bcachefs: Add a pre-reserve mechanism for the journal

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

1 files changed, 27 insertions, 0 deletions

diff --git a/fs/bcachefs/journal_types.h b/fs/bcachefs/journal_types.h
index c91a21e07809..85bf5e2706f7 100644
--- a/fs/bcachefs/journal_types.h
+++ b/fs/bcachefs/journal_types.h
@@ -80,6 +80,14 @@ struct journal_res {
 	u64			seq;
 };
 
+/*
+ * For reserving space in the journal prior to getting a reservation on a
+ * particular journal entry:
+ */
+struct journal_preres {
+	unsigned		u64s;
+};
+
 union journal_res_state {
 	struct {
 		atomic64_t	counter;
@@ -98,6 +106,21 @@ union journal_res_state {
 	};
 };
 
+union journal_preres_state {
+	struct {
+		atomic64_t	counter;
+	};
+
+	struct {
+		u64		v;
+	};
+
+	struct {
+		u32		reserved;
+		u32		remaining;
+	};
+};
+
 /* bytes: */
 #define JOURNAL_ENTRY_SIZE_MIN		(64U << 10) /* 64k */
 #define JOURNAL_ENTRY_SIZE_MAX		(4U  << 20) /* 4M */
@@ -122,6 +145,7 @@ enum {
 	JOURNAL_STARTED,
 	JOURNAL_NEED_WRITE,
 	JOURNAL_NOT_EMPTY,
+	JOURNAL_MAY_GET_UNRESERVED,
 };
 
 /* Embedded in struct bch_fs */
@@ -142,6 +166,8 @@ struct journal {
 	 */
 	int			cur_entry_error;
 
+	union journal_preres_state prereserved;
+
 	/* Reserved space in journal entry to be used just prior to write */
 	unsigned		entry_u64s_reserved;
 
@@ -161,6 +187,7 @@ struct journal {
 	/* Used when waiting because the journal was full */
 	wait_queue_head_t	wait;
 	struct closure_waitlist	async_wait;
+	struct closure_waitlist	preres_wait;
 
 	struct closure		io;
 	struct delayed_work	write_work;