Re: [PATCH] btrfs: directly wake up cleaner kthread in the BTRFS_IOC_SYNC ioctl

[Boris Burkov <boris@bur.io>]

On Wed, Aug 07, 2024 at 06:47:50PM +0100, Filipe Manana wrote:
> The BTRFS_IOC_SYNC ioctl wants to wake up the cleaner kthread so that it
> does any pending work (subvolume deletion, delayed iputs, etc), however
> it is waking up the transaction kthread, which in turn wakes up the
> cleaner. Since we don't have any transaction to commit, as any ongoing
> transaction was already committed when it called btrfs_sync_fs() and
> the goal is just to wake up the cleaner thread, directly wake up the
> cleaner instead of the transaction kthread.
> 
> Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Boris Burkov <boris@bur.io>
> ---
>  fs/btrfs/ioctl.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index e0a664b8a46a..ee01cc828883 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -4765,11 +4765,10 @@ long btrfs_ioctl(struct file *file, unsigned int
>  			return ret;
>  		ret = btrfs_sync_fs(inode->i_sb, 1);
>  		/*
> -		 * The transaction thread may want to do more work,
> -		 * namely it pokes the cleaner kthread that will start
> -		 * processing uncleaned subvols.
> +		 * There may be work for the cleaner kthread to do (subvolume
> +		 * deletion, delayed iputs, defrag inodes, etc), so wake it up.
>  		 */
> -		wake_up_process(fs_info->transaction_kthread);
> +		wake_up_process(fs_info->cleaner_kthread);
>  		return ret;
>  	}
>  	case BTRFS_IOC_START_SYNC:
> -- 
> 2.43.0