[PATCH] dma-buf: fix dma_buf_export init order
T.J. Mercier
tjmercier at google.com
Tue Dec 6 19:10:23 UTC 2022
On Tue, Dec 6, 2022 at 7:12 AM Christian König
<ckoenig.leichtzumerken at gmail.com> wrote:
>
> The init order and resulting error handling in dma_buf_export
> was pretty messy.
>
> Subordinate objects like the file and the sysfs kernel objects
> were initializing and wiring itself up with the object in the
> wrong order resulting not only in complicating and partially
> incorrect error handling, but also in publishing only halve
> initialized DMA-buf objects.
>
> Clean this up thoughtfully by allocating the file independent
> of the DMA-buf object. Then allocate and initialize the DMA-buf
> object itself, before publishing it through sysfs. If everything
> works as expected the file is then connected with the DMA-buf
> object and publish it through debugfs.
>
> Also adds the missing dma_resv_fini() into the error handling.
>
> Signed-off-by: Christian König <christian.koenig at amd.com>
> ---
> drivers/dma-buf/dma-buf-sysfs-stats.c | 7 +--
> drivers/dma-buf/dma-buf-sysfs-stats.h | 4 +-
> drivers/dma-buf/dma-buf.c | 65 +++++++++++++--------------
> 3 files changed, 34 insertions(+), 42 deletions(-)
>
> diff --git a/drivers/dma-buf/dma-buf-sysfs-stats.c b/drivers/dma-buf/dma-buf-sysfs-stats.c
> index 2bba0babcb62..4b680e10c15a 100644
> --- a/drivers/dma-buf/dma-buf-sysfs-stats.c
> +++ b/drivers/dma-buf/dma-buf-sysfs-stats.c
> @@ -168,14 +168,11 @@ void dma_buf_uninit_sysfs_statistics(void)
> kset_unregister(dma_buf_stats_kset);
> }
>
> -int dma_buf_stats_setup(struct dma_buf *dmabuf)
> +int dma_buf_stats_setup(struct dma_buf *dmabuf, struct file *file)
> {
> struct dma_buf_sysfs_entry *sysfs_entry;
> int ret;
>
> - if (!dmabuf || !dmabuf->file)
> - return -EINVAL;
> -
> if (!dmabuf->exp_name) {
> pr_err("exporter name must not be empty if stats needed\n");
> return -EINVAL;
> @@ -192,7 +189,7 @@ int dma_buf_stats_setup(struct dma_buf *dmabuf)
>
> /* create the directory for buffer stats */
> ret = kobject_init_and_add(&sysfs_entry->kobj, &dma_buf_ktype, NULL,
> - "%lu", file_inode(dmabuf->file)->i_ino);
> + "%lu", file_inode(file)->i_ino);
> if (ret)
> goto err_sysfs_dmabuf;
>
> diff --git a/drivers/dma-buf/dma-buf-sysfs-stats.h b/drivers/dma-buf/dma-buf-sysfs-stats.h
> index a49c6e2650cc..7a8a995b75ba 100644
> --- a/drivers/dma-buf/dma-buf-sysfs-stats.h
> +++ b/drivers/dma-buf/dma-buf-sysfs-stats.h
> @@ -13,7 +13,7 @@
> int dma_buf_init_sysfs_statistics(void);
> void dma_buf_uninit_sysfs_statistics(void);
>
> -int dma_buf_stats_setup(struct dma_buf *dmabuf);
> +int dma_buf_stats_setup(struct dma_buf *dmabuf, struct file *file);
>
> void dma_buf_stats_teardown(struct dma_buf *dmabuf);
> #else
> @@ -25,7 +25,7 @@ static inline int dma_buf_init_sysfs_statistics(void)
>
> static inline void dma_buf_uninit_sysfs_statistics(void) {}
>
> -static inline int dma_buf_stats_setup(struct dma_buf *dmabuf)
> +static inline int dma_buf_stats_setup(struct dma_buf *dmabuf, struct file *file)
> {
> return 0;
> }
> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> index e6f36c014c4c..ea08049b70ae 100644
> --- a/drivers/dma-buf/dma-buf.c
> +++ b/drivers/dma-buf/dma-buf.c
