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Subject[PATCH 0/6] convert locked_vm from unsigned long to atomic64_t
Date
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

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