Re: [PATCH] btrfs: Take trans lock before access running trans in check_delayed_ref

[Greg KH <gregkh@linuxfoundation.org>]

On Thu, May 17, 2018 at 05:01:45PM +0800, ethanwu wrote:
> commit 998ac6d21cfd6efd58f5edf420bae8839dda9f2a upstream
> 
> 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>
> ---
>  fs/btrfs/extent-tree.c | 7 +++++++
>  1 file changed, 7 insertions(+)

Thanks for the backport, now queued up.

greg k-h