[PATCH] ext2: conditional removal of NFSD code

[PATCH] ext2: conditional removal of NFSD code

[Alexey Dobriyan]

Nor me nor my box is going to act as NFS server, so ifdef all
exporting code.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---

 fs/ext2/namei.c |    2 ++
 fs/ext2/super.c |    4 ++++
 2 files changed, 6 insertions(+)

--- a/fs/ext2/namei.c
+++ b/fs/ext2/namei.c
@@ -70,6 +70,7 @@ static struct dentry *ext2_lookup(struct
 	return d_splice_alias(inode, dentry);
 }
 
+#if defined(CONFIG_EXPORTFS) || defined(CONFIG_EXPORTFS_MODULE)
 struct dentry *ext2_get_parent(struct dentry *child)
 {
 	unsigned long ino;
@@ -94,6 +95,7 @@ struct dentry *ext2_get_parent(struct de
 	}
 	return parent;
 } 
+#endif
 
 /*
  * By the time this is called, we already have created
--- a/fs/ext2/super.c
+++ b/fs/ext2/super.c
@@ -250,6 +250,7 @@ #ifdef CONFIG_QUOTA
 #endif
 };
 
+#if defined(CONFIG_EXPORTFS) || defined(CONFIG_EXPORTFS_MODULE)
 static struct dentry *ext2_get_dentry(struct super_block *sb, void *vobjp)
 {
 	__u32 *objp = vobjp;
@@ -297,6 +298,7 @@ static struct export_operations ext2_exp
 	.get_parent = ext2_get_parent,
 	.get_dentry = ext2_get_dentry,
 };
+#endif
 
 static unsigned long get_sb_block(void **data)
 {
@@ -916,7 +918,9 @@ static int ext2_fill_super(struct super_
 	 * set up enough so that it can read an inode
 	 */
 	sb->s_op = &ext2_sops;
+#if defined(CONFIG_EXPORTFS) || defined(CONFIG_EXPORTFS_MODULE)
 	sb->s_export_op = &ext2_export_ops;
+#endif
 	sb->s_xattr = ext2_xattr_handlers;
 	root = iget(sb, EXT2_ROOT_INO);
 	sb->s_root = d_alloc_root(root);

Re: [PATCH] ext2: conditional removal of NFSD code

[Andrew Morton]

On Sat, 6 Jan 2007 22:58:31 +0300
Alexey Dobriyan <adobriyan@gmail.com> wrote:

> --- a/fs/ext2/namei.c
> +++ b/fs/ext2/namei.c
> @@ -70,6 +70,7 @@ static struct dentry *ext2_lookup(struct
>  	return d_splice_alias(inode, dentry);
>  }
>  
> +#if defined(CONFIG_EXPORTFS) || defined(CONFIG_EXPORTFS_MODULE)
>  struct dentry *ext2_get_parent(struct dentry *child)

hm.  Officially, one module isn't supposed to know about the presence of
another one at compile-time.  Someone might want to come along and later
configure and compile the nfsd module and then try to load it into a kernel
which wasn't compiled with nfsd enabled.

But given that both modules are in mainline I suspect that nobody would
really be doing that in practice, and in the case of nfsd it might not even
work.

Re: [PATCH] ext2: conditional removal of NFSD code

[Alexey Dobriyan]

On Sat, Jan 06, 2007 at 12:16:11PM -0800, Andrew Morton wrote:
> On Sat, 6 Jan 2007 22:58:31 +0300
> Alexey Dobriyan <adobriyan@gmail.com> wrote:
> > --- a/fs/ext2/namei.c
> > +++ b/fs/ext2/namei.c
> > @@ -70,6 +70,7 @@ static struct dentry *ext2_lookup(struct
> >  	return d_splice_alias(inode, dentry);
> >  }
> >
> > +#if defined(CONFIG_EXPORTFS) || defined(CONFIG_EXPORTFS_MODULE)
> >  struct dentry *ext2_get_parent(struct dentry *child)
>
> hm.  Officially, one module isn't supposed to know about the presence of
> another one at compile-time.

Whole new requirement.

> Someone might want to come along and later
> configure and compile the nfsd module and then try to load it into a kernel
> which wasn't compiled with nfsd enabled.

methinks, this is not a case.

	agrep _MODULE -n | grep defined -w

shows plenty of cases, where code is conditionally compiled out with
CONFIG_IPV6 being the major "offender".

> But given that both modules are in mainline I suspect that nobody would
> really be doing that in practice, and in the case of nfsd it might not even
> work.

Yes, compat_sys_nfsservctl() is conditionally compiled in.

I interpret CONFIG_FOO=n as
"I am not going to use FOO, not now, not in future".

Re: [PATCH] ext2: conditional removal of NFSD code

[Matthew Wilcox]

On Sat, Jan 06, 2007 at 10:58:31PM +0300, Alexey Dobriyan wrote:
> Nor me nor my box is going to act as NFS server, so ifdef all
> exporting code.

> @@ -916,7 +918,9 @@ static int ext2_fill_super(struct super_
>  	 * set up enough so that it can read an inode
>  	 */
>  	sb->s_op = &ext2_sops;
> +#if defined(CONFIG_EXPORTFS) || defined(CONFIG_EXPORTFS_MODULE)
>  	sb->s_export_op = &ext2_export_ops;
> +#endif

To avoid putting ifdefs within a function, how about adding:

#if defined(CONFIG_EXPORTFS) || defined(CONFIG_EXPORTFS_MODULE)
#define set_export_ops(sb, ops)		sb->s_export_op = ops
#else
#define set_export_ops(sb, ops)		0
#endif

That way you can get rid of the function pointer from the struct
superblock too.

