+ arm64-mm-accelerate-pagefault-when-vm_fault_badaccess.patch added to mm-unstable branch

+ arm64-mm-accelerate-pagefault-when-vm_fault_badaccess.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: arm64: mm: accelerate pagefault when VM_FAULT_BADACCESS
has been added to the -mm mm-unstable branch.  Its filename is
     arm64-mm-accelerate-pagefault-when-vm_fault_badaccess.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/arm64-mm-accelerate-pagefault-when-vm_fault_badaccess.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: Kefeng Wang <wangkefeng.wang@huawei.com>
Subject: arm64: mm: accelerate pagefault when VM_FAULT_BADACCESS
Date: Wed, 3 Apr 2024 16:38:00 +0800

The vm_flags of vma already checked under per-VMA lock, if it is a bad
access, directly set fault to VM_FAULT_BADACCESS and handle error, no need
to retry with mmap_lock again, the latency time reduces 34% in 'lat_sig -P
1 prot lat_sig' from lmbench testcase.

Since the page fault is handled under per-VMA lock, count it as a vma lock
event with VMA_LOCK_SUCCESS.

Link: https://lkml.kernel.org/r/20240403083805.1818160-3-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 arch/arm64/mm/fault.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/arch/arm64/mm/fault.c~arm64-mm-accelerate-pagefault-when-vm_fault_badaccess
+++ a/arch/arm64/mm/fault.c
@@ -572,7 +572,9 @@ static int __kprobes do_page_fault(unsig
 
 	if (!(vma->vm_flags & vm_flags)) {
 		vma_end_read(vma);
-		goto lock_mmap;
+		fault = VM_FAULT_BADACCESS;
+		count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
+		goto done;
 	}
 	fault = handle_mm_fault(vma, addr, mm_flags | FAULT_FLAG_VMA_LOCK, regs);
 	if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))
_

Patches currently in -mm which might be from wangkefeng.wang@huawei.com are

mm-backing-dev-use-group-allocation-free-of-per-cpu-counters-api.patch
mm-remove-__set_page_dirty_nobuffers.patch
arm64-mm-cleanup-__do_page_fault.patch
arm64-mm-accelerate-pagefault-when-vm_fault_badaccess.patch
arm-mm-accelerate-pagefault-when-vm_fault_badaccess.patch
powerpc-mm-accelerate-pagefault-when-badaccess.patch
riscv-mm-accelerate-pagefault-when-badaccess.patch
s390-mm-accelerate-pagefault-when-badaccess.patch
x86-mm-accelerate-pagefault-when-badaccess.patch