From: Kent Overstreet <kent.overstreet@gmail.com>
Date: Mon, 18 Jul 2022 00:22:30 +0000 (-0400)
Subject: bcachefs: Inject transaction restarts in debug mode
X-Git-Tag: v6.7-rc1~201^2~865
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=a0cb8d784f309d22323974e47b103bf01d0b62c0;p=thirdparty%2Fkernel%2Flinux.git

bcachefs: Inject transaction restarts in debug mode

In CONFIG_BCACHEFS_DEBUG mode, we'll now randomly issue transaction
restarts - with a decaying probability based on the number of restarts
we've already had, to ensure that transactions eventually make forward
progress. This should help shake out some bugs.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
---

diff --git a/fs/bcachefs/btree_iter.c b/fs/bcachefs/btree_iter.c
index db247c96298f4..777e41a122462 100644
--- a/fs/bcachefs/btree_iter.c
+++ b/fs/bcachefs/btree_iter.c
@@ -17,6 +17,7 @@
 #include "subvolume.h"
 #include "trace.h"
 
+#include <linux/random.h>
 #include <linux/prefetch.h>
 
 static inline void btree_path_list_remove(struct btree_trans *, struct btree_path *);
@@ -1660,6 +1661,16 @@ out:
 int __must_check bch2_btree_path_traverse(struct btree_trans *trans,
 					  struct btree_path *path, unsigned flags)
 {
+	if (IS_ENABLED(CONFIG_BCACHEFS_DEBUG)) {
+		unsigned restart_probability_bits = 4 << min(trans->restart_count, 32U);
+		u64 max = ~(~0ULL << restart_probability_bits);
+
+		if (!get_random_u32_below(max)) {
+			trace_transaction_restart_injected(trans->fn, _RET_IP_);
+			return btree_trans_restart(trans, BCH_ERR_transaction_restart_fault_inject);
+		}
+	}
+
 	if (path->uptodate < BTREE_ITER_NEED_RELOCK)
 		return 0;
 
diff --git a/fs/bcachefs/trace.h b/fs/bcachefs/trace.h
index a52da91f279e6..1e9e93161509c 100644
--- a/fs/bcachefs/trace.h
+++ b/fs/bcachefs/trace.h
@@ -707,6 +707,12 @@ DEFINE_EVENT(transaction_event,	transaction_restart_ip,
 	TP_ARGS(trans_fn, caller_ip)
 );
 
+DEFINE_EVENT(transaction_event,	transaction_restart_injected,
+	TP_PROTO(const char *trans_fn,
+		 unsigned long caller_ip),
+	TP_ARGS(trans_fn, caller_ip)
+);
+
 DEFINE_EVENT(transaction_event,	trans_blocked_journal_reclaim,
 	TP_PROTO(const char *trans_fn,
 		 unsigned long caller_ip),