Michal Hocko 696ce77bba mm, proc: be more verbose about unstable VMA flags in /proc/<pid>/smaps ... [ Upstream commit 7550c60798 ] Patch series "THP eligibility reporting via proc". This series of three patches aims at making THP eligibility reporting much more robust and long term sustainable. The trigger for the change is a regression report [2] and the long follow up discussion. In short the specific application didn't have good API to query whether a particular mapping can be backed by THP so it has used VMA flags to workaround that. These flags represent a deep internal state of VMAs and as such they should be used by userspace with a great deal of caution. A similar has happened for [3] when users complained that VM_MIXEDMAP is no longer set on DAX mappings. Again a lack of a proper API led to an abuse. The first patch in the series tries to emphasise that that the semantic of flags might change and any application consuming those should be really careful. The remaining two patches provide a more suitable interface to address [2] and provide a consistent API to query the THP status both for each VMA and process wide as well. [1] http://lkml.kernel.org/r/20181120103515.25280-1-mhocko@kernel.org [2] http://lkml.kernel.org/r/http://lkml.kernel.org/r/alpine.DEB.2.21.1809241054050.224429@chino.kir.corp.google.com [3] http://lkml.kernel.org/r/20181002100531.GC4135@quack2.suse.cz This patch (of 3): Even though vma flags exported via /proc/<pid>/smaps are explicitly documented to be not guaranteed for future compatibility the warning doesn't go far enough because it doesn't mention semantic changes to those flags. And they are important as well because these flags are a deep implementation internal to the MM code and the semantic might change at any time. Let's consider two recent examples: http://lkml.kernel.org/r/20181002100531.GC4135@quack2.suse.cz : commit e1fb4a0864 "dax: remove VM_MIXEDMAP for fsdax and device dax" has : removed VM_MIXEDMAP flag from DAX VMAs. Now our testing shows that in the : mean time certain customer of ours started poking into /proc/<pid>/smaps : and looks at VMA flags there and if VM_MIXEDMAP is missing among the VMA : flags, the application just fails to start complaining that DAX support is : missing in the kernel. http://lkml.kernel.org/r/alpine.DEB.2.21.1809241054050.224429@chino.kir.corp.google.com : Commit 1860033237 ("mm: make PR_SET_THP_DISABLE immediately active") : introduced a regression in that userspace cannot always determine the set : of vmas where thp is ineligible. : Userspace relies on the "nh" flag being emitted as part of /proc/pid/smaps : to determine if a vma is eligible to be backed by hugepages. : Previous to this commit, prctl(PR_SET_THP_DISABLE, 1) would cause thp to : be disabled and emit "nh" as a flag for the corresponding vmas as part of : /proc/pid/smaps. After the commit, thp is disabled by means of an mm : flag and "nh" is not emitted. : This causes smaps parsing libraries to assume a vma is eligible for thp : and ends up puzzling the user on why its memory is not backed by thp. In both cases userspace was relying on a semantic of a specific VMA flag. The primary reason why that happened is a lack of a proper interface. While this has been worked on and it will be fixed properly, it seems that our wording could see some refinement and be more vocal about semantic aspect of these flags as well. Link: http://lkml.kernel.org/r/20181211143641.3503-2-mhocko@kernel.org Signed-off-by: Michal Hocko <mhocko@suse.com> Acked-by: Jan Kara <jack@suse.cz> Acked-by: Dan Williams <dan.j.williams@intel.com> Acked-by: David Rientjes <rientjes@google.com> Acked-by: Mike Rapoport <rppt@linux.ibm.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Dan Williams <dan.j.williams@intel.com> Cc: David Rientjes <rientjes@google.com> Cc: Paul Oppenheimer <bepvte@gmail.com> Cc: William Kucharski <william.kucharski@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org>		2019-01-26 09:37:07 +01:00
..
