bcachefs: rebalance_work

This adds a new btree, rebalance_work, to eliminate scanning required
for finding extents that need work done on them in the background - i.e.
for the background_target and background_compression options.

rebalance_work is a bitset btree, where a KEY_TYPE_set corresponds to an
extent in the extents or reflink btree at the same pos.

A new extent field is added, bch_extent_rebalance, which indicates that
this extent has work that needs to be done in the background - and which
options to use. This allows per-inode options to be propagated to
indirect extents - at least in some circumstances. In this patch,
changing IO options on a file will not propagate the new options to
indirect extents pointed to by that file.

Updating (setting/clearing) the rebalance_work btree is done by the
extent trigger, which looks at the bch_extent_rebalance field.

Scanning is still requrired after changing IO path options - either just
for a given inode, or for the whole filesystem. We indicate that
scanning is required by adding a KEY_TYPE_cookie key to the
rebalance_work btree: the cookie counter is so that we can detect that
scanning is still required when an option has been flipped mid-way
through an existing scan.

Future possible work:
 - Propagate options to indirect extents when being changed
 - Add other IO path options - nr_replicas, ec, to rebalance_work so
   they can be applied in the background when they change
 - Add a counter, for bcachefs fs usage output, showing the pending
   amount of rebalance work: we'll probably want to do this after the
   disk space accounting rewrite (moving it to a new btree)

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

1 files changed, 21 insertions, 10 deletions

diff --git a/fs/bcachefs/rebalance_types.h b/fs/bcachefs/rebalance_types.h
index 7462a92e9598..0fffb536c1d0 100644
--- a/fs/bcachefs/rebalance_types.h
+++ b/fs/bcachefs/rebalance_types.h
@@ -2,25 +2,36 @@
 #ifndef _BCACHEFS_REBALANCE_TYPES_H
 #define _BCACHEFS_REBALANCE_TYPES_H
 
+#include "bbpos_types.h"
 #include "move_types.h"
 
-enum rebalance_state {
-	REBALANCE_WAITING,
-	REBALANCE_THROTTLED,
-	REBALANCE_RUNNING,
+#define BCH_REBALANCE_STATES()		\
+	x(waiting)			\
+	x(working)			\
+	x(scanning)
+
+enum bch_rebalance_states {
+#define x(t)	BCH_REBALANCE_##t,
+	BCH_REBALANCE_STATES()
+#undef x
 };
 
 struct bch_fs_rebalance {
-	struct task_struct __rcu *thread;
+	struct task_struct __rcu	*thread;
 	struct bch_pd_controller pd;
 
-	atomic64_t		work_unknown_dev;
+	enum bch_rebalance_states	state;
+	u64				wait_iotime_start;
+	u64				wait_iotime_end;
+	u64				wait_wallclock_start;
+
+	struct bch_move_stats		work_stats;
 
-	enum rebalance_state	state;
-	u64			throttled_until_iotime;
-	unsigned long		throttled_until_cputime;
+	struct bbpos			scan_start;
+	struct bbpos			scan_end;
+	struct bch_move_stats		scan_stats;
 
-	unsigned		enabled:1;
+	unsigned			enabled:1;
 };
 
 #endif /* _BCACHEFS_REBALANCE_TYPES_H */