Matthew Wilcox:
> > I _think_ it's sufficient to make the affected callers of
> > lookup_one_len() lock the parent's i_mutex for themselves before calling
> > it. I'll take a closer look...
>
> Should we also add this?
:::
> @@ -1244,6 +1244,7 @@ struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
> int err;
> struct qstr this;
>
> + BUG_ON(!mutex_is_locked(&base->d_inode->i_mutex));
> err = __lookup_one_len(name, &this, base, len);
That was how I found this problem actually. :-)
I implemented very similar debug code in aufs which is compiled when
CONFIG_AUFS_DEBUG is enabled.
(in aufs header files)
#ifdef CONFIG_AUFS_DEBUG
#define AuDebugOn(a) BUG_ON(a)
:::
#endif
/* to debug easier, do not make them inlined functions */
#define MtxMustLock(mtx) AuDebugOn(!mutex_is_locked(mtx))
#define IMustLock(i) MtxMustLock(&(i)->i_mutex)
(in ->lookup of aufs)
static struct dentry *aufs_lookup(struct inode *dir, struct dentry *dentry,
struct nameidata *nd)
{
:::
IMustLock(dir);
J. R. Okajima
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