| Message ID | 20190830233954.GC2263813@devbig004.ftw2.facebook.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [block/for-next] writeback: don't access page->mapping directly in track_foreign_dirty TP | expand |
On 8/30/19 5:39 PM, Tejun Heo wrote: > page->mapping may encode different values in it and page_mapping() > should always be used to access the mapping pointer. > track_foreign_dirty tracepoint was incorrectly accessing page->mapping > directly. Use page_mapping() instead. Also, add NULL checks while at > it. Applied, thanks.
On Fri 30-08-19 16:39:54, Tejun Heo wrote: > page->mapping may encode different values in it and page_mapping() > should always be used to access the mapping pointer. > track_foreign_dirty tracepoint was incorrectly accessing page->mapping > directly. Use page_mapping() instead. Also, add NULL checks while at > it. > > Signed-off-by: Tejun Heo <tj@kernel.org> > Reported-by: Jan Kara <jack@suse.cz> > Fixes: 3a8e9ac89e6a ("writeback: add tracepoints for cgroup foreign writebacks") I can see Jens already picked this up so this is just informative: The patch now looks good to me. Honza > --- > include/trace/events/writeback.h | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h > index 3dc9fb9e7c78..3a27335fce2c 100644 > --- a/include/trace/events/writeback.h > +++ b/include/trace/events/writeback.h > @@ -251,9 +251,12 @@ TRACE_EVENT(track_foreign_dirty, > ), > > TP_fast_assign( > + struct address_space *mapping = page_mapping(page); > + struct inode *inode = mapping ? mapping->host : NULL; > + > strncpy(__entry->name, dev_name(wb->bdi->dev), 32); > __entry->bdi_id = wb->bdi->id; > - __entry->ino = page->mapping->host->i_ino; > + __entry->ino = inode ? inode->i_ino : 0; > __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;
diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h index 3dc9fb9e7c78..3a27335fce2c 100644 --- a/include/trace/events/writeback.h +++ b/include/trace/events/writeback.h @@ -251,9 +251,12 @@ TRACE_EVENT(track_foreign_dirty, ), TP_fast_assign( + struct address_space *mapping = page_mapping(page); + struct inode *inode = mapping ? mapping->host : NULL; + strncpy(__entry->name, dev_name(wb->bdi->dev), 32); __entry->bdi_id = wb->bdi->id; - __entry->ino = page->mapping->host->i_ino; + __entry->ino = inode ? inode->i_ino : 0; __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;
page->mapping may encode different values in it and page_mapping() should always be used to access the mapping pointer. track_foreign_dirty tracepoint was incorrectly accessing page->mapping directly. Use page_mapping() instead. Also, add NULL checks while at it. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Jan Kara <jack@suse.cz> Fixes: 3a8e9ac89e6a ("writeback: add tracepoints for cgroup foreign writebacks") --- include/trace/events/writeback.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)