bcachefs: Update data move path for snapshots

The data move path operates on existing extents, and not within a
subvolume as the regular IO paths do. It needs to change because it may
cause existing extents to be split, and when splitting an existing
extent in an ancestor snapshot we need to make sure the new split has
the same visibility in child snapshots as the existing extent.

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

1 files changed, 38 insertions, 0 deletions

diff --git a/fs/bcachefs/subvolume.h b/fs/bcachefs/subvolume.h
index cea4c665af32..0740c7b7f772 100644
--- a/fs/bcachefs/subvolume.h
+++ b/fs/bcachefs/subvolume.h
@@ -54,6 +54,44 @@ static inline bool bch2_snapshot_is_ancestor(struct bch_fs *c, u32 id, u32 ances
 	return id == ancestor;
 }
 
+struct snapshots_seen {
+	struct bpos			pos;
+	size_t				nr;
+	size_t				size;
+	u32				*d;
+};
+
+static inline void snapshots_seen_exit(struct snapshots_seen *s)
+{
+	kfree(s->d);
+	s->d = NULL;
+}
+
+static inline void snapshots_seen_init(struct snapshots_seen *s)
+{
+	memset(s, 0, sizeof(*s));
+}
+
+static inline int snapshots_seen_add(struct bch_fs *c, struct snapshots_seen *s, u32 id)
+{
+	if (s->nr == s->size) {
+		size_t new_size = max(s->size, 128UL) * 2;
+		u32 *d = krealloc(s->d, new_size * sizeof(s->d[0]), GFP_KERNEL);
+
+		if (!d) {
+			bch_err(c, "error reallocating snapshots_seen table (new size %zu)",
+				new_size);
+			return -ENOMEM;
+		}
+
+		s->size = new_size;
+		s->d	= d;
+	}
+
+	s->d[s->nr++] = id;
+	return 0;
+}
+
 int bch2_fs_snapshots_check(struct bch_fs *);
 void bch2_fs_snapshots_exit(struct bch_fs *);
 int bch2_fs_snapshots_start(struct bch_fs *);