From f9f063cb82f41932ff1fba2acd01e643d2c2eaed Mon Sep 17 00:00:00 2001
From: ethanwu <ethanwu@synology.com>
Date: Sun, 29 Apr 2018 15:59:42 +0800
Subject: [PATCH] btrfs: Take trans lock before access running trans in
check_delayed_ref
Git-commit: 998ac6d21cfd6efd58f5edf420bae8839dda9f2a
Patch-mainline: v4.17-rc4
References: bsc#1097105
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 increasing the use_count.
Fixes: e4c3b2dcd144 ("Btrfs: kill trans in run_delalloc_nocow and btrfs_cross_ref_exist")
CC: stable@vger.kernel.org # 4.14+
Signed-off-by: ethanwu <ethanwu@synology.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Acked-by: Nikolay Borisov <nborisov@suse.com>
---
fs/btrfs/extent-tree.c | 7 +++++++
1 file changed, 7 insertions(+)
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3073,7 +3073,11 @@ static noinline int check_delayed_ref(st
struct rb_node *node;
int ret = 0;
+ spin_lock(&root->fs_info->trans_lock);
cur_trans = root->fs_info->running_transaction;
+ if (cur_trans)
+ refcount_inc(&cur_trans->use_count);
+ spin_unlock(&root->fs_info->trans_lock);
if (!cur_trans)
return 0;
@@ -3082,6 +3086,7 @@ static noinline int check_delayed_ref(st
head = btrfs_find_delayed_ref_head(delayed_refs, bytenr);
if (!head) {
spin_unlock(&delayed_refs->lock);
+ btrfs_put_transaction(cur_trans);
return 0;
}
@@ -3098,6 +3103,7 @@ static noinline int check_delayed_ref(st
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);
@@ -3130,6 +3136,7 @@ static noinline int check_delayed_ref(st
}
spin_unlock(&head->lock);
mutex_unlock(&head->mutex);
+ btrfs_put_transaction(cur_trans);
return ret;
}