Patch "s390/pai_ext: replace atomic_t with refcount_t" has been added to the 6.1-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    s390/pai_ext: replace atomic_t with refcount_t

to the 6.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     s390-pai_ext-replace-atomic_t-with-refcount_t.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 117b4dfc411cc5896e800a18ff9469c9f9db7da2
Author: Thomas Richter <tmricht@xxxxxxxxxxxxx>
Date:   Thu Apr 27 10:33:31 2023 +0200

    s390/pai_ext: replace atomic_t with refcount_t
    
    [ Upstream commit 1f2597cd3686955a4d64e01909dbfe625a2a35a1 ]
    
    The s390 PMU of PAI extension 1 NNPA counters uses atomic_t for
    reference counting. Replace this with the proper data type
    refcount_t.
    
    No functional change.
    
    Signed-off-by: Thomas Richter <tmricht@xxxxxxxxxxxxx>
    Acked-by: Sumanth Korikkar <sumanthk@xxxxxxxxxxxxx>
    Signed-off-by: Alexander Gordeev <agordeev@xxxxxxxxxxxxx>
    Stable-dep-of: e9f3af02f639 ("s390/pai: fix sampling event removal for PMU device driver")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/arch/s390/kernel/perf_pai_ext.c b/arch/s390/kernel/perf_pai_ext.c
index b4d89654183a2..d6bc919530143 100644
--- a/arch/s390/kernel/perf_pai_ext.c
+++ b/arch/s390/kernel/perf_pai_ext.c
@@ -56,7 +56,7 @@ struct paiext_map {
 	struct pai_userdata *save;	/* Area to store non-zero counters */
 	enum paiext_mode mode;		/* Type of event */
 	unsigned int active_events;	/* # of PAI Extension users */
-	unsigned int refcnt;
+	refcount_t refcnt;
 	struct perf_event *event;	/* Perf event for sampling */
 	struct paiext_cb *paiext_cb;	/* PAI extension control block area */
 };
@@ -66,14 +66,14 @@ struct paiext_mapptr {
 };
 
 static struct paiext_root {		/* Anchor to per CPU data */
-	int refcnt;			/* Overall active events */
+	refcount_t refcnt;		/* Overall active events */
 	struct paiext_mapptr __percpu *mapptr;
 } paiext_root;
 
 /* Free per CPU data when the last event is removed. */
 static void paiext_root_free(void)
 {
-	if (!--paiext_root.refcnt) {
+	if (refcount_dec_and_test(&paiext_root.refcnt)) {
 		free_percpu(paiext_root.mapptr);
 		paiext_root.mapptr = NULL;
 	}
@@ -86,7 +86,7 @@ static void paiext_root_free(void)
  */
 static int paiext_root_alloc(void)
 {
-	if (++paiext_root.refcnt == 1) {
+	if (!refcount_inc_not_zero(&paiext_root.refcnt)) {
 		/* The memory is already zeroed. */
 		paiext_root.mapptr = alloc_percpu(struct paiext_mapptr);
 		if (!paiext_root.mapptr) {
@@ -97,6 +97,7 @@ static int paiext_root_alloc(void)
 			 */
 			return -ENOMEM;
 		}
+		refcount_set(&paiext_root.refcnt, 1);
 	}
 	return 0;
 }
@@ -128,7 +129,7 @@ static void paiext_event_destroy(struct perf_event *event)
 
 	mutex_lock(&paiext_reserve_mutex);
 	cpump->event = NULL;
-	if (!--cpump->refcnt)		/* Last reference gone */
+	if (refcount_dec_and_test(&cpump->refcnt))	/* Last reference gone */
 		paiext_free(mp);
 	paiext_root_free();
 	mutex_unlock(&paiext_reserve_mutex);
@@ -169,7 +170,7 @@ static int paiext_alloc(struct perf_event_attr *a, struct perf_event *event)
 		rc = -ENOMEM;
 		cpump = kzalloc(sizeof(*cpump), GFP_KERNEL);
 		if (!cpump)
-			goto unlock;
+			goto undo;
 
 		/* Allocate memory for counter area and counter extraction.
 		 * These are
@@ -189,8 +190,9 @@ static int paiext_alloc(struct perf_event_attr *a, struct perf_event *event)
 					     GFP_KERNEL);
 		if (!cpump->save || !cpump->area || !cpump->paiext_cb) {
 			paiext_free(mp);
-			goto unlock;
+			goto undo;
 		}
+		refcount_set(&cpump->refcnt, 1);
 		cpump->mode = a->sample_period ? PAI_MODE_SAMPLING
 					       : PAI_MODE_COUNTER;
 	} else {
@@ -201,15 +203,15 @@ static int paiext_alloc(struct perf_event_attr *a, struct perf_event *event)
 		if (cpump->mode == PAI_MODE_SAMPLING ||
 		    (cpump->mode == PAI_MODE_COUNTER && a->sample_period)) {
 			rc = -EBUSY;
-			goto unlock;
+			goto undo;
 		}
+		refcount_inc(&cpump->refcnt);
 	}
 
 	rc = 0;
 	cpump->event = event;
-	++cpump->refcnt;
 
-unlock:
+undo:
 	if (rc) {
 		/* Error in allocation of event, decrement anchor. Since
 		 * the event in not created, its destroy() function is never
@@ -217,6 +219,7 @@ static int paiext_alloc(struct perf_event_attr *a, struct perf_event *event)
 		 */
 		paiext_root_free();
 	}
+unlock:
 	mutex_unlock(&paiext_reserve_mutex);
 	/* If rc is non-zero, no increment of counter/sampler was done. */
 	return rc;