There is no explanation about subdir-y.

Let's document it.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>

The difference between extra-y and always-y is obscure.

Basically, Kbuild builds targets listed in extra-y and always-y in
visited Makefiles without relying on any dependency.

The difference is that extra-y is used to list the targets needed for
vmlinux whereas always-y is used to list the targets that must be always
built irrespective of final targets.

Kbuild skips extra-y when it is building only modules (i.e.
'make modules'). This is the long-standing behavior since extra-y was
introduced in 2003, and it is explained in that commit log [1].

For clarification, this is the extra-y vs always-y table:

                  extra-y    always-y
  'make'             y          y
  'make vmlinux'     y          y
  'make modules'     n          y

Kbuild skips extra-y also when building external modules since obviously
it never builds vmlinux.

Unfortunately, extra-y is wrongly used in many places of upstream code,
and even in external modules.

Using extra-y in external module Makefiles is wrong. What you should
use is probably always-y or 'targets'.

The current documentation for extra-y is misleading. I rewrote it, and
moved it to the section 3.7.

always-y is not documented anywhere. I added.

[1]: https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git/commit/?id=f94e5fd7e5d09a56a60670a9bb211a791654bba8Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>

The if_changed macro is currently explained in the section
"Commands useful for building a boot image", but the use of
if_changed is not limited to the boot image.

It is often used together with custom rules. Let's split it as a
separate section, and insert it after the "Custom Rules" section.

I slightly reworded the explanation, re-numbered to fill the <deleted>
section, and also fixed the broken indentation of the Note: part.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

The two sections "3.10 Special Rules" and "7.8 Custom kbuild commands"
are related because you must understand both of them when you write
custom rules.

Actually I do not understand the policy about what to go into
"3 The kbuild files" and what into "7 Architecture Makefile".

This commit reworks the custom rule explanation as follows:

 - Merged "7.8 Custom kbuild commands" into "3.10 Special Rules".

 - Reword "Special Rules" to "Custom Rules" for consistency.

 - Update the example for kecho because the blackfin Makefile
   does not exist any more.

 - Replace the example for cmd_<command> with a simpler one.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Fix stale information:

 - Fix the section number in the reference from 6.4 to 7.4.

 - Remove init-y and net-y. They were removed by commit 23febe37
   ("kbuild: merge init-y into core-y") and commit 95fb6317
   ("kbuild: merge net-y and virt-y into drivers-y"), respectively.

 - Update the example because arch/sparc64/Makefile does not exit.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Precisely speaking, the arch directory is specified by $(SRCARCH),
not $(ARCH).

In old days, $(ARCH) actually matched to the arch directory because
32-bit and 64-bit were supported as separate architectures.

Most architectures (except arm/arm64) were unified like follows:

    arch/i386, arch/x86_64    ->  arch/x86
    arch/sh, arch/sh64        ->  arch/sh
    arch/sparc, arch/sparc64  ->  arch/sparc

To not break the user interface, commit 6752ed90 ("Kbuild: allow
arch/xxx to use a different source path") introduced SRCARCH to point
to the arch directory, still allowing to pass in the former ARCH=i386
or ARCH=x86_64.

Update the documents for preciseness, and add the explanation of SRCARCH.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>

This line was written in 2003. Now we have much more Makefiles.

The number of Makefiles is not important. The point is we have a
Makefile in (almost) every directory.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

The -Wnested-externs warning has become useless with gcc, since
this warns every time that BUILD_BUG_ON() or similar macros
are used.

With clang, the warning option does nothing to start with, so
just remove it entirely.
Suggested-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Change every shebang which does not need an argument to use /usr/bin/env.
This is needed as not every distro has everything under /usr/bin,
sometimes not even bash.
Signed-off-by: Finn Behrens <me@kloenk.de>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Pull char/misc driver fixes from Greg KH:
 "Here are some small driver fixes, and one "large" revert, for
  5.10-rc7.

  They include:

   - revert mei patch from 5.10-rc1 that was using a reserved userspace
     value. It will be resubmitted once the proper id has been assigned
     by the virtio people.

   - habanalabs fixes found by the fall-through audit from Gustavo

   - speakup driver fixes for reported issues

   - fpga config build fix for reported issue.

