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, 15 insertions, 6 deletions

diff --git a/fs/bcachefs/reflink.c b/fs/bcachefs/reflink.c
index 540c78cd4b0c..507100b38e29 100644
--- a/fs/bcachefs/reflink.c
+++ b/fs/bcachefs/reflink.c
@@ -7,6 +7,7 @@
 #include "inode.h"
 #include "io_misc.h"
 #include "io_write.h"
+#include "rebalance.h"
 #include "reflink.h"
 #include "subvolume.h"
 #include "super-io.h"
@@ -252,8 +253,9 @@ s64 bch2_remap_range(struct bch_fs *c,
 	struct bpos dst_start = POS(dst_inum.inum, dst_offset);
 	struct bpos src_start = POS(src_inum.inum, src_offset);
 	struct bpos dst_end = dst_start, src_end = src_start;
+	struct bch_io_opts opts;
 	struct bpos src_want;
-	u64 dst_done;
+	u64 dst_done = 0;
 	u32 dst_snapshot, src_snapshot;
 	int ret = 0, ret2 = 0;
 
@@ -269,6 +271,10 @@ s64 bch2_remap_range(struct bch_fs *c,
 	bch2_bkey_buf_init(&new_src);
 	trans = bch2_trans_get(c);
 
+	ret = bch2_inum_opts_get(trans, src_inum, &opts);
+	if (ret)
+		goto err;
+
 	bch2_trans_iter_init(trans, &src_iter, BTREE_ID_extents, src_start,
 			     BTREE_ITER_INTENT);
 	bch2_trans_iter_init(trans, &dst_iter, BTREE_ID_extents, dst_start,
@@ -352,10 +358,13 @@ s64 bch2_remap_range(struct bch_fs *c,
 				min(src_k.k->p.offset - src_want.offset,
 				    dst_end.offset - dst_iter.pos.offset));
 
-		ret = bch2_extent_update(trans, dst_inum, &dst_iter,
-					 new_dst.k, &disk_res,
-					 new_i_size, i_sectors_delta,
-					 true);
+		ret =   bch2_bkey_set_needs_rebalance(c, new_dst.k,
+					opts.background_target,
+					opts.background_compression) ?:
+			bch2_extent_update(trans, dst_inum, &dst_iter,
+					new_dst.k, &disk_res,
+					new_i_size, i_sectors_delta,
+					true);
 		bch2_disk_reservation_put(c, &disk_res);
 	}
 	bch2_trans_iter_exit(trans, &dst_iter);
@@ -386,7 +395,7 @@ s64 bch2_remap_range(struct bch_fs *c,
 
 		bch2_trans_iter_exit(trans, &inode_iter);
 	} while (bch2_err_matches(ret2, BCH_ERR_transaction_restart));
-
+err:
 	bch2_trans_put(trans);
 	bch2_bkey_buf_exit(&new_src, c);
 	bch2_bkey_buf_exit(&new_dst, c);