Pages used in scatterlist can be mapped page cache pages (and often are),
so we must use flush_dcache_page here instead of the more limited
flush_kernel_dcache_page that is intended for highmem pages only.

Also remove the PageSlab check given that page_mapping_file as used by the
flush_dcache_page implementations already contains that check.

Link: https://lkml.kernel.org/r/20210712060928.4161649-5-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Alex Shi <alexs@kernel.org>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Greentime Hu <green.hu@gmail.com>
Cc: Guo Ren <guoren@kernel.org>
Cc: Helge Deller <deller@gmx.de>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Nick Hu <nickhu@andestech.com>
Cc: Paul Cercueil <paul@crapouillou.net>
Cc: Rich Felker <dalias@libc.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Vincent Chen <deanbo422@gmail.com>
Cc: Yoshinori Sato <ysato@users.osdn.me>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pages passed to block drivers can be mapped page cache pages, so we must
use flush_dcache_page here instead of the more limited
flush_kernel_dcache_page that is intended for highmem pages only.

Link: https://lkml.kernel.org/r/20210712060928.4161649-3-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Alex Shi <alexs@kernel.org>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Greentime Hu <green.hu@gmail.com>
Cc: Guo Ren <guoren@kernel.org>
Cc: Helge Deller <deller@gmx.de>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Nick Hu <nickhu@andestech.com>
Cc: Paul Cercueil <paul@crapouillou.net>
Cc: Rich Felker <dalias@libc.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Vincent Chen <deanbo422@gmail.com>
Cc: Yoshinori Sato <ysato@users.osdn.me>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Patch series "_kernel_dcache_page fixes and removal".

While looking to convert the block layer away from kmap_atomic towards
kmap_local_page and prefeably the helpers that abstract it away I noticed
that a few block drivers directly or implicitly call
flush_kernel_dcache_page before kunmapping a page that has been written
to.

flush_kernel_dcache_page is documented to to be used in such cases, but
flush_dcache_page is actually required when the page could be in the page
cache and mapped to userspace, which is pretty much always the case when
kmapping an arbitrary page.  Unfortunately the documentation doesn't
exactly make that clear, which lead to this misused.  And it turns out
that only the copy_strings / copy_string_kernel in the exec code were
actually correct users of flush_kernel_dcache_page, which is why I think
we should just remove it and eat the very minor overhead in exec rather
than confusing poor driver writers.

This patch (of 6):

MIPS now implements flush_kernel_dcache_page (as an alias to
flush_dcache_page).

Link: https://lkml.kernel.org/r/20210712060928.4161649-1-hch@lst.de
Link: https://lkml.kernel.org/r/20210712060928.4161649-2-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Guo Ren <guoren@kernel.org>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Nick Hu <nickhu@andestech.com>
Cc: Greentime Hu <green.hu@gmail.com>
Cc: Vincent Chen <deanbo422@gmail.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Yoshinori Sato <ysato@users.osdn.me>
Cc: Rich Felker <dalias@libc.org>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Paul Cercueil <paul@crapouillou.net>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Alex Shi <alexs@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

There is a spelling mistake in an error message. Fix it.

Link: https://lkml.kernel.org/r/20210826121217.12885-1-colin.king@canonical.com
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

There are several test cases in the vm directory are still using exit 0
when they need to be skipped.  Use the kselftest framework to skip code
instead so it can help us to distinguish the return status.

Criterion to filter out what should be fixed in vm directory:
  grep -r "exit 0" -B1 | grep -i skip

This change might cause some false-positives if people are running these
test scripts directly and only checking their return codes, which will
change from 0 to 4.  However I think the impact should be small as most of
our scripts here are already using this skip code.  And there will be no
such issue if running them with the kselftest framework.

Link: https://lkml.kernel.org/r/20210823073433.37653-1-po-hsu.lin@canonical.com
Signed-off-by: Po-Hsu Lin <po-hsu.lin@canonical.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The memcg->event_list_lock is usually taken in the normal context but when
the userspace closes the corresponding eventfd, eventfd_release through
memcg_event_wake takes memcg->event_list_lock with interrupts disabled.
This is not an issue on its own but it creates a nested dependency from
eventfd_ctx->wqh.lock to memcg->event_list_lock.

