Subject: linux-next: build failure after merge of the mm tree

From: Stephen Rothwell <[email-masked]>
Date: Tue, 23 Apr 2024 10:22:53 +1000

Hi all,

After merging the mm tree, today's linux-next build (arm
multi_v7_defconfig) failed like this:

mm/backing-dev.c: In function 'wb_stats_show':
mm/backing-dev.c:175:33: error: 'struct bdi_writeback' has no member named 'memcg_css'
  175 |                    cgroup_ino(wb->memcg_css->cgroup),
      |                                 ^~

Caused by commit

  3acd401af0c9 ("writeback: support retrieving per group debug writeback stats of bdi")

from the mm-unstable branch of the mm tree.

I have applied the following (hack) patch for today.

From: Stephen Rothwell <[email-masked]>
Date: Tue, 23 Apr 2024 10:06:13 +1000
Subject: [PATCH] fixup for "writeback: support retrieving per group debug
 writeback stats of bdi"

Signed-off-by: Stephen Rothwell <[email-masked]>
---
 mm/backing-dev.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 481886f47164..af8c81adf7a4 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -172,7 +172,11 @@ static void wb_stats_show(struct seq_file *m, struct bdi_writeback *wb,
 		   "b_more_io:         %10lu\n"
 		   "b_dirty_time:      %10lu\n"
 		   "state:             %10lx\n\n",
+#ifdef CONFIG_CGROUP_WRITEBACK
 		   cgroup_ino(wb->memcg_css->cgroup),
+#else
+		   (ino_t)0,
+#endif
 		   K(stats->nr_writeback),
 		   K(stats->nr_reclaimable),
 		   K(stats->wb_thresh),
-- 
2.43.0

-- 
Cheers,
Stephen Rothwell