[PATCH v2] bcachefs: fix deadlock in journal_entry_open()

[Jeongjun Park <aha310510@gmail.com>]

In the previous commit b3d82c2f2761, code was added to prevent journal sequence
overflow. Among them, the code added to journal_entry_open() uses the
bch2_fs_fatal_err_on() function to handle errors.

However, __journal_res_get() , which calls journal_entry_open() , calls
journal_entry_open() while holding journal->lock , but bch2_fs_fatal_err_on()
internally tries to acquire journal->lock , which results in a deadlock.

Therefore, we need to add bch2_fs_fatal_err_on_locked() to handle fatal errors
even when journal->lock is held.

Fixes: b3d82c2f2761 ("bcachefs: Guard against journal seq overflow")
Signed-off-by: Jeongjun Park <aha310510@gmail.com>
---
 fs/bcachefs/error.c   |  6 ++++++
 fs/bcachefs/error.h   | 16 ++++++++++++++++
 fs/bcachefs/journal.c | 10 +++++++++-
 fs/bcachefs/journal.h |  1 +
 fs/bcachefs/super.c   | 11 +++++++++++
 fs/bcachefs/super.h   |  1 +
 6 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/fs/bcachefs/error.c b/fs/bcachefs/error.c
index 038da6a61f6b..25f51dec732d 100644
--- a/fs/bcachefs/error.c
+++ b/fs/bcachefs/error.c
@@ -50,6 +50,12 @@ void bch2_fatal_error(struct bch_fs *c)
 		bch_err(c, "fatal error - emergency read only");
 }
 
+void bch2_fatal_error_locked(struct bch_fs *c)
+{
+	if (bch2_fs_emergency_read_only_locked(c))
+		bch_err(c, "fatal error - emergency read only");
+}
+
 void bch2_io_error_work(struct work_struct *work)
 {
 	struct bch_dev *ca = container_of(work, struct bch_dev, io_error_work);
diff --git a/fs/bcachefs/error.h b/fs/bcachefs/error.h
index 7acf2a27ca28..760623c07e67 100644
--- a/fs/bcachefs/error.h
+++ b/fs/bcachefs/error.h
@@ -189,6 +189,7 @@ do {									\
  */
 
 void bch2_fatal_error(struct bch_fs *);
+void bch2_fatal_error_locked(struct bch_fs *);
 
 #define bch2_fs_fatal_error(c, _msg, ...)				\
 do {									\
@@ -205,6 +206,21 @@ do {									\
 	_ret;								\
 })
 
+#define bch2_fs_fatal_error_locked(c, _msg, ...)		\
+do {									\
+	bch_err(c, "%s(): fatal error " _msg, __func__, ##__VA_ARGS__);	\
+	bch2_fatal_error_locked(c);					\
+} while (0)
+
+#define bch2_fs_fatal_err_on_locked(cond, c, ...)		\
+({									\
+	bool _ret = unlikely(!!(cond));					\
+									\
+	if (_ret)							\
+		bch2_fs_fatal_error_locked(c, __VA_ARGS__);		\
+	_ret;								\
+})
+
 /*
  * IO errors: either recoverable metadata IO (because we have replicas), or data
  * IO - we need to log it and print out a message, but we don't (necessarily)
diff --git a/fs/bcachefs/journal.c b/fs/bcachefs/journal.c
index 2cd20114b74b..12e3b4024494 100644
--- a/fs/bcachefs/journal.c
+++ b/fs/bcachefs/journal.c
@@ -320,6 +320,14 @@ void bch2_journal_halt(struct journal *j)
 	spin_unlock(&j->lock);
 }
 
+void bch2_journal_halt_locked(struct journal *j)
+{
+	__journal_entry_close(j, JOURNAL_ENTRY_ERROR_VAL, true);
+	if (!j->err_seq)
+		j->err_seq = journal_cur_seq(j);
+	journal_wake(j);
+}
+
 static bool journal_entry_want_write(struct journal *j)
 {
 	bool ret = !journal_entry_is_open(j) ||
@@ -382,7 +390,7 @@ static int journal_entry_open(struct journal *j)
 	if (nr_unwritten_journal_entries(j) == ARRAY_SIZE(j->buf))
 		return JOURNAL_ERR_max_in_flight;
 
-	if (bch2_fs_fatal_err_on(journal_cur_seq(j) >= JOURNAL_SEQ_MAX,
+	if (bch2_fs_fatal_err_on_locked(journal_cur_seq(j) >= JOURNAL_SEQ_MAX,
 				 c, "cannot start: journal seq overflow"))
 		return JOURNAL_ERR_insufficient_devices; /* -EROFS */
 
diff --git a/fs/bcachefs/journal.h b/fs/bcachefs/journal.h
index cb0df0663946..416fbed447de 100644
--- a/fs/bcachefs/journal.h
+++ b/fs/bcachefs/journal.h
@@ -408,6 +408,7 @@ bool bch2_journal_noflush_seq(struct journal *, u64, u64);
 int bch2_journal_meta(struct journal *);
 
 void bch2_journal_halt(struct journal *);
+void bch2_journal_halt_locked(struct journal *);
 
 static inline int bch2_journal_error(struct journal *j)
 {
diff --git a/fs/bcachefs/super.c b/fs/bcachefs/super.c
index d97ea7bd1171..6d97d412fed9 100644
--- a/fs/bcachefs/super.c
+++ b/fs/bcachefs/super.c
@@ -411,6 +411,17 @@ bool bch2_fs_emergency_read_only(struct bch_fs *c)
 	return ret;
 }
 
+bool bch2_fs_emergency_read_only_locked(struct bch_fs *c)
+{
+	bool ret = !test_and_set_bit(BCH_FS_emergency_ro, &c->flags);
+
+	bch2_journal_halt_locked(&c->journal);
+	bch2_fs_read_only_async(c);
+
+	wake_up(&bch2_read_only_wait);
+	return ret;
+}
+
 static int bch2_fs_read_write_late(struct bch_fs *c)
 {
 	int ret;
diff --git a/fs/bcachefs/super.h b/fs/bcachefs/super.h
index fa6d52216510..04f8287eff5c 100644
--- a/fs/bcachefs/super.h
+++ b/fs/bcachefs/super.h
@@ -29,6 +29,7 @@ int bch2_dev_resize(struct bch_fs *, struct bch_dev *, u64);
 struct bch_dev *bch2_dev_lookup(struct bch_fs *, const char *);
 
 bool bch2_fs_emergency_read_only(struct bch_fs *);
+bool bch2_fs_emergency_read_only_locked(struct bch_fs *);
 void bch2_fs_read_only(struct bch_fs *);
 
 int bch2_fs_read_write(struct bch_fs *);
--