On Fri, Nov 15, 2019 at 04:12:43AM +0000, Al Viro wrote: > On Fri, Nov 15, 2019 at 11:27:59AM +0800, Greg KH wrote: > > On Fri, Nov 15, 2019 at 11:27:50AM +0800, yu kuai wrote: > > > 'dentry_d_lock_class' can be used for spin_lock_nested in case lockdep > > > confused about two different dentry take the 'd_lock'. > > > > > > However, a single 'DENTRY_D_LOCK_NESTED' may not be enough if more than > > > two dentry are involed. So, and in 'DENTRY_D_LOCK_NESTED_2' > > > > > > Signed-off-by: yu kuai <yukuai3@xxxxxxxxxx> > > > --- > > > include/linux/dcache.h | 3 ++- > > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > > > diff --git a/include/linux/dcache.h b/include/linux/dcache.h > > > index 10090f1..8eb84ef 100644 > > > --- a/include/linux/dcache.h > > > +++ b/include/linux/dcache.h > > > @@ -129,7 +129,8 @@ struct dentry { > > > enum dentry_d_lock_class > > > { > > > DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */ > > > - DENTRY_D_LOCK_NESTED > > > + DENTRY_D_LOCK_NESTED, > > > + DENTRY_D_LOCK_NESTED_2 > > > > You should document this, as "_2" does not make much sense to anyone > > only looking at the code :( > > > > Or rename it better. > > FWIW, I'm not sure it's a good solution. What are the rules for callers > of that thing, anyway? If it can be called when somebody is creating > more files in that subtree, we almost certainly will have massive > problems with the lifetimes of underlying objects... > > Could somebody familiar with debugfs explain how is that thing actually > used and what is required from/promised to its callers? I can try and > grep through the tree and guess what the rules are, but I've way too > much on my platter right now and I don't want to get sidetracked into yet > another tree-wide search and analysis session ;-/ Yu wants to use simple_empty() in debugfs_remove_recursive() instead of manually checking: if (!list_empty(&child->d_subdirs)) { See patch 3 of this series for that change and why they feel it is needed: https://lore.kernel.org/lkml/1573788472-87426-4-git-send-email-yukuai3@xxxxxxxxxx/ As to if patch 3 really is needed, I'll leave that up to Yu given that I thought we had resolved these types of issues already a year or so ago. thanks, greg k-h