  All of these except the revert have been in linux-next with no
  reported issues. The revert is "clean" and just removes a
  previously-added driver, so no real issue there"

* tag 'char-misc-5.10-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc:
  Revert "mei: virtio: virtualization frontend driver"
  fpga: Specify HAS_IOMEM dependency for FPGA_DFL
  habanalabs: put devices before driver removal
  habanalabs: free host huge va_range if not used
  speakup: Reject setting the speakup line discipline outside of speakup

Pull tty fixes from Greg KH:
 "Here are two tty core fixes for 5.10-rc7.

  They resolve some reported locking issues in the tty core. While they
  have not been in a released linux-next yet, they have passed all of
  the 0-day bot testing as well as the submitter's testing"

* tag 'tty-5.10-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty:
  tty: Fix ->session locking
  tty: Fix ->pgrp locking in tiocspgrp()

Pull USB fixes from Greg KH:
 "Here are some small USB fixes for 5.10-rc7 that resolve a number of
  reported issues, and add some new device ids.

  Nothing major here, but these solve some problems that people were
  having with the 5.10-rc tree:

   - reverts for USB storage dma settings that broke working devices

   - thunderbolt use-after-free fix

   - cdns3 driver fixes

   - gadget driver userspace copy fix

   - new device ids

  All of these except for the reverts have been in linux-next with no
  reported issues. The reverts are "clean" and were tested by Hans, as
  well as passing the 0-day tests"

* tag 'usb-5.10-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb:
  usb: gadget: f_fs: Use local copy of descriptors for userspace copy
  usb: ohci-omap: Fix descriptor conversion
  Revert "usb-storage: fix sdev->host->dma_dev"
  Revert "uas: fix sdev->host->dma_dev"
  Revert "uas: bump hw_max_sectors to 2048 blocks for SS or faster drives"
  USB: serial: kl5kusb105: fix memleak on open
  USB: serial: ch341: sort device-id entries
  USB: serial: ch341: add new Product ID for CH341A
  USB: serial: option: fix Quectel BG96 matching
  usb: cdns3: core: fix goto label for error path
  usb: cdns3: gadget: clear trb->length as zero after preparing every trb
  usb: cdns3: Fix hardware based role switch
  USB: serial: option: add support for Thales Cinterion EXS82
  USB: serial: option: add Fibocom NL668 variants
  thunderbolt: Fix use-after-free in remove_unplugged_switch()

Pull x86 fixes from Thomas Gleixner:
 "A set of fixes for x86:

   - Make the AMD L3 QoS code and data priorization enable/disable
     mechanism work correctly.

     The control bit was only set/cleared on one of the CPUs in a L3
     domain, but it has to be modified on all CPUs in the domain. The
     initial documentation was not clear about this, but the updated one
     from Oct 2020 spells it out.

   - Fix an off by one in the UV platform detection code which causes
     the UV hubs to be identified wrongly.

     The chip revisions start at 1 not at 0.

   - Fix a long standing bug in the evaluation of prefixes in the
     uprobes code which fails to handle repeated prefixes properly.

     The aggregate size of the prefixes can be larger than the bytes
     array but the code blindly iterated over the aggregate size beyond
     the array boundary. Add a macro to handle this case properly and
     use it at the affected places"

* tag 'x86-urgent-2020-12-06' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/sev-es: Use new for_each_insn_prefix() macro to loop over prefixes bytes
  x86/insn-eval: Use new for_each_insn_prefix() macro to loop over prefixes bytes
  x86/uprobes: Do not use prefixes.nbytes when looping over prefixes.bytes
  x86/platform/uv: Fix UV4 hub revision adjustment
  x86/resctrl: Fix AMD L3 QOS CDP enable/disable

Pull perf fixes from Thomas Gleixner:
 "Two fixes for performance monitoring on X86:

   - Add recursion protection to another callchain invoked from
     x86_pmu_stop() which can recurse back into x86_pmu_stop(). The
     first attempt to fix this missed this extra code path.

   - Use the already filtered status variable to check for PEBS counter
     overflow bits and not the unfiltered full status read from
     IA32_PERF_GLOBAL_STATUS which can have unrelated bits check which
     would be evaluated incorrectly"

* tag 'perf-urgent-2020-12-06' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf/x86/intel: Check PEBS status correctly
  perf/x86/intel: Fix a warning on x86_pmu_stop() with large PEBS

Pull irq fixes from Thomas Gleixner:
 "A set of updates for the interrupt subsystem:

   - Make multiqueue devices which use the managed interrupt affinity
     infrastructure work on PowerPC/Pseries. PowerPC does not use the
     generic infrastructure for setting up PCI/MSI interrupts and the
     multiqueue changes failed to update the legacy PCI/MSI
     infrastructure. Make this work by passing the affinity setup
     information down to the mapping and allocation functions.

