netfs: Fix the netfs_folio tracepoint to handle NULL mapping

Fix the netfs_folio tracepoint to handle folios that have a NULL mapping
pointer.  In such a case, just substitute a zero inode number.

Fixes: c38f4e96e605 ("netfs: Provide func to copy data to pagecache for buffered write")
Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/2917423.1727697556@warthog.procyon.org.uk
cc: Jeff Layton <jlayton@kernel.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/include/trace/events/netfs.h b/include/trace/events/netfs.h
index 76bd42a968155d0ad1fabcc0505319b0ffde5700..1d7c52821e5505e263019b8b8596d9993253d323 100644 (file)
--- a/include/trace/events/netfs.h
+++ b/include/trace/events/netfs.h
@@ -448,7 +448,8 @@ TRACE_EVENT(netfs_folio,
                             ),
 
            TP_fast_assign(
-                   __entry->ino = folio->mapping->host->i_ino;
+                   struct address_space *__m = READ_ONCE(folio->mapping);
+                   __entry->ino = __m ? __m->host->i_ino : 0;
                    __entry->why = why;
                    __entry->index = folio_index(folio);
                    __entry->nr = folio_nr_pages(folio);