[RFC] powerpc/hugetlb: Add warning message when gpage allocation request fails

[Anshuman Khandual]

When a 16GB huge page is requested on POWER platform through kernel command
line interface, it silently fails because of the lack of any gigantic pages
on the system which the platform should have communicated through 16GB memory
blocks in the device tree during boot time. For example

[    0.480940] HugeTLB registered 16 GB page size, pre-allocated 0 pages
[    0.480945] HugeTLB registered 16 MB page size, pre-allocated 16 pages

This adds a warning message during alloc_bootmem_huge_page request both on
book3e and book3s powerpc platforms. After this change

[    0.000000] Gigantic HugeTLB page not available
[    0.473417] HugeTLB registered 16 GB page size, pre-allocated 0 pages
[    0.473423] HugeTLB registered 16 MB page size, pre-allocated 16 pages

Signed-off-by: Anshuman Khandual <khandual at linux.vnet.ibm.com>
---
 arch/powerpc/mm/hugetlbpage.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
index 06c1452..54f3e42 100644
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -307,8 +307,10 @@ int alloc_bootmem_huge_page(struct hstate *hstate)
 	int idx = shift_to_mmu_psize(huge_page_shift(hstate));
 	int nr_gpages = gpage_freearray[idx].nr_gpages;
 
-	if (nr_gpages == 0)
+	if (nr_gpages == 0) {
+		printk(KERN_WARNING "Gigantic HugeTLB page not available\n");
 		return 0;
+	}
 
 #ifdef CONFIG_HIGHMEM
 	/*
@@ -429,8 +431,10 @@ void add_gpage(u64 addr, u64 page_size, unsigned long number_of_pages)
 int alloc_bootmem_huge_page(struct hstate *hstate)
 {
 	struct huge_bootmem_page *m;
-	if (nr_gpages == 0)
+	if (nr_gpages == 0) {
+		printk(KERN_WARNING "Gigantic HugeTLB page not available\n");
 		return 0;
+	}
 	m = phys_to_virt(gpage_freearray[--nr_gpages]);
 	gpage_freearray[nr_gpages] = 0;
 	list_add(&m->list, &huge_boot_pages);
-- 
2.1.0