   - Move Jason Cooper from MAINTAINERS to CREDITS as his mail is
     bouncing and he's not reachable. We hope all is well with him and
     say thanks for his work over the years"

* tag 'irq-urgent-2020-12-06' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  powerpc/pseries: Pass MSI affinity to irq_create_mapping()
  genirq/irqdomain: Add an irq_create_mapping_affinity() function
  MAINTAINERS: Move Jason Cooper to CREDITS

Pull intel_idle build fix from Thomas Gleixner:
 "A tiny build fix for a recent change in the intel_idle driver which
  missed a CONFIG dependency and broke the build for certain
  configurations"

* tag 'locking-urgent-2020-12-06' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  intel_idle: Build fix

Merge tag 'kbuild-fixes-v5.10-2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild fixes from Masahiro Yamada:

 - Move -Wcast-align to W=3, which tends to be false-positive and there
   is no tree-wide solution.

 - Pass -fmacro-prefix-map to KBUILD_CPPFLAGS because it is a
   preprocessor option and makes sense for .S files as well.

 - Disable -gdwarf-2 for Clang's integrated assembler to avoid warnings.

 - Disable --orphan-handling=warn for LLD 10.0.1 to avoid warnings.

 - Fix undesirable line breaks in *.mod files.

* tag 'kbuild-fixes-v5.10-2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
  kbuild: avoid split lines in .mod files
  kbuild: Disable CONFIG_LD_ORPHAN_WARN for ld.lld 10.0.1
  kbuild: Hoist '--orphan-handling' into Kconfig
  Kbuild: do not emit debug info for assembly with LLVM_IAS=1
  kbuild: use -fmacro-prefix-map for .S sources
  Makefile.extrawarn: move -Wcast-align to W=3

Merge misc fixes from Andrew Morton:
 "12 patches.

  Subsystems affected by this patch series: mm (memcg, zsmalloc, swap,
  mailmap, selftests, pagecache, hugetlb, pagemap), lib, and coredump"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>:
  mm/mmap.c: fix mmap return value when vma is merged after call_mmap()
  hugetlb_cgroup: fix offline of hugetlb cgroup with reservations
  mm/filemap: add static for function __add_to_page_cache_locked
  userfaultfd: selftests: fix SIGSEGV if huge mmap fails
  tools/testing/selftests/vm: fix build error
  mailmap: add two more addresses of Uwe Kleine-König
  mm/swapfile: do not sleep with a spin lock held
  mm/zsmalloc.c: drop ZSMALLOC_PGTABLE_MAPPING
  mm: list_lru: set shrinker map bit when child nr_items is not zero
  mm: memcg/slab: fix obj_cgroup_charge() return value handling
  coredump: fix core_pattern parse error
  zlib: export S390 symbols for zlib modules

On success, mmap should return the begin address of newly mapped area,
but patch "mm: mmap: merge vma after call_mmap() if possible" set
vm_start of newly merged vma to return value addr.  Users of mmap will
get wrong address if vma is merged after call_mmap().  We fix this by
moving the assignment to addr before merging vma.

We have a driver which changes vm_flags, and this bug is found by our
testcases.

Fixes: d70cec89 ("mm: mmap: merge vma after call_mmap() if possible")
Signed-off-by: Liu Zixian <liuzixian4@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Hongxiang Lou <louhongxiang@huawei.com>
Cc: Hu Shiyuan <hushiyuan@huawei.com>
Cc: Matthew Wilcox <willy@infradead.org>
Link: https://lkml.kernel.org/r/20201203085350.22624-1-liuzixian4@huawei.comSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Adrian Moreno was ruuning a kubernetes 1.19 + containerd/docker workload
using hugetlbfs.  In this environment the issue is reproduced by:

 - Start a simple pod that uses the recently added HugePages medium
   feature (pod yaml attached)

 - Start a DPDK app. It doesn't need to run successfully (as in transfer
   packets) nor interact with real hardware. It seems just initializing
   the EAL layer (which handles hugepage reservation and locking) is
   enough to trigger the issue

 - Delete the Pod (or let it "Complete").