ABI	x86/bugs, kvm: Introduce boot-time control of L1TF mitigations	2018-08-15 18:12:56 +02:00
EDID	drm: use .hword to represent 16-bit numbers	2017-03-30 10:15:19 +02:00
PCI	docs: update old references for DocBook from the documentation	2017-05-16 08:44:19 -03:00
RCU	doc: Set down RCU's scheduling-clock-interrupt needs	2017-08-17 07:31:14 -07:00
accounting	…
acpi	This is the bulk of GPIO changes for the v4.13 series:	2017-07-07 12:40:27 -07:00
admin-guide	x86/speculation/l1tf: Drop the swap storage limit restriction when l1tf=off	2019-01-09 17:14:48 +01:00
aoe	…
arm	Documentation: arm: Replace use of virt_to_phys with __pa_symbol	2017-07-17 13:43:58 -06:00
arm64	arm64: Add work around for Arm Cortex-A55 Erratum 1024718	2018-05-16 10:10:25 +02:00
auxdisplay	…
backlight	…
blackfin	…
block	doc, block, bfq: better describe how to properly configure bfq	2017-08-31 13:55:26 -06:00
blockdev	SCSI misc on 20170907	2017-09-07 21:11:05 -07:00
bus-devices	…
cdrom	cdrom: Make device operations read-only	2017-02-14 08:29:56 -07:00
cgroup-v1	mm, vmpressure: pass-through notification support	2017-07-10 16:32:31 -07:00
cma	…
connector	…
console	…
core-api	doc: Fix RCU's docbook options	2017-10-19 22:26:11 -04:00
cpu-freq	cpufreq: docs: Drop intel-pstate.txt from index.txt	2017-09-28 02:08:43 +02:00
cpuidle	…
cris	…
crypto	KEYS: Add documentation for asymmetric keyring restrictions	2017-07-14 11:01:38 +10:00
dev-tools	kmemcheck: rip it out	2018-02-22 15:42:24 +01:00
device-mapper	dm thin: fix documentation relative to low water mark threshold	2018-04-26 11:02:07 +02:00
devicetree	can: hi311x: Use level-triggered interrupt	2018-12-01 09:42:53 +01:00
dmaengine	Merge branch 'topic/dmatest' into for-linus	2017-09-06 21:55:10 +05:30
doc-guide	sphinx.rst: Allow Sphinx version 1.6 at the docs	2017-08-26 15:50:27 -06:00
driver-api	PM: docs: Drop an excess character from devices.rst	2017-09-19 22:57:38 +02:00
driver-model	driver core: remove DRIVER_ATTR	2017-09-19 09:20:33 +02:00
early-userspace	Documentation: Fix dead URLs to ftp.kernel.org	2017-03-29 15:46:06 -06:00
extcon	extcon: Remove porting compatibility of swich class	2017-04-06 10:55:24 +09:00
fault-injection	fault-inject: add /proc/<pid>/fail-nth	2017-07-14 15:05:13 -07:00
fb	fbcon: remove restriction on margin color	2017-09-04 16:00:49 +02:00
features	docs/features: parisc implements tracehook	2017-08-07 14:18:40 -06:00
filesystems	mm, proc: be more verbose about unstable VMA flags in /proc/<pid>/smaps	2019-01-26 09:37:07 +01:00
firmware_class	firmware: revamp firmware documentation	2017-01-11 09:42:59 +01:00
fmc	…
fpga	fpga: Add scatterlist based programming	2017-02-10 15:20:44 +01:00
frv	…
gpio	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input	2017-09-07 13:39:21 -07:00
gpu	Merge tag 'drm-intel-next-2017-08-18' of git://anongit.freedesktop.org/git/drm-intel into drm-next	2017-08-22 10:03:07 +10:00
hid	Documentation: hid: fix path to input bus definitions	2017-03-13 17:15:19 -06:00
hwmon	hwmon: (ina2xx) fix sysfs shunt resistor read access	2018-10-03 17:00:58 -07:00
i2c	i2c: i801: Add support for Intel Cedar Fork	2017-10-05 14:44:56 +02:00
ia64	…
ide	…
iio	iio: adc: New driver for Cirrus Logic EP93xx ADC	2017-07-25 19:56:23 +01:00
