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SubjectRe: [PATCH] tracing: fix referencing after memory freeing and refactors code
On Thu, 17 Oct 2013 22:44:56 -0300
"Geyslan G. Bem" <geyslan@gmail.com> wrote:

> Restructures function logic conditions testing 'tracing_open_generic'
> return before the others. It avoids: unnecessary trace_array_get and
> kzalloc when tracing is disabled; and fix the possible 'dir'
> assignment after freeing it.
>
> Centralizes the exiting, ensuring the 'trace_array_put' on error,
> in accordance to Coding Style, Chapter 7.
>
> Signed-off-by: Geyslan G. Bem <geyslan@gmail.com>
> ---
> kernel/trace/trace_events.c | 22 ++++++++++++----------
> 1 file changed, 12 insertions(+), 10 deletions(-)
>
> diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
> index 368a4d5..8232362 100644
> --- a/kernel/trace/trace_events.c
> +++ b/kernel/trace/trace_events.c
> @@ -1108,26 +1108,28 @@ static int system_tr_open(struct inode *inode, struct file *filp)
> struct trace_array *tr = inode->i_private;
> int ret;
>
> - if (trace_array_get(tr) < 0)
> - return -ENODEV;
> + ret = tracing_open_generic(inode, filp);
> + if (ret)
> + return ret;
> +
> + ret = trace_array_get(tr);
> + if (ret)
> + return ret;

Hmm,

I'm thinking of just nuking the tracing_open_generic() here. The only
thing it does here is the tracing_disabled check. The assignment of
inode->i_private to filp->private_data is pointless as it just
reassigns it anyway.

We could add a tracing_is_disabled() function to test instead.

-- Steve

>
> /* Make a temporary dir that has no system but points to tr */
> dir = kzalloc(sizeof(*dir), GFP_KERNEL);
> if (!dir) {
> - trace_array_put(tr);
> - return -ENOMEM;
> + ret = -ENOMEM;
> + goto err_dir;
> }
>
> dir->tr = tr;
>
> - ret = tracing_open_generic(inode, filp);
> - if (ret < 0) {
> - trace_array_put(tr);
> - kfree(dir);
> - }
> -
> filp->private_data = dir;
> + return 0;
>
> +err_dir:
> + trace_array_put(tr);
> return ret;
> }
>



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