linux/drivers/xen
Michal Hocko 93065ac753 mm, oom: distinguish blockable mode for mmu notifiers
There are several blockable mmu notifiers which might sleep in
mmu_notifier_invalidate_range_start and that is a problem for the
oom_reaper because it needs to guarantee a forward progress so it cannot
depend on any sleepable locks.

Currently we simply back off and mark an oom victim with blockable mmu
notifiers as done after a short sleep.  That can result in selecting a new
oom victim prematurely because the previous one still hasn't torn its
memory down yet.

We can do much better though.  Even if mmu notifiers use sleepable locks
there is no reason to automatically assume those locks are held.  Moreover
majority of notifiers only care about a portion of the address space and
there is absolutely zero reason to fail when we are unmapping an unrelated
range.  Many notifiers do really block and wait for HW which is harder to
handle and we have to bail out though.

This patch handles the low hanging fruit.
__mmu_notifier_invalidate_range_start gets a blockable flag and callbacks
are not allowed to sleep if the flag is set to false.  This is achieved by
using trylock instead of the sleepable lock for most callbacks and
continue as long as we do not block down the call chain.

I think we can improve that even further because there is a common pattern
to do a range lookup first and then do something about that.  The first
part can be done without a sleeping lock in most cases AFAICS.

The oom_reaper end then simply retries if there is at least one notifier
which couldn't make any progress in !blockable mode.  A retry loop is
already implemented to wait for the mmap_sem and this is basically the
same thing.

The simplest way for driver developers to test this code path is to wrap
userspace code which uses these notifiers into a memcg and set the hard
limit to hit the oom.  This can be done e.g.  after the test faults in all
the mmu notifier managed memory and set the hard limit to something really
small.  Then we are looking for a proper process tear down.

[akpm@linux-foundation.org: coding style fixes]
[akpm@linux-foundation.org: minor code simplification]
Link: http://lkml.kernel.org/r/20180716115058.5559-1-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Christian König <christian.koenig@amd.com> # AMD notifiers
Acked-by: Leon Romanovsky <leonro@mellanox.com> # mlx and umem_odp
Reported-by: David Rientjes <rientjes@google.com>
Cc: "David (ChunMing) Zhou" <David1.Zhou@amd.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Doug Ledford <dledford@redhat.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Mike Marciniszyn <mike.marciniszyn@intel.com>
Cc: Dennis Dalessandro <dennis.dalessandro@intel.com>
Cc: Sudeep Dutt <sudeep.dutt@intel.com>
Cc: Ashutosh Dixit <ashutosh.dixit@intel.com>
Cc: Dimitri Sivanich <sivanich@sgi.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: "Jérôme Glisse" <jglisse@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Felix Kuehling <felix.kuehling@amd.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-08-22 10:52:44 -07:00
..
events xen: Remove unnecessary BUG_ON from __unbind_from_irq() 2018-06-22 08:32:52 +02:00
xen-pciback treewide: kmalloc() -> kmalloc_array() 2018-06-12 16:19:22 -07:00
xenbus xen/store: do not store local values in xen_start_info 2018-05-17 08:39:13 +02:00
xenfs License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
Kconfig xen/gntdev: Add initial support for dma-buf UAPI 2018-07-26 23:05:14 -04:00
Makefile xen/gntdev: Add initial support for dma-buf UAPI 2018-07-26 23:05:14 -04:00
acpi.c xen: rename dom0_op to platform_op 2015-12-21 14:40:55 +00:00
arm-device.c treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
balloon.c xen/balloon: Share common memory reservation routines 2018-07-26 23:05:13 -04:00
biomerge.c xen/biomerge: Use true and false for boolean values 2018-08-06 10:20:57 -04:00
cpu_hotplug.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
dbgp.c
efi.c xen: Implement EFI reset_system callback 2017-05-02 12:06:50 +02:00
evtchn.c treewide: kvmalloc() -> kvmalloc_array() 2018-06-12 16:19:22 -07:00
fallback.c
features.c xen: audit usages of module.h ; remove unnecessary instances 2016-03-21 15:13:32 +00:00
gntalloc.c mm: treewide: remove GFP_TEMPORARY allocation flag 2017-09-13 18:53:16 -07:00
gntdev-common.h xen/gntdev: Add initial support for dma-buf UAPI 2018-07-26 23:05:14 -04:00
gntdev-dmabuf.c drm pull for 4.19-rc1 2018-08-15 17:39:07 -07:00
gntdev-dmabuf.h xen/gntdev: Add initial support for dma-buf UAPI 2018-07-26 23:05:14 -04:00
gntdev.c mm, oom: distinguish blockable mode for mmu notifiers 2018-08-22 10:52:44 -07:00
grant-table.c xen/grant-table: Allow allocating buffers suitable for DMA 2018-07-26 23:05:14 -04:00
manage.c xen: add error handling for xenbus_printf 2018-06-19 14:27:41 +02:00
mcelog.c vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
mem-reservation.c xen/balloon: Share common memory reservation routines 2018-07-26 23:05:13 -04:00
pci.c xen/pci: Try harder to get PXM information for Xen 2015-04-15 10:57:28 +01:00
pcpu.c xen: rename dom0_op to platform_op 2015-12-21 14:40:55 +00:00
platform-pci.c xen-platform: constify pci_device_id. 2017-08-31 09:45:55 -04:00
preempt.c xen/preempt: use need_resched() instead of should_resched() 2015-08-20 12:24:14 +01:00
privcmd-buf.c xen: add new hypercall buffer mapping device 2018-06-22 08:26:42 +02:00
privcmd.c xen: add new hypercall buffer mapping device 2018-06-22 08:26:42 +02:00
privcmd.h xen: add new hypercall buffer mapping device 2018-06-22 08:26:42 +02:00
pvcalls-back.c xen/pvcalls: fix null pointer dereference on map->sock 2018-02-26 17:13:12 +01:00
pvcalls-front.c pvcalls-front: 64-bit align flags 2018-03-01 07:23:36 +01:00
pvcalls-front.h xen: fix poll misannotation 2018-02-01 10:07:32 -05:00
swiotlb-xen.c xen-swiotlb: fix the check condition for xen_swiotlb_free_coherent 2018-05-18 14:37:16 -04:00
sys-hypervisor.c xen: add sysfs node for hypervisor build id 2017-06-15 08:50:37 +02:00
time.c xen: features and fixes for v4.15-rc1 2017-11-16 13:06:27 -08:00
tmem.c mm, swap, frontswap: fix THP swap if frontswap enabled 2018-02-21 15:35:43 -08:00
xen-acpi-cpuhotplug.c xen: rename dom0_op to platform_op 2015-12-21 14:40:55 +00:00
xen-acpi-memhotplug.c
xen-acpi-pad.c xen: rename dom0_op to platform_op 2015-12-21 14:40:55 +00:00
xen-acpi-processor.c xen/acpi: off by one in read_acpi_id() 2018-03-30 11:30:13 -04:00
xen-balloon.c xen/balloon: fix balloon initialization for PVH Dom0 2018-08-08 11:03:20 -04:00
xen-scsiback.c SCSI misc on 20180815 2018-08-15 22:06:26 -07:00
xen-selfballoon.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
xen-stub.c
xlate_mmu.c Xen: xlate: Use page_to_xen_pfn instead of page_to_pfn 2016-07-06 10:34:42 +01:00