bcachefs: Start using bpos.snapshot field

This patch starts treating the bpos.snapshot field like part of the key
in the btree code:

* bpos_successor() and bpos_predecessor() now include the snapshot field
* Keys in btrees that will be using snapshots (extents, inodes, dirents
  and xattrs) now always have their snapshot field set to U32_MAX

The btree iterator code gets a new flag, BTREE_ITER_ALL_SNAPSHOTS, that
determines whether we're iterating over keys in all snapshots or not -
internally, this controlls whether bkey_(successor|predecessor)
increment/decrement the snapshot field, or only the higher bits of the
key.

We add a new member to struct btree_iter, iter->snapshot: when
BTREE_ITER_ALL_SNAPSHOTS is not set, iter->pos.snapshot should always
equal iter->snapshot, which will be 0 for btrees that don't use
snapshots, and alsways U32_MAX for btrees that will use snapshots
(until we enable snapshot creation).

This patch also introduces a new metadata version number, and compat
code for reading from/writing to older versions - this isn't a forced
upgrade (yet).

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

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/bcachefs/inode.c b/fs/bcachefs/inode.c
index f676daf404a2..7044ab73831c 100644
--- a/fs/bcachefs/inode.c
+++ b/fs/bcachefs/inode.c
@@ -332,6 +332,7 @@ int bch2_inode_write(struct btree_trans *trans,
 		return PTR_ERR(inode_p);
 
 	bch2_inode_pack(trans->c, inode_p, inode);
+	inode_p->inode.k.p.snapshot = iter->snapshot;
 	bch2_trans_update(trans, iter, &inode_p->inode.k_i, 0);
 	return 0;
 }