bcachefs: Deferred btree updates

Will be used in the future for inode updates, which will be very helpful
for multithreaded workloads that have to update the inode with every
extent update (appends, or updates that change i_sectors)

Also will be used eventually for fully persistent alloc info

However - we still need a mechanism for reserving space in the journal
prior to getting a journal reservation, so it's not technically safe to
make use of this just yet, we could deadlock with the journal full
(although not likely to be an issue in practice)

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

1 files changed, 19 insertions, 0 deletions

diff --git a/fs/bcachefs/journal_reclaim.c b/fs/bcachefs/journal_reclaim.c
index 6ada63f1bb25..770a6e0c7d97 100644
--- a/fs/bcachefs/journal_reclaim.c
+++ b/fs/bcachefs/journal_reclaim.c
@@ -75,6 +75,25 @@ void bch2_journal_pin_drop(struct journal *j,
 	spin_unlock(&j->lock);
 }
 
+void bch2_journal_pin_update(struct journal *j, u64 seq,
+			     struct journal_entry_pin *pin,
+			     journal_pin_flush_fn flush_fn)
+{
+	spin_lock(&j->lock);
+
+	if (pin->seq != seq) {
+		__journal_pin_drop(j, pin);
+		__journal_pin_add(j, seq, pin, flush_fn);
+	} else {
+		struct journal_entry_pin_list *pin_list =
+			journal_seq_pin(j, seq);
+
+		list_move(&pin->list, &pin_list->list);
+	}
+
+	spin_unlock(&j->lock);
+}
+
 void bch2_journal_pin_add_if_older(struct journal *j,
 				  struct journal_entry_pin *src_pin,
 				  struct journal_entry_pin *pin,