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.
Thanks.
>
> #define DEFINE_SHOW_ATTRIBUTE(__name) \
> static int __name ## _open(struct inode *inode, struct file *file) \
> { \
> return single_open(file, __name ## _show, inode->i_private); \
> } \
> \
> static const struct file_operations __name ## _fops = { \
> .owner = THIS_MODULE, \
> .open = __name ## _open, \
> .read = seq_read, \
> .llseek = seq_lseek, \
> .release = single_release, \
> }
>
> #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); \
> } \
>
> Can't you just replace the single instance where
> DEFINE_PROC_SHOW_ATTRIBUTE with DEFINE_SHOW_ATTRIBUTE() and remove
> DEFINE_PROC_SHOW_ATTRIBUTE completely?
>
> Christian
