+ s390-mm-try-vma-lock-based-page-fault-handling-first.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: s390/mm: try VMA lock-based page fault handling first
has been added to the -mm mm-unstable branch.  Its filename is
     s390-mm-try-vma-lock-based-page-fault-handling-first.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/s390-mm-try-vma-lock-based-page-fault-handling-first.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Heiko Carstens <hca@linux.ibm.com>
Subject: s390/mm: try VMA lock-based page fault handling first
Date: Tue, 14 Mar 2023 14:28:08 +0100

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".

Link: https://lkml.kernel.org/r/20230314132808.1266335-1-hca@linux.ibm.com
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---


--- a/arch/s390/Kconfig~s390-mm-try-vma-lock-based-page-fault-handling-first
+++ a/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
--- a/arch/s390/mm/fault.c~s390-mm-try-vma-lock-based-page-fault-handling-first
+++ a/arch/s390/mm/fault.c
@@ -407,6 +407,30 @@ static inline vm_fault_t do_exception(st
 		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;
_

Patches currently in -mm which might be from hca@linux.ibm.com are

s390-mm-try-vma-lock-based-page-fault-handling-first.patch