Hello, Jan. On Fri, Aug 30, 2019 at 05:40:23PM +0200, Jan Kara wrote: > > + TP_fast_assign( > > + strncpy(__entry->name, dev_name(wb->bdi->dev), 32); > > + __entry->bdi_id = wb->bdi->id; > > + __entry->ino = page->mapping->host->i_ino; > > + __entry->memcg_id = wb->memcg_css->id; > > + __entry->cgroup_ino = __trace_wb_assign_cgroup(wb); > > + __entry->page_cgroup_ino = > > page->mem_cgroup->css.cgroup->kn->id.ino; > > + ), > > Are the page dereferences above safe? I suppose lock_page_memcg() protects > the page->mem_cgroup->css.cgroup->kn->id dereference? But page->mapping > does not seem to be protected by page lock?
Hah, I assumed it would work because there are preceding if (page_mapping()) tests in the dirty paths - e.g. __set_page_dirty_nobuffers(). Oh, regardless of that assumption, I should have used page_mapping(). Thanks. -- tejun
