bcachefs: trace_read_nopromote()

Add a tracepoint to print the reason a read wasn't promoted.

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

diff --git a/fs/bcachefs/errcode.h b/fs/bcachefs/errcode.h
index 379d9d7..56b6ce2 100644 (file)
--- a/fs/bcachefs/errcode.h
+++ b/fs/bcachefs/errcode.h
@@ -218,7 +218,14 @@
        x(BCH_ERR_btree_node_read_err,  btree_node_read_err_want_retry)         \
        x(BCH_ERR_btree_node_read_err,  btree_node_read_err_must_retry)         \
        x(BCH_ERR_btree_node_read_err,  btree_node_read_err_bad_node)           \
-       x(BCH_ERR_btree_node_read_err,  btree_node_read_err_incompatible)
+       x(BCH_ERR_btree_node_read_err,  btree_node_read_err_incompatible)       \
+       x(0,                            nopromote)                              \
+       x(BCH_ERR_nopromote,            nopromote_may_not)                      \
+       x(BCH_ERR_nopromote,            nopromote_already_promoted)             \
+       x(BCH_ERR_nopromote,            nopromote_unwritten)                    \
+       x(BCH_ERR_nopromote,            nopromote_congested)                    \
+       x(BCH_ERR_nopromote,            nopromote_in_flight)                    \
+       x(BCH_ERR_nopromote,            nopromote_enomem)
 
 enum bch_errcode {
        BCH_ERR_START           = 2048,

diff --git a/fs/bcachefs/io_read.c b/fs/bcachefs/io_read.c
index cd62bf7..5ff430e 100644 (file)
--- a/fs/bcachefs/io_read.c
+++ b/fs/bcachefs/io_read.c
@@ -87,33 +87,30 @@ static const struct rhashtable_params bch_promote_params = {
        .key_len        = sizeof(struct bpos),
 };
 
-static inline bool should_promote(struct bch_fs *c, struct bkey_s_c k,
+static inline int should_promote(struct bch_fs *c, struct bkey_s_c k,
                                  struct bpos pos,
                                  struct bch_io_opts opts,
                                  unsigned flags)
 {
-       if (!(flags & BCH_READ_MAY_PROMOTE))
-               return false;
+       BUG_ON(!opts.promote_target);
 
-       if (!opts.promote_target)
-               return false;
+       if (!(flags & BCH_READ_MAY_PROMOTE))
+               return -BCH_ERR_nopromote_may_not;
 
        if (bch2_bkey_has_target(c, k, opts.promote_target))
-               return false;
+               return -BCH_ERR_nopromote_already_promoted;
 
        if (bkey_extent_is_unwritten(k))
-               return false;
+               return -BCH_ERR_nopromote_unwritten;
 
-       if (bch2_target_congested(c, opts.promote_target)) {
-               /* XXX trace this */
-               return false;
-       }
+       if (bch2_target_congested(c, opts.promote_target))
+               return -BCH_ERR_nopromote_congested;
 
        if (rhashtable_lookup_fast(&c->promote_table, &pos,
                                   bch_promote_params))
-               return false;
+               return -BCH_ERR_nopromote_in_flight;
 
-       return true;
+       return 0;
 }
 
 static void promote_free(struct bch_fs *c, struct promote_op *op)
@@ -264,21 +261,28 @@ static struct promote_op *promote_alloc(struct btree_trans *trans,
                ? bkey_start_pos(k.k)
                : POS(k.k->p.inode, iter.bi_sector);
        struct promote_op *promote;
+       int ret;
 
-       if (!should_promote(c, k, pos, opts, flags))
-               return NULL;
+       ret = should_promote(c, k, pos, opts, flags);
+       if (ret)
+               goto nopromote;
 
        promote = __promote_alloc(trans,
                                  k.k->type == KEY_TYPE_reflink_v
                                  ? BTREE_ID_reflink
                                  : BTREE_ID_extents,
                                  k, pos, pick, opts, sectors, rbio);
-       if (!promote)
-               return NULL;
+       if (!promote) {
+               ret = -BCH_ERR_nopromote_enomem;
+               goto nopromote;
+       }
 
        *bounce         = true;
        *read_full      = promote_full;
        return promote;
+nopromote:
+       trace_read_nopromote(c, ret);
+       return NULL;
 }
 
 /* Read */

diff --git a/fs/bcachefs/trace.h b/fs/bcachefs/trace.h
index 97fe774..1926449 100644 (file)
--- a/fs/bcachefs/trace.h
+++ b/fs/bcachefs/trace.h
@@ -137,6 +137,25 @@ DEFINE_EVENT(bio, read_promote,
        TP_ARGS(bio)
 );
 
+TRACE_EVENT(read_nopromote,
+       TP_PROTO(struct bch_fs *c, int ret),
+       TP_ARGS(c, ret),
+
+       TP_STRUCT__entry(
+               __field(dev_t,          dev             )
+               __array(char,           ret, 32         )
+       ),
+
+       TP_fast_assign(
+               __entry->dev            = c->dev;
+               strscpy(__entry->ret, bch2_err_str(ret), sizeof(__entry->ret));
+       ),
+
+       TP_printk("%d,%d ret %s",
+                 MAJOR(__entry->dev), MINOR(__entry->dev),
+                 __entry->ret)
+);
+
 DEFINE_EVENT(bio, read_bounce,
        TP_PROTO(struct bio *bio),
        TP_ARGS(bio)