+ kvm-book3s-drop-mmap_sem-now-that-locked_vm-is-atomic.patch added to -mm tree

[akpm@xxxxxxxxxxxxxxxxxxxx]

The patch titled
     Subject: kvm/book3s: drop mmap_sem now that locked_vm is atomic
has been added to the -mm tree.  Its filename is
     kvm-book3s-drop-mmap_sem-now-that-locked_vm-is-atomic.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/kvm-book3s-drop-mmap_sem-now-that-locked_vm-is-atomic.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/kvm-book3s-drop-mmap_sem-now-that-locked_vm-is-atomic.patch

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------------------------------------------------------
From: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx>
Subject: kvm/book3s: drop mmap_sem now that locked_vm is atomic

With locked_vm now an atomic, there is no need to take mmap_sem as writer.
Delete and refactor accordingly.

Link: http://lkml.kernel.org/r/20190402204158.27582-7-daniel.m.jordan@xxxxxxxxxx
Signed-off-by: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx>
Cc: Alexey Kardashevskiy <aik@xxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxxx>
Cc: Alan Tull <atull@xxxxxxxxxx>
Cc: Alex Williamson <alex.williamson@xxxxxxxxxx>
Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
Cc: Moritz Fischer <mdf@xxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Wu Hao <hao.wu@xxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 arch/powerpc/kvm/book3s_64_vio.c |   34 ++++++++++-------------------
 1 file changed, 12 insertions(+), 22 deletions(-)

--- a/arch/powerpc/kvm/book3s_64_vio.c~kvm-book3s-drop-mmap_sem-now-that-locked_vm-is-atomic
+++ a/arch/powerpc/kvm/book3s_64_vio.c
@@ -56,7 +56,7 @@ static unsigned long kvmppc_stt_pages(un
 	return tce_pages + ALIGN(stt_bytes, PAGE_SIZE) / PAGE_SIZE;
 }
 
-static long kvmppc_account_memlimit(unsigned long stt_pages, bool inc)
+static long kvmppc_account_memlimit(unsigned long pages, bool inc)
 {
 	long ret = 0;
 	s64 locked_vm;
@@ -64,33 +64,23 @@ static long kvmppc_account_memlimit(unsi
 	if (!current || !current->mm)
 		return ret; /* process exited */
 
-	down_write(&current->mm->mmap_sem);
-
-	locked_vm = atomic64_read(&current->mm->locked_vm);
 	if (inc) {
-		unsigned long locked, lock_limit;
+		unsigned long lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
 
-		locked = locked_vm + stt_pages;
-		lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
-		if (locked > lock_limit && !capable(CAP_IPC_LOCK))
+		locked_vm = atomic64_add_return(pages, &current->mm->locked_vm);
+		if (locked_vm > lock_limit && !capable(CAP_IPC_LOCK)) {
 			ret = -ENOMEM;
-		else
-			atomic64_add(stt_pages, &current->mm->locked_vm);
+			atomic64_sub(pages, &current->mm->locked_vm);
+		}
 	} else {
-		if (WARN_ON_ONCE(stt_pages > locked_vm))
-			stt_pages = locked_vm;
-
-		atomic64_sub(stt_pages, &current->mm->locked_vm);
+		locked_vm = atomic64_sub_return(pages, &current->mm->locked_vm);
+		WARN_ON_ONCE(locked_vm < 0);
 	}
 
-	pr_debug("[%d] RLIMIT_MEMLOCK KVM %c%ld %ld/%ld%s\n", current->pid,
-			inc ? '+' : '-',
-			stt_pages << PAGE_SHIFT,
-			atomic64_read(&current->mm->locked_vm) << PAGE_SHIFT,
-			rlimit(RLIMIT_MEMLOCK),
-			ret ? " - exceeded" : "");
-
-	up_write(&current->mm->mmap_sem);
+	pr_debug("[%d] RLIMIT_MEMLOCK KVM %c%lu %lld/%lu%s\n", current->pid,
+			inc ? '+' : '-', pages << PAGE_SHIFT,
+			locked_vm << PAGE_SHIFT,
+			rlimit(RLIMIT_MEMLOCK), ret ? " - exceeded" : "");
 
 	return ret;
 }
_

Patches currently in -mm which might be from daniel.m.jordan@xxxxxxxxxx are

mm-change-locked_vms-type-from-unsigned-long-to-atomic64_t.patch
vfio-type1-drop-mmap_sem-now-that-locked_vm-is-atomic.patch
vfio-spapr_tce-drop-mmap_sem-now-that-locked_vm-is-atomic.patch
fpga-dlf-afu-drop-mmap_sem-now-that-locked_vm-is-atomic.patch
powerpc-mmu-drop-mmap_sem-now-that-locked_vm-is-atomic.patch
kvm-book3s-drop-mmap_sem-now-that-locked_vm-is-atomic.patch