infiniband	Documentation: Hardware tag matching	2017-08-29 08:30:21 -04:00
input	Documentation:input: fix typo	2017-08-30 15:18:24 -06:00
ioctl	scsi: cxlflash: Introduce host ioctl support	2017-06-26 15:01:11 -04:00
isdn	…
kbuild	kbuild: delete INSTALL_FW_PATH from kbuild documentation	2018-07-17 11:39:30 +02:00
kdump	kexec/kdump: minor Documentation updates for arm64 and Image	2017-07-12 16:26:00 -07:00
kernel-hacking	There has been a fair amount of activity in the docs tree this time	2017-07-03 21:13:25 -07:00
laptops	platform/x86: thinkpad_acpi: Fix warning about deprecated hwmon_device_register	2017-08-18 15:57:24 -07:00
leds	Documentaion: leds: leds-lp55xx.txt: Fix typos	2017-03-17 13:06:14 -06:00
lightnvm	lightnvm: physical block device (pblk) target	2017-04-16 10:06:33 -06:00
livepatch	livepatch: allow removal of a disabled patch	2017-03-08 09:38:43 +01:00
locking	Merge branch 'linus' into locking/core, to fix up conflicts	2017-09-04 11:01:18 +02:00
m68k	…
md	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/shli/md	2017-05-03 10:05:38 -07:00
media	media: media colorspaces*.rst: rename AdobeRGB to opRGB	2018-11-13 11:15:12 -08:00
memory-devices	…
metag	…
mic	…
mips	…
misc-devices	Documentation: misc-devices: Add Documentation for pci-endpoint-test driver	2017-04-28 10:23:19 -05:00
mmc	MMC core:	2017-05-02 17:34:32 -07:00
mn10300	…
mtd	spi-nor: Add support for Intel SPI serial flash controller	2017-01-03 17:33:36 +00:00
namespaces	…
netlabel	…
networking	inet: frags: break the 2GB limit for frags storage	2018-09-19 22:43:46 +02:00
nfc	…
nios2	…
nvdimm	…
nvmem	NVMEM documentation fix: A minor typo	2017-08-24 13:31:58 -06:00
parisc	…
pcmcia	…
perf	perf: qcom: Add L3 cache PMU driver	2017-04-03 18:53:50 +01:00
phy	…
platform	…
power	Merge branch 'pm-sleep'	2017-09-04 00:06:02 +02:00
powerpc	powerpc updates for 4.13	2017-07-07 13:55:45 -07:00
pps	drivers/pps: aesthetic tweaks to PPS-related content	2017-09-08 18:26:51 -07:00
process	kbuild: verify that $DEPMOD is installed	2018-08-17 21:01:10 +02:00
pti	…
ptp	…
rapidio	…
s390	docs: add documentation for vfio-ccw	2017-03-31 12:55:11 +02:00
scheduler	sched/deadline: Add documentation about GRUB reclaiming	2017-06-08 10:31:56 +02:00
scsi	scsi: make asynchronous aborts mandatory	2017-04-06 13:07:33 -04:00
security	docs: ReSTify table of contents in core.rst	2017-08-30 15:27:58 -06:00
serial	tty: n_gsm: do not send/receive in ldisc close path	2017-06-03 18:48:52 +09:00
sh	docs-rst: convert sh book to ReST	2017-05-16 08:44:18 -03:00
sound	sound updates for 4.13-rc1	2017-07-06 10:56:51 -07:00
sparc	Documentation/sparc: Steps for sending break on sunhv console	2017-02-23 08:27:25 -08:00
sphinx	Documentation/sphinx: Fix Directive import error	2018-03-15 10:54:32 +01:00
sphinx-static	docs RTD theme: code-block with line nos - lines and line numbers don't line up.	2017-07-17 13:48:45 -06:00
spi	spi: Document SPI slave controller support	2017-05-26 13:11:00 +01:00
sysctl	namei: allow restricted O_CREAT of FIFOs and regular files	2018-12-01 09:42:59 +01:00
target	Documentation/target: add an example script to configure an iSCSI target	2017-05-01 22:21:35 -07:00
