In preivous patch:
Btrfs: kill trans in run_delalloc_nocow and btrfs_cross_ref_exist
We avoid starting btrfs transaction and get this information from
fs_info->running_transaction directly.
When accessing running_transaction in check_delayed_ref, there's a
chance that current transaction will be freed by commit transaction
after the NULL pointer check of running_transaction is passed.
After looking all the other places using fs_info->running_transaction,
they are either protected by trans_lock or holding the transactions.
Fix this by using trans_lock and incrementing the use_count.
Signed-off-by: ethanwu <ethanwu@xxxxxxxxxxxx>
---
fs/btrfs/extent-tree.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index c1618ab..c8fd37b 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3149,7 +3149,11 @@ static noinline int check_delayed_ref(struct btrfs_root *root,
struct rb_node *node;
int ret = 0;
+ spin_lock(&root->fs_info->trans_lock);
cur_trans = root->fs_info->running_transaction;
+ if (cur_trans)
+ atomic_inc(&cur_trans->use_count);
+ spin_unlock(&root->fs_info->trans_lock);
if (!cur_trans)
return 0;
@@ -3158,6 +3162,7 @@ static noinline int check_delayed_ref(struct btrfs_root *root,
head = btrfs_find_delayed_ref_head(delayed_refs, bytenr);
if (!head) {
spin_unlock(&delayed_refs->lock);
+ btrfs_put_transaction(cur_trans);
return 0;
}
@@ -3174,6 +3179,7 @@ static noinline int check_delayed_ref(struct btrfs_root *root,
mutex_lock(&head->mutex);
mutex_unlock(&head->mutex);
btrfs_put_delayed_ref_head(head);
+ btrfs_put_transaction(cur_trans);
return -EAGAIN;
}
spin_unlock(&delayed_refs->lock);
@@ -3206,6 +3212,7 @@ static noinline int check_delayed_ref(struct btrfs_root *root,
}
spin_unlock(&head->lock);
mutex_unlock(&head->mutex);
+ btrfs_put_transaction(cur_trans);
return ret;
}
--
1.9.1
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