The device node is used for UDCs integrated into Broadcom's
iProc family of SoCs'. The UDC is based on Synopsys Designware
Cores AHB Subsystem USB Device Controller IP.
Signed-off-by: Raviteja Garimella <raviteja.garimella@broadcom.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

Change the argument from NULL to a struct device for the
dma_pool_create call during dma init.
Signed-off-by: Raviteja Garimella <raviteja.garimella@broadcom.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

This patch adds a struct device member to UDC data structure and
makes changes to the arguments of dev_err and dev_dbg calls so that
the debug prints work for both pci and platform devices.
Signed-off-by: Raviteja Garimella <raviteja.garimella@broadcom.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

This patch renames the amd5536udc.c that has the core driver
functionality of Synopsys UDC to snps_udc_core.c

The symbols exported here can be used by any UDC driver that uses
the same Synopsys IP.
Signed-off-by: Raviteja Garimella <raviteja.garimella@broadcom.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

Other unsigned properties return hexadecimal values, follow this
convention when printing b_vendor_code too. Also add newlines to
the OS Descriptor support related properties, like other sysfs
files use.
Reviewed-by: Krzysztof Opasiak <k.opasiak@samsung.com>
Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

Currently qw_sign requires UTF-8 character to set, but returns UTF-16
when read. This isn't obvious when simply using cat since the null
characters are not visible, but hexdump unveils the true string:

  # echo MSFT100 > os_desc/qw_sign
  # hexdump -C os_desc/qw_sign
  00000000  4d 00 53 00 46 00 54 00  31 00 30 00 30 00        |M.S.F.T.1.0.0.|

Make qw_sign symmetric by returning an UTF-8 string too. Also follow
common convention and add a new line at the end.
Reviewed-by: Krzysztof Opasiak <k.opasiak@samsung.com>
Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

This commit allows a gadget that does not support SuperSpeed to indicate
that it supports LPM. It does this by setting the 'lpm_capable' flag in
the gadget structure.

If a gadget sets this, the composite gadget framework will set the
bcdUSB to 0x0201 to indicate that this supports BOS descriptors, and
also return a USB 2.0 Extension descriptor as part of the BOS descriptor
set.

See USB 2.0 LPM ECN Section 3.
Signed-off-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Sevak Arakelyan <sevaka@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

Don't send the SuperSpeed USB Device Capability descriptor if
the gadget is not capable of SuperSpeed.
Signed-off-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Sevak Arakelyan <sevaka@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

There were individual waitqueues for each epfile but eps_enable
would iterate through all of them, resulting in essentially the
same wakeup time.

The waitqueue represents the function being enabled, so a central
waitqueue in ffs_data makes more sense and is less redundant.

Also use wake_up_interruptible to reflect use of
wait_event_interruptible.
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Jerry Zhang <zhangjerry@google.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

This allows users to make an ioctl call as the first action on a
connection. Ex, some functions might want to get endpoint size
before making any i/os.

Previously, calling ioctls before read/write would depending on the
timing of endpoints being enabled.

ESHUTDOWN is now a possible return value and ENODEV is not, so change
docs accordingly.
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Jerry Zhang <zhangjerry@google.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

The assignment ret = ret is redundant and can be removed.
Reviewed-by: Krzysztof Opasiak <k.opasiak@samsung.com>
Reviewed-by: Peter Chen <peter.chen@nxp.com>
Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

This is where all other USB ReST documentation has moved to.
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

Document a few details about DWC3 in order to help people report bugs
and debug DWC3.
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

Instead of *always* dumping raw ctrl bytes, let's decode standard
requests which will make the lives of those debugging DWC3 quite a bit
easier.

Output will now look like so:

