[RFC PATCH v3 1/3] powerpc: Move the setting of rflags out of loop in __hash_page_huge

[RFC PATCH v3 1/3] powerpc: Move the setting of rflags out of loop in __hash_page_huge

[Li Zhong]

It seems that new_pte and rflags don't get changed in the repeating loop, so
move their assignment out of the loop.

Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com>
---
 arch/powerpc/mm/hugetlbpage-hash64.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/mm/hugetlbpage-hash64.c b/arch/powerpc/mm/hugetlbpage-hash64.c
index cecad34..edb4129 100644
--- a/arch/powerpc/mm/hugetlbpage-hash64.c
+++ b/arch/powerpc/mm/hugetlbpage-hash64.c
@@ -87,10 +87,6 @@ int __hash_page_huge(unsigned long ea, unsigned long access, unsigned long vsid,
 
 		pa = pte_pfn(__pte(old_pte)) << PAGE_SHIFT;
 
-repeat:
-		hpte_group = ((hash & htab_hash_mask) *
-			      HPTES_PER_GROUP) & ~0x7UL;
-
 		/* clear HPTE slot informations in new PTE */
 #ifdef CONFIG_PPC_64K_PAGES
 		new_pte = (new_pte & ~_PAGE_HPTEFLAGS) | _PAGE_HPTE_SUB0;
@@ -101,6 +97,10 @@ repeat:
 		rflags |= (new_pte & (_PAGE_WRITETHRU | _PAGE_NO_CACHE |
 				      _PAGE_COHERENT | _PAGE_GUARDED));
 
+repeat:
+		hpte_group = ((hash & htab_hash_mask) *
+			      HPTES_PER_GROUP) & ~0x7UL;
+
 		/* Insert into the hash table, primary slot */
 		slot = ppc_md.hpte_insert(hpte_group, vpn, pa, rflags, 0,
 					  mmu_psize, ssize);
-- 
1.7.9.5

[RFC PATCH v3 2/3] powerpc: Split the code trying to insert hpte repeatedly as an helper function

[Li Zhong]

Move the logic trying to insert hpte in __hash_page_huge() to an helper
function, so it could also be used by others.

Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com>
---
 arch/powerpc/mm/hash_utils_64.c      |   35 ++++++++++++++++++++++++++++++++++
 arch/powerpc/mm/hugetlbpage-hash64.c |   31 ++++++------------------------
 2 files changed, 41 insertions(+), 25 deletions(-)

diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
index f410c3e..ead9fa8 100644
--- a/arch/powerpc/mm/hash_utils_64.c
+++ b/arch/powerpc/mm/hash_utils_64.c
@@ -1230,6 +1230,41 @@ void low_hash_fault(struct pt_regs *regs, unsigned long address, int rc)
 		bad_page_fault(regs, address, SIGBUS);
 }
 
+long hpte_insert_repeating(unsigned long hash, unsigned long vpn,
+			   unsigned long pa, unsigned long rflags,
+			   unsigned long vflags, int psize, int ssize)
+{
+	unsigned long hpte_group;
+	long slot;
+
+repeat:
+	hpte_group = ((hash & htab_hash_mask) *
+		       HPTES_PER_GROUP) & ~0x7UL;
+
+	/* Insert into the hash table, primary slot */
+	slot = ppc_md.hpte_insert(hpte_group, vpn, pa, rflags, vflags,
+				  psize, ssize);
+
+	/* Primary is full, try the secondary */
+	if (unlikely(slot == -1)) {
+		hpte_group = ((~hash & htab_hash_mask) *
+			      HPTES_PER_GROUP) & ~0x7UL;
+		slot = ppc_md.hpte_insert(hpte_group, vpn, pa, rflags,
+					  vflags | HPTE_V_SECONDARY,
+					  psize, ssize);
+		if (slot == -1) {
+			if (mftb() & 0x1)
+				hpte_group = ((hash & htab_hash_mask) *
+					      HPTES_PER_GROUP)&~0x7UL;
+
+			ppc_md.hpte_remove(hpte_group);
+			goto repeat;
+		}
+	}
+
+	return slot;
+}
+
 #ifdef CONFIG_DEBUG_PAGEALLOC
 static void kernel_map_linear_page(unsigned long vaddr, unsigned long lmi)
 {
diff --git a/arch/powerpc/mm/hugetlbpage-hash64.c b/arch/powerpc/mm/hugetlbpage-hash64.c
index edb4129..b913f41 100644
--- a/arch/powerpc/mm/hugetlbpage-hash64.c
+++ b/arch/powerpc/mm/hugetlbpage-hash64.c
@@ -14,6 +14,10 @@
 #include <asm/cacheflush.h>
 #include <asm/machdep.h>
 
