bcachefs: bch2_extent_ptr_desired_durability()

This adds a new helper for getting a pointer's durability irrespective
of the device state, and uses it in the the data update path.

This fixes a bug where we do a data update but request 0 replicas to be
allocated, because the replica being rewritten is on a device marked as
failed.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/data_update.c

@@ -474,7 +474,7 @@ int bch2_data_update_init(struct btree_trans *trans,
 			if (crc_is_compressed(p.crc))
 				reserve_sectors += k.k->size;
 
-			m->op.nr_replicas += bch2_extent_ptr_durability(c, &p);
+			m->op.nr_replicas += bch2_extent_ptr_desired_durability(c, &p);
 		} else if (!p.ptr.cached) {
 			bch2_dev_list_add_dev(&m->op.devs_have, p.ptr.dev);
 		}

fs/bcachefs/extents.c

@@ -641,9 +641,8 @@ unsigned bch2_bkey_replicas(struct bch_fs *c, struct bkey_s_c k)
 	return replicas;
 }
 
-unsigned bch2_extent_ptr_durability(struct bch_fs *c, struct extent_ptr_decoded *p)
+unsigned bch2_extent_ptr_desired_durability(struct bch_fs *c, struct extent_ptr_decoded *p)
 {
-	unsigned durability = 0;
 	struct bch_dev *ca;
 
 	if (p->ptr.cached)
@@ -651,13 +650,28 @@ unsigned bch2_extent_ptr_durability(struct bch_fs *c, struct extent_ptr_decoded
 
 	ca = bch_dev_bkey_exists(c, p->ptr.dev);
 
-	if (ca->mi.state != BCH_MEMBER_STATE_failed)
-		durability = max_t(unsigned, durability, ca->mi.durability);
+	return ca->mi.durability +
+		(p->has_ec
+		 ? p->ec.redundancy
+		 : 0);
+}
 
-	if (p->has_ec)
-		durability += p->ec.redundancy;
+unsigned bch2_extent_ptr_durability(struct bch_fs *c, struct extent_ptr_decoded *p)
+{
+	struct bch_dev *ca;
 
-	return durability;
+	if (p->ptr.cached)
+		return 0;
+
+	ca = bch_dev_bkey_exists(c, p->ptr.dev);
+
+	if (ca->mi.state == BCH_MEMBER_STATE_failed)
+		return 0;
+
+	return ca->mi.durability +
+		(p->has_ec
+		 ? p->ec.redundancy
+		 : 0);
 }
 
 unsigned bch2_bkey_durability(struct bch_fs *c, struct bkey_s_c k)

fs/bcachefs/extents.h

@@ -610,6 +610,7 @@ bool bch2_bkey_is_incompressible(struct bkey_s_c);
 unsigned bch2_bkey_sectors_compressed(struct bkey_s_c);
 
 unsigned bch2_bkey_replicas(struct bch_fs *, struct bkey_s_c);
+unsigned bch2_extent_ptr_desired_durability(struct bch_fs *, struct extent_ptr_decoded *);
 unsigned bch2_extent_ptr_durability(struct bch_fs *, struct extent_ptr_decoded *);
 unsigned bch2_bkey_durability(struct bch_fs *, struct bkey_s_c);