irq/34-dwc3-1594  [000] d..1   107.573081: dwc3_ctrl_req: Get Device Descriptor(Index = 0, Length = 18)
irq/34-dwc3-1594  [000] d..1   107.573694: dwc3_ctrl_req: Set Address(Addr = 01)
irq/34-dwc3-1594  [000] d..1   107.588319: dwc3_ctrl_req: Get Device Descriptor(Index = 0, Length = 18)
irq/34-dwc3-1594  [000] d..1   107.588816: dwc3_ctrl_req: Get Configuration Descriptor(Index = 0, Length = 9)
irq/34-dwc3-1594  [000] d..1   107.589191: dwc3_ctrl_req: Set Configuration(Config = 3)
irq/34-dwc3-1594  [000] d..1   107.589846: dwc3_ctrl_req: Get BOS Descriptor(Index = 0, Length = 5)
irq/34-dwc3-1594  [000] d..1   107.590146: dwc3_ctrl_req: Get BOS Descriptor(Index = 0, Length = 22)
irq/34-dwc3-1594  [000] d..1   107.590546: dwc3_ctrl_req: Get Configuration Descriptor(Index = 0, Length = 9)
irq/34-dwc3-1594  [000] d..1   107.590840: dwc3_ctrl_req: Get Configuration Descriptor(Index = 0, Length = 69)
irq/34-dwc3-1594  [000] d..1   107.591138: dwc3_ctrl_req: Get Configuration Descriptor(Index = 1, Length = 9)
irq/34-dwc3-1594  [000] d..1   107.591541: dwc3_ctrl_req: Get Configuration Descriptor(Index = 1, Length = 32)
irq/34-dwc3-1594  [000] d..1   107.591834: dwc3_ctrl_req: Get Device Descriptor(Index = 0, Length = 18)
irq/34-dwc3-1594  [000] d..1   114.701005: dwc3_ctrl_req: Get Device Descriptor(Index = 0, Length = 18)
irq/34-dwc3-1594  [000] d..1   114.721080: dwc3_ctrl_req: Get Device Descriptor(Index = 0, Length = 18)
irq/34-dwc3-1594  [000] d..1   114.722709: dwc3_ctrl_req: Get Device Descriptor(Index = 0, Length = 18)
irq/34-dwc3-1594  [000] d..1   114.728979: dwc3_ctrl_req: Get Device Descriptor(Index = 0, Length = 18)
irq/34-dwc3-1594  [000] d..1   114.730544: dwc3_ctrl_req: Get Device Qualifier Descriptor(Index = 0, Length = 10)
irq/34-dwc3-1594  [000] d..1   115.776018: dwc3_ctrl_req: Get Configuration Descriptor(Index = 0, Length = 9)
irq/34-dwc3-1594  [000] d..1   115.776760: dwc3_ctrl_req: Set Configuration(Config = 0)
irq/34-dwc3-1594  [000] d..1   115.777676: dwc3_ctrl_req: Get Configuration(Length = 1)
irq/34-dwc3-1594  [000] d..1   115.924797: dwc3_ctrl_req: Get Device Descriptor(Index = 0, Length = 18)
irq/34-dwc3-1594  [000] d..1   115.929025: dwc3_ctrl_req: Get String Descriptor(Index = 0, Length = 500)
irq/34-dwc3-1594  [000] d..1   115.929566: dwc3_ctrl_req: Get String Descriptor(Index = 1, Length = 500)
irq/34-dwc3-1594  [000] d..1   115.930911: dwc3_ctrl_req: Get String Descriptor(Index = 0, Length = 500)
irq/34-dwc3-1594  [000] d..1   115.931528: dwc3_ctrl_req: Get String Descriptor(Index = 2, Length = 500)
irq/34-dwc3-1594  [000] d..1   115.932950: dwc3_ctrl_req: Get String Descriptor(Index = 0, Length = 500)
irq/34-dwc3-1594  [000] d..1   115.933533: dwc3_ctrl_req: Get String Descriptor(Index = 3, Length = 500)

Note that Class and Vendor requests won't be decoded for obvious
reasons. Those will be printed as a raw sequence of bytes.

This patch has been tested against a normal host (both Linux and
Windows) and USB30CV Chapter 9 tests.
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

Instead, we can require caller to pass a buffer for the function to
use. This cleans things quite a bit.
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

Instead of going for a 512 byte buffer and using snprintf(), let's
rely on helps __string() and __assign_str() where possible.
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

No functional changes, just a slight readability improvement.
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

Instead of printing out enqueue and dequeue pointer value as a header
to the output, let's mark the TRBs in question with 'E' and 'D'. The
output looks slightly easier to read.
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

No functional changes, just making sure we can use these for ReST docs
later.
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

Currently, default vary will not accomodate superspeed endpoints
causing unexpected babble errors in the IN direction. Let's update
default 'vary' parameter so that we can maintain a "short-less"
transfer as hinted at the comment.
Reported-by: Ammy Yi <ammy.yi@intel.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

%p will leak kernel pointers, so let's not expose the information on
dmesg and instead use %pK. %pK will only show the actual addresses if
explicitly enabled under /proc/sys/kernel/kptr_restrict.

Cc: <stable@vger.kernel.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

"ep->udc->lock" and "udc->lock" are the same thing.  It confuses Smatch
if we don't use the same name consistently.
Reviewed-by: Sören Brinkmann <soren.brinkmann@xilinx.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

This patch adds a quirk to disable USB 2.0 MAC linestate check
during HS transmit. Refer the dwc3 databook, we can use it for
some special platforms if the linestate not reflect the expected
line state(J) during transmission.

