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 X-Spam-Level: X-Spam-Status: No, score=-0.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, T_DKIMWL_WL_HIGH,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by aws-us-west-2-korg-lkml-1.web.codeaurora.org (Postfix) with ESMTP id A82E4C433EF for ; Wed, 13 Jun 2018 02:58:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3D97C20891 for ; Wed, 13 Jun 2018 02:58:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="DWg9e/1X" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3D97C20891 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=oracle.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933609AbeFMC6r (ORCPT ); Tue, 12 Jun 2018 22:58:47 -0400 Received: from userp2120.oracle.com ([156.151.31.85]:54624 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932697AbeFMC6p (ORCPT ); Tue, 12 Jun 2018 22:58:45 -0400 Received: from pps.filterd (userp2120.oracle.com [127.0.0.1]) by userp2120.oracle.com (8.16.0.22/8.16.0.22) with SMTP id w5D2uqcd051250; Wed, 13 Jun 2018 02:58:34 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=corp-2017-10-26; bh=Tp5dlHUkCApYbdF1Xq/1fs7BszQnnpM3VzSdOlNlSZM=; b=DWg9e/1X9nqbBeQfnBcas44kxZj+o9o4614alw7muba0HB3c2bOKXItuzsJSNNMSBefc Ks2loE6Lwqpc2zT+WOmYgfwDBuFXcojOPGuLsG0Cq0Je9kEuliaJjcaWpQmzA6pYdaMu kcPyvJQJDMBBlrao4wc3XwmjllDOyR/yZ4C+kqpexKCtY+/gUGk8bLeKgqP8894HtIVN I9bZfwSAVg4IYzcWdVfju1Y6UIUuS336rs/DLKTzxPqf0FeUTGZ2x9B8n0ulkLTjDjtZ jBMKx2m9N8s2wCcQsvpUElgCpONnj9DH6CgtSiKAXSl9VuaiYptHPHkokdTU6KPYzRB1 zQ== Received: from userv0022.oracle.com (userv0022.oracle.com [156.151.31.74]) by userp2120.oracle.com with ESMTP id 2jjp6brgmd-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 13 Jun 2018 02:58:34 +0000 Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by userv0022.oracle.com (8.14.4/8.14.4) with ESMTP id w5D2wYMw021204 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 13 Jun 2018 02:58:34 GMT Received: from abhmp0016.oracle.com (abhmp0016.oracle.com [141.146.116.22]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id w5D2wXro015704; Wed, 13 Jun 2018 02:58:33 GMT Received: from [10.154.144.7] (/10.154.144.7) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 12 Jun 2018 19:58:32 -0700 Subject: Re: [PATCH v3 8/9] xen/gntdev: Implement dma-buf export functionality To: Oleksandr Andrushchenko , xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-media@vger.kernel.org, jgross@suse.com, konrad.wilk@oracle.com Cc: daniel.vetter@intel.com, dongwon.kim@intel.com, matthew.d.roper@intel.com, Oleksandr Andrushchenko References: <20180612134200.17456-1-andr2000@gmail.com> <20180612134200.17456-9-andr2000@gmail.com> From: Boris Ostrovsky Message-ID: Date: Tue, 12 Jun 2018 22:58:30 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: <20180612134200.17456-9-andr2000@gmail.