bcachefs: Ensure bch2_btree_node_get() calls relock() after unlock()

Fix a bug where bch2_btree_node_get() might call bch2_trans_unlock() (in
fill) without calling bch2_trans_relock(); this is a bug when it's done
in the core btree code.

Also, twea bch2_btree_node_mem_alloc() to drop btree locks before doing
a blocking memory allocation.

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

diff --git a/fs/bcachefs/btree_cache.c b/fs/bcachefs/btree_cache.c
index 58ef9e7b4bdf6c0e8422ac2e23a069fd666bf07e..681a47b70a65bd0b34b37456c16e2dda45adccef 100644 (file)
--- a/fs/bcachefs/btree_cache.c
+++ b/fs/bcachefs/btree_cache.c
@@ -587,9 +587,10 @@ struct btree *bch2_btree_node_mem_alloc(struct btree_trans *trans, bool pcpu_rea
                        goto got_node;
                }
 
-       b = __btree_node_mem_alloc(c, __GFP_NOWARN);
+       b = __btree_node_mem_alloc(c, GFP_NOWAIT|__GFP_NOWARN);
        if (!b) {
                mutex_unlock(&bc->lock);
+               bch2_trans_unlock(trans);
                b = __btree_node_mem_alloc(c, GFP_KERNEL);
                if (!b)
                        goto err;
@@ -618,8 +619,11 @@ got_node:
 
        mutex_unlock(&bc->lock);
 
-       if (btree_node_data_alloc(c, b, __GFP_NOWARN|GFP_KERNEL))
-               goto err;
+       if (btree_node_data_alloc(c, b, GFP_NOWAIT|__GFP_NOWARN)) {
+               bch2_trans_unlock(trans);
+               if (btree_node_data_alloc(c, b, GFP_KERNEL|__GFP_NOWARN))
+                       goto err;
+       }
 
        mutex_lock(&bc->lock);
        bc->used++;
@@ -812,6 +816,7 @@ static struct btree *__bch2_btree_node_get(struct btree_trans *trans, struct btr
        struct btree_cache *bc = &c->btree_cache;
        struct btree *b;
        struct bset_tree *t;
+       bool need_relock = false;
        int ret;
 
        EBUG_ON(level >= BTREE_MAX_DEPTH);
@@ -825,6 +830,7 @@ retry:
                 */
                b = bch2_btree_node_fill(trans, path, k, path->btree_id,
                                         level, lock_type, true);
+               need_relock = true;
 
                /* We raced and found the btree node in the cache */
                if (!b)
@@ -863,6 +869,7 @@ retry:
 
                six_unlock_type(&b->c.lock, lock_type);
                bch2_trans_unlock(trans);
+               need_relock = true;
 
                bch2_btree_node_wait_on_read(b);
 
@@ -870,19 +877,19 @@ retry:
                 * should_be_locked is not set on this path yet, so we need to
                 * relock it specifically:
                 */
-               if (trans) {
-                       int ret = bch2_trans_relock(trans) ?:
-                               bch2_btree_path_relock_intent(trans, path);
-                       if (ret) {
-                               BUG_ON(!trans->restarted);
-                               return ERR_PTR(ret);
-                       }
-               }
-
                if (!six_relock_type(&b->c.lock, lock_type, seq))
                        goto retry;
        }
 
+       if (unlikely(need_relock)) {
+               int ret = bch2_trans_relock(trans) ?:
+                       bch2_btree_path_relock_intent(trans, path);
+               if (ret) {
+                       six_unlock_type(&b->c.lock, lock_type);
+                       return ERR_PTR(ret);
+               }
+       }
+
        prefetch(b->aux_data);
 
        for_each_bset(b, t) {