Independently, for unrelated eventfd, eventfd_signal() can be called in
the irq context, thus making eventfd_ctx->wqh.lock an irq lock.  For
example, FPGA DFL driver, VHOST VPDA driver and couple of VFIO drivers.
This will force memcg->event_list_lock to be an irqsafe lock as well.

One way to break the nested dependency between eventfd_ctx->wqh.lock and
memcg->event_list_lock is to add an indirection.  However the simplest
solution would be to make memcg->event_list_lock irqsafe.  This is cgroup
v1 feature, is in maintenance and may get deprecated in near future.  So,
no need to add more code.

BTW this has been discussed previously [1] but there weren't irq users of
eventfd_signal() at the time.

[1] https://www.spinics.net/lists/cgroups/msg06248.html

Link: https://lkml.kernel.org/r/20210830172953.207257-1-shakeelb@google.com
Signed-off-by: Shakeel Butt <shakeelb@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Thomas and Vlastimil have noticed that the comment in drain_local_stock
doesn't quite make sense.  It talks about a synchronization with the
memory hotplug but there is no actual memory hotplug involvement here.  I
meant to talk about cpu hotplug here.  Fix that up and hopefuly make the
comment more helpful by referencing the cpu hotplug callback as well.

Link: https://lkml.kernel.org/r/YRDwOhVglJmY7ES5@dhcp22.suse.cz
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Add 'else' to save some atomic ops in obj_stock_flush_required() when
flush is already true.  No functional change intended here.

Link: https://lkml.kernel.org/r/20210807082835.61281-3-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Roman Gushchin <guro@fb.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Alex Shi <alexs@kernel.org>
Cc: Wei Yang <richard.weiyang@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Since commit 2d146aa3 ("mm: memcontrol: switch to rstat"), last user
of memcg_stat_item_in_bytes() is gone.  And since commit fa40d1ee


("mm: vmscan: memcontrol: remove mem_cgroup_select_victim_node()"), only
the declaration of mem_cgroup_select_victim_node() is remained here.
Remove them.

Link: https://lkml.kernel.org/r/20210807082835.61281-2-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Roman Gushchin <guro@fb.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Alex Shi <alexs@kernel.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Since commit c843966c ("mm: allow swappiness that prefers reclaiming
anon over the file workingset") has expended the swappiness value to make
swap to be preferred in some systems.  We should also change the memcg
swappiness restriction to allow memcg swap-preferred.

Link: https://lkml.kernel.org/r/d77469b90c45c49953ccbc51e54a1d465bc18f70.1627626255.git.baolin.wang@linux.alibaba.com
Fixes: c843966c

 ("mm: allow swappiness that prefers reclaiming anon over the file workingset")
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

set_active_memcg() uses in_interrupt() check to select proper storage for
cgroup: pointer on task struct or per-cpu pointer.

It isn't fully correct: obsoleted in_interrupt() includes tasks with
disabled BH.  It's better to use '!in_task()' instead.

Link: https://lkml.org/lkml/2021/7/26/487
Link: https://lkml.kernel.org/r/ed4448b0-4970-616f-7368-ef9dd3cb628d@virtuozzo.com
Fixes: 37d5985c

 ("mm: kmem: prepare remote memcg charging infra for interrupt contexts")
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Roman Gushchin <guro@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

We used to have per-cpu memcg and lruvec stats and the readers have to
traverse and sum the stats from each cpu.  This summing was racy and may
expose transient negative values.  So, an explicit check was added to
avoid such scenarios.  Now these stats are moved to rstat infrastructure
and are no more per-cpu, so we can remove the fixup for transient negative
values.

Link: https://lkml.kernel.org/r/20210728012243.3369123-1-shakeelb@google.com
Signed-off-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Roman Gushchin <guro@fb.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Each task can request own LDT and force the kernel to allocate up to 64Kb
memory per-mm.

