bcachefs: Be stricter in bch2_read_retry_nodecode()

Now that data_update embeds bch_read_bio, BCH_READ_NODECODE means that
the read is embedded in a a data_update - and we can check in the retry
path if the extent has changed and bail out.

This likely fixes some subtle bugs with read errors and data moves.

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

diff --git a/fs/bcachefs/io_read.c b/fs/bcachefs/io_read.c
index b00d43c4fdcf8b38bf765445a1980ca4ad48c1ea..829a4f1b2f0393a84ebc3acb0cbee8f5ea5c9d9e 100644 (file)
--- a/fs/bcachefs/io_read.c
+++ b/fs/bcachefs/io_read.c
@@ -369,61 +369,47 @@ static void bch2_rbio_done(struct bch_read_bio *rbio)
        bio_endio(&rbio->bio);
 }
 
-static void bch2_read_retry_nodecode(struct bch_fs *c, struct bch_read_bio *rbio,
+static noinline void bch2_read_retry_nodecode(struct bch_fs *c, struct bch_read_bio *rbio,
                                     struct bvec_iter bvec_iter,
                                     struct bch_io_failures *failed,
                                     unsigned flags)
 {
+       struct data_update *u = container_of(rbio, struct data_update, rbio);
        struct btree_trans *trans = bch2_trans_get(c);
-       struct btree_iter iter;
-       struct bkey_buf sk;
-       struct bkey_s_c k;
-       int ret;
-
-       flags &= ~BCH_READ_last_fragment;
-       flags |= BCH_READ_must_clone;
-
-       bch2_bkey_buf_init(&sk);
-
-       bch2_trans_iter_init(trans, &iter, rbio->data_btree,
-                            rbio->read_pos, BTREE_ITER_slots);
 retry:
        bch2_trans_begin(trans);
-       rbio->bio.bi_status = 0;
 
-       ret = lockrestart_do(trans, bkey_err(k = bch2_btree_iter_peek_slot(&iter)));
+       struct btree_iter iter;
+       struct bkey_s_c k;
+       int ret = lockrestart_do(trans,
+               bkey_err(k = bch2_bkey_get_iter(trans, &iter,
+                               u->btree_id, bkey_start_pos(&u->k.k->k),
+                               0)));
        if (ret)
                goto err;
 
-       bch2_bkey_buf_reassemble(&sk, c, k);
-       k = bkey_i_to_s_c(sk.k);
-
-       if (!bch2_bkey_matches_ptr(c, k,
-                                  rbio->pick.ptr,
-                                  rbio->data_pos.offset -
-                                  rbio->pick.crc.offset)) {
+       if (!bkey_and_val_eq(k, bkey_i_to_s_c(u->k.k))) {
                /* extent we wanted to read no longer exists: */
                rbio->hole = true;
-               goto out;
+               goto err;
        }
 
        ret = __bch2_read_extent(trans, rbio, bvec_iter,
-                                rbio->read_pos,
-                                rbio->data_btree,
-                                k, 0, failed, flags);
+                                bkey_start_pos(&u->k.k->k),
+                                u->btree_id,
+                                bkey_i_to_s_c(u->k.k),
+                                0, failed, flags);
+err:
+       bch2_trans_iter_exit(trans, &iter);
+
        if (ret == READ_RETRY)
                goto retry;
        if (ret)
-               goto err;
-out:
+               rbio->bio.bi_status = BLK_STS_IOERR;
+
+       BUG_ON(atomic_read(&rbio->bio.__bi_remaining) != 1);
        bch2_rbio_done(rbio);
-       bch2_trans_iter_exit(trans, &iter);
        bch2_trans_put(trans);
-       bch2_bkey_buf_exit(&sk, c);
-       return;
-err:
-       rbio->bio.bi_status = BLK_STS_IOERR;
-       goto out;
 }
 
 static void bch2_rbio_retry(struct work_struct *work)
@@ -451,15 +437,13 @@ static void bch2_rbio_retry(struct work_struct *work)
 
        flags |= BCH_READ_in_retry;
        flags &= ~BCH_READ_may_promote;
+       flags &= ~BCH_READ_last_fragment;
+       flags |= BCH_READ_must_clone;
 
-       if (flags & BCH_READ_data_update) {
+       if (flags & BCH_READ_data_update)
                bch2_read_retry_nodecode(c, rbio, iter, &failed, flags);
-       } else {
-               flags &= ~BCH_READ_last_fragment;
-               flags |= BCH_READ_must_clone;
-
+       else
                __bch2_read(c, rbio, iter, inum, &failed, flags);
-       }
 }
 
 static void bch2_rbio_error(struct bch_read_bio *rbio, int retry,