When use this quirk, the controller implements a fixed 40-bit
TxEndDelay after the packet is given on UTMI and ignores the
linestate during the transmit of a token (during token-to-token
and token-to-data IPGAP).

On some rockchip platforms (e.g. rk3399), it requires to disable
the u2mac linestate check to decrease the SSPLIT token to SETUP
token inter-packet delay from 566ns to 466ns, and fix the issue
that FS/LS devices not recognized if inserted through USB 3.0 HUB.
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Signed-off-by: William Wu <william.wu@rock-chips.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

Add null check before dereferencing dev->regs pointer inside
net2280_led_shutdown() function.

Addresses-Coverity-ID: 101783
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

Since usb phy core has added common code to register or unregister
extcon device, then phy-msm-usb driver does not need its own
code to register/unregister extcon device, then remove them.
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

Since usb phy core has added common code to register or unregister
extcon device, then phy-qcom-8x16-usb driver does not need its own
code to register/unregister extcon device, then remove them.
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

Usually usb phy need register one extcon device to get the connection
notifications. It will remove some duplicate code if the extcon device
is registered using common code instead of each phy driver having its
own related extcon APIs. So we add one pointer of extcon device into
usb phy structure, and some other helper functions to register extcon.
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

The USB gadget documentation is not at DocBook anymore.
The main file was converted to ReST, and stored at
Documentation/driver-api/usb/gadget.rst, but there are
still several plain text files related to gadget under
Documentation/usb.

So, be generic and just mention documentation
without specifying where it is.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

Calculate wMaxPacketSize before endpoint matching the
descriptor is found.

This allows audio gadget to be used with controllers
which have a shortage or unavailability of endpoints
that can handle max packet size of 1023 (FS) or 1024
(HS).

With this audio gadget can be used on TI's OMAP-L138 SoC
which has a MUSB HS controller with endpoints having max
packet size much less than 1023 or 1024. See mode_2_cfg in
drivers/usb/musb/musb_core.c
Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

Some functions might want to have very, very long request queues. We
can't make any assumptions about how many requests we *are* able to
map, so instead of mapping requests early, let's map them late. This
way, functions can queue as many requests as they'd like but we won't
take DMA resources until they are needed.

Also, we can now stop processing requests when we run out of DMA
resources but still keep requests in the queue for late processing.
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

We don't need a big fat warning with stack dump at all. Running out of
TRBs is a normal condition and we will have more TRBs available as
soon as some transfers complete.
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

This patch reworks the way f_mass_storage.c handles memory barriers
and synchronization:

	The driver now uses a wait_queue instead of doing its own
	task-state manipulations (even though only one task will ever
	use the wait_queue).

	The thread_wakeup_needed variable is removed.  It was only a
	source of trouble; although it was what the driver tested to
	see whether it should wake up, what we really wanted to see
	was whether a USB transfer had completed.

	All the explicit memory barriers scattered throughout the
	driver are replaced by a few calls to smp_load_acquire() and
	smp_store_release().

	The inreq_busy and outreq_busy fields are removed.  In their
	place, the driver keeps track of the current I/O direction by
	splitting BUF_STATE_BUSY into two states: BUF_STATE_SENDING
	and BUF_STATE_RECEIVING.

	The buffer states are no longer protected by a lock.  Mutual
	exclusion isn't needed; the state is changed only by the
	driver's main thread when it owns the buffer, and only by the
	request completion routine when the gadget core owns the buffer.

	The do_write() and throw_away_data() routines were reorganized
	to make efficient use of the new sleeping mechanism.  This
	resulted in the removal of one indentation level in those
	routines, making the patch appear to be more more complicated
	than it really is.

	In a few places, the driver allowed itself to be frozen although
	it really shouldn't have (in the middle of executing a SCSI
	command).  Those places have been fixed.

	The logic in the exception handler for aborting transfers and
	waiting for them to stop has been simplified.
Tested-by: Thinh Nguyen <thinhn@synopsys.com>
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

This patch makes several adjustments to the way f_mass_storage.c
handles its internal state and asynchronous notifications (AKA
exceptions):

	A number of states weren't being used for anything.
	They are removed.

	The FSG_STATE_IDLE state was renamed to FSG_STATE_NORMAL,
	because it now applies whenever the gadget is operating
	normally, not just when the gadget is idle.

	The FSG_STATE_RESET state was renamed to
	FSG_STATE_PROTOCOL_RESET, indicating that it represents a
	Bulk-Only Transport protocol reset and not a general USB
	reset.

