linux-kernel - [PATCH 0/6] convert locked_vm from unsigned long to atomic64

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Date:   Tue,  2 Apr 2019 16:41:52 -0400
From:   Daniel Jordan <daniel.m.jordan@...cle.com>
To:     akpm@...ux-foundation.org
Cc:     daniel.m.jordan@...cle.com, Alan Tull <atull@...nel.org>,
        Alexey Kardashevskiy <aik@...abs.ru>,
        Alex Williamson <alex.williamson@...hat.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Christoph Lameter <cl@...ux.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Michael Ellerman <mpe@...erman.id.au>,
        Moritz Fischer <mdf@...nel.org>,
        Paul Mackerras <paulus@...abs.org>, Wu Hao <hao.wu@...el.com>,
        linux-mm@...ck.org, kvm@...r.kernel.org, kvm-ppc@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-fpga@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 0/6] convert locked_vm from unsigned long to atomic64_t

Hi,

>From patch 1:

  Taking and dropping mmap_sem to modify a single counter, locked_vm, is
  overkill when the counter could be synchronized separately.
  
  Make mmap_sem a little less coarse by changing locked_vm to an atomic,
  the 64-bit variety to avoid issues with overflow on 32-bit systems.

This is a more conservative alternative to [1] with no user-visible
effects.  Thanks to Alexey Kardashevskiy for pointing out the racy
atomics and to Alex Williamson, Christoph Lameter, Ira Weiny, and Jason
Gunthorpe for their comments on [1].

Davidlohr Bueso recently did a similar conversion for pinned_vm[2].

Testing
 1. passes LTP mlock[all], munlock[all], fork, mmap, and mremap tests in an
    x86 kvm guest
 2. a VFIO-enabled x86 kvm guest shows the same VmLck in
    /proc/pid/status before and after this change
 3. cross-compiles on powerpc

The series is based on v5.1-rc3.  Please consider for 5.2.

Daniel

[1] https://lore.kernel.org/linux-mm/20190211224437.25267-1-daniel.m.jordan@oracle.com/
[2] https://lore.kernel.org/linux-mm/20190206175920.31082-1-dave@stgolabs.net/

Daniel Jordan (6):
  mm: change locked_vm's type from unsigned long to atomic64_t
  vfio/type1: drop mmap_sem now that locked_vm is atomic
  vfio/spapr_tce: drop mmap_sem now that locked_vm is atomic
  fpga/dlf/afu: drop mmap_sem now that locked_vm is atomic
  powerpc/mmu: drop mmap_sem now that locked_vm is atomic
  kvm/book3s: drop mmap_sem now that locked_vm is atomic

 arch/powerpc/kvm/book3s_64_vio.c    | 34 ++++++++++--------------
 arch/powerpc/mm/mmu_context_iommu.c | 28 +++++++++-----------
 drivers/fpga/dfl-afu-dma-region.c   | 40 ++++++++++++-----------------
 drivers/vfio/vfio_iommu_spapr_tce.c | 37 ++++++++++++--------------
 drivers/vfio/vfio_iommu_type1.c     | 31 +++++++++-------------
 fs/proc/task_mmu.c                  |  2 +-
 include/linux/mm_types.h            |  2 +-
 kernel/fork.c                       |  2 +-
 mm/debug.c                          |  5 ++--
 mm/mlock.c                          |  4 +--
 mm/mmap.c                           | 18 ++++++-------
 mm/mremap.c                         |  6 ++---
 12 files changed, 89 insertions(+), 120 deletions(-)


base-commit: 79a3aaa7b82e3106be97842dedfd8429248896e6
-- 
2.21.0