Re: [PATCH v3 15/28] xfs: introduce workqueue for post read IO work

["Darrick J. Wong" <djwong@kernel.org>]

On Fri, Oct 06, 2023 at 08:49:09PM +0200, Andrey Albershteyn wrote:
> As noted by Dave there are two problems with using fs-verity's
> workqueue in XFS:
> 
> 1. High priority workqueues are used within XFS to ensure that data
>    IO completion cannot stall processing of journal IO completions.
>    Hence using a WQ_HIGHPRI workqueue directly in the user data IO
>    path is a potential filesystem livelock/deadlock vector.
> 
> 2. The fsverity workqueue is global - it creates a cross-filesystem
>    contention point.
> 
> This patch adds per-filesystem, per-cpu workqueue for fsverity
> work.

If we ever want to implement compression and/or fscrypt, can we use this
pread workqueue for that too?

Sounds good to me...
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D


> Signed-off-by: Andrey Albershteyn <aalbersh@redhat.com>
> ---
>  fs/xfs/xfs_mount.h | 1 +
>  fs/xfs/xfs_super.c | 9 +++++++++
>  2 files changed, 10 insertions(+)
> 
> diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
> index d19cca099bc3..3d77844b255e 100644
> --- a/fs/xfs/xfs_mount.h
> +++ b/fs/xfs/xfs_mount.h
> @@ -109,6 +109,7 @@ typedef struct xfs_mount {
>  	struct xfs_mru_cache	*m_filestream;  /* per-mount filestream data */
>  	struct workqueue_struct *m_buf_workqueue;
>  	struct workqueue_struct	*m_unwritten_workqueue;
> +	struct workqueue_struct	*m_postread_workqueue;
>  	struct workqueue_struct	*m_reclaim_workqueue;
>  	struct workqueue_struct	*m_sync_workqueue;
>  	struct workqueue_struct *m_blockgc_wq;
> diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> index 819a3568b28f..5e1ec5978176 100644
> --- a/fs/xfs/xfs_super.c
> +++ b/fs/xfs/xfs_super.c
> @@ -554,6 +554,12 @@ xfs_init_mount_workqueues(
>  	if (!mp->m_unwritten_workqueue)
>  		goto out_destroy_buf;
>  
> +	mp->m_postread_workqueue = alloc_workqueue("xfs-pread/%s",
> +			XFS_WQFLAGS(WQ_FREEZABLE | WQ_MEM_RECLAIM),
> +			0, mp->m_super->s_id);
> +	if (!mp->m_postread_workqueue)
> +		goto out_destroy_postread;
> +
>  	mp->m_reclaim_workqueue = alloc_workqueue("xfs-reclaim/%s",
>  			XFS_WQFLAGS(WQ_FREEZABLE | WQ_MEM_RECLAIM),
>  			0, mp->m_super->s_id);
> @@ -587,6 +593,8 @@ xfs_init_mount_workqueues(
>  	destroy_workqueue(mp->m_reclaim_workqueue);
>  out_destroy_unwritten:
>  	destroy_workqueue(mp->m_unwritten_workqueue);
> +out_destroy_postread:
> +	destroy_workqueue(mp->m_postread_workqueue);
>  out_destroy_buf:
>  	destroy_workqueue(mp->m_buf_workqueue);
>  out:
> @@ -602,6 +610,7 @@ xfs_destroy_mount_workqueues(
>  	destroy_workqueue(mp->m_inodegc_wq);
>  	destroy_workqueue(mp->m_reclaim_workqueue);
>  	destroy_workqueue(mp->m_unwritten_workqueue);
> +	destroy_workqueue(mp->m_postread_workqueue);
>  	destroy_workqueue(mp->m_buf_workqueue);
>  }
>  
> -- 
> 2.40.1
>