On Thu, Jan 09, 2014 at 04:27:31PM -0500, Steven Rostedt wrote:
> Note, the crash came from stressing the deletion and reading of debugfs
> files. I was not able to recreate this via normal files. But I'm not
> sure they are safe. It may just be that the race window is much harder
> to hit.
But "normal" files have a 'destroy_inode' method. So you've basically
only fixed it for debugfs (and maybe a few other unusual filesystems).
Why doesn't the code look like this:
static void i_callback(struct rcu_head *head)
{
struct inode *inode = container_of(head, struct inode, i_rcu);
__destroy_inode(inode);
if (inode->i_sb->s_op->destroy_inode)
inode->i_sb->s_op->destroy_inode(inode);
else
kmem_cache_free(inode_cachep, inode);
}
static void destroy_inode(struct inode *inode)
{
BUG_ON(!list_empty(&inode->i_lru));
call_rcu(&inode->i_rcu, i_callback);
}
We'd then have to get rid of all the call_rcu() invocations in individual
filesystems' destroy_inode methods, but that doesn't sound like a bad
thing to me.
--
Matthew Wilcox Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours. We can't possibly take such
a retrograde step."
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