bcachefs: btree iter tracepoints

We've been seeing some livelock-ish behavior in the index update part of
the main write path, and while we've got low level btree path
tracepoints, we've been lacking high level btree iterator tracepoints.

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

diff --git a/fs/bcachefs/btree_iter.c b/fs/bcachefs/btree_iter.c
index b78403376c07fe7da0240b6a6421e4a959ed1de4..b586ecf2fdfa15e77616a2b86b713456ae2facfd 100644 (file)
--- a/fs/bcachefs/btree_iter.c
+++ b/fs/bcachefs/btree_iter.c
@@ -2326,6 +2326,20 @@ static struct bkey_s_c __bch2_btree_iter_peek(struct btree_trans *trans, struct
        }
 
        bch2_btree_iter_verify(trans, iter);
+
+       if (trace___btree_iter_peek_enabled()) {
+               CLASS(printbuf, buf)();
+
+               int ret = bkey_err(k);
+               if (ret)
+                       prt_str(&buf, bch2_err_str(ret));
+               else if (k.k)
+                       bch2_bkey_val_to_text(&buf, trans->c, k);
+               else
+                       prt_str(&buf, "(null)");
+               trace___btree_iter_peek(trans->c, buf.buf);
+       }
+
        return k;
 }
 
@@ -2484,6 +2498,19 @@ out_no_locked:
 
        bch2_btree_iter_verify_entry_exit(iter);
 
+       if (trace_btree_iter_peek_max_enabled()) {
+               CLASS(printbuf, buf)();
+
+               int ret = bkey_err(k);
+               if (ret)
+                       prt_str(&buf, bch2_err_str(ret));
+               else if (k.k)
+                       bch2_bkey_val_to_text(&buf, trans->c, k);
+               else
+                       prt_str(&buf, "(null)");
+               trace_btree_iter_peek_max(trans->c, buf.buf);
+       }
+
        return k;
 end:
        bch2_btree_iter_set_pos(trans, iter, end);
@@ -2724,6 +2751,19 @@ out_no_locked:
 
        bch2_btree_iter_verify_entry_exit(iter);
        bch2_btree_iter_verify(trans, iter);
+
+       if (trace_btree_iter_peek_prev_min_enabled()) {
+               CLASS(printbuf, buf)();
+
+               int ret = bkey_err(k);
+               if (ret)
+                       prt_str(&buf, bch2_err_str(ret));
+               else if (k.k)
+                       bch2_bkey_val_to_text(&buf, trans->c, k);
+               else
+                       prt_str(&buf, "(null)");
+               trace_btree_iter_peek_prev_min(trans->c, buf.buf);
+       }
        return k;
 end:
        bch2_btree_iter_set_pos(trans, iter, end);
@@ -2767,8 +2807,10 @@ struct bkey_s_c bch2_btree_iter_peek_slot(struct btree_trans *trans, struct btre
        /* extents can't span inode numbers: */
        if ((iter->flags & BTREE_ITER_is_extents) &&
            unlikely(iter->pos.offset == KEY_OFFSET_MAX)) {
-               if (iter->pos.inode == KEY_INODE_MAX)
-                       return bkey_s_c_null;
+               if (iter->pos.inode == KEY_INODE_MAX) {
+                       k = bkey_s_c_null;
+                       goto out2;
+               }
 
                bch2_btree_iter_set_pos(trans, iter, bpos_nosnap_successor(iter->pos));
        }
@@ -2785,8 +2827,10 @@ struct bkey_s_c bch2_btree_iter_peek_slot(struct btree_trans *trans, struct btre
        }
 
        struct btree_path *path = btree_iter_path(trans, iter);
-       if (unlikely(!btree_path_node(path, path->level)))
-               return bkey_s_c_null;
+       if (unlikely(!btree_path_node(path, path->level))) {
+               k = bkey_s_c_null;
+               goto out2;
+       }
 
        btree_path_set_should_be_locked(trans, path);
 
@@ -2879,7 +2923,20 @@ out:
        bch2_btree_iter_verify(trans, iter);
        ret = bch2_btree_iter_verify_ret(trans, iter, k);
        if (unlikely(ret))
-               return bkey_s_c_err(ret);
+               k = bkey_s_c_err(ret);
+out2:
+       if (trace_btree_iter_peek_slot_enabled()) {
+               CLASS(printbuf, buf)();
+
+               int ret = bkey_err(k);
+               if (ret)
+                       prt_str(&buf, bch2_err_str(ret));
+               else if (k.k)
+                       bch2_bkey_val_to_text(&buf, trans->c, k);
+               else
+                       prt_str(&buf, "(null)");
+               trace_btree_iter_peek_slot(trans->c, buf.buf);
+       }
 
        return k;
 }

diff --git a/fs/bcachefs/trace.h b/fs/bcachefs/trace.h
index 41efebdd06efd34ecba8fb79ec687856295c4004..e759c9ff39658ac6135b8ca4ad99affa8b99c005 100644 (file)
--- a/fs/bcachefs/trace.h
+++ b/fs/bcachefs/trace.h
@@ -1495,6 +1495,26 @@ DEFINE_EVENT(fs_str, extent_trim_atomic,
        TP_ARGS(c, str)
 );
 
+DEFINE_EVENT(fs_str, btree_iter_peek_slot,
+       TP_PROTO(struct bch_fs *c, const char *str),
+       TP_ARGS(c, str)
+);
+
+DEFINE_EVENT(fs_str, __btree_iter_peek,
+       TP_PROTO(struct bch_fs *c, const char *str),
+       TP_ARGS(c, str)
+);
+
+DEFINE_EVENT(fs_str, btree_iter_peek_max,
+       TP_PROTO(struct bch_fs *c, const char *str),
+       TP_ARGS(c, str)
+);
+
+DEFINE_EVENT(fs_str, btree_iter_peek_prev_min,
+       TP_PROTO(struct bch_fs *c, const char *str),
+       TP_ARGS(c, str)
+);
+
 #ifdef CONFIG_BCACHEFS_PATH_TRACEPOINTS
 
 TRACE_EVENT(update_by_path,