mm/memory_hotplug: fix memmap_on_memory sysfs value retrieval

JIRA: https://issues.redhat.com/browse/RHEL-23824

commit 1168413
Author: Sumanth Korikkar <sumanthk@linux.ibm.com>
Date:   Wed Jan 10 15:01:27 2024 +0100

    mm/memory_hotplug: fix memmap_on_memory sysfs value retrieval
    
    set_memmap_mode() stores the kernel parameter memmap mode as an integer.
    However, the get_memmap_mode() function utilizes param_get_bool() to fetch
    the value as a boolean, leading to potential endianness issue.  On
    Big-endian architectures, the memmap_on_memory is consistently displayed
    as 'N' regardless of its actual status.
    
    To address this endianness problem, the solution involves obtaining the
    mode as an integer.  This adjustment ensures the proper display of the
    memmap_on_memory parameter, presenting it as one of the following options:
    Force, Y, or N.
    
    Link: https://lkml.kernel.org/r/20240110140127.241451-1-sumanthk@linux.ibm.com
    Fixes: 2d1f649 ("mm/memory_hotplug: support memmap_on_memory when memmap is not aligned to pageblocks")
    Signed-off-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
    Suggested-by: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
    Acked-by: David Hildenbrand <david@redhat.com>
    Cc: Alexander Gordeev <agordeev@linux.ibm.com>
    Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
    Cc: Heiko Carstens <hca@linux.ibm.com>
    Cc: Michal Hocko <mhocko@suse.com>
    Cc: Oscar Salvador <osalvador@suse.de>
    Cc: Vasily Gorbik <gor@linux.ibm.com>
    Cc: <stable@vger.kernel.org>    [6.6+]
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Signed-off-by: Jeff Moyer <jmoyer@redhat.com>

Author: JeffMoyer

mm/memory_hotplug.c

@@ -102,9 +102,11 @@ static int set_memmap_mode(const char *val, const struct kernel_param *kp)
 
 static int get_memmap_mode(char *buffer, const struct kernel_param *kp)
 {
-	if (*((int *)kp->arg) == MEMMAP_ON_MEMORY_FORCE)
-		return sprintf(buffer,  "force\n");
-	return param_get_bool(buffer, kp);
+	int mode = *((int *)kp->arg);
+
+	if (mode == MEMMAP_ON_MEMORY_FORCE)
+		return sprintf(buffer, "force\n");
+	return sprintf(buffer, "%c\n", mode ? 'Y' : 'N');
 }
 
 static const struct kernel_param_ops memmap_mode_ops = {