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Re: [PATCH] s390/pci: Remove unnecessary if condition

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  Re: [PATCH] s390/pci: Remove unnecessary if condition Sebastian Ott <sebott@linux.vnet.ibm.com> - 2016-07-29 10:40 +0200
    Re: [PATCH] s390/pci: Remove unnecessary if condition Julia Lawall <julia.lawall@lip6.fr> - 2016-07-29 10:50 +0200
      Re: [PATCH] s390/pci: Remove unnecessary if condition Sebastian Ott <sebott@linux.vnet.ibm.com> - 2016-07-29 11:50 +0200
        Re: [PATCH] s390/pci: Remove unnecessary if condition Julia Lawall <julia.lawall@lip6.fr> - 2016-08-01 08:40 +0200

#1452317 — Re: [PATCH] s390/pci: Remove unnecessary if condition

On Fri, 29 Jul 2016, Amitoj Kaur Chawla wrote:
> Remove unnecessary error handling because the only failure value that
> can be returned is NULL and so the test can never be true.
> 
> The Coccinelle semantic patch used to make this change is as follows:
> @@
> expression e;
> @@
> 
>   e = debugfs_create_file(...);
> - if(IS_ERR(e)) { e = NULL; }

Nope. For !CONFIG_DEBUG_FS debugfs_create_file returns an ERR_PTR.

Regards,
Sebastian

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#1452326

On Fri, 29 Jul 2016, Sebastian Ott wrote:

> On Fri, 29 Jul 2016, Amitoj Kaur Chawla wrote:
> > Remove unnecessary error handling because the only failure value that
> > can be returned is NULL and so the test can never be true.
> >
> > The Coccinelle semantic patch used to make this change is as follows:
> > @@
> > expression e;
> > @@
> >
> >   e = debugfs_create_file(...);
> > - if(IS_ERR(e)) { e = NULL; }
>
> Nope. For !CONFIG_DEBUG_FS debugfs_create_file returns an ERR_PTR.

Clicking around in lxr doesn't show that, but perhaps an alternative
definition is overlooked?

julia

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#1452356

On Fri, 29 Jul 2016, Julia Lawall wrote:
> On Fri, 29 Jul 2016, Sebastian Ott wrote:
> > On Fri, 29 Jul 2016, Amitoj Kaur Chawla wrote:
> > > Remove unnecessary error handling because the only failure value that
> > > can be returned is NULL and so the test can never be true.
> > >
> > > The Coccinelle semantic patch used to make this change is as follows:
> > > @@
> > > expression e;
> > > @@
> > >
> > >   e = debugfs_create_file(...);
> > > - if(IS_ERR(e)) { e = NULL; }
> >
> > Nope. For !CONFIG_DEBUG_FS debugfs_create_file returns an ERR_PTR.
> 
> Clicking around in lxr doesn't show that, but perhaps an alternative
> definition is overlooked?

It looks that way.


[sebott@schleppi linux]$ git grep -W "debugfs_create_file(" include/linux/debugfs.h
include/linux/debugfs.h:struct dentry *debugfs_create_file(const char *name, umode_t mode,
include/linux/debugfs.h-                                   struct dentry *parent, void *data,
include/linux/debugfs.h-                                   const struct file_operations *fops);
--
include/linux/debugfs.h:static inline struct dentry *debugfs_create_file(const char *name, umode_t mode,
include/linux/debugfs.h-                                        struct dentry *parent, void *data,
include/linux/debugfs.h-                                        const struct file_operations *fops)
include/linux/debugfs.h-{
include/linux/debugfs.h-        return ERR_PTR(-ENODEV);
include/linux/debugfs.h-}
include/linux/debugfs.h-

Regards,
Sebastian

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#1453006

On Fri, 29 Jul 2016, Sebastian Ott wrote:

> On Fri, 29 Jul 2016, Julia Lawall wrote:
> > On Fri, 29 Jul 2016, Sebastian Ott wrote:
> > > On Fri, 29 Jul 2016, Amitoj Kaur Chawla wrote:
> > > > Remove unnecessary error handling because the only failure value that
> > > > can be returned is NULL and so the test can never be true.
> > > >
> > > > The Coccinelle semantic patch used to make this change is as follows:
> > > > @@
> > > > expression e;
> > > > @@
> > > >
> > > >   e = debugfs_create_file(...);
> > > > - if(IS_ERR(e)) { e = NULL; }
> > >
> > > Nope. For !CONFIG_DEBUG_FS debugfs_create_file returns an ERR_PTR.
> >
> > Clicking around in lxr doesn't show that, but perhaps an alternative
> > definition is overlooked?
>
> It looks that way.
>
>
> [sebott@schleppi linux]$ git grep -W "debugfs_create_file(" include/linux/debugfs.h
> include/linux/debugfs.h:struct dentry *debugfs_create_file(const char *name, umode_t mode,
> include/linux/debugfs.h-                                   struct dentry *parent, void *data,
> include/linux/debugfs.h-                                   const struct file_operations *fops);
> --
> include/linux/debugfs.h:static inline struct dentry *debugfs_create_file(const char *name, umode_t mode,
> include/linux/debugfs.h-                                        struct dentry *parent, void *data,
> include/linux/debugfs.h-                                        const struct file_operations *fops)
> include/linux/debugfs.h-{
> include/linux/debugfs.h-        return ERR_PTR(-ENODEV);
> include/linux/debugfs.h-}
> include/linux/debugfs.h-

Thanks for the pointer.  I guess that if the result of debugfs_create_file
is actully dereferenced, then both test should be present, eg:

drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c

       ent = debugfs_create_file(name,
                                 S_IFREG | S_IRUGO, root,
                                 ring, &amdgpu_debugfs_ring_fops);
       if (IS_ERR(ent))
		return PTR_ERR(ent);

       i_size_write(ent->d_inode, ring->ring_size + 12);

This problem seems to only occur in this directory.

thanks,
julia

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