	When a signal arrives, it's silly for the signal handler to
	send itself another signal!  Now it takes care of everything
	inline.

Along with an assortment of other minor changes in the same category.
Tested-by: Thinh Nguyen <thinhn@synopsys.com>
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

Pull some more input subsystem updates from Dmitry Torokhov:
 "An updated xpad driver with a few more recognized device IDs, and a
  new psxpad-spi driver, allowing connecting Playstation 1 and 2 joypads
  via SPI bus"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input:
  Input: cros_ec_keyb - remove extraneous 'const'
  Input: add support for PlayStation 1/2 joypads connected via SPI
  Input: xpad - add USB IDs for Mad Catz Brawlstick and Razer Sabertooth
  Input: xpad - sync supported devices with xboxdrv
  Input: xpad - sort supported devices by USB ID

Pull UBI/UBIFS updates from Richard Weinberger:

 - new config option CONFIG_UBIFS_FS_SECURITY

 - minor improvements

 - random fixes

* tag 'upstream-4.12-rc1' of git://git.infradead.org/linux-ubifs:
  ubi: Add debugfs file for tracking PEB state
  ubifs: Fix a typo in comment of ioctl2ubifs & ubifs2ioctl
  ubifs: Remove unnecessary assignment
  ubifs: Fix cut and paste error on sb type comparisons
  ubi: fastmap: Fix slab corruption
  ubifs: Add CONFIG_UBIFS_FS_SECURITY to disable/enable security labels
  ubi: Make mtd parameter readable
  ubi: Fix section mismatch

Pull UML fixes from Richard Weinberger:
 "No new stuff, just fixes"

* 'for-linus-4.12-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/uml:
  um: Add missing NR_CPUS include
  um: Fix to call read_initrd after init_bootmem
  um: Include kbuild.h instead of duplicating its macros
  um: Fix PTRACE_POKEUSER on x86_64
  um: Set number of CPUs
  um: Fix _print_addr()

Merge misc fixes from Andrew Morton:
 "15 fixes"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>:
  mm, docs: update memory.stat description with workingset* entries
  mm: vmscan: scan until it finds eligible pages
  mm, thp: copying user pages must schedule on collapse
  dax: fix PMD data corruption when fault races with write
  dax: fix data corruption when fault races with write
  ext4: return to starting transaction in ext4_dax_huge_fault()
  mm: fix data corruption due to stale mmap reads
  dax: prevent invalidation of mapped DAX entries
  Tigran has moved
  mm, vmalloc: fix vmalloc users tracking properly
  mm/khugepaged: add missed tracepoint for collapse_huge_page_swapin
  gcov: support GCC 7.1
  mm, vmstat: Remove spurious WARN() during zoneinfo print
  time: delete current_fs_time()
  hwpoison, memcg: forcibly uncharge LRU pages

Commit 4b4cea91691d ("mm: vmscan: fix IO/refault regression in cache
workingset transition") introduced three new entries in memory stat
file:

 - workingset_refault
 - workingset_activate
 - workingset_nodereclaim

This commit adds a corresponding description to the cgroup v2 docs.

Link: http://lkml.kernel.org/r/1494530293-31236-1-git-send-email-guro@fb.comSigned-off-by: Roman Gushchin <guro@fb.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Li Zefan <lizefan@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Although there are a ton of free swap and anonymous LRU page in elgible
zones, OOM happened.