+extern long hpte_insert_repeating(unsigned long hash, unsigned long vpn,
+				  unsigned long pa, unsigned long rlags,
+				  unsigned long vflags, int psize, int ssize);
+
 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)
@@ -83,7 +87,6 @@ int __hash_page_huge(unsigned long ea, unsigned long access, unsigned long vsid,
 
 	if (likely(!(old_pte & _PAGE_HASHPTE))) {
 		unsigned long hash = hpt_hash(vpn, shift, ssize);
-		unsigned long hpte_group;
 
 		pa = pte_pfn(__pte(old_pte)) << PAGE_SHIFT;
 
@@ -97,30 +100,8 @@ int __hash_page_huge(unsigned long ea, unsigned long access, unsigned long vsid,
 		rflags |= (new_pte & (_PAGE_WRITETHRU | _PAGE_NO_CACHE |
 				      _PAGE_COHERENT | _PAGE_GUARDED));
 
-repeat:
-		hpte_group = ((hash & htab_hash_mask) *
-			      HPTES_PER_GROUP) & ~0x7UL;
-
-		/* Insert into the hash table, primary slot */
-		slot = ppc_md.hpte_insert(hpte_group, vpn, pa, rflags, 0,
-					  mmu_psize, ssize);
-
-		/* Primary is full, try the secondary */
-		if (unlikely(slot == -1)) {
-			hpte_group = ((~hash & htab_hash_mask) *
-				      HPTES_PER_GROUP) & ~0x7UL;
-			slot = ppc_md.hpte_insert(hpte_group, vpn, pa, rflags,
-						  HPTE_V_SECONDARY,
-						  mmu_psize, ssize);
-			if (slot == -1) {
-				if (mftb() & 0x1)
-					hpte_group = ((hash & htab_hash_mask) *
-						      HPTES_PER_GROUP)&~0x7UL;
-
-				ppc_md.hpte_remove(hpte_group);
-				goto repeat;
-                        }
-		}
+		slot = hpte_insert_repeating(hash, vpn, pa, rflags, 0,
+					     mmu_psize, ssize);
 
 		/*
 		 * Hypervisor failure. Restore old pte and return -1
-- 
1.7.9.5

[RFC PATCH v3 3/3] powerpc: Try to insert the hptes repeatedly in kernel_map_linear_page()

[Li Zhong]

This patch fixes the following oops, which could be trigged by build the kernel
with many concurrent threads, under CONFIG_DEBUG_PAGEALLOC.

hpte_insert() might return -1, indicating that the bucket (primary here)
is full. We are not necessarily reporting a BUG in this case. Instead, we could
try repeatedly (try secondary, remove and try again) until we find a slot.

