Subject: [Saphira] Linux 7.3: treat 7.3 as mnt_idmap-era (2.4.4 port)

Saphira-Port-By: Muse Spark 1.3 Contributor for AKADATA LIMITED
(Andrew Smalley, Director)
Note: The API moved; the data must not. Re-derived hunk by hunk
for 2.4.4 and proven by boot, not by inspection.

On 7.3 none of the old HAVE_IOPS_CREATE_* macros are defined (the 4-arg
signatures are gone), so zidmap_t fell back to struct user_namespace
while VFS now demands struct mnt_idmap: every idmap call site failed
with incompatible-pointer-type. With HAVE_IOPS_CREATE_NO_FLAG_ARG the
tree is mnt_idmap-based exactly like the IDMAP era, so the era checks
cover it: zidmap_t typedef, zfs_get_init_idmap, and the four cred.h
fast paths. HAVE_IDMAP_NO_USERNS (struct layout probe) resolves the
inner flavor on its own. No upstream commit to credit: robn's branch
targets master, whose refactor already removed this fallback chain.

--- a/include/os/linux/spl/sys/types.h
+++ b/include/os/linux/spl/sys/types.h
@@ -58,7 +58,7 @@
 typedef int			minor_t;
 
 struct user_namespace;
-#ifdef HAVE_IOPS_CREATE_IDMAP
+#if defined(HAVE_IOPS_CREATE_IDMAP) || defined(HAVE_IOPS_CREATE_NO_FLAG_ARG)
 #include <linux/refcount.h>
 #ifdef HAVE_IDMAP_NO_USERNS
 #include <linux/user_namespace.h>
--- a/module/os/linux/spl/spl-cred.c
+++ b/module/os/linux/spl/spl-cred.c
@@ -133,7 +133,7 @@
 zidmap_t *
 zfs_get_init_idmap(void)
 {
-#ifdef HAVE_IOPS_CREATE_IDMAP
+#if defined(HAVE_IOPS_CREATE_IDMAP) || defined(HAVE_IOPS_CREATE_NO_FLAG_ARG)
 	return ((zidmap_t *)&nop_mnt_idmap);
 #else
 	return ((zidmap_t *)&init_user_ns);
--- a/include/os/linux/spl/sys/cred.h
+++ b/include/os/linux/spl/sys/cred.h
@@ -78,7 +78,7 @@
     struct user_namespace *fs_userns, uid_t uid)
 {
 	struct user_namespace *owner;
-#ifdef HAVE_IOPS_CREATE_IDMAP
+#if defined(HAVE_IOPS_CREATE_IDMAP) || defined(HAVE_IOPS_CREATE_NO_FLAG_ARG)
 	if (mnt_userns == zfs_init_idmap)
 		return (uid);
 #endif
@@ -102,7 +102,7 @@
     struct user_namespace *fs_userns, gid_t gid)
 {
 	struct user_namespace *owner;
-#ifdef HAVE_IOPS_CREATE_IDMAP
+#if defined(HAVE_IOPS_CREATE_IDMAP) || defined(HAVE_IOPS_CREATE_NO_FLAG_ARG)
 	if (mnt_userns == zfs_init_idmap)
 		return (gid);
 #endif
@@ -126,7 +126,7 @@
     struct user_namespace *fs_userns, uid_t uid)
 {
 	struct user_namespace *owner;
-#ifdef HAVE_IOPS_CREATE_IDMAP
+#if defined(HAVE_IOPS_CREATE_IDMAP) || defined(HAVE_IOPS_CREATE_NO_FLAG_ARG)
 	if (mnt_userns == zfs_init_idmap)
 		return (uid);
 #endif
@@ -151,7 +151,7 @@
     struct user_namespace *fs_userns, gid_t gid)
 {
 	struct user_namespace *owner;
-#ifdef HAVE_IOPS_CREATE_IDMAP
+#if defined(HAVE_IOPS_CREATE_IDMAP) || defined(HAVE_IOPS_CREATE_NO_FLAG_ARG)
 	if (mnt_userns == zfs_init_idmap)
 		return (gid);
 #endif