git: fb0943711a7e - stable/12 - linuxkpi: avoid counting per-thread use for the embedded linux cdevs

[Konstantin Belousov]

The branch stable/12 has been updated by kib:

URL: https://cgit.FreeBSD.org/src/commit/?id=fb0943711a7ebde92bcc7257174167a6df9833f2

commit fb0943711a7ebde92bcc7257174167a6df9833f2
Author:     Konstantin Belousov <kib at FreeBSD.org>
AuthorDate: 2021-03-30 08:45:24 +0000
Commit:     Konstantin Belousov <kib at FreeBSD.org>
CommitDate: 2021-05-01 00:38:28 +0000

    linuxkpi: avoid counting per-thread use for the embedded linux cdevs
    
    (cherry picked from commit f6b108837e7df7d7bfb35ec447f7cb62afa79441)
---
 sys/compat/linuxkpi/common/src/linux_compat.c      | 31 ++++++++++++++--------
 sys/compat/linuxkpi/common/src/linux_compat.c.orig | 13 ++++++---
 2 files changed, 30 insertions(+), 14 deletions(-)

diff --git a/sys/compat/linuxkpi/common/src/linux_compat.c b/sys/compat/linuxkpi/common/src/linux_compat.c
index 6058af9c3395..4a734bb495ce 100644
--- a/sys/compat/linuxkpi/common/src/linux_compat.c
+++ b/sys/compat/linuxkpi/common/src/linux_compat.c
@@ -722,15 +722,19 @@ linux_get_fop(struct linux_file *filp, const struct file_operations **fop,
 	ldev = filp->f_cdev;
 	*fop = filp->f_op;
 	if (ldev != NULL) {
-		for (siref = ldev->siref;;) {
-			if ((siref & LDEV_SI_DTR) != 0) {
-				ldev = &dummy_ldev;
-				siref = ldev->siref;
-				*fop = ldev->ops;
-				MPASS((ldev->siref & LDEV_SI_DTR) == 0);
-			} else if (atomic_fcmpset_int(&ldev->siref, &siref,
-			    siref + LDEV_SI_REF)) {
-				break;
+		if (ldev->kobj.ktype == &linux_cdev_static_ktype) {
+			refcount_acquire(&ldev->refs);
+		} else {
+			for (siref = ldev->siref;;) {
+				if ((siref & LDEV_SI_DTR) != 0) {
+					ldev = &dummy_ldev;
+					*fop = ldev->ops;
+					siref = ldev->siref;
+					MPASS((ldev->siref & LDEV_SI_DTR) == 0);
+				} else if (atomic_fcmpset_int(&ldev->siref,
+				    &siref, siref + LDEV_SI_REF)) {
+					break;
+				}
 			}
 		}
 	}
@@ -743,8 +747,13 @@ linux_drop_fop(struct linux_cdev *ldev)
 
 	if (ldev == NULL)
 		return;
-	MPASS((ldev->siref & ~LDEV_SI_DTR) != 0);
-	atomic_subtract_int(&ldev->siref, LDEV_SI_REF);
+	if (ldev->kobj.ktype == &linux_cdev_static_ktype) {
+		linux_cdev_deref(ldev);
+	} else {
+		MPASS(ldev->kobj.ktype == &linux_cdev_ktype);
+		MPASS((ldev->siref & ~LDEV_SI_DTR) != 0);
+		atomic_subtract_int(&ldev->siref, LDEV_SI_REF);
+	}
 }
 
 #define	OPW(fp,td,code) ({			\
diff --git a/sys/compat/linuxkpi/common/src/linux_compat.c.orig b/sys/compat/linuxkpi/common/src/linux_compat.c.orig
index 0731859e7a53..71ea7e0844dc 100644
--- a/sys/compat/linuxkpi/common/src/linux_compat.c.orig
+++ b/sys/compat/linuxkpi/common/src/linux_compat.c.orig
@@ -2199,8 +2199,8 @@ linux_completion_done(struct completion *c)
 static void
 linux_cdev_deref(struct linux_cdev *ldev)
 {
-
-	if (refcount_release(&ldev->refs))
+	if (refcount_release(&ldev->refs) &&
+	    ldev->kobj.ktype == &linux_cdev_ktype)
 		kfree(ldev);
 }
 
@@ -2220,12 +2220,17 @@ linux_cdev_release(struct kobject *kobj)
 static void
 linux_cdev_static_release(struct kobject *kobj)
 {
+	struct cdev *cdev;
 	struct linux_cdev *ldev;
 	struct kobject *parent;
 
 	ldev = container_of(kobj, struct linux_cdev, kobj);
 	parent = kobj->parent;
-	linux_destroy_dev(ldev);
+	cdev = ldev->cdev;
+	if (cdev != NULL) {
+		destroy_dev(cdev);
+		ldev->cdev = NULL;
+	}
 	kobject_put(parent);
 }
 
@@ -2237,6 +2242,8 @@ linux_destroy_dev(struct linux_cdev *ldev)
 		return;
 
 	MPASS((ldev->siref & LDEV_SI_DTR) == 0);
+	MPASS(ldev->kobj.ktype == &linux_cdev_ktype);
+
 	atomic_set_int(&ldev->siref, LDEV_SI_DTR);
 	while ((atomic_load_int(&ldev->siref) & ~LDEV_SI_DTR) != 0)
 		pause("ldevdtr", hz / 4);