[Cluster-devel] [PATCH v2 12/23] xfs: introduce workqueue for post read IO work

[Andrey Albershteyn]

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.

Signed-off-by: Andrey Albershteyn <aalbe...@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 f3269c0626f0..53a4a9304937 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -107,6 +107,7 @@ 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 4f814f9e12ab..d6f22cb94ee2 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -548,6 +548,12 @@ 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);
@@ -581,6 +587,8 @@ 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:
@@ -596,6 +604,7 @@ 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);
 }
 
-- 
2.38.4