thermal	Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/rzhang/linux	2017-05-12 11:58:45 -07:00
timers	rcu: Eliminate NOCBs CPU-state Kconfig options	2017-06-08 18:52:43 -07:00
trace	stm class: Document the stm_ftrace	2017-08-25 17:58:34 +03:00
translations	kokr/memory-barriers.txt: Apply atomic_t.txt change	2017-09-08 10:10:53 -06:00
usb	usb: gadget: add f_uac1 variant based on a new u_audio api	2017-06-19 09:22:47 +03:00
userspace-api	x86/speculation: Add prctl() control for indirect branch speculation	2018-12-05 19:41:22 +01:00
virtual	KVM: x86: Add a framework for supporting MSR-based features	2018-08-15 18:12:59 +02:00
vm	hmm: heterogeneous memory management documentation	2017-09-08 18:26:45 -07:00
w1	w1: add documentation for w1_ds2438	2017-03-17 15:10:49 +09:00
watchdog	watchdog: Revert "iTCO_wdt: all versions count down twice"	2017-09-09 17:41:24 +02:00
wimax	…
x86	x86/mm: Move LDT remap out of KASLR region on 5-level paging	2018-11-27 16:10:50 +01:00
xtensa	of: update ePAPR references to point to Devicetree Specification	2017-06-22 11:22:06 -05:00
.gitignore	…
00-INDEX	linux-kselftest-4.13-rc1-update	2017-07-07 14:04:47 -07:00
Changes	docs: add back 'Documentation/Changes' file (as symlink)	2016-12-14 16:30:12 -08:00
CodingStyle	…
DMA-API-HOWTO.txt	DMA-API-HOWTO.txt: standardize document format	2017-07-14 13:51:32 -06:00
DMA-API.txt	dma-coherent: remove the DMA_MEMORY_MAP and DMA_MEMORY_IO flags	2017-09-01 11:59:17 +02:00
DMA-ISA-LPC.txt	DMA-ISA-LPC.txt: standardize document format	2017-07-14 13:51:33 -06:00
DMA-attributes.txt	DMA-attributes.txt: standardize document format	2017-07-14 13:51:33 -06:00
IPMI.txt	IPMI.txt: standardize document format	2017-07-14 13:51:40 -06:00
IRQ-affinity.txt	IRQ-affinity.txt: standardize document format	2017-07-14 13:51:41 -06:00
IRQ-domain.txt	IRQ-domain.txt: standardize document format	2017-07-14 13:51:41 -06:00
IRQ.txt	IRQ.txt: add a markup for its title	2017-07-14 13:51:42 -06:00
Intel-IOMMU.txt	Intel-IOMMU.txt: standardize document format	2017-07-14 13:51:38 -06:00
Makefile	doc: Makefile: if sphinx is not found, run a check script	2017-08-24 13:18:30 -06:00
SAK.txt	SAK.txt: standardize document format	2017-07-14 13:58:04 -06:00
SM501.txt	SM501.txt: standardize document format	2017-07-14 13:58:06 -06:00
SubmittingPatches	…
atomic_bitops.txt	Documentation/locking/atomic: Add documents for new atomic_t APIs	2017-08-10 12:29:00 +02:00
atomic_t.txt	Documentation/locking/atomic: Finish the document...	2017-08-25 11:06:33 +02:00
bcache.txt	bcache.txt: standardize document format	2017-07-14 13:51:27 -06:00
bt8xxgpio.txt	bt8xxgpio.txt: standardize document format	2017-07-14 13:51:27 -06:00
btmrvl.txt	btmrvl.txt: standardize document format	2017-07-14 13:51:27 -06:00
bus-virt-phys-mapping.txt	bus-virt-phys-mapping.txt: standardize document format	2017-07-14 13:51:28 -06:00
cachetlb.txt	cachetlb.txt: standardize document format	2017-07-14 13:51:28 -06:00
cgroup-v2.txt	cgroup: add cgroup.stat interface with basic hierarchy stats	2017-08-02 12:05:20 -07:00
circular-buffers.txt	circular-buffers.txt: standardize document format	2017-07-14 13:51:29 -06:00
clk.txt	clk.txt: standardize document format	2017-07-14 13:51:29 -06:00
