Eric Biggers says:
====================
Patches 1-2 fix the memory leaks that syzbot has reported in net/llc:
memory leak in llc_ui_create (2)
memory leak in llc_ui_sendmsg
memory leak in llc_conn_ac_send_sabme_cmd_p_set_x
Patches 3-4 fix related bugs that I noticed while reading this code.
Note: I've tested that this fixes the syzbot bugs, but otherwise I don't
know of any way to test this code.
====================
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
If llc_conn_state_process() sees that llc_conn_service() put the skb on
a list, it will drop one fewer references to it. This is wrong because
the current behavior is that llc_conn_service() never consumes a
reference to the skb.
The code also makes the number of skb references being dropped
conditional on which of ind_prim and cfm_prim are nonzero, yet neither
of these affects how many references are *acquired*. So there is extra
code that tries to fix this up by sometimes taking another reference.
Remove the unnecessary/broken refcounting logic and instead just add an
skb_get() before the only two places where an extra reference is
actually consumed.
Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
All callers of llc_conn_state_process() except llc_build_and_send_pkt()
(via llc_ui_sendmsg() -> llc_ui_send_data()) assume that it always
consumes a reference to the skb. Fix this caller to do the same.
Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
syzbot reported:
BUG: memory leak
unreferenced object 0xffff888116270800 (size 224):
comm "syz-executor641", pid 7047, jiffies 4294947360 (age 13.860s)
hex dump (first 32 bytes):
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00 20 e1 2a 81 88 ff ff 00 40 3d 2a 81 88 ff ff . .*.....@=*....
backtrace:
[<000000004d41b4cc>] kmemleak_alloc_recursive include/linux/kmemleak.h:55 [inline]
[<000000004d41b4cc>] slab_post_alloc_hook mm/slab.h:439 [inline]
[<000000004d41b4cc>] slab_alloc_node mm/slab.c:3269 [inline]
[<000000004d41b4cc>] kmem_cache_alloc_node+0x153/0x2a0 mm/slab.c:3579
[<00000000506a5965>] __alloc_skb+0x6e/0x210 net/core/skbuff.c:198
[<000000001ba5a161>] alloc_skb include/linux/skbuff.h:1058 [inline]
[<000000001ba5a161>] alloc_skb_with_frags+0x5f/0x250 net/core/skbuff.c:5327
[<0000000047d9c78b>] sock_alloc_send_pskb+0x269/0x2a0 net/core/sock.c:2225
[<000000003828fe54>] sock_alloc_send_skb+0x32/0x40 net/core/sock.c:2242
[<00000000e34d94f9>] llc_ui_sendmsg+0x10a/0x540 net/llc/af_llc.c:933
[<00000000de2de3fb>] sock_sendmsg_nosec net/socket.c:652 [inline]
[<00000000de2de3fb>] sock_sendmsg+0x54/0x70 net/socket.c:671
[<000000008fe16e7a>] __sys_sendto+0x148/0x1f0 net/socket.c:1964
[...]
The bug is that llc_sap_state_process() always takes an extra reference
to the skb, but sometimes neither llc_sap_next_state() nor
llc_sap_state_process() itself drops this reference.
Fix it by changing llc_sap_next_state() to never consume a reference to
the skb, rather than sometimes do so and sometimes not. Then remove the
extra skb_get() and kfree_skb() from llc_sap_state_process().
Reported-by: syzbot+6bf095f9becf5efef645@syzkaller.appspotmail.com
Reported-by: syzbot+31c16aa4202dace3812e@syzkaller.appspotmail.com
Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Add pointer to my git tree to MAINTAINERS. I'd like to maintain
linux-leds for-next branch for 5.5.
Signed-off-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>
Update the leds.h structure documentation to define the
correct arguments.
Signed-off-by: Dan Murphy <dmurphy@ti.com>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>
drivers/md/dm-clone-target.c:594:34: warning:
symbol '__hash_find' was not declared. Should it be static?
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Pull GPIO fixes from Linus Walleij:
- don't clear FLAG_IS_OUT when emulating open drain/source in gpiolib
- fix up the usage of nonexclusive GPIO descriptors from device trees
- fix the incorrect IEC offset when toggling trigger edge in the
Spreadtrum driver
- use the correct unit for debounce settings in the MAX77620 driver
* tag 'gpio-v5.4-2' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-gpio:
gpio: max77620: Use correct unit for debounce times
gpio: eic: sprd: Fix the incorrect EIC offset when toggling
gpio: fix getting nonexclusive gpiods from DT
gpiolib: don't clear FLAG_IS_OUT when emulating open-drain/open-source
Pull selinuxfix from Paul Moore:
"One patch to ensure we don't copy bad memory up into userspace"
* tag 'selinux-pr-20191007' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux:
selinux: fix context string corruption in convert_context()
Pull Kselftest fixes from Shuah Khan:
"Fixes for existing tests and the framework.
Cristian Marussi's patches add the ability to skip targets (tests) and
exclude tests that didn't build from run-list. These patches improve
the Kselftest results. Ability to skip targets helps avoid running
tests that aren't supported in certain environments. As an example,
bpf tests from mainline aren't supported on stable kernels and have
dependency on bleeding edge llvm. Being able to skip bpf on systems
that can't meet this llvm dependency will be helpful.
Kselftest can be built and installed from the main Makefile. This
change help simplify Kselftest use-cases which addresses request from
users.
Kees Cook added per test timeout support to limit individual test
run-time"
* tag 'linux-kselftest-5.4-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest:
selftests: watchdog: Add command line option to show watchdog_info
selftests: watchdog: Validate optional file argument
selftests/kselftest/runner.sh: Add 45 second timeout per test
kselftest: exclude failed TARGETS from runlist
kselftest: add capability to skip chosen TARGETS
selftests: Add kselftest-all and kselftest-install targets
The driver does not use input subsystem so we do not need this header,
and it is being removed, so stop pulling it in.
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
We discussed a better location for this file, and agreed that
core-api/ is a good fit. Rename it to symbol-namespaces.rst
for disambiguation, and also add it to index.rst and MAINTAINERS.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Matthias Maennich <maennich@google.com>
Signed-off-by: Jessica Yu <jeyu@kernel.org>
The clkctrl code searches for the parent clockdomain based on the name
of the CM provider node. The introduction of SGX node for omap5 made
the node name for the gpu_cm to be clock-controller. There is no
clockdomain named like this, so the lookup fails. Fix by changing
the node name properly.
Fixes: 394534cb07 ("ARM: dts: Configure sgx for omap5")
Signed-off-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
There are no return value checking when using kzalloc() and kcalloc() for
memory allocation. so add it.
Signed-off-by: Yunfeng Ye <yeyunfeng@huawei.com>
Signed-off-by: Will Deacon <will@kernel.org>
Allow the user to select the workaround for TX2-219, and update
the silicon-errata.rst file to reflect this.
Cc: <stable@vger.kernel.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
As a PRFM instruction racing against a TTBR update can have undesirable
effects on TX2, NOP-out such PRFM on cores that are affected by
the TX2-219 erratum.
Cc: <stable@vger.kernel.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
It appears that the only case where we need to apply the TX2_219_TVM
mitigation is when the core is in SMT mode. So let's condition the
enabling on detecting a CPU whose MPIDR_EL1.Aff0 is non-zero.
Cc: <stable@vger.kernel.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
In order to workaround the TX2-219 erratum, it is necessary to trap
TTBRx_EL1 accesses to EL2. This is done by setting HCR_EL2.TVM on
guest entry, which has the side effect of trapping all the other
VM-related sysregs as well.
To minimize the overhead, a fast path is used so that we don't
have to go all the way back to the main sysreg handling code,
unless the rest of the hypervisor expects to see these accesses.
Cc: <stable@vger.kernel.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
GCC throws warning message as below:
‘clone_src_i_size’ may be used uninitialized in this function
[-Wmaybe-uninitialized]
#define IS_ALIGNED(x, a) (((x) & ((typeof(x))(a) - 1)) == 0)
^
fs/btrfs/send.c:5088:6: note: ‘clone_src_i_size’ was declared here
u64 clone_src_i_size;
^
The clone_src_i_size is only used as call-by-reference
in a call to get_inode_info().
Silence the warning by initializing clone_src_i_size to 0.
Note that the warning is a false positive and reported by older versions
of GCC (eg. 7.x) but not eg 9.x. As there have been numerous people, the
patch is applied. Setting clone_src_i_size to 0 does not otherwise make
sense and would not do any action in case the code changes in the future.
Signed-off-by: Austin Kim <austindh.kim@gmail.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ add note ]
Signed-off-by: David Sterba <dsterba@suse.com>
Any changes interesting to tasks waiting in io_cqring_wait() are
commited with io_cqring_ev_posted(). However, io_ring_drop_ctx_refs()
also tries to do that but with no reason, that means spurious wakeups
every io_free_req() and io_uring_enter().
