On Fri, Oct 29, 2021 at 04:43:40PM +0800, Muchun Song wrote:
> On Fri, Oct 29, 2021 at 4:26 PM Christian Brauner
> <christian.brauner@xxxxxxxxxx> wrote:
> >
> > On Fri, Oct 29, 2021 at 11:26:38AM +0800, Muchun Song wrote:
> > > DEFINE_PROC_SHOW_ATTRIBUTE() is supposed to be used to define a series
> > > of functions and variables to register proc file easily. And the users
> > > can use proc_create_data() to pass their own private data and get it
> > > via seq->private in the callback. Unfortunately, the proc file system
> > > use PDE_DATA() to get private data instead of inode->i_private. So fix
> > > it. Fortunately, there only one user of it which does not pass any
> > > private data, so this bug does not break any in-tree codes.
> > >
> > > Fixes: 97a32539b956 ("proc: convert everything to "struct proc_ops"")
> > > Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
> > > ---
> > > include/linux/seq_file.h | 2 +-
> > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h
> > > index 103776e18555..72dbb44a4573 100644
> > > --- a/include/linux/seq_file.h
> > > +++ b/include/linux/seq_file.h
> > > @@ -209,7 +209,7 @@ static const struct file_operations __name ## _fops = { \
> > > #define DEFINE_PROC_SHOW_ATTRIBUTE(__name) \
> > > static int __name ## _open(struct inode *inode, struct file *file) \
> > > { \
> > > - return single_open(file, __name ## _show, inode->i_private); \
> > > + return single_open(file, __name ## _show, PDE_DATA(inode)); \
> > > } \
> > > \
> > > static const struct proc_ops __name ## _proc_ops = { \
> >
> > Hm, after your change DEFINE_SHOW_ATTRIBUTE() and
> > DEFINE_PROC_SHOW_ATTRIBUTE() macros do exactly the same things, right?:
>
> Unfortunately, they are not the same. The difference is the
> operation structure, namely "struct file_operations" and
> "struct proc_ops".
>
> DEFINE_SHOW_ATTRIBUTE() is usually used by
> debugfs while DEFINE_SHOW_ATTRIBUTE() is
> used by procfs.
Ugh, right, thanks for pointing that out. I overlooked the _proc_ops
appendix. Not sure what's right here. There seem to have been earlier
callers to DEFINE_PROC_SHOW_ATTRIBUTE() that relied on PDE_DATA() but
there's only one caller so that change wouldn't be too bad, I guess.