This would result in a kworker thread going into a tight loop (top output):

   1425 root      20   0       0      0      0 R  99.7   0.0   5:22.45 kworker/28:7+cgroup_destroy

'perf top -g' reports:

  -   63.28%     0.01%  [kernel]                    [k] worker_thread
     - 49.97% worker_thread
        - 52.64% process_one_work
           - 62.08% css_killed_work_fn
              - hugetlb_cgroup_css_offline
                   41.52% _raw_spin_lock
                 - 2.82% _cond_resched
                      rcu_all_qs
                   2.66% PageHuge
        - 0.57% schedule
           - 0.57% __schedule

We are spinning in the do-while loop in hugetlb_cgroup_css_offline.
Worse yet, we are holding the master cgroup lock (cgroup_mutex) while
infinitely spinning.  Little else can be done on the system as the
cgroup_mutex can not be acquired.

Do note that the issue can be reproduced by simply offlining a hugetlb
cgroup containing pages with reservation counts.

The loop in hugetlb_cgroup_css_offline is moving page counts from the
cgroup being offlined to the parent cgroup.  This is done for each
hstate, and is repeated until hugetlb_cgroup_have_usage returns false.
The routine moving counts (hugetlb_cgroup_move_parent) is only moving
'usage' counts.  The routine hugetlb_cgroup_have_usage is checking for
both 'usage' and 'reservation' counts.  Discussion about what to do with
reservation counts when reparenting was discussed here:

https://lore.kernel.org/linux-kselftest/CAHS8izMFAYTgxym-Hzb_JmkTK1N_S9tGN71uS6MFV+R7swYu5A@mail.gmail.com/

The decision was made to leave a zombie cgroup for with reservation
counts.  Unfortunately, the code checking reservation counts was
incorrectly added to hugetlb_cgroup_have_usage.

To fix the issue, simply remove the check for reservation counts.  While
fixing this issue, a related bug in hugetlb_cgroup_css_offline was
noticed.  The hstate index is not reinitialized each time through the
do-while loop.  Fix this as well.

Fixes: 1adc4d41 ("hugetlb_cgroup: add interface for charge/uncharge hugetlb reservations")
Reported-by: Adrian Moreno <amorenoz@redhat.com>
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Adrian Moreno <amorenoz@redhat.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Sandipan Das <sandipan@linux.ibm.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20201203220242.158165-1-mike.kravetz@oracle.comSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

  mm/filemap.c:830:14: warning: no previous prototype for `__add_to_page_cache_locked' [-Wmissing-prototypes]
Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Link: https://lkml.kernel.org/r/1604661895-5495-1-git-send-email-alex.shi@linux.alibaba.comSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The error handling in hugetlb_allocate_area() was incorrect for the
hugetlb_shared test case.

Previously the behavior was:

- mmap a hugetlb area
  - If this fails, set the pointer to NULL, and carry on
- mmap an alias of the same hugetlb fd
  - If this fails, munmap the original area

If the original mmap failed, it's likely the second one did too.  If
both failed, we'd blindly try to munmap a NULL pointer, causing a
SIGSEGV.  Instead, "goto fail" so we return before trying to mmap the
alias.

This issue can be hit "in real life" by forgetting to set
/proc/sys/vm/nr_hugepages (leaving it at 0), and then trying to run the
hugetlb_shared test.

Another small improvement is, when the original mmap fails, don't just
print "it failed": perror(), so we can see *why*.  :)
Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Joe Perches <joe@perches.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Alan Gilbert <dgilbert@redhat.com>
Link: https://lkml.kernel.org/r/20201204203443.2714693-1-axelrasmussen@google.comSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Only x86 and PowerPC implement the pkey-xxx.h, and an error was reported
when compiling protection_keys.c.

Add a Arch judgment to compile "protection_keys" in the Makefile.