conf.py	docs-rst: don't require adjustbox anymore	2017-09-08 10:02:55 -06:00
cpu-load.txt	cpu-load: standardize document format	2017-07-14 13:51:30 -06:00
cputopology.txt	cputopology.txt: standardize document format	2017-07-14 13:51:30 -06:00
crc32.txt	crc32.txt: standardize document format	2017-07-14 13:51:30 -06:00
dcdbas.txt	dcdbas.txt: standardize document format	2017-07-14 13:51:31 -06:00
debugging-modules.txt	…
debugging-via-ohci1394.txt	debugging-via-ohci1394.txt: standardize document format	2017-07-14 13:51:34 -06:00
dell_rbu.txt	dell_rbu.txt: standardize document format	2017-07-14 13:58:12 -06:00
digsig.txt	digsig.txt: standardize document format	2017-07-14 13:51:31 -06:00
docutils.conf	…
dontdiff	Remove gperf usage from toolchain	2017-08-19 11:02:53 -07:00
efi-stub.txt	efi-stub.txt: standardize document format	2017-07-14 13:51:34 -06:00
eisa.txt	eisa.txt: standardize document format	2017-07-14 13:51:34 -06:00
errseq.rst	Documentation: add some docs for errseq_t	2017-07-29 09:01:02 -04:00
flexible-arrays.txt	flexible-arrays.txt: standardize document format	2017-07-14 13:51:35 -06:00
futex-requeue-pi.txt	futex-requeue-pi.txt: standardize document format	2017-07-14 13:51:35 -06:00
gcc-plugins.txt	gcc-plugins.txt: standardize document format	2017-07-14 13:51:36 -06:00
highuid.txt	highuid.txt: standardize document format	2017-07-14 13:51:36 -06:00
hw_random.txt	hw_random.txt: standardize document format	2017-07-14 13:51:37 -06:00
hwspinlock.txt	hwspinlock.txt: standardize document format	2017-07-14 13:51:37 -06:00
index.rst	Make the main documentation title less Geocities	2017-06-23 14:02:27 -06:00
intel_txt.txt	intel_txt.txt: standardize document format	2017-07-14 13:51:38 -06:00
io-mapping.txt	io-mapping.txt: standardize document format	2017-07-14 13:51:38 -06:00
io_ordering.txt	io_ordering.txt: standardize document format	2017-07-14 13:51:39 -06:00
iostats.txt	iostats.txt: update it to cover recent Kernels	2017-07-14 13:51:40 -06:00
irqflags-tracing.txt	irqflags-tracing.txt: standardize document format	2017-07-14 13:51:42 -06:00
isa.txt	isa.txt: standardize document format	2017-07-14 13:51:43 -06:00
isapnp.txt	isapnp.txt: promote title level	2017-07-14 13:51:43 -06:00
kernel-doc-nano-HOWTO.txt	docs: update old references for DocBook from the documentation	2017-05-16 08:44:19 -03:00
kernel-per-CPU-kthreads.txt	kernel-per-CPU-kthreads.txt: standardize document format	2017-07-14 13:51:43 -06:00
kobject.txt	kobject.txt: standardize document format	2017-07-14 13:51:44 -06:00
kprobes.txt	docs: kprobes.txt: Fix whitespacing	2017-07-14 13:58:14 -06:00
kref.txt	kref.txt: standardize document format	2017-07-14 13:51:45 -06:00
ldm.txt	ldm.txt: standardize document format	2017-07-14 13:51:45 -06:00
lockup-watchdogs.txt	lockup-watchdogs.txt: standardize document format	2017-07-14 13:51:46 -06:00
logo.gif	…
logo.txt	…
lsm.txt	docs-rst: convert lsm from DocBook to ReST	2017-05-16 08:44:19 -03:00
lzo.txt	lzo.txt: standardize document format	2017-07-14 13:51:46 -06:00
mailbox.txt	mailbox.txt: standardize document format	2017-07-14 13:51:47 -06:00
memory-barriers.txt	Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2017-09-04 11:52:29 -07:00