Just use percpu_ref_put() instead.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
A parent device can have child devices that it adds when it probes. But
this probing of the parent device can happen way after kernel init is done
-- for example, when the parent device's driver is loaded as a module.
In such cases, if the child devices depend on a supplier in the system, we
need to make sure the supplier gets the sync_state() callback only after
these child devices are added and probed.
To achieve this, when creating device links for a device by looking at its
DT node, don't just look at DT references at the top node level. Look at DT
references in all the descendant nodes too and create device links from the
ancestor device to all these supplier devices.
This way, when the parent device probes and adds child devices, the child
devices can then create their own device links to the suppliers and further
delay the supplier's sync_state() callback to after the child devices are
probed.
Example:
In this illustration, -> denotes DT references and indentation
represents child status.
Device node A
Device node B -> D
Device node C -> B, D
Device node D
Assume all these devices have their drivers loaded as modules.
Without this patch, this is the sequence of events:
1. D is added.
2. A is added.
3. Device D probes.
4. Device D gets its sync_state() callback.
5. Device B and C might malfunction because their resources got
altered/turned off before they can make active requests for them.
With this patch, this is the sequence of events:
1. D is added.
2. A is added and creates device links to D.
3. Device link from A to B is not added because A is a parent of B.
4. Device D probes.
5. Device D does not get it's sync_state() callback because consumer A
hasn't probed yet.
5. Device A probes.
5. a. Devices B and C are added.
5. b. Device links from B and C to D are added.
5. c. Device A's probe completes.
6. Device D does not get it's sync_state() callback because consumer A
has probed but consumers B and C haven't probed yet.
7. Device B and C probe.
8. Device D gets it's sync_state() callback because all its consumers
have probed.
9. None of the devices malfunction.
Signed-off-by: Saravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20190904211126.47518-7-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry-picked from commit d4387cd117https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core.git driver-core-next)
Fixes: 141703324
Change-Id: I38186d6cc4671bd8747dae8c440b09717a487088
When all the top level devices are populated from DT during kernel
init, the supplier devices could be added and probed before the
consumer devices are added and linked to the suppliers. To avoid the
sync_state() callback from being called prematurely, pause the
sync_state() callbacks before populating the devices and resume them
at late_initcall_sync().
Similarly, when children devices are populated from a module using
of_platform_populate(), there could be supplier-consumer dependencies
between the children devices that are populated. To avoid the same
problem with sync_state() being called prematurely, pause and resume
sync_state() callbacks across of_platform_populate().
Signed-off-by: Saravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20190904211126.47518-6-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry-picked from commit 5e6669387ehttps://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core.git driver-core-next)
Bug: 141703324
Change-Id: Ia43ebbc9071d4d6a59b347ccae99fcf0ab192269
This sync_state driver/bus callback is called once all the consumers
of a supplier have probed successfully.
This allows the supplier device's driver/bus to sync the supplier
device's state to the software state with the guarantee that all the
consumers are actively managing the resources provided by the supplier
device.
To maintain backwards compatibility and ease transition from existing
frameworks and resource cleanup schemes, late_initcall_sync is the
earliest when the sync_state callback might be called.
There is no upper bound on the time by which the sync_state callback
has to be called. This is because if a consumer device never probes,
the supplier has to maintain its resources in the state left by the
bootloader. For example, if the bootloader leaves the display
backlight at a fixed voltage and the backlight driver is never probed,
you don't want the backlight to ever be turned off after boot up.
Also, when multiple devices are added after kernel init, some
suppliers could be added before their consumer devices get added. In
these instances, the supplier devices could get their sync_state
callback called right after they probe because the consumers devices
haven't had a chance to create device links to the suppliers.
To handle this correctly, this change also provides APIs to
pause/resume sync state callbacks so that when multiple devices are
added, their sync_state callback evaluation can be postponed to happen
after all of them are added.
kbuild test robot reported missing documentation for device.state_synced
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Saravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20190904211126.47518-5-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry-picked from commit fc5a251d0fhttps://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core.git driver-core-next)
Bug: 141703324
Change-Id: I3e0a483c76d6ae3e5fe5aa6b3df65d0417c65ebb
Add device links after the devices are created (but before they are
probed) by looking at common DT bindings like clocks and
interconnects.