There are legitimate workloads with hundreds of processes and there can be
hundreds of workloads running on large machines.  The unaccounted memory
can cause isolation issues between the workloads particularly on highly
utilized machines.

It makes sense to account for this objects to restrict the host's memory
consumption from inside the memcg-limited container.

Link: https://lkml.kernel.org/r/38010594-50fe-c06d-7cb0-d1f77ca422f3@virtuozzo.com
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Acked-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrei Vagin <avagin@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Yutian Yang <nglaive@gmail.com>
Cc: Zefan Li <lizefan.x@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

A program may create multiple interval timers using timer_create().  For
each timer the kernel preallocates a "queued real-time signal",
Consequently, the number of timers is limited by the RLIMIT_SIGPENDING
resource limit.  The allocated object is quite small, ~250 bytes, but even
the default signal limits allow to consume up to 100 megabytes per user.

It makes sense to account for them to limit the host's memory consumption
from inside the memcg-limited container.

Link: https://lkml.kernel.org/r/57795560-025c-267c-6b1a-dea852d95530@virtuozzo.com
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrei Vagin <avagin@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Yutian Yang <nglaive@gmail.com>
Cc: Zefan Li <lizefan.x@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

When a user send a signal to any another processes it forces the kernel to
allocate memory for 'struct sigqueue' objects.  The number of signals is
limited by RLIMIT_SIGPENDING resource limit, but even the default settings
allow each user to consume up to several megabytes of memory.

It makes sense to account for these allocations to restrict the host's
memory consumption from inside the memcg-limited container.

Link: https://lkml.kernel.org/r/e34e958c-e785-712e-a62a-2c7b66c646c7@virtuozzo.com
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrei Vagin <avagin@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Yutian Yang <nglaive@gmail.com>
Cc: Zefan Li <lizefan.x@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

When user creates IPC objects it forces kernel to allocate memory for
these long-living objects.

It makes sense to account them to restrict the host's memory consumption
from inside the memcg-limited container.

This patch enables accounting for IPC shared memory segments, messages
semaphores and semaphore's undo lists.

Link: https://lkml.kernel.org/r/d6507b06-4df6-78f8-6c54-3ae86e3b5339@virtuozzo.com
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrei Vagin <avagin@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "J. Bruce Fi...

Container admin can create new namespaces and force kernel to allocate up
to several pages of memory for the namespaces and its associated
structures.

Net and uts namespaces have enabled accounting for such allocations.  It
makes sense to account for rest ones to restrict the host's memory
consumption from inside the memcg-limited container.

Link: https://lkml.kernel.org/r/5525bcbf-533e-da27-79b7-158686c64e13@virtuozzo.com
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Acked-by: Serge Hallyn <serge@hallyn.com>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Acked-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrei Vagin <avagin@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc:...

fasync_struct is used by almost all character device drivers to set up the
fasync queue, and for regular files by the file lease code.  This
structure is quite small but long-living and it can be assigned for any
open file.

It makes sense to account for its allocations to restrict the host's
memory consumption from inside the memcg-limited container.

Link: https://lkml.kernel.org/r/1b408625-d71c-0b26-b0b6-9baf00f93e69@virtuozzo.com
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrei Vagin <avagin@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Yutian Yang <nglaive@gmail.com>
Cc: Zefan Li <lizefan.x@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

User can create file locks for each open file and force kernel to allocate
small but long-living objects per each open file.

It makes sense to account for these objects to limit the host's memory
consumption from inside the memcg-limited container.

Link: https://lkml.kernel.org/r/b009f4c7-f0ab-c0ec-8e83-918f47d677da@virtuozzo.com
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrei Vagin <avagin@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Yutian Yang <nglaive@gmail.com>
Cc: Zefan Li <lizefan.x@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

User can call select/poll system calls with a large number of assigned
file descriptors and force kernel to allocate up to several pages of
memory till end of these sleeping system calls.  We have here long-living
unaccounted per-task allocations.

