powerpc/book3s64/hugetlb: Fix disabling hugetlb when fadump is active

JIRA: https://issues.redhat.com/browse/RHEL-73488

commit d629d7a
Author: Sourabh Jain <sourabhjain@linux.ibm.com>
Date:   Tue Dec 17 13:16:40 2024 +0530

    powerpc/book3s64/hugetlb: Fix disabling hugetlb when fadump is active

    Commit 8597538 ("powerpc/fadump: Do not use hugepages when fadump
    is active") disabled hugetlb support when fadump is active by returning
    early from hugetlbpage_init():arch/powerpc/mm/hugetlbpage.c and not
    populating hpage_shift/HPAGE_SHIFT.

    Later, commit 2354ad2 ("powerpc/mm: Update default hugetlb size
    early") moved the allocation of hpage_shift/HPAGE_SHIFT to early boot,
    which inadvertently re-enabled hugetlb support when fadump is active.

    Fix this by implementing hugepages_supported() on powerpc. This ensures
    that disabling hugetlb for the fadump kernel is independent of
    hpage_shift/HPAGE_SHIFT.

    Fixes: 2354ad2 ("powerpc/mm: Update default hugetlb size early")
    Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
    Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com>
    Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
    Link: https://patch.msgid.link/20241217074640.1064510-1-sourabhjain@linux.ibm.com

Signed-off-by: Mamatha Inamdar <minamdar@redhat.com>

Author: Mamatha Inamdar

arch/powerpc/include/asm/hugetlb.h

@@ -15,6 +15,15 @@
 
 extern bool hugetlb_disabled;
 
+static inline bool hugepages_supported(void)
+{
+	if (hugetlb_disabled)
+		return false;
+
+	return HPAGE_SHIFT != 0;
+}
+#define hugepages_supported hugepages_supported
+
 void __init hugetlbpage_init_defaultsize(void);
 
 int slice_is_hugepage_only_range(struct mm_struct *mm, unsigned long addr,