Automatically adding device links for functional dependencies at the
framework level provides the following benefits:
- Optimizes device probe order and avoids the useless work of
attempting probes of devices that will not probe successfully
(because their suppliers aren't present or haven't probed yet).
For example, in a commonly available mobile SoC, registering just
one consumer device's driver at an initcall level earlier than the
supplier device's driver causes 11 failed probe attempts before the
consumer device probes successfully. This was with a kernel with all
the drivers statically compiled in. This problem gets a lot worse if
all the drivers are loaded as modules without direct symbol
dependencies.
- Supplier devices like clock providers, interconnect providers, etc
need to keep the resources they provide active and at a particular
state(s) during boot up even if their current set of consumers don't
request the resource to be active. This is because the rest of the
consumers might not have probed yet and turning off the resource
before all the consumers have probed could lead to a hang or
undesired user experience.
Some frameworks (Eg: regulator) handle this today by turning off
"unused" resources at late_initcall_sync and hoping all the devices
have probed by then. This is not a valid assumption for systems with
loadable modules. Other frameworks (Eg: clock) just don't handle
this due to the lack of a clear signal for when they can turn off
resources. This leads to downstream hacks to handle cases like this
that can easily be solved in the upstream kernel.
By linking devices before they are probed, we give suppliers a clear
count of the number of dependent consumers. Once all of the
consumers are active, the suppliers can turn off the unused
resources without making assumptions about the number of consumers.
By default we just add device-links to track "driver presence" (probe
succeeded) of the supplier device. If any other functionality provided
by device-links are needed, it is left to the consumer/supplier
devices to change the link when they probe.
kbuild test robot reported clang error about missing const
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Saravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20190904211126.47518-4-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry-picked from commit a3e1d1a7f5https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core.git driver-core-next)
Bug: 141703324
Change-Id: I54a2dc3c4e91e418bcf1895c16bb8658dcfe1bee
The firmware corresponding to a device (dev.fwnode) might be able to
provide functional dependency information between a device and its
supplier and consumer devices. Tracking this functional dependency
allows optimizing device probe order and informing a supplier when all
its consumers have probed (and thereby actively managing their
resources).
The existing device links feature allows tracking and using
supplier-consumer relationships. So, this patch adds the add_links()
fwnode callback to allow firmware to create device links for each
device as the device is added.
However, when consumer devices are added, they might not have a supplier
device to link to despite needing mandatory resources/functionality from
one or more suppliers. A waiting_for_suppliers list is created to track
such consumers and retry linking them when new devices get added.
Signed-off-by: Saravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20190904211126.47518-3-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry-picked from commit e2ae9bcc4ahttps://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core.git driver-core-next)
Bug: 141703324
Change-Id: I97ffa57fa71588bf198e78d8b5a313b860b17bf5
Merge misc fixes from Andrew Morton:
"The usual shower of hotfixes.
Chris's memcg patches aren't actually fixes - they're mature but a few
niggling review issues were late to arrive.
The ocfs2 fixes are quite old - those took some time to get reviewer
attention.
Subsystems affected by this patch series: ocfs2, hotfixes, mm/memcg,
mm/slab-generic"
* emailed patches from Andrew Morton <akpm@linux-foundation.org>:
mm, sl[aou]b: guarantee natural alignment for kmalloc(power-of-two)
mm, sl[ou]b: improve memory accounting
mm, memcg: make scan aggression always exclude protection
mm, memcg: make memory.emin the baseline for utilisation determination
mm, memcg: proportional memory.{low,min} reclaim
mm/vmpressure.c: fix a signedness bug in vmpressure_register_event()
mm/page_alloc.c: fix a crash in free_pages_prepare()
mm/z3fold.c: claim page in the beginning of free
kernel/sysctl.c: do not override max_threads provided by userspace
memcg: only record foreign writebacks with dirty pages when memcg is not disabled
mm: fix -Wmissing-prototypes warnings
writeback: fix use-after-free in finish_writeback_work()
mm/memremap: drop unused SECTION_SIZE and SECTION_MASK
panic: ensure preemption is disabled during panic()
fs: ocfs2: fix a possible null-pointer dereference in ocfs2_info_scan_inode_alloc()
fs: ocfs2: fix a possible null-pointer dereference in ocfs2_write_end_nolock()
fs: ocfs2: fix possible null-pointer dereferences in ocfs2_xa_prepare_entry()
ocfs2: clear zero in unaligned direct IO
In most configurations, kmalloc() happens to return naturally aligned
(i.e. aligned to the block size itself) blocks for power of two sizes.
