[RFC PATCH 1/3] powerpc/mm: Handle page table allocation failures

["Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>]

This fixes the below crash that arises due to not handling page table allocation
failures while allocating hugetlb page table.

Fixes: e2b3d202d1db ("powerpc: Switch 16GB and 16MB explicit hugepages to a different page table format")
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
---
 arch/powerpc/mm/hugetlbpage.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
index c5c9ff2d7afc..ae9d71da5219 100644
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -130,6 +130,8 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, unsigned long addr, unsigned long sz
 	} else {
 		pdshift = PUD_SHIFT;
 		pu = pud_alloc(mm, pg, addr);
+		if (!pu)
+			return NULL;
 		if (pshift == PUD_SHIFT)
 			return (pte_t *)pu;
 		else if (pshift > PMD_SHIFT) {
@@ -138,6 +140,8 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, unsigned long addr, unsigned long sz
 		} else {
 			pdshift = PMD_SHIFT;
 			pm = pmd_alloc(mm, pu, addr);
+			if (!pm)
+				return NULL;
 			if (pshift == PMD_SHIFT)
 				/* 16MB hugepage */
 				return (pte_t *)pm;
@@ -154,12 +158,16 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, unsigned long addr, unsigned long sz
 	} else {
 		pdshift = PUD_SHIFT;
 		pu = pud_alloc(mm, pg, addr);
+		if (!pu)
+			return NULL;
 		if (pshift >= PUD_SHIFT) {
 			ptl = pud_lockptr(mm, pu);
 			hpdp = (hugepd_t *)pu;
 		} else {
 			pdshift = PMD_SHIFT;
 			pm = pmd_alloc(mm, pu, addr);
+			if (!pm)
+				return NULL;
 			ptl = pmd_lockptr(mm, pm);
 			hpdp = (hugepd_t *)pm;
 		}
-- 
2.21.0