From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CA3D3C433FE for ; Tue, 12 Oct 2021 08:39:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AA2C3604D2 for ; Tue, 12 Oct 2021 08:39:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235122AbhJLIl0 (ORCPT ); Tue, 12 Oct 2021 04:41:26 -0400 Received: from mailgw02.mediatek.com ([210.61.82.184]:42782 "EHLO mailgw02.mediatek.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S234870AbhJLIlZ (ORCPT ); Tue, 12 Oct 2021 04:41:25 -0400 X-UUID: 4cf412d9876e48d4b14de15c2228a019-20211012 X-UUID: 4cf412d9876e48d4b14de15c2228a019-20211012 Received: from mtkmbs10n1.mediatek.inc [(172.21.101.34)] by mailgw02.mediatek.com (envelope-from ) (Generic MTA with TLSv1.2 ECDHE-RSA-AES256-GCM-SHA384 256/256) with ESMTP id 1964211283; Tue, 12 Oct 2021 16:39:21 +0800 Received: from mtkcas11.mediatek.inc (172.21.101.40) by mtkmbs10n2.mediatek.inc (172.21.101.183) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id 15.2.792.3; Tue, 12 Oct 2021 16:39:20 +0800 Received: from mszswglt01.gcn.mediatek.inc (10.16.20.20) by mtkcas11.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.0.1497.2 via Frontend Transport; Tue, 12 Oct 2021 16:39:20 +0800 From: To: CC: , , , , , , , , , , , Guangming Cao Subject: Re: [PATCH v2] dma-buf: remove restriction of IOCTL:DMA_BUF_SET_NAME Date: Tue, 12 Oct 2021 16:41:09 +0800 Message-ID: <20211012084109.176542-1-guangming.cao@mediatek.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain X-MTK: N Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Guangming Cao > Am 09.10.21 um 07:55 schrieb guangming.cao@mediatek.com: > From: Guangming Cao > > > > If dma-buf don't want userspace users to touch the dmabuf buffer, > > it seems we should add this restriction into dma_buf_ops.mmap, > > not in this IOCTL:DMA_BUF_SET_NAME. > > > > With this restriction, we can only know the kernel users of the dmabuf > > by attachments. > > However, for many userspace users, such as userpsace users of dma_heap, > > they also need to mark the usage of dma-buf, and they don't care about > > who attached to this dmabuf, and seems it's no meaning to be waiting for > > IOCTL:DMA_BUF_SET_NAME rather than mmap. > > Sounds valid to me, but I have no idea why this restriction was added in > the first place. > > Can you double check the git history and maybe identify when that was > added? Mentioning this change in the commit message then might make > things a bit easier to understand. > > Thanks, > Christian. It was add in this patch: https://patchwork.freedesktop.org/patch/310349/. However, there is no illustration about it. I guess it wants users to set_name when no attachments on the dmabuf, for case with attachments, we can find owner by device in attachments. But just I said in commit message, this is might not a good idea. Do you have any idea? > > > > > Signed-off-by: Guangming Cao > > --- > > drivers/dma-buf/dma-buf.c | 14 ++------------ > > 1 file changed, 2 insertions(+), 12 deletions(-) > > > > diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c > > index 511fe0d217a0..db2f4efdec32 100644 > > --- a/drivers/dma-buf/dma-buf.c > > +++ b/drivers/dma-buf/dma-buf.c > > @@ -325,10 +325,8 @@ static __poll_t dma_buf_poll(struct file *file, poll_table *poll) > > > > /** > > * dma_buf_set_name - Set a name to a specific dma_buf to track the usage. > > - * The name of the dma-buf buffer can only be set when the dma-buf is not > > - * attached to any devices. It could theoritically support changing the > > - * name of the dma-buf if the same piece of memory is used for multiple > > - * purpose between different devices. > > + * It could theoretically support changing the name of the dma-buf if the same > > + * piece of memory is used for multiple purpose between different devices. > > * > > * @dmabuf: [in] dmabuf buffer that will be renamed. > > * @buf: [in] A piece of userspace memory that contains the name of > > @@ -346,19 +344,11 @@ static long dma_buf_set_name(struct dma_buf *dmabuf, const char __user *buf) > > if (IS_ERR(name)) > > return PTR_ERR(name); > > > > - dma_resv_lock(dmabuf->resv, NULL); > > - if (!list_empty(&dmabuf->attachments)) { > > - ret = -EBUSY; > > - kfree(name); > > - goto out_unlock; > > - } > > spin_lock(&dmabuf->name_lock); > > kfree(dmabuf->name); > > dmabuf->name = name; > > spin_unlock(&dmabuf->name_lock); > > > > -out_unlock: > > - dma_resv_unlock(dmabuf->resv); > > return ret; > > } > >