[PATCH 02/14] xfs: introduce all-mounts list for cpu hotplug notifications

Darrick J. Wong
2021-08-05T02:06:35Z

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>
[djwong: expand some comments about mount list setup ordering rules]
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
fs/xfs/xfs_mount.h | 1 +
fs/xfs/xfs_super.c | 40 ++++++++++++++++++++++++++++++++++++++++
2 files changed, 41 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 d47fac7c8afd..c2c9c02b9d62 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,
@@ -1038,6 +1060,7 @@ 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);
@@ -1409,6 +1432,13 @@ xfs_fs_fill_super(
if (error)
goto out_destroy_workqueues;

+ /*
+ * 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) {
@@ -1617,6 +1647,7 @@ 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);
@@ -2116,6 +2147,15 @@ 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;
}