Re: [TRIVIAL] Error checks omitted in init_tmpfs() in mm/tiny-shmem.c

[Hareesh Nagarajan]

Matt Mackall wrote:
> On Mon, Oct 24, 2005 at 03:56:47AM -0500, Hareesh Nagarajan wrote:
> > Matt Mackall wrote:
> > > On Mon, Oct 24, 2005 at 12:29:45AM -0500, Hareesh Nagarajan wrote:
> > > > The existing code in init_tmpfs() in mm/tiny-shmem.c does not handle the 
> > > > cases when the calls to register_filesystem() and kern_mount() fail. 
> > > > This patch adds those checks.

[ Snip ]

> A couple more comments..
>
> > Signed-off-by: Hareesh Nagarajan <hnagar2@xxxxxxxxx>
>
> > --- linux-2.6.13.4/mm/tiny-shmem.c	2005-10-10 13:54:29.000000000 -0500
> > +++ linux-2.6.13.4-edit/mm/tiny-shmem.c	2005-10-24 03:43:38.614071000 -0500
> > @@ -31,12 +31,18 @@
> >  
> >  static int __init init_tmpfs(void)
> >  {
> > -	register_filesystem(&tmpfs_fs_type);
> > +	int error;
> > +
> > +	error = register_filesystem(&tmpfs_fs_type);
> > +	BUG_ON(error);
>
> Can we just do BUG_ON(register_filesystem() != 0)?
>
> Strictly speaking, the != 0 is redundant, but as this goes slightly
> against the grain of normal usage, it's a good indicator of intent.

It shows intent well. That goes into my book for good programming 
practices. No more BUG_ON(foo) :)

> >  #ifdef CONFIG_TMPFS
> >  	devfs_mk_dir("shm");
> >  #endif
> >  	shm_mnt = kern_mount(&tmpfs_fs_type);
> > -	return 0;
> > +	BUG_ON(IS_ERR(shm_mnt));
> > +
> > +	return error;
>
> We can never return non-zero here. Returning error implies we can, so
> it's confusing.

Makes sense again. Patch follows.

Signed-off-by: Hareesh Nagarajan <hnagar2@xxxxxxxxx>
--- linux-2.6.13.4/mm/tiny-shmem.c	2005-10-10 13:54:29.000000000 -0500
+++ linux-2.6.13.4-edit/mm/tiny-shmem.c	2005-10-24 19:05:28.058897000 -0500
@@ -31,11 +31,14 @@
 
 static int __init init_tmpfs(void)
 {
-	register_filesystem(&tmpfs_fs_type);
+	BUG_ON(register_filesystem(&tmpfs_fs_type) != 0);
+
 #ifdef CONFIG_TMPFS
 	devfs_mk_dir("shm");
 #endif
 	shm_mnt = kern_mount(&tmpfs_fs_type);
+	BUG_ON(IS_ERR(shm_mnt));
+
 	return 0;
 }
 module_init(init_tmpfs)