3 files changed, 34 insertions, 6 deletions

diff --git a/arch/powerpc/include/asm/mmu-hash64.h b/arch/powerpc/include/asm/mmu-hash64.h
index 2102b214a87c..0e398cfee2c8 100644
--- a/arch/powerpc/include/asm/mmu-hash64.h
+++ b/arch/powerpc/include/asm/mmu-hash64.h
@@ -250,7 +250,9 @@ extern int hash_page(unsigned long ea, unsigned long access, unsigned long trap)
 int __hash_page_huge(unsigned long ea, unsigned long access, unsigned long vsid,
                      pte_t *ptep, unsigned long trap, int local, int ssize,
                      unsigned int shift, unsigned int mmu_psize);
-
+extern void hash_failure_debug(unsigned long ea, unsigned long access,
+                               unsigned long vsid, unsigned long trap,
+                               int ssize, int psize, unsigned long pte);
 extern int htab_bolt_mapping(unsigned long vstart, unsigned long vend,
                              unsigned long pstart, unsigned long prot,
                              int psize, int ssize);
diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
index 40847a9dd6db..09dffe6efa46 100644
--- a/arch/powerpc/mm/hash_utils_64.c
+++ b/arch/powerpc/mm/hash_utils_64.c
@@ -871,6 +871,18 @@ static inline int subpage_protection(struct mm_struct *mm, unsigned long ea)
 }
 #endif
 
+void hash_failure_debug(unsigned long ea, unsigned long access,
+                        unsigned long vsid, unsigned long trap,
+                        int ssize, int psize, unsigned long pte)
+{
+        if (!printk_ratelimit())
+                return;
+        pr_info("mm: Hashing failure ! EA=0x%lx access=0x%lx current=%s\n",
+                ea, access, current->comm);
+        pr_info("    trap=0x%lx vsid=0x%lx ssize=%d psize=%d pte=0x%lx\n",
+                trap, vsid, ssize, psize, pte);
+}
+
 /* Result code is:
  *  0 - handled
  *  1 - normal page fault
@@ -1036,6 +1048,12 @@ int hash_page(unsigned long ea, unsigned long access, unsigned long trap)
                                             local, ssize, spp);
         }
 
+        /* Dump some info in case of hash insertion failure, they should
+         * never happen so it is really useful to know if/when they do
+         */
+        if (rc == -1)
+                hash_failure_debug(ea, access, vsid, trap, ssize, psize,
+                                   pte_val(*ptep));
 #ifndef CONFIG_PPC_64K_PAGES
         DBG_LOW(" o-pte: %016lx\n", pte_val(*ptep));
 #else
@@ -1054,8 +1072,7 @@ void hash_preload(struct mm_struct *mm, unsigned long ea,
         void *pgdir;
         pte_t *ptep;
         unsigned long flags;
-        int local = 0;
-        int ssize;
+        int rc, ssize, local = 0;
 
         BUG_ON(REGION_ID(ea) != USER_REGION_ID);
 
@@ -1101,11 +1118,18 @@ void hash_preload(struct mm_struct *mm, unsigned long ea,
         /* Hash it in */
 #ifdef CONFIG_PPC_HAS_HASH_64K
         if (mm->context.user_psize == MMU_PAGE_64K)
-                __hash_page_64K(ea, access, vsid, ptep, trap, local, ssize);
+                rc = __hash_page_64K(ea, access, vsid, ptep, trap, local, ssize);
         else
 #endif /* CONFIG_PPC_HAS_HASH_64K */
-                __hash_page_4K(ea, access, vsid, ptep, trap, local, ssize,
-                               subpage_protection(pgdir, ea));
+                rc = __hash_page_4K(ea, access, vsid, ptep, trap, local, ssize,
+                                    subpage_protection(pgdir, ea));
+
+        /* Dump some info in case of hash insertion failure, they should
+         * never happen so it is really useful to know if/when they do
+         */
+        if (rc == -1)
+                hash_failure_debug(ea, access, vsid, trap, ssize,
+                                   mm->context.user_psize, pte_val(*ptep));
 
         local_irq_restore(flags);
 }
diff --git a/arch/powerpc/mm/hugetlbpage-hash64.c b/arch/powerpc/mm/hugetlbpage-hash64.c
index faae9ec4cb04..cc5c273086cf 100644
--- a/arch/powerpc/mm/hugetlbpage-hash64.c
+++ b/arch/powerpc/mm/hugetlbpage-hash64.c
@@ -127,6 +127,8 @@ repeat:
                  */
                 if (unlikely(slot == -2)) {
                         *ptep = __pte(old_pte);
+                        hash_failure_debug(ea, access, vsid, trap, ssize,
+                                           mmu_psize, old_pte);
                         return -1;
                 }