> @@ -614,19 +614,11 @@ struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
> size_t alloc_size = sizeof(struct dma_buf);
> int ret;
>
> - if (!exp_info->resv)
> - alloc_size += sizeof(struct dma_resv);
> - else
> - /* prevent &dma_buf[1] == dma_buf->resv */
> - alloc_size += 1;
> -
> - if (WARN_ON(!exp_info->priv
> - || !exp_info->ops
> - || !exp_info->ops->map_dma_buf
> - || !exp_info->ops->unmap_dma_buf
> - || !exp_info->ops->release)) {
> + if (WARN_ON(!exp_info->priv || !exp_info->ops
> + || !exp_info->ops->map_dma_buf
> + || !exp_info->ops->unmap_dma_buf
> + || !exp_info->ops->release))
> return ERR_PTR(-EINVAL);
> - }
>
> if (WARN_ON(exp_info->ops->cache_sgt_mapping &&
> (exp_info->ops->pin || exp_info->ops->unpin)))
> @@ -638,10 +630,21 @@ struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
> if (!try_module_get(exp_info->owner))
> return ERR_PTR(-ENOENT);
>
> + file = dma_buf_getfile(exp_info->size, exp_info->flags);
> + if (IS_ERR(file)) {
> + ret = PTR_ERR(file);
> + goto err_module;
> + }
> +
> + if (!exp_info->resv)
> + alloc_size += sizeof(struct dma_resv);
> + else
> + /* prevent &dma_buf[1] == dma_buf->resv */
> + alloc_size += 1;
> dmabuf = kzalloc(alloc_size, GFP_KERNEL);
> if (!dmabuf) {
> ret = -ENOMEM;
> - goto err_module;
> + goto err_file;
> }
>
> dmabuf->priv = exp_info->priv;
> @@ -653,44 +656,36 @@ struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
> init_waitqueue_head(&dmabuf->poll);
> dmabuf->cb_in.poll = dmabuf->cb_out.poll = &dmabuf->poll;
> dmabuf->cb_in.active = dmabuf->cb_out.active = 0;
> + mutex_init(&dmabuf->lock);
> + INIT_LIST_HEAD(&dmabuf->attachments);
>
> if (!resv) {
> - resv = (struct dma_resv *)&dmabuf[1];
> - dma_resv_init(resv);
> + dmabuf->resv = (struct dma_resv *)&dmabuf[1];
> + dma_resv_init(dmabuf->resv);
> + } else {
> + dmabuf->resv = resv;
> }
I like this, but I think it'd be even better to remove the local
struct dma_resv *resv variable since it's just a copy of
exp_info->resv and doesn't get modified any longer. More typing but
less to keep track of.
> - dmabuf->resv = resv;
>
> - file = dma_buf_getfile(dmabuf, exp_info->flags);
> - if (IS_ERR(file)) {
> - ret = PTR_ERR(file);
> + ret = dma_buf_stats_setup(dmabuf, file);
> + if (ret)
> goto err_dmabuf;
> - }
>
> + file->private_data = dmabuf;
> + file->f_path.dentry->d_fsdata = dmabuf;
> dmabuf->file = file;
>
> - mutex_init(&dmabuf->lock);
> - INIT_LIST_HEAD(&dmabuf->attachments);
> -
> mutex_lock(&db_list.lock);
> list_add(&dmabuf->list_node, &db_list.head);
> mutex_unlock(&db_list.lock);
Unrelated: I'm kind of surprised we bother with this db_list when
CONFIG_DEBUG_FS isn't defined.
>
> - ret = dma_buf_stats_setup(dmabuf);
> - if (ret)
> - goto err_sysfs;
> -
> return dmabuf;
>
> -err_sysfs:
> - /*
> - * Set file->f_path.dentry->d_fsdata to NULL so that when
> - * dma_buf_release() gets invoked by dentry_ops, it exits
> - * early before calling the release() dma_buf op.
> - */
> - file->f_path.dentry->d_fsdata = NULL;
> - fput(file);
> err_dmabuf:
> + if (!resv)
> + dma_resv_fini(dmabuf->resv);
> kfree(dmabuf);
> +err_file:
> + fput(file);
> err_module:
> module_put(exp_info->owner);
> return ERR_PTR(ret);
> --
> 2.34.1
>
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