That means some kmalloc() users might unknowingly rely on that
alignment, until stuff breaks when the kernel is built with e.g.
CONFIG_SLUB_DEBUG or CONFIG_SLOB, and blocks stop being aligned. Then
developers have to devise workaround such as own kmem caches with
specified alignment [1], which is not always practical, as recently
evidenced in [2].
The topic has been discussed at LSF/MM 2019 [3]. Adding a
'kmalloc_aligned()' variant would not help with code unknowingly relying
on the implicit alignment. For slab implementations it would either
require creating more kmalloc caches, or allocate a larger size and only
give back part of it. That would be wasteful, especially with a generic
alignment parameter (in contrast with a fixed alignment to size).
Ideally we should provide to mm users what they need without difficult
workarounds or own reimplementations, so let's make the kmalloc()
alignment to size explicitly guaranteed for power-of-two sizes under all
configurations. What this means for the three available allocators?
* SLAB object layout happens to be mostly unchanged by the patch. The
implicitly provided alignment could be compromised with
CONFIG_DEBUG_SLAB due to redzoning, however SLAB disables redzoning for
caches with alignment larger than unsigned long long. Practically on at
least x86 this includes kmalloc caches as they use cache line alignment,
which is larger than that. Still, this patch ensures alignment on all
arches and cache sizes.
* SLUB layout is also unchanged unless redzoning is enabled through
CONFIG_SLUB_DEBUG and boot parameter for the particular kmalloc cache.
With this patch, explicit alignment is guaranteed with redzoning as
well. This will result in more memory being wasted, but that should be
acceptable in a debugging scenario.
* SLOB has no implicit alignment so this patch adds it explicitly for
kmalloc(). The potential downside is increased fragmentation. While
pathological allocation scenarios are certainly possible, in my testing,
after booting a x86_64 kernel+userspace with virtme, around 16MB memory
was consumed by slab pages both before and after the patch, with
difference in the noise.
[1] https://lore.kernel.org/linux-btrfs/c3157c8e8e0e7588312b40c853f65c02fe6c957a.1566399731.git.christophe.leroy@c-s.fr/
[2] https://lore.kernel.org/linux-fsdevel/20190225040904.5557-1-ming.lei@redhat.com/
[3] https://lwn.net/Articles/787740/
[akpm@linux-foundation.org: documentation fixlet, per Matthew]
Link: http://lkml.kernel.org/r/20190826111627.7505-3-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Christoph Hellwig <hch@lst.de>
Cc: David Sterba <dsterba@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: "Darrick J . Wong" <darrick.wong@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "guarantee natural alignment for kmalloc()", v2.
This patch (of 2):
SLOB currently doesn't account its pages at all, so in /proc/meminfo the
Slab field shows zero. Modifying a counter on page allocation and
freeing should be acceptable even for the small system scenarios SLOB is
intended for. Since reclaimable caches are not separated in SLOB,
account everything as unreclaimable.
SLUB currently doesn't account kmalloc() and kmalloc_node() allocations
larger than order-1 page, that are passed directly to the page
allocator. As they also don't appear in /proc/slabinfo, it might look
like a memory leak. For consistency, account them as well. (SLAB
doesn't actually use page allocator directly, so no change there).
Ideally SLOB and SLUB would be handled in separate patches, but due to
the shared kmalloc_order() function and different kfree()
implementations, it's easier to patch both at once to prevent
inconsistencies.
Link: http://lkml.kernel.org/r/20190826111627.7505-2-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: "Darrick J . Wong" <darrick.wong@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patch is an incremental improvement on the existing
memory.{low,min} relative reclaim work to base its scan pressure
calculations on how much protection is available compared to the current
usage, rather than how much the current usage is over some protection
threshold.
This change doesn't change the experience for the user in the normal
case too much. One benefit is that it replaces the (somewhat arbitrary)
100% cutoff with an indefinite slope, which makes it easier to ballpark
a memory.low value.
As well as this, the old methodology doesn't quite apply generically to
machines with varying amounts of physical memory. Let's say we have a
top level cgroup, workload.slice, and another top level cgroup,
system-management.slice. We want to roughly give 12G to
system-management.slice, so on a 32GB machine we set memory.low to 20GB
in workload.slice, and on a 64GB machine we set memory.low to 52GB.
