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    SubjectRe: [RFC PATCH 00/19] mm: Introduce a cgroup to limit the amount of locked and pinned memory
    On Mon, Jan 23, 2023 at 9:43 PM Alistair Popple <apopple@nvidia.com> wrote:
    >
    > Having large amounts of unmovable or unreclaimable memory in a system
    > can lead to system instability due to increasing the likelihood of
    > encountering out-of-memory conditions. Therefore it is desirable to
    > limit the amount of memory users can lock or pin.
    >
    > From userspace such limits can be enforced by setting
    > RLIMIT_MEMLOCK. However there is no standard method that drivers and
    > other in-kernel users can use to check and enforce this limit.
    >
    > This has lead to a large number of inconsistencies in how limits are
    > enforced. For example some drivers will use mm->locked_mm while others
    > will use mm->pinned_mm or user->locked_mm. It is therefore possible to
    > have up to three times RLIMIT_MEMLOCKED pinned.
    >
    > Having pinned memory limited per-task also makes it easy for users to
    > exceed the limit. For example drivers that pin memory with
    > pin_user_pages() it tends to remain pinned after fork. To deal with
    > this and other issues this series introduces a cgroup for tracking and
    > limiting the number of pages pinned or locked by tasks in the group.
    >
    > However the existing behaviour with regards to the rlimit needs to be
    > maintained. Therefore the lesser of the two limits is
    > enforced. Furthermore having CAP_IPC_LOCK usually bypasses the rlimit,
    > but this bypass is not allowed for the cgroup.
    >
    > The first part of this series converts existing drivers which
    > open-code the use of locked_mm/pinned_mm over to a common interface
    > which manages the refcounts of the associated task/mm/user
    > structs. This ensures accounting of pages is consistent and makes it
    > easier to add charging of the cgroup.
    >
    > The second part of the series adds the cgroup and converts core mm
    > code such as mlock over to charging the cgroup before finally
    > introducing some selftests.


    I didn't go through the entire series, so apologies if this was
    mentioned somewhere, but do you mind elaborating on why this is added
    as a separate cgroup controller rather than an extension of the memory
    cgroup controller?

    >
    >
    > As I don't have access to systems with all the various devices I
    > haven't been able to test all driver changes. Any help there would be
    > appreciated.
    >
    > Alistair Popple (19):
    > mm: Introduce vm_account
    > drivers/vhost: Convert to use vm_account
    > drivers/vdpa: Convert vdpa to use the new vm_structure
    > infiniband/umem: Convert to use vm_account
    > RMDA/siw: Convert to use vm_account
    > RDMA/usnic: convert to use vm_account
    > vfio/type1: Charge pinned pages to pinned_vm instead of locked_vm
    > vfio/spapr_tce: Convert accounting to pinned_vm
    > io_uring: convert to use vm_account
    > net: skb: Switch to using vm_account
    > xdp: convert to use vm_account
    > kvm/book3s_64_vio: Convert account_locked_vm() to vm_account_pinned()
    > fpga: dfl: afu: convert to use vm_account
    > mm: Introduce a cgroup for pinned memory
    > mm/util: Extend vm_account to charge pages against the pin cgroup
    > mm/util: Refactor account_locked_vm
    > mm: Convert mmap and mlock to use account_locked_vm
    > mm/mmap: Charge locked memory to pins cgroup
    > selftests/vm: Add pins-cgroup selftest for mlock/mmap
    >
    > MAINTAINERS | 8 +-
    > arch/powerpc/kvm/book3s_64_vio.c | 10 +-
    > arch/powerpc/mm/book3s64/iommu_api.c | 29 +--
    > drivers/fpga/dfl-afu-dma-region.c | 11 +-
    > drivers/fpga/dfl-afu.h | 1 +-
    > drivers/infiniband/core/umem.c | 16 +-
    > drivers/infiniband/core/umem_odp.c | 6 +-
    > drivers/infiniband/hw/usnic/usnic_uiom.c | 13 +-
    > drivers/infiniband/hw/usnic/usnic_uiom.h | 1 +-
    > drivers/infiniband/sw/siw/siw.h | 2 +-
    > drivers/infiniband/sw/siw/siw_mem.c | 20 +--
    > drivers/infiniband/sw/siw/siw_verbs.c | 15 +-
    > drivers/vdpa/vdpa_user/vduse_dev.c | 20 +--
    > drivers/vfio/vfio_iommu_spapr_tce.c | 15 +-
    > drivers/vfio/vfio_iommu_type1.c | 59 +----
    > drivers/vhost/vdpa.c | 9 +-
    > drivers/vhost/vhost.c | 2 +-
    > drivers/vhost/vhost.h | 1 +-
    > include/linux/cgroup.h | 20 ++-
    > include/linux/cgroup_subsys.h | 4 +-
    > include/linux/io_uring_types.h | 3 +-
    > include/linux/kvm_host.h | 1 +-
    > include/linux/mm.h | 5 +-
    > include/linux/mm_types.h | 88 ++++++++-
    > include/linux/skbuff.h | 6 +-
    > include/net/sock.h | 2 +-
    > include/net/xdp_sock.h | 2 +-
    > include/rdma/ib_umem.h | 1 +-
    > io_uring/io_uring.c | 20 +--
    > io_uring/notif.c | 4 +-
    > io_uring/notif.h | 10 +-
    > io_uring/rsrc.c | 38 +---
    > io_uring/rsrc.h | 9 +-
    > mm/Kconfig | 11 +-
    > mm/Makefile | 1 +-
    > mm/internal.h | 2 +-
    > mm/mlock.c | 76 +------
    > mm/mmap.c | 76 +++----
    > mm/mremap.c | 54 +++--
    > mm/pins_cgroup.c | 273 ++++++++++++++++++++++++-
    > mm/secretmem.c | 6 +-
    > mm/util.c | 196 +++++++++++++++--
    > net/core/skbuff.c | 47 +---
    > net/rds/message.c | 9 +-
    > net/xdp/xdp_umem.c | 38 +--
    > tools/testing/selftests/vm/Makefile | 1 +-
    > tools/testing/selftests/vm/pins-cgroup.c | 271 ++++++++++++++++++++++++-
    > virt/kvm/kvm_main.c | 3 +-
    > 48 files changed, 1114 insertions(+), 401 deletions(-)
    > create mode 100644 mm/pins_cgroup.c
    > create mode 100644 tools/testing/selftests/vm/pins-cgroup.c
    >
    > base-commit: 2241ab53cbb5cdb08a6b2d4688feb13971058f65
    > --
    > git-series 0.9.1
    >

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