Re: [PATCH] wil6210: fix debugfs_simple_attr.cocci warnings

YueHaibing
2018-10-05T11:51:18Z

On 2018/10/5 19:04, Kalle Valo wrote:
> YueHaibing <yuehaibing@huawei.com> writes:
>
>> Use DEFINE_DEBUGFS_ATTRIBUTE rather than DEFINE_SIMPLE_ATTRIBUTE
>> for debugfs files.
>>
>> Semantic patch information:
>> Rationale: DEFINE_SIMPLE_ATTRIBUTE + debugfs_create_file()
>> imposes some significant overhead as compared to
>> DEFINE_DEBUGFS_ATTRIBUTE + debugfs_create_file_unsafe().
>>
>> Generated by: scripts/coccinelle/api/debugfs/debugfs_simple_attr.cocci
>
> Just out of curiosity, what kind of overhead are we talking about here?

commit 5103068eaca2 ("debugfs, coccinelle: check for obsolete DEFINE_SIMPLE_ATTRIBUTE() usage")
said this:

In order to protect against file removal races, debugfs files created via
debugfs_create_file() now get wrapped by a struct file_operations at their
opening.

If the original struct file_operations are known to be safe against removal
races by themselves already, the proxy creation may be bypassed by creating
the files through debugfs_create_file_unsafe().

In order to help debugfs users who use the common
DEFINE_SIMPLE_ATTRIBUTE() + debugfs_create_file()
idiom to transition to removal safe struct file_operations, the helper
macro DEFINE_DEBUGFS_ATTRIBUTE() has been introduced.

>