It makes sense to account for these allocations to restrict the host's
memory consumption from inside the memcg-limited container.

Link: https://lkml.kernel.org/r/56e31cb5-6e1e-bdba-d7ca-be64b9842363@virtuozzo.com
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrei Vagin <avagin@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Yutian Yang <nglaive@gmail.com>
Cc: Zefan Li <lizefan.x@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Patch series "memcg accounting from OpenVZ", v7.

OpenVZ uses memory accounting 20+ years since v2.2.x linux kernels.
Initially we used our own accounting subsystem, then partially committed
it to upstream, and a few years ago switched to cgroups v1.  Now we're
rebasing again, revising our old patches and trying to push them upstream.

We try to protect the host system from any misuse of kernel memory
allocation triggered by untrusted users inside the containers.

Patch-set is addressed mostly to cgroups maintainers and cgroups@ mailing
list, though I would be very grateful for any comments from maintainersi
of affected subsystems or other people added in cc:

Compared to the upstream, we additionally account the following kernel objects:
- network devices and its Tx/Rx queues
- ipv4/v6 addresses and routing-related objects
- inet_bind_bucket cache objects
- VLAN group arrays
- ipv6/sit: ip_tunnel_prl
- scm_fp_list objects used by SCM_RIGHTS messages of Unix sockets
- nsproxy and namespace objects itself
- IPC objects: semaphores, message queues and share memory segments
- mounts
- pollfd and select bits arrays
- signals and posix timers
- file lock
- fasync_struct used by the file lease code and driver's fasync queues
- tty objects
- per-mm LDT

We have an incorrect/incomplete/obsoleted accounting for few other kernel
objects: sk_filter, af_packets, netlink and xt_counters for iptables.
They require rework and probably will be dropped at all.

Also we're going to add an accounting for nft, however it is not ready
yet.

We have not tested performance on upstream, however, our performance team
compares our current RHEL7-based production kernel and reports that they
are at least not worse as the according original RHEL7 kernel.

This patch (of 10):

The kernel allocates ~400 bytes of 'struct mount' for any new mount.
Creating a new mount namespace clones most of the parent mounts, and this
can be repeated many times.  Additionally, each mount allocates up to
PATH_MAX=4096 bytes for mnt->mnt_devname.

It makes sense to account for these allocations to restrict the host's
memory consumption from inside the memcg-limited container.

Link: https://lkml.kernel.org/r/045db11f-4a45-7c9b-2664-5b32c2b44943@virtuozzo.com
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Yutian Yang <nglaive@gmail.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrei Vagin <avagin@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Zefan Li <lizefan.x@bytedance.com>
Cc: Borislav Petkov <bp@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This patch adds accounting flags to fs_context and legacy_fs_context
allocation sites so that kernel could correctly charge these objects.

We have written a PoC to demonstrate the effect of the missing-charging
bugs.  The PoC takes around 1,200MB unaccounted memory, while it is
charged for only 362MB memory usage.  We evaluate the PoC on QEMU x86_64
v5.2.90 + Linux kernel v5.10.19 + Debian buster.  All the limitations
including ulimits and sysctl variables are set as default.  Specifically,
the hard NOFILE limit and nr_open in sysctl are both 1,048,576.

/*------------------------- POC code ----------------------------*/

#define _GNU_SOURCE
#include <sys/types.h>
#include <sys/file.h>
#include <time.h>
#include <sys/wait.h>
#include <stdint.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <signal.h>
#include <sched.h>
#include <fcntl.h>
#include <linux/mount.h>

#define errExit(msg)    do { perror(msg); exit(EXIT_FAILURE); \
                        } while (0)