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=8922 signatures=668702 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=2 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1805220000 definitions=main-1806130033 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/12/2018 09:41 AM, Oleksandr Andrushchenko wrote: > From: Oleksandr Andrushchenko > > 1. Create a dma-buf from grant references provided by the foreign > domain. By default dma-buf is backed by system memory pages, but > by providing GNTDEV_DMA_FLAG_XXX flags it can also be created > as a DMA write-combine/coherent buffer, e.g. allocated with > corresponding dma_alloc_xxx API. > Export the resulting buffer as a new dma-buf. > > 2. Implement waiting for the dma-buf to be released: block until the > dma-buf with the file descriptor provided is released. > If within the time-out provided the buffer is not released then > -ETIMEDOUT error is returned. If the buffer with the file descriptor > does not exist or has already been released, then -ENOENT is > returned. For valid file descriptors this must not be treated as > error. > > 3. Make gntdev's common code and structures available to dma-buf. > > Signed-off-by: Oleksandr Andrushchenko > --- > drivers/xen/gntdev-common.h | 4 + > drivers/xen/gntdev-dmabuf.c | 470 +++++++++++++++++++++++++++++++++++- > drivers/xen/gntdev.c | 10 + > 3 files changed, 482 insertions(+), 2 deletions(-) > > diff --git a/drivers/xen/gntdev-common.h b/drivers/xen/gntdev-common.h > index a3408fd39b07..72f80dbce861 100644 > --- a/drivers/xen/gntdev-common.h > +++ b/drivers/xen/gntdev-common.h > @@ -89,4 +89,8 @@ bool gntdev_account_mapped_pages(int count); > > int gntdev_map_grant_pages(struct gntdev_grant_map *map); > > +#ifdef CONFIG_XEN_GNTDEV_DMABUF > +void gntdev_remove_map(struct gntdev_priv *priv, struct gntdev_grant_map *map); > +#endif > + > #endif > diff --git a/drivers/xen/gntdev-dmabuf.c b/drivers/xen/gntdev-dmabuf.c > index dc57c6a25525..84cba67c6ad7 100644 > --- a/drivers/xen/gntdev-dmabuf.c > +++ b/drivers/xen/gntdev-dmabuf.c > @@ -3,13 +3,53 @@ > /* > * Xen dma-buf functionality for gntdev. > * > + * DMA buffer implementation is based on drivers/gpu/drm/drm_prime.c. > + * > * Copyright (c) 2018 Oleksandr Andrushchenko, EPAM Systems Inc. > */ > > +#include > #include > > +#include > +#include > + > +#include "gntdev-common.h" > #include "gntdev-dmabuf.h" > > +struct gntdev_dmabuf { > + struct gntdev_dmabuf_priv *priv; > + struct dma_buf *dmabuf; > + struct list_head next; > + int fd; > + > + union { > + struct { > + /* Exported buffers are reference counted. */ > + struct kref refcount; > + > + struct gntdev_priv *priv; > + struct gntdev_grant_map *map; > + } exp; > + } u; > + > + /* Number of pages this buffer has. */ > + int nr_pages; > + /* Pages of this buffer. */ > + struct page **pages; > +}; > + > +struct gntdev_dmabuf_wait_obj { > + struct list_head next; > + struct gntdev_dmabuf *gntdev_dmabuf; > + struct completion completion; > +}; > + > +struct gntdev_dmabuf_attachment { > + struct sg_table *sgt; > + enum dma_data_direction dir; > +}; > + > struct gntdev_dmabuf_priv { > /* List of exported DMA buffers. */ > struct list_head exp_list; > @@ -23,17 +63,439 @@ struct gntdev_dmabuf_priv { > > /* Implementation of wait for exported DMA buffer to be released. */ > > +static void dmabuf_exp_release(struct kref *kref); > + > +static struct gntdev_dmabuf_wait_obj * > +dmabuf_exp_wait_obj_new(struct gntdev_dmabuf_priv *priv, > + struct gntdev_dmabuf *gntdev_dmabuf) > +{ > + struct gntdev_dmabuf_wait_obj *obj; > + > + obj = kzalloc(sizeof(*obj), GFP_KERNEL); > + if (!obj) > + return ERR_PTR(-ENOMEM); > + > + init_completion(&obj->completion); > + obj->gntdev_dmabuf = gntdev_dmabuf; > + > + mutex_lock(&priv->lock); > + list_add(&obj->next, &priv->exp_wait_list); > + /* Put our reference and wait for gntdev_dmabuf's release to fire. */ > + kref_put(&gntdev_dmabuf->u.exp.refcount, dmabuf_exp_release); > + mutex_unlock(&priv->lock); > + return obj; > +} > + > +static void dmabuf_exp_wait_obj_free(struct gntdev_dmabuf_priv *priv, > + struct gntdev_dmabuf_wait_obj *obj) > +{ > + struct gntdev_dmabuf_wait_obj *cur_obj, *q; > + > + mutex_lock(&priv->lock); > + list_for_each_entry_safe(cur_obj, q, &priv->exp_wait_list, next) > + if (cur_obj == obj) { > + list_del(&obj->next); > + kfree(obj); > + break; > + } > + mutex_unlock(&priv->lock); Do we really need to walk the list? And if we do, do we need the safe variant of the walk? We are holding the lock. Here and elsewhere. > +} > + > +static int dmabuf_exp_wait_obj_wait(struct gntdev_dmabuf_wait_obj *obj, > + u32 wait_to_ms) > +{ > + if (wait_for_completion_timeout(&obj->completion, > + msecs_to_jiffies(wait_to_ms)) <= 0) > + return -ETIMEDOUT; > + > + return 0; > +} > + > +static void dmabuf_exp_wait_obj_signal(struct gntdev_dmabuf_priv *priv, > + struct gntdev_dmabuf *gntdev_dmabuf) > +{ > + struct gntdev_dmabuf_wait_obj *obj, *q; > + > + list_for_each_entry_safe(obj, q, &priv->exp_wait_list, next) > + if (obj->gntdev_dmabuf == gntdev_dmabuf) { > + pr_debug("Found gntdev_dmabuf in the wait list, wake\n"); > + complete_all(&obj->completion); > + break; > + } > +} > + > +static struct gntdev_dmabuf * > +dmabuf_exp_wait_obj_get_by_fd(struct gntdev_dmabuf_priv *priv, int fd) The name of this routine implies (to me) that we are getting a wait object but IIUIC we are getting a gntdev_dmabuf that we are going to later associate with a wait object. > +{ > + struct gntdev_dmabuf *q, *gntdev_dmabuf, *ret = ERR_PTR(-ENOENT); > + > + mutex_lock(&priv->lock); > + list_for_each_entry_safe(gntdev_dmabuf, q, &priv->exp_list, next) > + if (gntdev_dmabuf->fd == fd) { > + pr_debug("Found gntdev_dmabuf in the wait list\n"); > + kref_get(&gntdev_dmabuf->u.exp.refcount); > + ret = gntdev_dmabuf; > + break; > + } > + mutex_unlock(&priv->lock); > + return ret; > +} > + > int gntdev_dmabuf_exp_wait_released(struct gntdev_dmabuf_priv *priv, int fd, > int wait_to_ms) > { > - return -EINVAL; > + struct gntdev_dmabuf *gntdev_dmabuf; > + struct gntdev_dmabuf_wait_obj *obj; > + int ret; > + > + pr_debug("Will wait for dma-buf with fd %d\n", fd); > + /* > + * Try to find the DMA buffer: if not found means that > + * either the buffer has already been released or file descriptor > + * provided is wrong. > + */ > + gntdev_dmabuf = dmabuf_exp_wait_obj_get_by_fd(priv, fd); > + if (IS_ERR(gntdev_dmabuf)) > + return PTR_ERR(gntdev_dmabuf); > + > + /* > + * gntdev_dmabuf still exists and is reference count locked by us now, > + * so prepare to wait: allocate wait object and add it to the wait list, > + * so we can find it on release. > + */ > + obj = dmabuf_exp_wait_obj_new(priv, gntdev_dmabuf); > + if (IS_ERR(obj)) > + return PTR_ERR(obj); > + > + ret = dmabuf_exp_wait_obj_wait(obj, wait_to_ms); > + dmabuf_exp_wait_obj_free(priv, obj); > + return ret; > +} > + > +/* DMA buffer export support. */ > + > +static struct sg_table * > +dmabuf_pages_to_sgt(struct page **pages, unsigned int nr_pages) > +{ > + struct sg_table *sgt; > + int ret; > + > + sgt = kmalloc(sizeof(*sgt), GFP_KERNEL); > + if (!sgt) { > + ret = -ENOMEM; > + goto out; > + } > + > + ret = sg_alloc_table_from_pages(sgt, pages, nr_pages, 0, > + nr_pages << PAGE_SHIFT, > + GFP_KERNEL); > + if (ret) > + goto out; > + > + return sgt; > + > +out: > + kfree(sgt); > + return ERR_PTR(ret); > +} > + > +static int dmabuf_exp_ops_attach(struct dma_buf *dma_buf, > + struct device *target_dev, > + struct dma_buf_attachment *attach) > +{ > + struct gntdev_dmabuf_attachment *gntdev_dmabuf_attach; > + > + gntdev_dmabuf_attach = kzalloc(sizeof(*gntdev_dmabuf_attach), > + GFP_KERNEL); > + if (!gntdev_dmabuf_attach) > + return -ENOMEM; > + > + gntdev_dmabuf_attach->dir = DMA_NONE; > + attach->priv = gntdev_dmabuf_attach; > + return 0; > +} > + > +static void dmabuf_exp_ops_detach(struct dma_buf *dma_buf, > + struct dma_buf_attachment *attach) > +{ > + struct gntdev_dmabuf_attachment *gntdev_dmabuf_attach = attach->priv; > + > + if (gntdev_dmabuf_attach) { > + struct sg_table *sgt = gntdev_dmabuf_attach->sgt; > + > + if (sgt) { > + if (gntdev_dmabuf_attach->dir != DMA_NONE) > + dma_unmap_sg_attrs(attach->dev, sgt->sgl, > + sgt->nents, > + gntdev_dmabuf_attach->dir, > + DMA_ATTR_SKIP_CPU_SYNC); > + sg_free_table(sgt); > + } > + > + kfree(sgt); > + kfree(gntdev_dmabuf_attach); > + attach->priv = NULL; > + } > +} > + > +static struct sg_table * > +dmabuf_exp_ops_map_dma_buf(struct dma_buf_attachment *attach, > + enum dma_data_direction dir) > +{ > + struct gntdev_dmabuf_attachment *gntdev_dmabuf_attach = attach->priv; > + struct gntdev_dmabuf *gntdev_dmabuf = attach->dmabuf->priv; > + struct sg_table *sgt; > + > + pr_debug("Mapping %d pages for dev %p\n", gntdev_dmabuf->nr_pages, > + attach->dev); > + > + if (dir == DMA_NONE || !gntdev_dmabuf_attach) > + return ERR_PTR(-EINVAL); > + > + /* Return the cached mapping when possible. */ > + if (gntdev_dmabuf_attach->dir == dir) > + return gntdev_dmabuf_attach->sgt; > + > + /* > + * Two mappings with different directions for the same attachment are > + * not allowed. > + */ > + if (gntdev_dmabuf_attach->dir != DMA_NONE) > + return ERR_PTR(-EBUSY); > + > + sgt = dmabuf_pages_to_sgt(gntdev_dmabuf->pages, > + gntdev_dmabuf->nr_pages); > + if (!IS_ERR(sgt)) { > + if (!dma_map_sg_attrs(attach->dev, sgt->sgl, sgt->nents, dir, > + DMA_ATTR_SKIP_CPU_SYNC)) { > + sg_free_table(sgt); > + kfree(sgt); > + sgt = ERR_PTR(-ENOMEM); > + } else { > + gntdev_dmabuf_attach->sgt = sgt; > + gntdev_dmabuf_attach->dir = dir; > + } > + } > + if (IS_ERR(sgt)) > + pr_debug("Failed to map sg table for dev %p\n", attach->dev); > + return sgt; > +} > + > +static void dmabuf_exp_ops_unmap_dma_buf(struct dma_buf_attachment *attach, > + struct sg_table *sgt, > + enum dma_data_direction dir) > +{ > + /* Not implemented. The unmap is done at dmabuf_exp_ops_detach(). */ > +} > + > +static void dmabuf_exp_release(struct kref *kref) > +{ > + struct gntdev_dmabuf *gntdev_dmabuf = > + container_of(kref, struct gntdev_dmabuf, u.exp.refcount); > + > + dmabuf_exp_wait_obj_signal(gntdev_dmabuf->priv, gntdev_dmabuf); > + list_del(&gntdev_dmabuf->next); > + kfree(gntdev_dmabuf); > +} > + > +static void dmabuf_exp_ops_release(struct dma_buf *dma_buf) > +{ > + struct gntdev_dmabuf *gntdev_dmabuf = dma_buf->priv; > + struct gntdev_dmabuf_priv *priv = gntdev_dmabuf->priv; > + > + gntdev_remove_map(gntdev_dmabuf->u.exp.priv, gntdev_dmabuf->u.exp.map); > + mutex_lock(&priv->lock); > + kref_put(&gntdev_dmabuf->u.exp.refcount, dmabuf_exp_release); > + mutex_unlock(&priv->lock); > +} > + > +static void *dmabuf_exp_ops_kmap_atomic(struct dma_buf *dma_buf, > + unsigned long page_num) > +{ > + /* Not implemented. */ > + return NULL; > +} > + > +static void dmabuf_exp_ops_kunmap_atomic(struct dma_buf *dma_buf, > + unsigned long page_num, void *addr) > +{ > + /* Not implemented. */ > +} > + > +static void *dmabuf_exp_ops_kmap(struct dma_buf *dma_buf, > + unsigned long page_num) > +{ > + /* Not implemented. */ > + return NULL; > +} > + > +static void dmabuf_exp_ops_kunmap(struct dma_buf *dma_buf, > + unsigned long page_num, void *addr) > +{ > + /* Not implemented. */ > +} > + > +static int dmabuf_exp_ops_mmap(struct dma_buf *dma_buf, > + struct vm_area_struct *vma) > +{ > + /* Not implemented. */ > + return 0; > +} > + > +static const struct dma_buf_ops dmabuf_exp_ops = { > + .attach = dmabuf_exp_ops_attach, > + .detach = dmabuf_exp_ops_detach, > + .map_dma_buf = dmabuf_exp_ops_map_dma_buf, > + .unmap_dma_buf = dmabuf_exp_ops_unmap_dma_buf, > + .release = dmabuf_exp_ops_release, > + .map = dmabuf_exp_ops_kmap, > + .map_atomic = dmabuf_exp_ops_kmap_atomic, > + .unmap = dmabuf_exp_ops_kunmap, > + .unmap_atomic = dmabuf_exp_ops_kunmap_atomic, > + .mmap = dmabuf_exp_ops_mmap, > +}; > + > +struct gntdev_dmabuf_export_args { > + struct gntdev_priv *priv; > + struct gntdev_grant_map *map; > + struct gntdev_dmabuf_priv *dmabuf_priv; > + struct device *dev; > + int count; > + struct page **pages; > + u32 fd; > +}; > + > +static int dmabuf_exp_from_pages(struct gntdev_dmabuf_export_args *args) > +{ > + DEFINE_DMA_BUF_EXPORT_INFO(exp_info); > + struct gntdev_dmabuf *gntdev_dmabuf; > + int ret = 0; Not necessary. > + > + gntdev_dmabuf = kzalloc(sizeof(*gntdev_dmabuf), GFP_KERNEL); > + if (!gntdev_dmabuf) > + return -ENOMEM; > + > + kref_init(&gntdev_dmabuf->u.exp.refcount); > + > + gntdev_dmabuf->priv = args->dmabuf_priv; > + gntdev_dmabuf->nr_pages = args->count; > + gntdev_dmabuf->pages = args->pages; > + gntdev_dmabuf->u.exp.priv = args->priv; > + gntdev_dmabuf->u.exp.map = args->map; > + > + exp_info.exp_name = KBUILD_MODNAME; > + if (args->dev->driver && args->dev->driver->owner) > + exp_info.owner = args->dev->driver->owner; > + else > + exp_info.owner = THIS_MODULE; > + exp_info.ops = &dmabuf_exp_ops; > + exp_info.size = args->count << PAGE_SHIFT; > + exp_info.flags = O_RDWR; > + exp_info.priv = gntdev_dmabuf; > + > + gntdev_dmabuf->dmabuf = dma_buf_export(&exp_info); > + if (IS_ERR(gntdev_dmabuf->dmabuf)) { > + ret = PTR_ERR(gntdev_dmabuf->dmabuf); > + gntdev_dmabuf->dmabuf = NULL; > + goto fail; > + } > + > + ret = dma_buf_fd(gntdev_dmabuf->dmabuf, O_CLOEXEC); > + if (ret < 0) > + goto fail; > + > + gntdev_dmabuf->fd = ret; > + args->fd = ret; > + > + pr_debug("Exporting DMA buffer with fd %d\n", ret); > + > + mutex_lock(&args->dmabuf_priv->lock); > + list_add(&gntdev_dmabuf->next, &args->dmabuf_priv->exp_list); > + mutex_unlock(&args->dmabuf_priv->lock); > + return 0; > + > +fail: > + if (gntdev_dmabuf->dmabuf) > + dma_buf_put(gntdev_dmabuf->dmabuf); > + kfree(gntdev_dmabuf); > + return ret; > +} > + > +static struct gntdev_grant_map * > +dmabuf_exp_alloc_backing_storage(struct gntdev_priv *priv, int dmabuf_flags, > + int count) > +{ > + struct gntdev_grant_map *map; > + > + if (unlikely(count <= 0)) > + return ERR_PTR(-EINVAL); > + > + if ((dmabuf_flags & GNTDEV_DMA_FLAG_WC) && > + (dmabuf_flags & GNTDEV_DMA_FLAG_COHERENT)) { > + pr_debug("Wrong dma-buf flags: either WC or coherent, not both\n"); Why not just print the value of the flags? > + return ERR_PTR(-EINVAL); > + } > + > + map = gntdev_alloc_map(priv, count, dmabuf_flags); > + if (!map) > + return ERR_PTR(-ENOMEM); > + > + if (unlikely(gntdev_account_mapped_pages(count))) { > + pr_debug("can't map: over limit\n"); I think printing @count value here would be useful. > + gntdev_put_map(NULL, map); > + return ERR_PTR(-ENOMEM); > + } > + return map; > } > > int gntdev_dmabuf_exp_from_refs(struct gntdev_priv *priv, int flags, > int count, u32 domid, u32 *refs, u32 *fd) > { > + struct gntdev_grant_map *map; > + struct gntdev_dmabuf_export_args args; > + int i, ret; > + > *fd = -1; Is this still needed? > - return -EINVAL; > + > + map = dmabuf_exp_alloc_backing_storage(priv, flags, count); > + if (IS_ERR(map)) > + return PTR_ERR(map); > + > + for (i = 0; i < count; i++) { > + map->grants[i].domid = domid; > + map->grants[i].ref = refs[i]; > + } > + > + mutex_lock(&priv->lock); > + gntdev_add_map(priv, map); > + mutex_unlock(&priv->lock); > + > + map->flags |= GNTMAP_host_map; > +#if defined(CONFIG_X86) > + map->flags |= GNTMAP_device_map; > +#endif > + > + ret = gntdev_map_grant_pages(map); > + if (ret < 0) > + goto out; > + > + args.priv = priv; > + args.map = map; > + args.dev = priv->dma_dev; > + args.dmabuf_priv = priv->dmabuf_priv; > + args.count = map->count; > + args.pages = map->pages; > + > + ret = dmabuf_exp_from_pages(&args); > + if (ret < 0) > + goto out; > + > + *fd = args.fd; > + return 0; > + > +out: > + gntdev_remove_map(priv, map); > + return ret; > } > > /* DMA buffer import support. */ > @@ -63,6 +525,10 @@ struct gntdev_dmabuf_priv *gntdev_dmabuf_init(void) > if (!priv) > return ERR_PTR(-ENOMEM); > > + mutex_init(&priv->lock); > + INIT_LIST_HEAD(&priv->exp_list); > + INIT_LIST_HEAD(&priv->exp_wait_list); > + > return priv; > } > > diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c > index e82660d81d7e..5f93cd534840 100644 > --- a/drivers/xen/gntdev.c > +++ b/drivers/xen/gntdev.c > @@ -262,6 +262,16 @@ void gntdev_put_map(struct gntdev_priv *priv, struct gntdev_grant_map *map) > gntdev_free_map(map); > } > > +#ifdef CONFIG_XEN_GNTDEV_DMABUF > +void gntdev_remove_map(struct gntdev_priv *priv, struct gntdev_grant_map *map) > +{ > + mutex_lock(&priv->lock); > + list_del(&map->next); > + gntdev_put_map(NULL /* already removed */, map); Why not pass call gntdev_put_map(priv, map) and then not have this routine at all? I really dislike the fact that we are taking a lock here that gntdev_put_map() takes as well, although not with NULL argument. (And yes, I see that gntdev_release() does it too.) -boris > + mutex_unlock(&priv->lock); > +} > +#endif > + > /* ------------------------------------------------------------------ */ > > static int find_grant_ptes(pte_t *pte, pgtable_t token, >