Forwarded: [PATCH] nilfs2: add debug instrumentation to nilfs_clean_segments

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Subject: [PATCH] nilfs2: add debug instrumentation to nilfs_clean_segments
Author: kartikey406@xxxxxxxxx

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master


Add temporary pr_err() calls to log ns_nsegments, nfreesegs, and
the first segment number on entry to nilfs_clean_segments(), and
to log the error code on each retry, to diagnose the hung task
reported by syzbot.

Link: https://syzkaller.appspot.com/bug?extid=155b515977fecb686986
Signed-off-by: Deepanshu Kartikey <kartikey406@xxxxxxxxx>
---
 fs/nilfs2/segment.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c
index 9332f5ac6083..219ae4ae0c03 100644
--- a/fs/nilfs2/segment.c
+++ b/fs/nilfs2/segment.c
@@ -2519,7 +2519,10 @@ int nilfs_clean_segments(struct super_block *sb, struct nilfs_argv *argv,
 		return -EROFS;
 
 	nilfs_transaction_lock(sb, &ti, 1);
-
+	pr_err("nilfs2: clean_segments: ns_nsegments=%lu nfreesegs=%zu segnums[0]=0x%llx\n",
+       nilfs->ns_nsegments,
+       nfreesegs,
+       nfreesegs > 0 ? segnumv[0] : 0ULL);
 	/*
 	 * Validate segment numbers under ns_segctor_sem (held for write
 	 * by nilfs_transaction_lock above) so the check is serialized
@@ -2559,7 +2562,7 @@ int nilfs_clean_segments(struct super_block *sb, struct nilfs_argv *argv,
 
 		if (likely(!err))
 			break;
-
+		pr_err("nilfs2: clean_segments retry: err=%d\n", err);
 		nilfs_warn(sb, "error %d cleaning segments", err);
 		set_current_state(TASK_INTERRUPTIBLE);
 		schedule_timeout(sci->sc_interval);
-- 
2.43.0