#define STACK_SIZE (8 * 1024)
#ifndef __NR_fsopen
#define __NR_fsopen 430
#endif
static inline int fsopen(const char *fs_name, unsigned int flags)
{
        return syscall(__NR_fsopen, fs_name, flags);
}

static char thread_stack[512][STACK_SIZE];

int thread_fn(void* arg)
{
  for (int i = 0; i< 800000; ++i) {
    int fsfd = fsopen("nfs", FSOPEN_CLOEXEC);
    if (fsfd == -1) {
      errExit("fsopen");
    }
  }
  while(1);
  return 0;
}

int main(int argc, char *argv[]) {
  int thread_pid;
  for (int i = 0; i < 1; ++i) {
    thread_pid = clone(thread_fn, thread_stack[i] + STACK_SIZE, \
      SIGCHLD, NULL);
  }
  while(1);
  return 0;
}

/*-------------------------- end --------------------------------*/

Link: https://lkml.kernel.org/r/1626517201-24086-1-git-send-email-nglaive@gmail.com
Signed-off-by: Yutian Yang <nglaive@gmail.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: <shenwenbo@zju.edu.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

At the moment memcg stats are read in four contexts:

1. memcg stat user interfaces
2. dirty throttling
3. page fault
4. memory reclaim

Currently the kernel flushes the stats for first two cases.  Flushing the
stats for remaining two casese may have performance impact.  Always
flushing the memcg stats on the page fault code path may negatively
impacts the performance of the applications.  In addition flushing in the
memory reclaim code path, though treated as slowpath, can become the
source of contention for the global lock taken for stat flushing because
when system or memcg is under memory pressure, many tasks may enter the
reclaim path.

This patch uses following mechanisms to solve these challenges:

1. Periodically flush the stats from root memcg every 2 seconds.  This
   will time limit the out of sync stats.

2. Asynchronously flush the stats after fixed number of stat updates.
   In the worst case the stat can be out of sync by O(nr_cpus * BATCH) for
   2 seconds.

3. For avoiding thundering herd to flush the stats particularly from
   the memory reclaim context, introduce memcg local spinlock and let only
   one flusher active at a time.  This could have been done through
   cgroup_rstat_lock lock but that lock is used by other subsystem and for
   userspace reading memcg stats.  So, it is better to keep flushers
   introduced by this patch decoupled from cgroup_rstat_lock.  However we
   would have to use irqsafe version of rstat flush but that is fine as
   this code path will be flushing for whole tree and do the work for
   everyone.  No one will be waiting for that worker.

[shakeelb@google.com: fix sleep-in-wrong context bug]
  Link: https://lkml.kernel.org/r/20210716212137.1391164-2-shakeelb@google.com

Link: https://lkml.kernel.org/r/20210714013948.270662-2-shakeelb@google.com
Signed-off-by: Shakeel Butt <shakeelb@google.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michal Koutný <mkoutny@suse.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The commit 2d146aa3 ("mm: memcontrol: switch to rstat") switched memcg
stats to rstat infrastructure but skipped the conversion of the lruvec
stats as such stats are read in the performance critical code paths and
flushing stats may have impacted the performances of the applications.
This patch converts the lruvec stats to rstat and later patches add
mechanisms to keep the performance impact to minimum.

The rstat conversion comes with the price i.e.  memory cost.  Effectively
this patch reverts the savings done by the commit f3344adf

 ("mm:
memcontrol: optimize per-lruvec stats counter memory usage").  However
this cost is justified due to negative impact of the inaccurate lruvec
stats on many heuristics.  One such case is reported in [1].

The memory reclaim code is filled with plethora of heuristics and many of
those heuristics reads the lruvec stats.  So, inaccurate stats can make
such heuristics ineffective.  [1] reports the impact of inaccurate lruvec
stats on the "cache trim mode" heuristic.  Inaccurate lruvec stats can
impact the deactivation and aging anon heuristics as well.

[1] https://lore.kernel.org/linux-mm/20210311004449.1170308-1-ying.huang@intel.com/

Link: https://lkml.kernel.org/r/20210716212137.1391164-1-shakeelb@google.com
Link: https://lkml.kernel.org/r/20210714013948.270662-1-shakeelb@google.com
Signed-off-by: Shakeel Butt <shakeelb@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Commit 5d097056 ("kmemcg: account certain kmem allocations to memcg")
enabled memcg accounting for pids allocated from init_pid_ns.pid_cachep,
but forgot to adjust the setting for nested pid namespaces.  As a result,
pid memory is not accounted exactly where it is really needed, inside
memcg-limited containers with their own pid namespaces.

