[PATCH 2/3] bcachefs: prepare journal buf put to handle pin put

[Brian Foster <bfoster@redhat.com>]

bcachefs freeze testing has uncovered some raciness between journal
entry open/close and pin list reference count management. The
details of the problem are described in a separate patch. In
preparation for the associated fix, refactor the journal buffer put
path a bit to allow it to eventually handle dropping the pin list
reference currently held by an open journal entry. Open code the
journal write dispatch since it is essentially a single line and
instead factor out the journal state update to be reused, consistent
with other journal state update helpers. No functional changes in
this patch.

Signed-off-by: Brian Foster <bfoster@redhat.com>
---
 fs/bcachefs/journal.c |  9 ---------
 fs/bcachefs/journal.h | 22 +++++++++++++++++-----
 2 files changed, 17 insertions(+), 14 deletions(-)

diff --git a/fs/bcachefs/journal.c b/fs/bcachefs/journal.c
index 055920c26da6..76ebcdb3e3b4 100644
--- a/fs/bcachefs/journal.c
+++ b/fs/bcachefs/journal.c
@@ -132,15 +132,6 @@ journal_error_check_stuck(struct journal *j, int error, unsigned flags)
 	return stuck;
 }
 
-/* journal entry close/open: */
-
-void __bch2_journal_buf_put(struct journal *j)
-{
-	struct bch_fs *c = container_of(j, struct bch_fs, journal);
-
-	closure_call(&j->io, bch2_journal_write, c->io_complete_wq, NULL);
-}
-
 /*
  * Returns true if journal entry is now closed:
  *
diff --git a/fs/bcachefs/journal.h b/fs/bcachefs/journal.h
index 008a2e25a4fa..c7a31da077c9 100644
--- a/fs/bcachefs/journal.h
+++ b/fs/bcachefs/journal.h
@@ -252,9 +252,10 @@ static inline bool journal_entry_empty(struct jset *j)
 	return true;
 }
 
-void __bch2_journal_buf_put(struct journal *);
-
-static inline void bch2_journal_buf_put(struct journal *j, unsigned idx)
+/*
+ * Drop reference on a buffer index and return true if the count has hit zero.
+ */
+static inline union journal_res_state journal_state_buf_put(struct journal *j, unsigned idx)
 {
 	union journal_res_state s;
 
@@ -264,9 +265,20 @@ static inline void bch2_journal_buf_put(struct journal *j, unsigned idx)
 				    .buf2_count = idx == 2,
 				    .buf3_count = idx == 3,
 				    }).v, &j->reservations.counter);
+	return s;
+}
 
-	if (!journal_state_count(s, idx) && idx == s.unwritten_idx)
-		__bch2_journal_buf_put(j);
+void bch2_journal_write(struct closure *);
+static inline void bch2_journal_buf_put(struct journal *j, unsigned idx)
+{
+	struct bch_fs *c = container_of(j, struct bch_fs, journal);
+	union journal_res_state s;
+
+	s = journal_state_buf_put(j, idx);
+	if (!journal_state_count(s, idx)) {
+		if (idx == s.unwritten_idx)
+			closure_call(&j->io, bch2_journal_write, c->io_complete_wq, NULL);
+	}
 }
 
 /*
-- 
2.41.0