If other arch implement this, add the arch name to the Makefile.
eg:
    ifneq (,$(findstring $(ARCH),powerpc mips ... ))

Following build errors:

    pkey-helpers.h:93:2: error: #error Architecture not supported
     #error Architecture not supported
    pkey-helpers.h:96:20: error: `PKEY_DISABLE_ACCESS' undeclared
     #define PKEY_MASK (PKEY_DISABLE_ACCESS | PKEY_DISABLE_WRITE)
                        ^
    protection_keys.c:218:45: error: `PKEY_DISABLE_WRITE' undeclared
     pkey_assert(flags & (PKEY_DISABLE_ACCESS | PKEY_DISABLE_WRITE));
                                                ^
Signed-off-by: Xingxing Su <suxingxing@loongson.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Sandipan Das <sandipan@linux.ibm.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: Mina Almasry <almasrymina@google.com>
Link: https://lkml.kernel.org/r/1606826876-30656-1-git-send-email-suxingxing@loongson.cnSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This fixes attribution for the commits (among others)

 - d4097456 ("video/framebuffer: move the probe func into
   .devinit.text in Blackfin LCD driver")

 - 0312e024 ("mfd: mc13xxx: Add support for mc34708")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Link: https://lkml.kernel.org/r/20201127213358.3440830-1-u.kleine-koenig@pengutronix.deSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

We can't call kvfree() with a spin lock held, so defer it.  Fixes a
might_sleep() runtime warning.

Fixes: 873d7bcf ("mm/swapfile.c: use kvzalloc for swap_info_struct allocation")
Signed-off-by: Qian Cai <qcai@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20201202151549.10350-1-qcai@redhat.comSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

While I was doing zram testing, I found sometimes decompression failed
since the compression buffer was corrupted.  With investigation, I found
below commit calls cond_resched unconditionally so it could make a
problem in atomic context if the task is reschedule.

  BUG: sleeping function called from invalid context at mm/vmalloc.c:108
  in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 946, name: memhog
  3 locks held by memhog/946:
   #0: ffff9d01d4b193e8 (&mm->mmap_lock#2){++++}-{4:4}, at: __mm_populate+0x103/0x160
   #1: ffffffffa3d53de0 (fs_reclaim){+.+.}-{0:0}, at: __alloc_pages_slowpath.constprop.0+0xa98/0x1160
   #2: ffff9d01d56b8110 (&zspage->lock){.+.+}-{3:3}, at: zs_map_object+0x8e/0x1f0
  CPU: 0 PID: 946 Comm: memhog Not tainted 5.9.3-00011-gc5bfc0287345-dirty #316
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1 04/01/2014
  Call Trace:
    unmap_kernel_range_noflush+0x2eb/0x350
    unmap_kernel_range+0x14/0x30
    zs_unmap_object+0xd5/0xe0
    zram_bvec_rw.isra.0+0x38c/0x8e0
    zram_rw_page+0x90/0x101
    bdev_write_page+0x92/0xe0
    __swap_writepage+0x94/0x4a0
    pageout+0xe3/0x3a0
    shrink_page_list+0xb94/0xd60
    shrink_inactive_list+0x158/0x460

We can fix this by removing the ZSMALLOC_PGTABLE_MAPPING feature (which
contains the offending calling code) from zsmalloc.

Even though this option showed some amount improvement(e.g., 30%) in
some arm32 platforms, it has been headache to maintain since it have
abused APIs[1](e.g., unmap_kernel_range in atomic context).

Since we are approaching to deprecate 32bit machines and already made
the config option available for only builtin build since v5.8, lastly it
has been not default option in zsmalloc, it's time to drop the option
for better maintenance.

[1] http://lore.kernel.org/linux-mm/20201105170249.387069-1-minchan@kernel.org

Fixes: e47110e9 ("mm/vunmap: add cond_resched() in vunmap_pmd_range")
Signed-off-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Tony Lindgren <tony@atomide.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Harish Sriram <harish@linux.ibm.com>
Cc: Uladzislau Rezki <urezki@gmail.com>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20201117202916.GA3856507@google.comSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

When investigating a slab cache bloat problem, significant amount of
negative dentry cache was seen, but confusingly they neither got shrunk
by reclaimer (the host has very tight memory) nor be shrunk by dropping
cache.  The vmcore shows there are over 14M negative dentry objects on
lru, but tracing result shows they were even not scanned at all.

Further investigation shows the memcg's vfs shrinker_map bit is not set.
So the reclaimer or dropping cache just skip calling vfs shrinker.  So
we have to reboot the hosts to get the memory back.