  balloon invoked oom-killer: gfp_mask=0x17080c0(GFP_KERNEL_ACCOUNT|__GFP_ZERO|__GFP_NOTRACK), nodemask=(null),  order=0, oom_score_adj=0
  CPU: 7 PID: 1138 Comm: balloon Not tainted 4.11.0-rc6-mm1-zram-00289-ge228d67e9677-dirty #17
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
  Call Trace:
   oom_kill_process+0x21d/0x3f0
   out_of_memory+0xd8/0x390
   __alloc_pages_slowpath+0xbc1/0xc50
   __alloc_pages_nodemask+0x1a5/0x1c0
   pte_alloc_one+0x20/0x50
   __pte_alloc+0x1e/0x110
   __handle_mm_fault+0x919/0x960
   handle_mm_fault+0x77/0x120
   __do_page_fault+0x27a/0x550
   trace_do_page_fault+0x43/0x150
   do_async_page_fault+0x2c/0x90
   async_page_fault+0x28/0x30
  Mem-Info:
  active_anon:424716 inactive_anon:65314 isolated_anon:0
   active_file:52 inactive_file:46 isolated_file:0
   unevictable:0 dirty:27 writeback:0 unstable:0
   slab_reclaimable:3967 slab_unreclaimable:4125
   mapped:133 shmem:43 pagetables:1674 bounce:0
   free:4637 free_pcp:225 free_cma:0
  Node 0 active_anon:1698864kB inactive_anon:261256kB active_file:208kB inactive_file:184kB unevictable:0kB isolated(anon):0kB isolated(file):0kB mapped:532kB dirty:108kB writeback:0kB shmem:172kB writeback_tmp:0kB unstable:0kB all_unreclaimable? no
  DMA free:7316kB min:32kB low:44kB high:56kB active_anon:8064kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB present:15992kB managed:15908kB mlocked:0kB slab_reclaimable:464kB slab_unreclaimable:40kB kernel_stack:0kB pagetables:24kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB
  lowmem_reserve[]: 0 992 992 1952
  DMA32 free:9088kB min:2048kB low:3064kB high:4080kB active_anon:952176kB inactive_anon:0kB active_file:36kB inactive_file:0kB unevictable:0kB writepending:88kB present:1032192kB managed:1019388kB mlocked:0kB slab_reclaimable:13532kB slab_unreclaimable:16460kB kernel_stack:3552kB pagetables:6672kB bounce:0kB free_pcp:56kB local_pcp:24kB free_cma:0kB
  lowmem_reserve[]: 0 0 0 959
  Movable free:3644kB min:1980kB low:2960kB high:3940kB active_anon:738560kB inactive_anon:261340kB active_file:188kB inactive_file:640kB unevictable:0kB writepending:20kB present:1048444kB managed:1010816kB mlocked:0kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:0kB bounce:0kB free_pcp:832kB local_pcp:60kB free_cma:0kB
  lowmem_reserve[]: 0 0 0 0
  DMA: 1*4kB (E) 0*8kB 18*16kB (E) 10*32kB (E) 10*64kB (E) 9*128kB (ME) 8*256kB (E) 2*512kB (E) 2*1024kB (E) 0*2048kB 0*4096kB = 7524kB
  DMA32: 417*4kB (UMEH) 181*8kB (UMEH) 68*16kB (UMEH) 48*32kB (UMEH) 14*64kB (MH) 3*128kB (M) 1*256kB (H) 1*512kB (M) 2*1024kB (M) 0*2048kB 0*4096kB = 9836kB
  Movable: 1*4kB (M) 1*8kB (M) 1*16kB (M) 1*32kB (M) 0*64kB 1*128kB (M) 2*256kB (M) 4*512kB (M) 1*1024kB (M) 0*2048kB 0*4096kB = 3772kB
  378 total pagecache pages
  17 pages in swap cache
  Swap cache stats: add 17325, delete 17302, find 0/27
  Free swap  = 978940kB
  Total swap = 1048572kB
  524157 pages RAM
  0 pages HighMem/MovableOnly
  12629 pages reserved
  0 pages cma reserved
  0 pages hwpoisoned
  [ pid ]   uid  tgid total_vm      rss nr_ptes nr_pmds swapents oom_score_adj name
  [  433]     0   433     4904        5      14       3       82             0 upstart-udev-br
  [  438]     0   438    12371        5      27       3      191         -1000 systemd-udevd

With investigation, skipping page of isolate_lru_pages makes reclaim
void because it returns zero nr_taken easily so LRU shrinking is
effectively nothing and just increases priority aggressively.  Finally,
OOM happens.

The problem is that get_scan_count determines nr_to_scan with eligible
zones so although priority drops to zero, it couldn't reclaim any pages
if the LRU contains mostly ineligible pages.

get_scan_count:

        size = lruvec_lru_size(lruvec, lru, sc->reclaim_idx);
	size = size >> sc->priority;

Assumes sc->priority is 0 and LRU list is as follows.

	N-N-N-N-H-H-H-H-H-H-H-H-H-H-H-H-H-H-H-H

(Ie, small eligible pages are in the head of LRU but others are
 almost ineligible pages)

In that case, size becomes 4 so VM want to scan 4 pages but 4 pages from
tail of the LRU are not eligible pages.  If get_scan_count counts
skipped pages, it doesn't reclaim any pages remained after scanning 4
pages so it ends up OOM happening.

This patch makes isolate_lru_pages try to scan pages until it encounters
eligible zones's pages.

[akpm@linux-foundation.org: clean up mind-bending `for' statement.  Tweak comment text]
Fixes: 3db65812 ("Revert "mm, vmscan: account for skipped pages as a partial scan"")
Link: http://lkml.kernel.org/r/1494457232-27401-1-git-send-email-minchan@kernel.orgSigned-off-by: Minchan Kim <minchan@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>