bcachefs: bch2_bkey_pick_read_device() can now specify a device

To be used for scrub, where we want the read to come from a specific
device.

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

fs/bcachefs/btree_io.c

@@ -1352,7 +1352,7 @@ start:
 
 		can_retry = bch2_bkey_pick_read_device(c,
 				bkey_i_to_s_c(&b->key),
-				&failed, &rb->pick) > 0;
+				&failed, &rb->pick, -1) > 0;
 
 		if (!bio->bi_status &&
 		    !bch2_btree_node_read_done(c, ca, b, can_retry, &saw_error)) {
@@ -1697,7 +1697,7 @@ void bch2_btree_node_read(struct btree_trans *trans, struct btree *b,
 		return;
 
 	ret = bch2_bkey_pick_read_device(c, bkey_i_to_s_c(&b->key),
-					 NULL, &pick);
+					 NULL, &pick, -1);
 
 	if (ret <= 0) {
 		struct printbuf buf = PRINTBUF;

fs/bcachefs/debug.c

@@ -191,7 +191,7 @@ void bch2_btree_node_ondisk_to_text(struct printbuf *out, struct bch_fs *c,
 	unsigned offset = 0;
 	int ret;
 
-	if (bch2_bkey_pick_read_device(c, bkey_i_to_s_c(&b->key), NULL, &pick) <= 0) {
+	if (bch2_bkey_pick_read_device(c, bkey_i_to_s_c(&b->key), NULL, &pick, -1) <= 0) {
 		prt_printf(out, "error getting device to read from: invalid device\n");
 		return;
 	}

fs/bcachefs/extents.c

@@ -114,8 +114,9 @@ static inline bool ptr_better(struct bch_fs *c,
  * other devices, it will still pick a pointer from avoid.
  */
 int bch2_bkey_pick_read_device(struct bch_fs *c, struct bkey_s_c k,
-			       struct bch_io_failures *failed,
-			       struct extent_ptr_decoded *pick)
+			      struct bch_io_failures *failed,
+			      struct extent_ptr_decoded *pick,
+			      int dev)
 {
 	struct bkey_ptrs_c ptrs = bch2_bkey_ptrs_c(k);
 	const union bch_extent_entry *entry;
@@ -137,6 +138,10 @@ int bch2_bkey_pick_read_device(struct bch_fs *c, struct bkey_s_c k,
 			break;
 		}
 
+		/* Are we being asked to read from a specific device? */
+		if (dev >= 0 && p.ptr.dev != dev)
+			continue;
+
 		/*
 		 * If there are any dirty pointers it's an error if we can't
 		 * read:

fs/bcachefs/extents.h

@@ -404,7 +404,7 @@ void bch2_mark_io_failure(struct bch_io_failures *,
 			  struct extent_ptr_decoded *);
 int bch2_bkey_pick_read_device(struct bch_fs *, struct bkey_s_c,
 			       struct bch_io_failures *,
-			       struct extent_ptr_decoded *);
+			       struct extent_ptr_decoded *, int);
 
 /* KEY_TYPE_btree_ptr: */
 

fs/bcachefs/io_read.c

@@ -436,7 +436,7 @@ retry:
 				 bkey_start_pos(&u->k.k->k),
 				 u->btree_id,
 				 bkey_i_to_s_c(u->k.k),
-				 0, failed, flags);
+				 0, failed, flags, -1);
 err:
 	bch2_trans_iter_exit(trans, &iter);
 
@@ -872,7 +872,7 @@ int __bch2_read_extent(struct btree_trans *trans, struct bch_read_bio *orig,
 		       struct bvec_iter iter, struct bpos read_pos,
 		       enum btree_id data_btree, struct bkey_s_c k,
 		       unsigned offset_into_extent,
-		       struct bch_io_failures *failed, unsigned flags)
+		       struct bch_io_failures *failed, unsigned flags, int dev)
 {
 	struct bch_fs *c = trans->c;
 	struct extent_ptr_decoded pick;
@@ -893,7 +893,7 @@ int __bch2_read_extent(struct btree_trans *trans, struct bch_read_bio *orig,
 		goto out_read_done;
 	}
 retry_pick:
-	pick_ret = bch2_bkey_pick_read_device(c, k, failed, &pick);
+	pick_ret = bch2_bkey_pick_read_device(c, k, failed, &pick, dev);
 
 	/* hole or reservation - just zero fill: */
 	if (!pick_ret)
@@ -1250,7 +1250,7 @@ void __bch2_read(struct bch_fs *c, struct bch_read_bio *rbio,
 
 		ret = __bch2_read_extent(trans, rbio, bvec_iter, iter.pos,
 					 data_btree, k,
-					 offset_into_extent, failed, flags);
+					 offset_into_extent, failed, flags, -1);
 		if (ret)
 			goto err;
 

fs/bcachefs/io_read.h

@@ -129,7 +129,7 @@ enum bch_read_flags {
 int __bch2_read_extent(struct btree_trans *, struct bch_read_bio *,
 		       struct bvec_iter, struct bpos, enum btree_id,
 		       struct bkey_s_c, unsigned,
-		       struct bch_io_failures *, unsigned);
+		       struct bch_io_failures *, unsigned, int);
 
 static inline void bch2_read_extent(struct btree_trans *trans,
 			struct bch_read_bio *rbio, struct bpos read_pos,
@@ -137,7 +137,7 @@ static inline void bch2_read_extent(struct btree_trans *trans,
 			unsigned offset_into_extent, unsigned flags)
 {
 	__bch2_read_extent(trans, rbio, rbio->bio.bi_iter, read_pos,
-			   data_btree, k, offset_into_extent, NULL, flags);
+			   data_btree, k, offset_into_extent, NULL, flags, -1);
 }
 
 void __bch2_read(struct bch_fs *, struct bch_read_bio *, struct bvec_iter,