However, because these are relative amounts to the total machine size,
while the amount of memory we want to generally be willing to yield to
system.slice is absolute (12G), we end up putting more pressure on
system.slice just because we have a larger machine and a larger workload
to fill it, which seems fairly unintuitive. With this new behaviour, we
don't end up with this unintended side effect.
Previously the way that memory.low protection works is that if you are
50% over a certain baseline, you get 50% of your normal scan pressure.
This is certainly better than the previous cliff-edge behaviour, but it
can be improved even further by always considering memory under the
currently enforced protection threshold to be out of bounds. This means
that we can set relatively low memory.low thresholds for variable or
bursty workloads while still getting a reasonable level of protection,
whereas with the previous version we may still trivially hit the 100%
clamp. The previous 100% clamp is also somewhat arbitrary, whereas this
one is more concretely based on the currently enforced protection
threshold, which is likely easier to reason about.
There is also a subtle issue with the way that proportional reclaim
worked previously -- it promotes having no memory.low, since it makes
pressure higher during low reclaim. This happens because we base our
scan pressure modulation on how far memory.current is between memory.min
and memory.low, but if memory.low is unset, we only use the overage
method. In most cromulent configurations, this then means that we end
up with *more* pressure than with no memory.low at all when we're in low
reclaim, which is not really very usable or expected.
With this patch, memory.low and memory.min affect reclaim pressure in a
more understandable and composable way. For example, from a user
standpoint, "protected" memory now remains untouchable from a reclaim
aggression standpoint, and users can also have more confidence that
bursty workloads will still receive some amount of guaranteed
protection.
Link: http://lkml.kernel.org/r/20190322160307.GA3316@chrisdown.name
Signed-off-by: Chris Down <chris@chrisdown.name>
Reviewed-by: Roman Gushchin <guro@fb.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Dennis Zhou <dennis@kernel.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>
Roman points out that when when we do the low reclaim pass, we scale the
reclaim pressure relative to position between 0 and the maximum
protection threshold.
However, if the maximum protection is based on memory.elow, and
memory.emin is above zero, this means we still may get binary behaviour
on second-pass low reclaim. This is because we scale starting at 0, not
starting at memory.emin, and since we don't scan at all below emin, we
end up with cliff behaviour.
This should be a fairly uncommon case since usually we don't go into the
second pass, but it makes sense to scale our low reclaim pressure
starting at emin.
You can test this by catting two large sparse files, one in a cgroup
with emin set to some moderate size compared to physical RAM, and
another cgroup without any emin. In both cgroups, set an elow larger
than 50% of physical RAM. The one with emin will have less page
scanning, as reclaim pressure is lower.
Rebase on top of and apply the same idea as what was applied to handle
cgroup_memory=disable properly for the original proportional patch
http://lkml.kernel.org/r/20190201045711.GA18302@chrisdown.name ("mm,
memcg: Handle cgroup_disable=memory when getting memcg protection").
Link: http://lkml.kernel.org/r/20190201051810.GA18895@chrisdown.name
Signed-off-by: Chris Down <chris@chrisdown.name>
Suggested-by: Roman Gushchin <guro@fb.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Dennis Zhou <dennis@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
cgroup v2 introduces two memory protection thresholds: memory.low
(best-effort) and memory.min (hard protection). While they generally do
what they say on the tin, there is a limitation in their implementation
that makes them difficult to use effectively: that cliff behaviour often
manifests when they become eligible for reclaim. This patch implements
more intuitive and usable behaviour, where we gradually mount more
reclaim pressure as cgroups further and further exceed their protection
thresholds.
This cliff edge behaviour happens because we only choose whether or not
to reclaim based on whether the memcg is within its protection limits
(see the use of mem_cgroup_protected in shrink_node), but we don't vary
our reclaim behaviour based on this information. Imagine the following
timeline, with the numbers the lruvec size in this zone:
1. memory.low=1000000, memory.current=999999. 0 pages may be scanned.
2. memory.low=1000000, memory.current=1000000. 0 pages may be scanned.
3. memory.low=1000000, memory.current=1000001. 1000001* pages may be
scanned. (?!)
* Of course, we won't usually scan all available pages in the zone even
without this patch because of scan control priority, over-reclaim
protection, etc. However, as shown by the tests at the end, these
techniques don't sufficiently throttle such an extreme change in input,
so cliff-like behaviour isn't really averted by their existence alone.
