Re: [PATCH] ext4: fix #11321: create /proc/ext4/*/stats et al more carefully

Alexey Dobriyan
2008-09-07T12:14:13Z

On Sat, Sep 06, 2008 at 01:57:13AM -0600, Andreas Dilger wrote:
> On Sep 06, 2008 01:06 +0400, Alexey Dobriyan wrote:
> > [PATCH] ext4: fix #11321: create /proc/ext4/*/stats more carefully
> >
> > ext4 creates per-suberblock directory in /proc/ext4/ . Name used as
> > basis is taken from bdevname, which, surprise, can contain slash.
> >
> > However, proc while allowing to use proc_create("a/b", parent) form of
> > PDE creation, assumes that parent/a was already created.
> >
> > bdevname in question is 'cciss/c0d0p9', directory is not created and all
> > this stuff goes directly into /proc (which is real bug).
> >
> > --- a/fs/ext4/mballoc.c
> > +++ b/fs/ext4/mballoc.c
> > @@ -2792,6 +2792,15 @@ static int ext4_mb_init_per_dev_proc(struct super_block *sb)
> > return -EINVAL;
> > }
> > bdevname(sb->s_bdev, devname);
> > + {
> > + char *p = devname;
> > +
> > + while (*p != '\0') {
> > + if (*p == '/')
> > + *p = '!';
> > + p++;
> > + }
> > + }
>
> Why not use strchr(), which is normally optimized assembly:
>
> char *p = devname;
> while ((p = strchr(p, '/'))
> *p = '_';
>
> Using '!' as the separator makes it harder to use from shells I suspect,
> so I'd suggest '_' instead.

bdevname is only 32 bytes and done once per mount, so nobody cares.

'!' is what other code does in this situation (reiserfs, md, ...).