But Dave Woodhouse is going to kill you for adding another
CONFIG_*_MODULE dependency.

Re: [PATCH] ext2: conditional removal of NFSD code

[Andrew Morton]

On Sat, 6 Jan 2007 22:58:31 +0300
Alexey Dobriyan <adobriyan@gmail.com> wrote:

> Nor me nor my box is going to act as NFS server, so ifdef all
> exporting code.
> 
> Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
> ---
> 
>  fs/ext2/namei.c |    2 ++
>  fs/ext2/super.c |    4 ++++
>  2 files changed, 6 insertions(+)
> 
> --- a/fs/ext2/namei.c
> +++ b/fs/ext2/namei.c
> @@ -70,6 +70,7 @@ static struct dentry *ext2_lookup(struct
>  	return d_splice_alias(inode, dentry);
>  }
>  
> +#if defined(CONFIG_EXPORTFS) || defined(CONFIG_EXPORTFS_MODULE)
>  struct dentry *ext2_get_parent(struct dentry *child)
>  {
>  	unsigned long ino;
> @@ -94,6 +95,7 @@ struct dentry *ext2_get_parent(struct de
>  	}
>  	return parent;
>  } 
> +#endif
>  
>  /*
>   * By the time this is called, we already have created
> --- a/fs/ext2/super.c
> +++ b/fs/ext2/super.c
> @@ -250,6 +250,7 @@ #ifdef CONFIG_QUOTA
>  #endif
>  };
>  
> +#if defined(CONFIG_EXPORTFS) || defined(CONFIG_EXPORTFS_MODULE)
>  static struct dentry *ext2_get_dentry(struct super_block *sb, void *vobjp)
>  {
>  	__u32 *objp = vobjp;
> @@ -297,6 +298,7 @@ static struct export_operations ext2_exp
>  	.get_parent = ext2_get_parent,
>  	.get_dentry = ext2_get_dentry,
>  };
> +#endif
>  
>  static unsigned long get_sb_block(void **data)
>  {
> @@ -916,7 +918,9 @@ static int ext2_fill_super(struct super_
>  	 * set up enough so that it can read an inode
>  	 */
>  	sb->s_op = &ext2_sops;
> +#if defined(CONFIG_EXPORTFS) || defined(CONFIG_EXPORTFS_MODULE)
>  	sb->s_export_op = &ext2_export_ops;
> +#endif
>  	sb->s_xattr = ext2_xattr_handlers;
>  	root = iget(sb, EXT2_ROOT_INO);
>  	sb->s_root = d_alloc_root(root);
> 

The linker will remove unreferenced static functions from vmlinux.  So a
better approach would be to move ext2_get_parent into super.c, make it
static and do Matthew's trick, yielding zero ifdefs.

That has the additional advantage that the nfsd-supporting code will always
be compiled.

Re: [PATCH] ext2: conditional removal of NFSD code

[Alexey Dobriyan]

On Sat, Jan 06, 2007 at 02:25:40PM -0700, Matthew Wilcox wrote:
> On Sat, Jan 06, 2007 at 10:58:31PM +0300, Alexey Dobriyan wrote:
> > Nor me nor my box is going to act as NFS server, so ifdef all
> > exporting code.
>
> > @@ -916,7 +918,9 @@ static int ext2_fill_super(struct super_
> >  	 * set up enough so that it can read an inode
> >  	 */
> >  	sb->s_op = &ext2_sops;
> > +#if defined(CONFIG_EXPORTFS) || defined(CONFIG_EXPORTFS_MODULE)
> >  	sb->s_export_op = &ext2_export_ops;
> > +#endif
>
> To avoid putting ifdefs within a function, how about adding:
>
> #if defined(CONFIG_EXPORTFS) || defined(CONFIG_EXPORTFS_MODULE)
> #define set_export_ops(sb, ops)		sb->s_export_op = ops
> #else
> #define set_export_ops(sb, ops)		0
> #endif
>
> That way you can get rid of the function pointer from the struct
> superblock too.

Exactly! I've just started with filesystems I use.

it should be wrapped in do {} while 0, of course.

> But Dave Woodhouse is going to kill you for adding another
> CONFIG_*_MODULE dependency.

I missed a flamewar on this topic?

Re: [PATCH] ext2: conditional removal of NFSD code

[Al Viro]

On Sun, Jan 07, 2007 at 12:44:56AM +0300, Alexey Dobriyan wrote:
> > #if defined(CONFIG_EXPORTFS) || defined(CONFIG_EXPORTFS_MODULE)
> > #define set_export_ops(sb, ops)		sb->s_export_op = ops
> > #else
> > #define set_export_ops(sb, ops)		0
> > #endif
> >
> > That way you can get rid of the function pointer from the struct
> > superblock too.
> 
> Exactly! I've just started with filesystems I use.
> 
> it should be wrapped in do {} while 0, of course.

What the hell for?  Repeat after me:
	* do {} while(0) is always inferior to ((void)0)
	* do { expr; } while(0) is always inferior to ((void)(expr))