 Dec 2024 21:54:36 +0000 In-Reply-To: <20241203215452.2820071-1-cmllamas@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20241203215452.2820071-1-cmllamas@google.com> X-Mailer: git-send-email 2.47.0.338.g60cca15819-goog Message-ID: <20241203215452.2820071-3-cmllamas@google.com> Subject: [PATCH v6 2/9] binder: concurrent page installation From: Carlos Llamas To: Greg Kroah-Hartman , "=?UTF-8?q?Arve=20Hj=C3=B8nnev=C3=A5g?=" , Todd Kjos , Martijn Coenen , Joel Fernandes , Christian Brauner , Carlos Llamas , Suren Baghdasaryan Cc: linux-kernel@vger.kernel.org, kernel-team@android.com, David Hildenbrand , Barry Song , "Liam R. Howlett" Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Allow multiple callers to install pages simultaneously by switching the mmap_sem from write-mode to read-mode. Races to the same PTE are handled using get_user_pages_remote() to retrieve the already installed page. This method significantly reduces contention in the mmap semaphore. To ensure safety, vma_lookup() is used (instead of alloc->vma) to avoid operating on an isolated VMA. In addition, zap_page_range_single() is called under the alloc->mutex to avoid racing with the shrinker. Many thanks to Barry Song who posted a similar approach [1]. Link: https://lore.kernel.org/all/20240902225009.34576-1-21cnbao@gmail.com/= [1] Cc: David Hildenbrand Cc: Barry Song Cc: Suren Baghdasaryan Cc: Liam R. Howlett Reviewed-by: Suren Baghdasaryan Signed-off-by: Carlos Llamas --- drivers/android/binder_alloc.c | 65 +++++++++++++++++++++------------- 1 file changed, 41 insertions(+), 24 deletions(-) diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c index 52f6aa3232e1..f26283c2c768 100644 --- a/drivers/android/binder_alloc.c +++ b/drivers/android/binder_alloc.c @@ -221,26 +221,14 @@ static int binder_install_single_page(struct binder_a= lloc *alloc, struct binder_lru_page *lru_page, unsigned long addr) { + struct vm_area_struct *vma; struct page *page; - int ret =3D 0; + long npages; + int ret; =20 if (!mmget_not_zero(alloc->mm)) return -ESRCH; =20 - /* - * Protected with mmap_sem in write mode as multiple tasks - * might race to install the same page. - */ - mmap_write_lock(alloc->mm); - if (binder_get_installed_page(lru_page)) - goto out; - - if (!alloc->vma) { - pr_err("%d: %s failed, no vma\n", alloc->pid, __func__); - ret =3D -ESRCH; - goto out; - } - page =3D alloc_page(GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO); if (!page) { pr_err("%d: failed to allocate page\n", alloc->pid); @@ -248,19 +236,48 @@ static int binder_install_single_page(struct binder_a= lloc *alloc, goto out; } =20 - ret =3D vm_insert_page(alloc->vma, addr, page); - if (ret) { + mmap_read_lock(alloc->mm); + vma =3D vma_lookup(alloc->mm, addr); + if (!vma || vma !=3D alloc->vma) { + __free_page(page); + pr_err("%d: %s failed, no vma\n", alloc->pid, __func__); + ret =3D -ESRCH; + goto unlock; + } + + ret =3D vm_insert_page(vma, addr, page); + switch (ret) { + case -EBUSY: + /* + * EBUSY is ok. Someone installed the pte first but the + * lru_page->page_ptr has not been updated yet. Discard + * our page and look up the one already installed. + */ + ret =3D 0; + __free_page(page); + npages =3D get_user_pages_remote(alloc->mm, addr, 1, + FOLL_NOFAULT, &page, NULL); + if (npages <=3D 0) { + pr_err("%d: failed to find page at offset %lx\n", + alloc->pid, addr - alloc->buffer); + ret =3D -ESRCH; + break; + } + fallthrough; + case 0: + /* Mark page installation complete and safe to use */ + binder_set_installed_page(lru_page, page); + break; + default: + __free_page(page); pr_err("%d: %s failed to insert page at offset %lx with %d\n", alloc->pid, __func__, addr - alloc->buffer, ret); - __free_page(page); ret =3D -ENOMEM; - goto out; + break; } - - /* Mark page installation complete and safe to use */ - binder_set_installed_page(lru_page, page); +unlock: + mmap_read_unlock(alloc->mm); out: - mmap_write_unlock(alloc->mm); mmput_async(alloc->mm); return ret; } @@ -1090,7 +1107,6 @@ enum lru_status binder_alloc_free_page(struct list_he= ad *item, trace_binder_unmap_kernel_end(alloc, index); =20 list_lru_isolate(lru, item); - mutex_unlock(&alloc->mutex); spin_unlock(&lru->lock); =20 if (vma) { @@ -1101,6 +1117,7 @@ enum lru_status binder_alloc_free_page(struct list_he= ad *item, trace_binder_unmap_user_end(alloc, index); } =20 + mutex_unlock(&alloc->mutex); mmap_read_unlock(mm); mmput_async(mm); __free_page(page_to_free); --=20 2.47.0.338.g60cca15819-goog