Here's an example of how this plays out in practice. At Facebook, we are
trying to protect various workloads from "system" software, like
configuration management tools, metric collectors, etc (see this[0] case
study). In order to find a suitable memory.low value, we start by
determining the expected memory range within which the workload will be
comfortable operating. This isn't an exact science -- memory usage deemed
"comfortable" will vary over time due to user behaviour, differences in
composition of work, etc, etc. As such we need to ballpark memory.low,
but doing this is currently problematic:
1. If we end up setting it too low for the workload, it won't have
*any* effect (see discussion above). The group will receive the full
weight of reclaim and won't have any priority while competing with the
less important system software, as if we had no memory.low configured
at all.
2. Because of this behaviour, we end up erring on the side of setting
it too high, such that the comfort range is reliably covered. However,
protected memory is completely unavailable to the rest of the system,
so we might cause undue memory and IO pressure there when we *know* we
have some elasticity in the workload.
3. Even if we get the value totally right, smack in the middle of the
comfort zone, we get extreme jumps between no pressure and full
pressure that cause unpredictable pressure spikes in the workload due
to the current binary reclaim behaviour.
With this patch, we can set it to our ballpark estimation without too much
worry. Any undesirable behaviour, such as too much or too little reclaim
pressure on the workload or system will be proportional to how far our
estimation is off. This means we can set memory.low much more
conservatively and thus waste less resources *without* the risk of the
workload falling off a cliff if we overshoot.
As a more abstract technical description, this unintuitive behaviour
results in having to give high-priority workloads a large protection
buffer on top of their expected usage to function reliably, as otherwise
we have abrupt periods of dramatically increased memory pressure which
hamper performance. Having to set these thresholds so high wastes
resources and generally works against the principle of work conservation.
In addition, having proportional memory reclaim behaviour has other
benefits. Most notably, before this patch it's basically mandatory to set
memory.low to a higher than desirable value because otherwise as soon as
you exceed memory.low, all protection is lost, and all pages are eligible
to scan again. By contrast, having a gradual ramp in reclaim pressure
means that you now still get some protection when thresholds are exceeded,
which means that one can now be more comfortable setting memory.low to
lower values without worrying that all protection will be lost. This is
important because workingset size is really hard to know exactly,
especially with variable workloads, so at least getting *some* protection
if your workingset size grows larger than you expect increases user
confidence in setting memory.low without a huge buffer on top being
needed.
Thanks a lot to Johannes Weiner and Tejun Heo for their advice and
assistance in thinking about how to make this work better.
In testing these changes, I intended to verify that:
1. Changes in page scanning become gradual and proportional instead of
binary.
To test this, I experimented stepping further and further down
memory.low protection on a workload that floats around 19G workingset
when under memory.low protection, watching page scan rates for the
workload cgroup:
+------------+-----------------+--------------------+--------------+
| memory.low | test (pgscan/s) | control (pgscan/s) | % of control |
+------------+-----------------+--------------------+--------------+
| 21G | 0 | 0 | N/A |
| 17G | 867 | 3799 | 23% |
| 12G | 1203 | 3543 | 34% |
| 8G | 2534 | 3979 | 64% |
| 4G | 3980 | 4147 | 96% |
| 0 | 3799 | 3980 | 95% |
+------------+-----------------+--------------------+--------------+
As you can see, the test kernel (with a kernel containing this
patch) ramps up page scanning significantly more gradually than the
control kernel (without this patch).
2. More gradual ramp up in reclaim aggression doesn't result in
premature OOMs.
To test this, I wrote a script that slowly increments the number of
pages held by stress(1)'s --vm-keep mode until a production system
entered severe overall memory contention. This script runs in a highly
protected slice taking up the majority of available system memory.
Watching vmstat revealed that page scanning continued essentially
nominally between test and control, without causing forward reclaim
progress to become arrested.
[0]: https://facebookmicrosites.github.io/cgroup2/docs/overview.html#case-study-the-fbtax2-project
[akpm@linux-foundation.org: reflow block comments to fit in 80 cols]
[chris@chrisdown.name: handle cgroup_disable=memory when getting memcg protection]
Link: http://lkml.kernel.org/r/20190201045711.GA18302@chrisdown.name
Link: http://lkml.kernel.org/r/20190124014455.GA6396@chrisdown.name
Signed-off-by: Chris Down <chris@chrisdown.name>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Roman Gushchin <guro@fb.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
