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, 10 insertions, 1 deletions

diff --git a/fs/bcachefs/io_misc.c b/fs/bcachefs/io_misc.c
index 119834cb8f9e..0979d5e05713 100644
--- a/fs/bcachefs/io_misc.c
+++ b/fs/bcachefs/io_misc.c
@@ -16,6 +16,7 @@
 #include "io_misc.h"
 #include "io_write.h"
 #include "logged_ops.h"
+#include "rebalance.h"
 #include "subvolume.h"
 
 /* Overwrites whatever was present with zeroes: */
@@ -355,6 +356,7 @@ static int __bch2_resume_logged_op_finsert(struct btree_trans *trans,
 	struct btree_iter iter;
 	struct bkey_i_logged_op_finsert *op = bkey_i_to_logged_op_finsert(op_k);
 	subvol_inum inum = { le32_to_cpu(op->v.subvol), le64_to_cpu(op->v.inum) };
+	struct bch_io_opts opts;
 	u64 dst_offset = le64_to_cpu(op->v.dst_offset);
 	u64 src_offset = le64_to_cpu(op->v.src_offset);
 	s64 shift = dst_offset - src_offset;
@@ -363,6 +365,10 @@ static int __bch2_resume_logged_op_finsert(struct btree_trans *trans,
 	bool insert = shift > 0;
 	int ret = 0;
 
+	ret = bch2_inum_opts_get(trans, inum, &opts);
+	if (ret)
+		return ret;
+
 	bch2_trans_iter_init(trans, &iter, BTREE_ID_extents,
 			     POS(inum.inum, 0),
 			     BTREE_ITER_INTENT);
@@ -443,7 +449,10 @@ case LOGGED_OP_FINSERT_shift_extents:
 
 		op->v.pos = cpu_to_le64(insert ? bkey_start_offset(&delete.k) : delete.k.p.offset);
 
-		ret =   bch2_btree_insert_trans(trans, BTREE_ID_extents, &delete, 0) ?:
+		ret =   bch2_bkey_set_needs_rebalance(c, copy,
+					opts.background_target,
+					opts.background_compression) ?:
+			bch2_btree_insert_trans(trans, BTREE_ID_extents, &delete, 0) ?:
 			bch2_btree_insert_trans(trans, BTREE_ID_extents, copy, 0) ?:
 			bch2_logged_op_update(trans, &op->k_i) ?:
 			bch2_trans_commit(trans, &disk_res, NULL, BTREE_INSERT_NOFAIL);