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) <[email protected]>
Signed-off-by: Sourabh Jain <[email protected]>
Signed-off-by: Madhavan Srinivasan <[email protected]>
Link: https://patch.msgid.link/[email protected]

Author: sourabhjains

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,