Pid was one the first kernel objects enabled for memcg accounting.
init_pid_ns.pid_cachep marked by SLAB_ACCOUNT and we can expect that any
new pids in the system are memcg-accounted.

Though recently I've noticed that it is wrong.  nested pid namespaces
creates own slab caches for pid objects, nested pids have increased size
because contain id both for all parent and for own pid namespaces.  The
problem is that these slab caches are _NOT_ marked by SLAB_ACCOUNT, as a
result any pids allocated in nested pid namespaces are not
memcg-accounted.

Pid struct in nested pid namespace consumes up to 500 bytes memory, 100000
such objects gives us up to ~50Mb unaccounted memory, this allow container
to exceed assigned memcg limits.

Link: https://lkml.kernel.org/r/8b6de616-fd1a-02c6-cbdb-976ecdcfa604@virtuozzo.com
Fixes: 5d097056

 ("kmemcg: account certain kmem allocations to memcg")
Cc: stable@vger.kernel.org
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Reviewed-by: Michal Koutný <mkoutny@suse.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Acked-by: Roman Gushchin <guro@fb.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Inline mem_cgroup_try_charge_swap, mem_cgroup_uncharge_swap and
cgroup_throttle_swaprate functions to perform mem_cgroup_disabled static
key check inline before calling the main body of the function.  This
minimizes the memcg overhead in the pagefault and exit_mmap paths when
memcgs are disabled using cgroup_disable=memory command-line option.  This
change results in ~1% overhead reduction when running PFT test [1]
comparing {CONFIG_MEMCG=n} against {CONFIG_MEMCG=y, cgroup_disable=memory}
configuration on an 8-core ARM64 Android device.

[1] https://lkml.org/lkml/2006/8/29/294 also used in mmtests suite

Link: https://lkml.kernel.org/r/20210713010934.299876-3-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Alex Shi <alexs@kernel.org>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Inline mem_cgroup_{charge/uncharge} and mem_cgroup_uncharge_list functions
functions to perform mem_cgroup_disabled static key check inline before
calling the main body of the function.  This minimizes the memcg overhead
in the pagefault and exit_mmap paths when memcgs are disabled using
cgroup_disable=memory command-line option.

This change results in ~0.4% overhead reduction when running PFT test [1]
comparing {CONFIG_MEMCG=n} against {CONFIG_MEMCG=y, cgroup_disable=memory}
configuration on an 8-core ARM64 Android device.

[1] https://lkml.org/lkml/2006/8/29/294 also used in mmtests suite

Link: https://lkml.kernel.org/r/20210713010934.299876-2-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Alex Shi <alexs@kernel.org>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Add mem_cgroup_disabled check in vmpressure, mem_cgroup_uncharge_swap and
cgroup_throttle_swaprate functions.  This minimizes the memcg overhead in
the pagefault and exit_mmap paths when memcgs are disabled using
cgroup_disable=memory command-line option.

This change results in ~2.1% overhead reduction when running PFT test [1]
comparing {CONFIG_MEMCG=n, CONFIG_MEMCG_SWAP=n} against {CONFIG_MEMCG=y,
CONFIG_MEMCG_SWAP=y, cgroup_disable=memory} configuration on an 8-core
ARM64 Android device.

[1] https://lkml.org/lkml/2006/8/29/294 also used in mmtests suite

Link: https://lkml.kernel.org/r/20210713010934.299876-1-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Alex Shi <alexs@kernel.org>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/gpu/drm/i915/gem/i915_gem_shmem.c contains a shmem_writeback()
which calls shmem_writepage() from a shrinker: that usually works well
enough; but if /sys/kernel/mm/transparent_hugepage/shmem_enabled has been
set to "always" (intended to be usable) or "force" (forces huge everywhere
for easy testing), shmem_writepage() is surprised to be called with a huge
page, and crashes on the VM_BUG_ON_PAGE(PageCompound) (I did not find out
where the crash happens when CONFIG_DEBUG_VM is off).

