bcachefs: Introduce a separate journal watermark for copygc

Since journal reclaim -> btree key cache flushing may require the
allocation of new btree nodes, it has an implicit dependency on copygc
in order to make forward progress - so we should avoid blocking copygc
unless the journal is really close to full.

This introduces watermarks to replace our single MAY_GET_UNRESERVED bit
in the journal, and adds a watermark for copygc and plumbs it through.

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

1 files changed, 31 insertions, 10 deletions

diff --git a/fs/bcachefs/journal_types.h b/fs/bcachefs/journal_types.h
index 91f829adf862..a41b915b3ac6 100644
--- a/fs/bcachefs/journal_types.h
+++ b/fs/bcachefs/journal_types.h
@@ -144,16 +144,45 @@ enum journal_space_from {
 enum {
 	JOURNAL_REPLAY_DONE,
 	JOURNAL_STARTED,
-	JOURNAL_MAY_GET_UNRESERVED,
 	JOURNAL_MAY_SKIP_FLUSH,
 };
 
+#define JOURNAL_WATERMARKS()		\
+	x(any)				\
+	x(copygc)			\
+	x(reserved)
+
+enum journal_watermark {
+#define x(n)	JOURNAL_WATERMARK_##n,
+	JOURNAL_WATERMARKS()
+#undef x
+};
+
+#define JOURNAL_WATERMARK_MASK	3
+
+/* Reasons we may fail to get a journal reservation: */
+#define JOURNAL_ERRORS()		\
+	x(ok)				\
+	x(blocked)			\
+	x(max_in_flight)		\
+	x(journal_full)			\
+	x(journal_pin_full)		\
+	x(journal_stuck)		\
+	x(insufficient_devices)
+
+enum journal_errors {
+#define x(n)	JOURNAL_ERR_##n,
+	JOURNAL_ERRORS()
+#undef x
+};
+
 /* Embedded in struct bch_fs */
 struct journal {
 	/* Fastpath stuff up front: */
 	struct {
 
 	union journal_res_state reservations;
+	enum journal_watermark	watermark;
 
 	union journal_preres_state prereserved;
 
@@ -173,15 +202,7 @@ struct journal {
 	 * 0, or -ENOSPC if waiting on journal reclaim, or -EROFS if
 	 * insufficient devices:
 	 */
-	enum {
-		cur_entry_ok,
-		cur_entry_blocked,
-		cur_entry_max_in_flight,
-		cur_entry_journal_full,
-		cur_entry_journal_pin_full,
-		cur_entry_journal_stuck,
-		cur_entry_insufficient_devices,
-	}			cur_entry_error;
+	enum journal_errors	cur_entry_error;
 
 	unsigned		buf_size_want;
 	/*