[PATCH] netfs: Fix the netfs_folio tracepoint to handle NULL mapping

[PATCH] netfs: Fix the netfs_folio tracepoint to handle NULL mapping

[David Howells]

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>
cc: Jeff Layton <jlayton@kernel.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
---
 include/trace/events/netfs.h |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/trace/events/netfs.h b/include/trace/events/netfs.h
index 76bd42a96815..1d7c52821e55 100644
--- 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);

Re: [PATCH] netfs: Fix the netfs_folio tracepoint to handle NULL mapping

[Christian Brauner]

On Mon, 30 Sep 2024 12:59:16 +0100, David Howells wrote:
> Fix the netfs_folio tracepoint to handle folios that have a NULL mapping
> pointer.  In such a case, just substitute a zero inode number.
> 
> 

Applied to the vfs.fixes branch of the vfs/vfs.git tree.
Patches in the vfs.fixes branch should appear in linux-next soon.

Please report any outstanding bugs that were missed during review in a
new review to the original patch series allowing us to drop it.

It's encouraged to provide Acked-bys and Reviewed-bys even though the
patch has now been applied. If possible patch trailers will be updated.

Note that commit hashes shown below are subject to change due to rebase,
trailer updates or similar. If in doubt, please check the listed branch.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
branch: vfs.fixes

[1/1] netfs: Fix the netfs_folio tracepoint to handle NULL mapping
      https://git.kernel.org/vfs/vfs/c/f801850bc263

[PATCH] netfs: Fix the netfs_folio tracepoint to handle NULL mapping

[exkc]

From: David Howells <dhowells@redhat.com>

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>
---
 include/trace/events/netfs.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/trace/events/netfs.h b/include/trace/events/netfs.h
index 76bd42a96815..1d7c52821e55 100644
--- 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);
-- 
2.46.1