On Thu, May 02, 2019 at 04:04:06AM +0100, Al Viro wrote: > On Wed, May 01, 2019 at 02:42:23PM +0800, Wenbin Zeng wrote: > > The newly added evict callback shall be called by nsfs_evict(). Currently > > only put() callback is called in nsfs_evict(), it is not able to release > > all netns refcount, for example, a rpc client holds two netns refcounts, > > these refcounts are supposed to be released when the rpc client is freed, > > but the code to free rpc client is normally triggered by put() callback > > only when netns refcount gets to 0, specifically: > > refcount=0 -> cleanup_net() -> ops_exit_list -> free rpc client > > But netns refcount will never get to 0 before rpc client gets freed, to > > break the deadlock, the code to free rpc client can be put into the newly > > added evict callback. > > > > Signed-off-by: Wenbin Zeng <wenbinzeng@xxxxxxxxxxx> > > --- > > fs/nsfs.c | 2 ++ > > include/linux/proc_ns.h | 1 + > > 2 files changed, 3 insertions(+) > > > > diff --git a/fs/nsfs.c b/fs/nsfs.c > > index 60702d6..5939b12 100644 > > --- a/fs/nsfs.c > > +++ b/fs/nsfs.c > > @@ -49,6 +49,8 @@ static void nsfs_evict(struct inode *inode) > > struct ns_common *ns = inode->i_private; > > clear_inode(inode); > > ns->ops->put(ns); > > + if (ns->ops->evict) > > + ns->ops->evict(ns); > > What's to guarantee that ns will not be freed by ->put()? > Confused... Hi Al, thank you very much. You are absolutely right. ->evict() should be called before ->put(), i.e.: @@ -49,6 +49,8 @@ static void nsfs_evict(struct inode *inode) struct ns_common *ns = inode->i_private; clear_inode(inode); + if (ns->ops->evict) + ns->ops->evict(ns); ns->ops->put(ns); } Does this look good?
