Attempt VMA lock-based page fault handling first, and fall back to the
existing mmap_lock-based handling if that fails.
This is the s390 variant of "x86/mm: try VMA lock-based page fault handling
first".
Signed-off-by: Heiko Carstens <hca@xxxxxxxxxxxxx>
---
arch/s390/Kconfig | 1 +
arch/s390/mm/fault.c | 24 ++++++++++++++++++++++++
2 files changed, 25 insertions(+)
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 9809c74e1240..548b5b587003 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -120,6 +120,7 @@ config S390
select ARCH_SUPPORTS_DEBUG_PAGEALLOC
select ARCH_SUPPORTS_HUGETLBFS
select ARCH_SUPPORTS_NUMA_BALANCING
+ select ARCH_SUPPORTS_PER_VMA_LOCK
select ARCH_USE_BUILTIN_BSWAP
select ARCH_USE_CMPXCHG_LOCKREF
select ARCH_WANTS_DYNAMIC_TASK_STRUCT
diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index a2632fd97d00..b65144c392b0 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -407,6 +407,30 @@ static inline vm_fault_t do_exception(struct pt_regs *regs, int access)
access = VM_WRITE;
if (access == VM_WRITE)
flags |= FAULT_FLAG_WRITE;
+#ifdef CONFIG_PER_VMA_LOCK
+ if (!(flags & FAULT_FLAG_USER))
+ goto lock_mmap;
+ vma = lock_vma_under_rcu(mm, address);
+ if (!vma)
+ goto lock_mmap;
+ if (!(vma->vm_flags & access)) {
+ vma_end_read(vma);
+ goto lock_mmap;
+ }
+ fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs);
+ vma_end_read(vma);
+ if (!(fault & VM_FAULT_RETRY)) {
+ count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
+ goto out;
+ }
+ count_vm_vma_lock_event(VMA_LOCK_RETRY);
+ /* Quick path to respond to signals */
+ if (fault_signal_pending(fault, regs)) {
+ fault = VM_FAULT_SIGNAL;
+ goto out;
+ }
+lock_mmap:
+#endif /* CONFIG_PER_VMA_LOCK */
mmap_read_lock(mm);
gmap = NULL;
--
2.37.2
