On Sun, Apr 19, 2020 at 03:57:58PM -0700, Bart Van Assche wrote:
> On 4/19/20 12:45 PM, Luis Chamberlain wrote:
> > Even though debugfs can be disabled, enabling BLK_DEV_IO_TRACE will
> > select DEBUG_FS, and blktrace exposes an API which userspace uses
> > relying on certain files created in debugfs. If files are not created
> > blktrace will not work correctly, so we do want to ensure that a
> > blktrace setup creates these files properly, and otherwise inform
> > userspace.
> >
> > Signed-off-by: Luis Chamberlain <mcgrof@xxxxxxxxxx>
> > ---
> > kernel/trace/blktrace.c | 8 +++++---
> > 1 file changed, 5 insertions(+), 3 deletions(-)
> >
> > diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
> > index 9cc0153849c3..fc32a8665ce8 100644
> > --- a/kernel/trace/blktrace.c
> > +++ b/kernel/trace/blktrace.c
> > @@ -552,17 +552,19 @@ static int blk_trace_create_debugfs_files(struct blk_user_trace_setup *buts,
> > struct dentry *dir,
> > struct blk_trace *bt)
> > {
> > - int ret = -EIO;
> > -
> > bt->dropped_file = debugfs_create_file("dropped", 0444, dir, bt,
> > &blk_dropped_fops);
> > + if (!bt->dropped_file)
> > + return -ENOMEM;
> > bt->msg_file = debugfs_create_file("msg", 0222, dir, bt, &blk_msg_fops);
> > + if (!bt->msg_file)
> > + return -ENOMEM;
> > bt->rchan = relay_open("trace", dir, buts->buf_size,
> > buts->buf_nr, &blk_relay_callbacks, bt);
> > if (!bt->rchan)
> > - return ret;
> > + return -EIO;
> > return 0;
> > }
>
> I should have had a look at this patch before I replied to the previous
> patch.
>
> Do you agree that the following code can be triggered by
> debugfs_create_file() and also that debugfs_create_file() never returns
> NULL?
If debugfs is enabled, and not that we know it is in this blktrace code,
as we select it, it can return ERR_PTR(-ERROR) if an error occurs.
Luis
