bcachefs: Fix another deadlock in btree_update_nodes_written()

We also can't be blocking on btree node write locks while holding
btree_interior_update_lock.

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

diff --git a/fs/bcachefs/btree_update_interior.c b/fs/bcachefs/btree_update_interior.c
index 153d13b9c96e68908972486c6338770a24db87b8..1f0d955588581c05f4a68a7b9b043cbca0051f86 100644 (file)
--- a/fs/bcachefs/btree_update_interior.c
+++ b/fs/bcachefs/btree_update_interior.c
@@ -609,6 +609,19 @@ static void bch2_btree_update_free(struct btree_update *as)
        mutex_unlock(&c->btree_interior_update_lock);
 }
 
+static inline bool six_trylock_intentwrite(struct six_lock *lock)
+{
+       if (!six_trylock_intent(lock))
+               return false;
+
+       if (!six_trylock_write(lock)) {
+               six_unlock_intent(lock);
+               return false;
+       }
+
+       return true;
+}
+
 static void btree_update_nodes_written(struct closure *cl)
 {
        struct btree_update *as = container_of(cl, struct btree_update, cl);
@@ -637,10 +650,15 @@ again:
        }
 
        b = as->b;
-       if (b && !six_trylock_intent(&b->c.lock)) {
+       if (b && !six_trylock_intentwrite(&b->c.lock)) {
                mutex_unlock(&c->btree_interior_update_lock);
+
                btree_node_lock_type(c, b, SIX_LOCK_intent);
+               six_lock_write(&b->c.lock, NULL, NULL);
+
+               six_unlock_write(&b->c.lock);
                six_unlock_intent(&b->c.lock);
+
                mutex_lock(&c->btree_interior_update_lock);
                goto again;
        }
@@ -648,7 +666,25 @@ again:
        list_del(&as->unwritten_list);
 
        ret = bch2_journal_res_get(&c->journal, &res, as->journal_u64s,
+                                  JOURNAL_RES_GET_NONBLOCK|
                                   JOURNAL_RES_GET_RESERVED);
+       if (ret == -EAGAIN) {
+               unsigned u64s = as->journal_u64s;
+
+               six_unlock_write(&b->c.lock);
+               six_unlock_intent(&b->c.lock);
+
+               mutex_unlock(&c->btree_interior_update_lock);
+
+               ret = bch2_journal_res_get(&c->journal, &res, u64s,
+                                          JOURNAL_RES_GET_CHECK|
+                                          JOURNAL_RES_GET_RESERVED);
+               if (!ret) {
+                       mutex_lock(&c->btree_interior_update_lock);
+                       goto again;
+               }
+       }
+
        if (ret) {
                BUG_ON(!bch2_journal_error(&c->journal));
                /* can't unblock btree writes */
@@ -671,7 +707,6 @@ again:
                /* @b is the node we did the final insert into: */
                BUG_ON(!res.ref);
 
-               six_lock_write(&b->c.lock, NULL, NULL);
                list_del(&as->write_blocked_list);
 
                i = btree_bset_last(b);
@@ -680,7 +715,6 @@ again:
                            le64_to_cpu(i->journal_seq)));
 
                bch2_btree_add_journal_pin(c, b, res.seq);
-               six_unlock_write(&b->c.lock);
                break;
 
        case BTREE_INTERIOR_UPDATING_AS:
@@ -709,6 +743,7 @@ again:
 free_update:
        /* Do btree write after dropping journal res: */
        if (b) {
+               six_unlock_write(&b->c.lock);
                /*
                 * b->write_blocked prevented it from being written, so
                 * write it now if it needs to be written: