linux-kernel - Re: [PATCH] fs: Add function declaration of simple

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Date:   Wed, 19 Aug 2020 12:34:24 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Leon Romanovsky <leon@...nel.org>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        Leon Romanovsky <leonro@...dia.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fs: Add function declaration of simple_dname

On Wed, Aug 19, 2020 at 11:32:59AM +0300, Leon Romanovsky wrote:
> From: Leon Romanovsky <leonro@...dia.com>
> 
> The simple_dname() is declared in internal header file as extern
> and this generates the following GCC warning.

The fact that it's declared as extern doesn't matter.  You don't need
the change to internal.h at all.  The use of 'extern' on a function
declaration is purely decorative:

  5 If the declaration of an identifier for a function has no
  storage-class specifier, its linkage is determined exactly as if it
  were declared with the storage-class specifier extern.

I'd drop the change to internal.h and fix the changelog.

> fs/d_path.c:311:7: warning: no previous prototype for 'simple_dname' [-Wmissing-prototypes]
>   311 | char *simple_dname(struct dentry *dentry, char *buffer, int buflen)
>       |       ^~~~~~~~~~~~
> 
> Instead of that extern, reuse the fact that internal.h file is internal to fs/* and
> declare simple_dname() like any other function.
> 
> Fixes: 7e5f7bb08b8c ("unexport simple_dname()")
> Signed-off-by: Leon Romanovsky <leonro@...dia.com>
> ---
>  fs/d_path.c   | 2 ++
>  fs/internal.h | 2 +-
>  2 files changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/d_path.c b/fs/d_path.c
> index 0f1fc1743302..4b89448cc78e 100644
> --- a/fs/d_path.c
> +++ b/fs/d_path.c
> @@ -8,6 +8,8 @@
>  #include <linux/prefetch.h>
>  #include "mount.h"
> 
> +#include "internal.h"
> +
>  static int prepend(char **buffer, int *buflen, const char *str, int namelen)
>  {
>  	*buflen -= namelen;
> diff --git a/fs/internal.h b/fs/internal.h
> index 10517ece4516..2def264272f4 100644
> --- a/fs/internal.h
> +++ b/fs/internal.h
> @@ -164,7 +164,7 @@ extern int d_set_mounted(struct dentry *dentry);
>  extern long prune_dcache_sb(struct super_block *sb, struct shrink_control *sc);
>  extern struct dentry *d_alloc_cursor(struct dentry *);
>  extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *);
> -extern char *simple_dname(struct dentry *, char *, int);
> +char *simple_dname(struct dentry *d, char *buf, int len);
>  extern void dput_to_list(struct dentry *, struct list_head *);
>  extern void shrink_dentry_list(struct list_head *);
> 
> --
> 2.26.2
>