Am 24.11.22 um 13:49 schrieb cuigaosheng:
I was already wondering why the order is this way.
Why is dma_buf_stats_setup() needing the file in the first place?
dmabuf->file will be used in dma_buf_stats_setup(), the
dma_buf_stats_setup() as follows:
171 int dma_buf_stats_setup(struct dma_buf *dmabuf)
172 {
173 struct dma_buf_sysfs_entry *sysfs_entry;
174 int ret;
175
176 if (!dmabuf || !dmabuf->file)
177 return -EINVAL;
178
179 if (!dmabuf->exp_name) {
180 pr_err("exporter name must not be empty if stats
needed\n");
181 return -EINVAL;
182 }
183
184 sysfs_entry = kzalloc(sizeof(struct dma_buf_sysfs_entry),
GFP_KERNEL);
185 if (!sysfs_entry)
186 return -ENOMEM;
187
188 sysfs_entry->kobj.kset = dma_buf_per_buffer_stats_kset;
189 sysfs_entry->dmabuf = dmabuf;
190
191 dmabuf->sysfs_entry = sysfs_entry;
192
193 /* create the directory for buffer stats */
194 ret = kobject_init_and_add(&sysfs_entry->kobj,
&dma_buf_ktype, NULL,
195 "%lu",
file_inode(dmabuf->file)->i_ino);
Ah, so it uses the i_ino of the file for the sysfs unique name.
I'm going to take another look how to properly clean this up.
Thanks for pointing this out,
Christian.
196 if (ret)
197 goto err_sysfs_dmabuf;
198
199 return 0;
200
201 err_sysfs_dmabuf:
202 kobject_put(&sysfs_entry->kobj);
203 dmabuf->sysfs_entry = NULL;
204 return ret;
205 }
Did I miss something?
Thanks.
On 2022/11/24 20:37, Christian König wrote:
Am 24.11.22 um 13:05 schrieb cuigaosheng:
Some tips:
Before we call the dma_buf_stats_setup(), we have to finish
creating the file,
otherwise dma_buf_stats_setup() will return -EINVAL, maybe we need
to think about
this when making a new patch.
I was already wondering why the order is this way.
Why is dma_buf_stats_setup() needing the file in the first place?
Thanks,
Christian.
Hope these tips are useful, thanks!
On 2022/11/24 13:56, Charan Teja Kalla wrote:
Thanks T.J and Christian for the inputs.
On 11/19/2022 7:00 PM, Christian König wrote:
Yes, exactly that's the idea.
The only alternatives I can see would be to either move
allocating
the
file and so completing the dma_buf initialization last again
or just
ignore errors from sysfs.
> If we still want to avoid calling
dmabuf->ops->release(dmabuf) in
> dma_buf_release like the comment says I guess we could use
sysfs_entry
> and ERR_PTR to flag that, otherwise it looks like we'd
need a bit
> somewhere.
No, this should be dropped as far as I can see. The sysfs
cleanup
code
looks like it can handle not initialized kobj pointers.
Yeah there is also the null check in dma_buf_stats_teardown() that
would prevent it from running, but I understood the comment to be
referring to the release() dma_buf_ops call into the exporter which
comes right after the teardown call. That looks like it's preventing
the fput task work calling back into the exporter after the exporter
already got an error from dma_buf_export(). Otherwise the exporter
sees a release() for a buffer that it doesn't know about / thinks
shouldn't exist. So I could imagine an exporter trying to double
free:
once for the failed dma_buf_export() call, and again when the
release() op is called later.
Oh, very good point as well. Yeah, then creating the file should
probably come last.
@Gaosheng: Could you please make these changes or you let me to do?
Regards,
Christian.
.
.
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