LRU page reclaim always splits the shmem huge page first: I'd prefer not
to demand that of i915, so check and split compound in shmem_writepage().

Patch history: when first sent last year
http://lkml.kernel.org/r/alpine.LSU.2.11.2008301401390.5954@eggly.anvils
https://lore.kernel.org/linux-mm/20200919042009.bomzxmrg7%25akpm@linux-foundation.org/
Matthew Wilcox noticed that tail pages were wrongly left clean.  This
version brackets the split with Set and Clear PageDirty as he suggested:
which works very well, even if it falls short of our aspirations.  And
recently I realized that the crash is not limited to the testing option
"force", but affects "always" too: which is more important to fix.

Link: https://lkml.kernel.org/r/bac6158c-8b3d-4dca-cffc-4982f58d9794@google.com
Fixes: 2d6692e6

 ("drm/i915: Start writeback from the shrinker")
Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Yang Shi <shy828301@gmail.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4.18 commit 89fdcd26

 ("mm: shmem: make stat.st_blksize return huge
page size if THP is on") added is_huge_enabled() to decide st_blksize: if
hugeness is to be defined per file, that will need to be replaced by
shmem_is_huge().

This does give a different answer (No) for small files on a
"huge=within_size" mount: but that can be considered a minor bugfix.  And
a different answer (No) for default files on a "huge=advise" mount: I'm
reluctant to complicate it, just to reproduce the same debatable answer as
before.

Link: https://lkml.kernel.org/r/af7fb3f9-4415-9e8e-fdac-b1a5253ad21@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Extend shmem_huge_enabled(vma) to shmem_is_huge(vma, inode, index), so
that a consistent set of checks can be applied, even when the inode is
accessed through read/write syscalls (with NULL vma) instead of mmaps (the
index argument is seldom of interest, but required by mount option
"huge=within_size").  Clean up and rearrange the checks a little.

This then replaces the checks which shmem_fault() and shmem_getpage_gfp()
were making, and eliminates the SGP_HUGE and SGP_NOHUGE modes.

Replace a couple of 0s by explicit SHMEM_HUGE_NEVERs; and replace the
obscure !shmem_mapping() symlink check by explicit S_ISLNK() - nothing
else needs that symlink check, so leave it there in shmem_getpage_gfp().

Link: https://lkml.kernel.org/r/23a77889-2ddc-b030-75cd-44ca27fd4d1@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

khugepaged's collapse_file() currently uses SGP_NOHUGE to tell
shmem_getpage() not to try allocating a huge page, in the very unlikely
event that a racing hole-punch removes the swapped or fallocated page as
soon as i_pages lock is dropped.

We want to consolidate shmem's huge decisions, removing SGP_HUGE and
SGP_NOHUGE; but cannot quite persuade ourselves that it's okay to regress
the protection in this case - Yang Shi points out that the huge page would
remain indefinitely, charged to root instead of the intended memcg.

collapse_file() should not even allocate a small page in this case: why
proceed if someone is punching a hole?  SGP_READ is almost the right flag
here, except that it optimizes away from a fallocated page, with NULL to
tell caller to fill with zeroes (like a hole); whereas collapse_file()'s
sequence relies on using a cache page.  Add SGP_NOALLOC just for this.

There are too many consecutive "if (page"s there in shmem_getpage_gfp():
group it better; and fix the outdated "bring it back from swap" comment.

Link: https://lkml.kernel.org/r/1355343b-acf-4653-ef79-6aee40214ac5@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

shmem_huge_enabled() is about to be enhanced into shmem_is_huge(), so that
it can be used more widely throughout: before making functional changes,
shift it to its final position (to avoid forward declaration).

