[PATCH, pre-03/20 #2] xfs: introduce all-mounts list for cpu hotplug notifications

[Dave Chinner <david@fromorbit.com>]

From: Dave Chinner <dchinner@redhat.com>

The inode inactivation and CIL tracking percpu structures are
per-xfs_mount structures. That means when we get a CPU dead
notification, we need to then iterate all the per-cpu structure
instances to process them. Rather than keeping linked lists of
per-cpu structures in each subsystem, add a list of all xfs_mounts
that the generic xfs_cpu_dead() function will iterate and call into
each subsystem appropriately.

This allows us to handle both per-mount and global XFS percpu state
from xfs_cpu_dead(), and avoids the need to link subsystem
structures that can be easily found from the xfs_mount into their
own global lists.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
 fs/xfs/xfs_mount.h |  1 +
 fs/xfs/xfs_super.c | 41 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+)

diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index c78b63fe779a..ed7064596f94 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -82,6 +82,7 @@ typedef struct xfs_mount {
 	xfs_buftarg_t		*m_ddev_targp;	/* saves taking the address */
 	xfs_buftarg_t		*m_logdev_targp;/* ptr to log device */
 	xfs_buftarg_t		*m_rtdev_targp;	/* ptr to rt device */
+	struct list_head	m_mount_list;	/* global mount list */
 	/*
 	 * Optional cache of rt summary level per bitmap block with the
 	 * invariant that m_rsum_cache[bbno] <= the minimum i for which
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index ffe1ecd048db..c27df85212d4 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -49,6 +49,28 @@ static struct kset *xfs_kset;		/* top-level xfs sysfs dir */
 static struct xfs_kobj xfs_dbg_kobj;	/* global debug sysfs attrs */
 #endif
 
+#ifdef CONFIG_HOTPLUG_CPU
+static LIST_HEAD(xfs_mount_list);
+static DEFINE_SPINLOCK(xfs_mount_list_lock);
+
+static inline void xfs_mount_list_add(struct xfs_mount *mp)
+{
+	spin_lock(&xfs_mount_list_lock);
+	list_add(&mp->m_mount_list, &xfs_mount_list);
+	spin_unlock(&xfs_mount_list_lock);
+}
+
+static inline void xfs_mount_list_del(struct xfs_mount *mp)
+{
+	spin_lock(&xfs_mount_list_lock);
+	list_del(&mp->m_mount_list);
+	spin_unlock(&xfs_mount_list_lock);
+}
+#else /* !CONFIG_HOTPLUG_CPU */
+static inline void xfs_mount_list_add(struct xfs_mount *mp) {}
+static inline void xfs_mount_list_del(struct xfs_mount *mp) {}
+#endif
+
 enum xfs_dax_mode {
 	XFS_DAX_INODE = 0,
 	XFS_DAX_ALWAYS = 1,
@@ -988,6 +1010,7 @@ xfs_fs_put_super(
 
 	xfs_freesb(mp);
 	free_percpu(mp->m_stats.xs_stats);
+	xfs_mount_list_del(mp);
 	xfs_destroy_percpu_counters(mp);
 	xfs_destroy_mount_workqueues(mp);
 	xfs_close_devices(mp);
@@ -1359,6 +1382,8 @@ xfs_fs_fill_super(
 	if (error)
 		goto out_destroy_workqueues;
 
+	xfs_mount_list_add(mp);
+
 	/* Allocate stats memory before we do operations that might use it */
 	mp->m_stats.xs_stats = alloc_percpu(struct xfsstats);
 	if (!mp->m_stats.xs_stats) {
@@ -1567,6 +1592,7 @@ xfs_fs_fill_super(
  out_free_stats:
 	free_percpu(mp->m_stats.xs_stats);
  out_destroy_counters:
+	xfs_mount_list_del(mp);
 	xfs_destroy_percpu_counters(mp);
  out_destroy_workqueues:
 	xfs_destroy_mount_workqueues(mp);
@@ -2061,10 +2087,20 @@ xfs_destroy_workqueues(void)
 	destroy_workqueue(xfs_alloc_wq);
 }
 
+#ifdef CONFIG_HOTPLUG_CPU
 static int
 xfs_cpu_dead(
 	unsigned int		cpu)
 {
+	struct xfs_mount	*mp, *n;
+
+	spin_lock(&xfs_mount_list_lock);
+	list_for_each_entry_safe(mp, n, &xfs_mount_list, m_mount_list) {
+		spin_unlock(&xfs_mount_list_lock);
+		/* xfs_subsys_dead(mp, cpu); */
+		spin_lock(&xfs_mount_list_lock);
+	}
+	spin_unlock(&xfs_mount_list_lock);
 	return 0;
 }
 
@@ -2090,6 +2126,11 @@ xfs_cpu_hotplug_destroy(void)
 	cpuhp_remove_state_nocalls(CPUHP_XFS_DEAD);
 }
 
+#else /* !CONFIG_HOTPLUG_CPU */
+static inline int xfs_cpu_hotplug_init(struct xfs_cil *cil) { return 0; }
+static inline void xfs_cpu_hotplug_destroy(struct xfs_cil *cil) {}
+#endif
+
 STATIC int __init
 init_xfs_fs(void)
 {