[  543.075675] ------------[ cut here ]------------
[  543.075701] kernel BUG at arch/powerpc/mm/hash_utils_64.c:1239!
[  543.075714] Oops: Exception in kernel mode, sig: 5 [#1]
[  543.075722] PREEMPT SMP NR_CPUS=16 DEBUG_PAGEALLOC NUMA pSeries
[  543.075741] Modules linked in: binfmt_misc ehea
[  543.075759] NIP: c000000000036eb0 LR: c000000000036ea4 CTR: c00000000005a594
[  543.075771] REGS: c0000000a90832c0 TRAP: 0700   Not tainted  (3.8.0-next-20130222)
[  543.075781] MSR: 8000000000029032 <SF,EE,ME,IR,DR,RI>  CR: 22224482  XER: 00000000
[  543.075816] SOFTE: 0
[  543.075823] CFAR: c00000000004c200
[  543.075830] TASK = c0000000e506b750[23934] 'cc1' THREAD: c0000000a9080000 CPU: 1
GPR00: 0000000000000001 c0000000a9083540 c000000000c600a8 ffffffffffffffff
GPR04: 0000000000000050 fffffffffffffffa c0000000a90834e0 00000000004ff594
GPR08: 0000000000000001 0000000000000000 000000009592d4d8 c000000000c86854
GPR12: 0000000000000002 c000000006ead300 0000000000a51000 0000000000000001
GPR16: f000000003354380 ffffffffffffffff ffffffffffffff80 0000000000000000
GPR20: 0000000000000001 c000000000c600a8 0000000000000001 0000000000000001
GPR24: 0000000003354380 c000000000000000 0000000000000000 c000000000b65950
GPR28: 0000002000000000 00000000000cd50e 0000000000bf50d9 c000000000c7c230
[  543.076005] NIP [c000000000036eb0] .kernel_map_pages+0x1e0/0x3f8
[  543.076016] LR [c000000000036ea4] .kernel_map_pages+0x1d4/0x3f8
[  543.076025] Call Trace:
[  543.076033] [c0000000a9083540] [c000000000036ea4] .kernel_map_pages+0x1d4/0x3f8 (unreliable)
[  543.076053] [c0000000a9083640] [c000000000167638] .get_page_from_freelist+0x6cc/0x8dc
[  543.076067] [c0000000a9083800] [c000000000167a48] .__alloc_pages_nodemask+0x200/0x96c
[  543.076082] [c0000000a90839c0] [c0000000001ade44] .alloc_pages_vma+0x160/0x1e4
[  543.076098] [c0000000a9083a80] [c00000000018ce04] .handle_pte_fault+0x1b0/0x7e8
[  543.076113] [c0000000a9083b50] [c00000000018d5a8] .handle_mm_fault+0x16c/0x1a0
[  543.076129] [c0000000a9083c00] [c0000000007bf1dc] .do_page_fault+0x4d0/0x7a4
[  543.076144] [c0000000a9083e30] [c0000000000090e8] handle_page_fault+0x10/0x30
[  543.076155] Instruction dump:
[  543.076163] 7c630038 78631d88 e80a0000 f8410028 7c0903a6 e91f01de e96a0010 e84a0008
[  543.076192] 4e800421 e8410028 7c7107b4 7a200fe0 <0b000000> 7f63db78 48785781 60000000
[  543.076224] ---[ end trace bd5807e8d6ae186b ]---

Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com>
---
 arch/powerpc/mm/hash_utils_64.c |   13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
index ead9fa8..1ed4419 100644
--- a/arch/powerpc/mm/hash_utils_64.c
+++ b/arch/powerpc/mm/hash_utils_64.c
@@ -1268,21 +1268,22 @@ repeat:
 #ifdef CONFIG_DEBUG_PAGEALLOC
 static void kernel_map_linear_page(unsigned long vaddr, unsigned long lmi)
 {
-	unsigned long hash, hpteg;
+	unsigned long hash;
 	unsigned long vsid = get_kernel_vsid(vaddr, mmu_kernel_ssize);
 	unsigned long vpn = hpt_vpn(vaddr, vsid, mmu_kernel_ssize);
 	unsigned long mode = htab_convert_pte_flags(PAGE_KERNEL);
-	int ret;
+	long ret;
 
 	hash = hpt_hash(vpn, PAGE_SHIFT, mmu_kernel_ssize);
-	hpteg = ((hash & htab_hash_mask) * HPTES_PER_GROUP);
 
 	/* Don't create HPTE entries for bad address */
 	if (!vsid)
 		return;
-	ret = ppc_md.hpte_insert(hpteg, vpn, __pa(vaddr),
-				 mode, HPTE_V_BOLTED,
-				 mmu_linear_psize, mmu_kernel_ssize);
+
+	ret = hpte_insert_repeating(hash, vpn, __pa(vaddr), mode,
+				    HPTE_V_BOLTED,
+				    mmu_linear_psize, mmu_kernel_ssize);
+
 	BUG_ON (ret < 0);
 	spin_lock(&linear_map_hash_lock);
 	BUG_ON(linear_map_hash_slots[lmi] & 0x80);
-- 
1.7.9.5