xfs: remove the all-mounts list

Revert commit 0ed17f01c8540 ("xfs: introduce all-mounts list for cpu
hotplug notifications") because the cpu hotplug hooks are now pointless,
so we don't need this list anymore.

Signed-off-by: Darrick J. Wong <[e-mail]>
Reviewed-by: Dave Chinner <[e-mail]>

fs/xfs/xfs_mount.h

···
 	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 */
 	void __percpu		*m_inodegc;	/* percpu inodegc structures */
 
 	/*

fs/xfs/xfs_super.c

···
 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,
···
 	xfs_freesb(mp);
 	xchk_mount_stats_free(mp);
 	free_percpu(mp->m_stats.xs_stats);
-	xfs_mount_list_del(mp);
 	xfs_inodegc_free_percpu(mp);
 	xfs_destroy_percpu_counters(mp);
 	xfs_destroy_mount_workqueues(mp);
···
 	if (error)
 		goto out_destroy_counters;
 
-	/*
-	 * All percpu data structures requiring cleanup when a cpu goes offline
-	 * must be allocated before adding this @mp to the cpu-dead handler's
-	 * mount list.
-	 */
-	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) {
···
  out_free_stats:
 	free_percpu(mp->m_stats.xs_stats);
  out_destroy_inodegc:
-	xfs_mount_list_del(mp);
 	xfs_inodegc_free_percpu(mp);
  out_destroy_counters:
 	xfs_destroy_percpu_counters(mp);
···
 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);
-		spin_lock(&xfs_mount_list_lock);
-	}
-	spin_unlock(&xfs_mount_list_lock);
 	return 0;
 }