memory-hotplug.txt	memory-hotplug.txt: standardize document format	2017-07-14 13:57:53 -06:00
men-chameleon-bus.txt	men-chameleon-bus.txt: standardize document format	2017-07-14 13:57:54 -06:00
nommu-mmap.txt	nommu-mmap.txt: don't use all upper case on titles	2017-07-14 13:57:55 -06:00
ntb.txt	This series converts a number of top-level documents to the RST format	2017-07-15 12:58:58 -07:00
numastat.txt	numastat.txt: standardize document format	2017-07-14 13:57:56 -06:00
padata.txt	padata.txt: standardize document format	2017-07-14 13:57:56 -06:00
parport-lowlevel.txt	parport-lowlevel.txt: standardize document format	2017-07-14 13:57:57 -06:00
percpu-rw-semaphore.txt	percpu-rw-semaphore.txt: standardize document format	2017-07-14 13:57:58 -06:00
phy.txt	phy.txt: standardize document format	2017-07-14 13:57:58 -06:00
pi-futex.txt	pi-futex.txt: standardize document format	2017-07-14 13:57:59 -06:00
pnp.txt	pnp.txt: standardize document format	2017-07-14 13:57:59 -06:00
preempt-locking.txt	preempt-locking.txt: standardize document format	2017-07-14 13:58:00 -06:00
printk-formats.txt	lib/vsprintf: Remove atomic-unsafe support for %pCr	2018-07-03 11:24:48 +02:00
pwm.txt	pwm: Standardize document format	2017-07-06 08:23:30 +02:00
rbtree.txt	rbtree: cache leftmost node internally	2017-09-08 18:26:48 -07:00
remoteproc.txt	remoteproc.txt: standardize document format	2017-07-14 13:58:02 -06:00
rfkill.txt	rfkill.txt: standardize document format	2017-07-14 13:58:02 -06:00
robust-futex-ABI.txt	robust-futex-ABI.txt: standardize document format	2017-07-14 13:58:03 -06:00
robust-futexes.txt	robust-futexes.txt: standardize document format	2017-07-14 13:58:03 -06:00
rpmsg.txt	rpmsg.txt: standardize document format	2017-07-14 13:58:04 -06:00
rtc.txt	rtc: add generic nvmem support	2017-07-07 13:14:14 +02:00
sgi-ioc4.txt	sgi-ioc4.txt: standardize document format	2017-07-14 13:58:05 -06:00
siphash.txt	siphash.txt: standardize document format	2017-07-14 13:58:06 -06:00
smsc_ece1099.txt	smsc_ece1099.txt: standardize document format	2017-07-14 13:58:07 -06:00
speculation.txt	Documentation: Document array_index_nospec	2018-02-07 11:12:22 -08:00
static-keys.txt	jump_label: Provide hotplug context variants	2017-08-10 12:28:59 +02:00
svga.txt	svga.txt: standardize document format	2017-07-14 13:58:08 -06:00
switchtec.txt	switchtec: Add IOCTLs to the Switchtec driver	2017-04-12 12:23:37 -05:00
sync_file.txt	sync_file.txt: standardize document format	2017-05-24 13:01:27 -03:00
tee.txt	tee.txt: standardize document format	2017-07-14 13:58:14 -06:00
this_cpu_ops.txt	this_cpu_ops.txt: standardize document format	2017-07-14 13:58:08 -06:00
unaligned-memory-access.txt	unaligned-memory-access.txt: standardize document format	2017-07-14 13:58:09 -06:00
vfio-mediated-device.txt	vfio/mdev: Check globally for duplicate devices	2018-08-03 07:50:22 +02:00
vfio.txt	vfio.txt: standardize document format	2017-07-14 13:58:10 -06:00
video-output.txt	…
xillybus.txt	xillybus.txt: standardize document format	2017-07-14 13:58:11 -06:00
xz.txt	xz.txt: standardize document format	2017-07-14 13:58:11 -06:00
zorro.txt	zorro.txt: standardize document format	2017-07-14 13:58:12 -06:00