[PATCH v10 13/17] fs/resctrl: Call architecture hooks for every mount/unmount

[Tony Luck]

The intel_pmt module should only be pinned while the resctrl file system
is mounted.

Add hooks for every mount/unmount of the resctrl file system so that
architecture code can increment the intel_pmt module reference count on
mount and decrement on unmount.

Signed-off-by: Tony Luck <tony.luck@xxxxxxxxx>
---
v10:
	Don't call resctrl_arch_unmount() when failing a nested mount.

 include/linux/resctrl.h |  2 +-
 fs/resctrl/rdtgroup.c   | 12 ++++++++++--
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
index 65245f2fdad0..1e4ca75a02de 100644
--- a/include/linux/resctrl.h
+++ b/include/linux/resctrl.h
@@ -576,7 +576,7 @@ void resctrl_online_cpu(unsigned int cpu);
 void resctrl_offline_cpu(unsigned int cpu);
 
 /*
- * Architecture hook called at beginning of first file system mount attempt.
+ * Architecture hook called before attempting to mount the file system.
  * No locks are held.
  */
 int resctrl_arch_pre_mount(void);
diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index 0a9645c35f43..6f12537f89b7 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -18,7 +18,6 @@
 #include <linux/fs_parser.h>
 #include <linux/sysfs.h>
 #include <linux/kernfs.h>
-#include <linux/once.h>
 #include <linux/resctrl.h>
 #include <linux/seq_buf.h>
 #include <linux/seq_file.h>
@@ -3166,6 +3165,8 @@ static void resctrl_unmount(void)
 	resctrl_mounted = false;
 	mutex_unlock(&rdtgroup_mutex);
 	cpus_read_unlock();
+
+	resctrl_arch_unmount();
 }
 
 static int rdt_get_tree(struct fs_context *fc)
@@ -3175,9 +3176,11 @@ static int rdt_get_tree(struct fs_context *fc)
 	struct kernfs_node *rdt_root_kn;
 	struct rdt_l3_mon_domain *dom;
 	struct rdt_resource *r;
+	bool cleanup = true;
 	int ret;
 
-	DO_ONCE_SLEEPABLE(resctrl_arch_pre_mount);
+	if (resctrl_arch_pre_mount() == -EBUSY)
+		return -EBUSY;
 
 	cpus_read_lock();
 	mutex_lock(&rdtgroup_mutex);
@@ -3186,6 +3189,7 @@ static int rdt_get_tree(struct fs_context *fc)
 	 */
 	if (resctrl_mounted) {
 		ret = -EBUSY;
+		cleanup = false;
 		goto out;
 	}
 
@@ -3316,6 +3320,10 @@ static int rdt_get_tree(struct fs_context *fc)
 out:
 	mutex_unlock(&rdtgroup_mutex);
 	cpus_read_unlock();
+
+	if (cleanup)
+		resctrl_arch_unmount();
+
 	return ret;
 }
 
-- 
2.55.0