Link: https://lkml.kernel.org/r/16fec7b7-5c84-415a-8586-69d8bf6a6685@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

5.14 commit e6be37b2

 ("mm/huge_memory.c: add missing read-only THP
checking in transparent_hugepage_enabled()") added transhuge_vma_enabled()
as a wrapper for two very different checks (one check is whether the app
has marked its address range not to use THPs, the other check is whether
the app is running in a hierarchy that has been marked never to use THPs).
shmem_huge_enabled() prefers to show those two checks explicitly, as
before.

Link: https://lkml.kernel.org/r/45e5338-18d-c6f9-c17e-34f510bc1728@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

There's a block of code in shmem_setattr() to add the inode to
shmem_unused_huge_shrink()'s shrinklist when lowering i_size: it dates
from before 5.7 changed truncation to do split_huge_page() for itself, and
should have been removed at that time.

I am over-stating that: split_huge_page() can fail (notably if there's an
extra reference to the page at that time), so there might be value in
retrying.  But there were already retries as truncation worked through the
tails, and this addition risks repeating unsuccessful retries
indefinitely: I'd rather remove it now, and work on reducing the chance of
split_huge_page() failures separately, if we need to.

Link: https://lkml.kernel.org/r/b73b3492-8822-18f9-83e2-938528cdde94@google.com
Fixes: 71725ed1

 ("mm: huge tmpfs: try to split_huge_page() when punching hole")
Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

A successful shmem_fallocate() guarantees that the extent has been
reserved, even beyond i_size when the FALLOC_FL_KEEP_SIZE flag was used.
But that guarantee is broken by shmem_unused_huge_shrink()'s attempts to
split huge pages and free their excess beyond i_size; and by other uses of
split_huge_page() near i_size.

It's sad to add a shmem inode field just for this, but I did not find a
better way to keep the guarantee.  A flag to say KEEP_SIZE has been used
would be cheaper, but I'm averse to unclearable flags.  The fallocend
field is not perfect either (many disjoint ranges might be fallocated),
but good enough; and gains another use later on.

Link: https://lkml.kernel.org/r/ca9a146-3a59-6cd3-7f28-e9a044bb1052@google.com
Fixes: 779750d2

 ("shmem: split huge pages beyond i_size under memory pressure")
Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Patch series "huge tmpfs: shmem_is_huge() fixes and cleanups".

A series of huge tmpfs fixes and cleanups.

This patch (of 9):

shmem_fallocate() goes to a lot of trouble to leave its newly allocated
pages !Uptodate, partly to identify and undo them on failure, partly to
leave the overhead of clearing them until later.  But the huge page case
did not skip to the end of the extent, walked through the tail pages one
by one, and appeared to work just fine: but in doing so, cleared and
Uptodated the huge page, so there was no way to undo it on failure.

And by setting Uptodate too soon, it messed up both its nr_falloced and
nr_unswapped counts, so that the intended "time to give up" heuristic did
not work at all.

Now advance immediately to the end of the huge extent, with a comment on
why this is more than just an optimization.  But although this speeds up
huge tmpfs fallocation, it does leave the clearing until first use, and
some users may have come to appreciate slow fallocate but fast first use:
if they complain, then we can consider adding a pass to clear at the end.

Link: https://lkml.kernel.org/r/da632211-8e3e-6b1-aee-ab24734429a0@google.com
Link: https://lkml.kernel.org/r/16201bd2-70e-37e2-e89b-5f929430da@google.com
Fixes: 800d8c63

 ("shmem: add huge pages support")
Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

It's bad to extern swap_info[] in .c.  Include corresponding header file
instead.

Link: https://lkml.kernel.org/r/20210812120350.49801-5-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The forward declaration for shmem_should_replace_page() and
shmem_replace_page() is unnecessary.  Remove them.

Link: https://lkml.kernel.org/r/20210812120350.49801-4-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mfill_atomic_install_pte() is introduced to install pte and update mmu
cache since commit bf6ebd97aba0 ("userfaultfd/shmem: modify
shmem_mfill_atomic_pte to use install_pte()").  So we should remove
tlbflush.h as update_mmu_cache() is not called here now.

Link: https://lkml.kernel.org/r/20210812120350.49801-3-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>