linux-ext4 - [PATCH v2 12/23] xfs: introduce workqueue for post read IO work

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Date:   Tue,  4 Apr 2023 16:53:08 +0200
From:   Andrey Albershteyn <aalbersh@...hat.com>
To:     djwong@...nel.org, dchinner@...hat.com, ebiggers@...nel.org,
        hch@...radead.org, linux-xfs@...r.kernel.org,
        fsverity@...ts.linux.dev
Cc:     rpeterso@...hat.com, agruenba@...hat.com, xiang@...nel.org,
        chao@...nel.org, damien.lemoal@...nsource.wdc.com, jth@...nel.org,
        linux-erofs@...ts.ozlabs.org, linux-btrfs@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net,
        cluster-devel@...hat.com, Andrey Albershteyn <aalbersh@...hat.com>
Subject: [PATCH v2 12/23] xfs: introduce workqueue for post read IO work

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 <aalbersh@...hat.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