bcachefs: fix deadlock in journal_entry_open()

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.

So we need to add a locked helper to handle fatal errors even when the
journal->lock is held.

Fixes: b3d82c2f2761 ("bcachefs: Guard against journal seq overflow")
Signed-off-by: Jeongjun Park <aha310510@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

1 files changed, 11 insertions, 0 deletions

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;