I didn't manage to come up with a reproducer in test environment, and
the problem can't be reproduced after rebooting.  But it seems there is
race between shrinker map bit clear and reparenting by code inspection.
The hypothesis is elaborated as below.

The memcg hierarchy on our production environment looks like:

                root
               /    \
          system   user

The main workloads are running under user slice's children, and it
creates and removes memcg frequently.  So reparenting happens very often
under user slice, but no task is under user slice directly.

So with the frequent reparenting and tight memory pressure, the below
hypothetical race condition may happen:

       CPU A                            CPU B
reparent
    dst->nr_items == 0
                                 shrinker:
                                     total_objects == 0
    add src->nr_items to dst
    set_bit
                                     return SHRINK_EMPTY
                                     clear_bit
child memcg offline
    replace child's kmemcg_id with
    parent's (in memcg_offline_kmem())
                                  list_lru_del() between shrinker runs
                                     see parent's kmemcg_id
                                     dec dst->nr_items
reparent again
    dst->nr_items may go negative
    due to concurrent list_lru_del()

                                 The second run of shrinker:
                                     read nr_items without any
                                     synchronization, so it may
                                     see intermediate negative
                                     nr_items then total_objects
                                     may return 0 coincidently

                                     keep the bit cleared
    dst->nr_items != 0
    skip set_bit
    add scr->nr_item to dst

After this point dst->nr_item may never go zero, so reparenting will not
set shrinker_map bit anymore.  And since there is no task under user
slice directly, so no new object will be added to its lru to set the
shrinker map bit either.  That bit is kept cleared forever.

How does list_lru_del() race with reparenting? It is because reparenting
replaces children's kmemcg_id to parent's without protecting from
nlru->lock, so list_lru_del() may see parent's kmemcg_id but actually
deleting items from child's lru, but dec'ing parent's nr_items, so the
parent's nr_items may go negative as commit 2788cf0c ("memcg:
reparent list_lrus and free kmemcg_id on css offline") says.

Since it is impossible that dst->nr_items goes negative and
src->nr_items goes zero at the same time, so it seems we could set the
shrinker map bit iff src->nr_items != 0.  We could synchronize
list_lru_count_one() and reparenting with nlru->lock, but it seems
checking src->nr_items in reparenting is the simplest and avoids lock
contention.

Fixes: fae91d6d ("mm/list_lru.c: set bit in memcg shrinker bitmap on first list_lru item appearance")
Suggested-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: <stable@vger.kernel.org>	[4.19]
Link: https://lkml.kernel.org/r/20201202171749.264354-1-shy828301@gmail.comSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Commit 10befea9 ("mm: memcg/slab: use a single set of kmem_caches
for all allocations") introduced a regression into the handling of the
obj_cgroup_charge() return value.  If a non-zero value is returned
(indicating of exceeding one of memory.max limits), the allocation
should fail, instead of falling back to non-accounted mode.

To make the code more readable, move memcg_slab_pre_alloc_hook() and
memcg_slab_post_alloc_hook() calling conditions into bodies of these
hooks.

Fixes: 10befea9 ("mm: memcg/slab: use a single set of kmem_caches for all allocations")
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20201127161828.GD840171@carbon.dhcp.thefacebook.comSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

'format_corename()' will splite 'core_pattern' on spaces when it is in
pipe mode, and take helper_argv[0] as the path to usermode executable.
It works fine in most cases.

However, if there is a space between '|' and '/file/path', such as
'| /usr/lib/systemd/systemd-coredump %P %u %g', then helper_argv[0] will
be parsed as '', and users will get a 'Core dump to | disabled'.

It is not friendly to users, as the pattern above was valid previously.
Fix this by ignoring the spaces between '|' and '/file/path'.

Fixes: 315c6926 ("coredump: split pipe command whitespace before expanding template")
Signed-off-by: Menglong Dong <dong.menglong@zte.com.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul Wise <pabs3@bonedaddy.net>
Cc: Jakub Wilk <jwilk@jwilk.net> [https://bugs.debian.org/924398]
Cc: Neil Horman <nhorman@tuxdriver.com>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/5fb62870.1c69fb81.8ef5d.af76@mx.google.comSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Fix build errors when ZLIB_INFLATE=m and ZLIB_DEFLATE=m and ZLIB_DFLTCC=y
by exporting the 2 needed symbols in dfltcc_inflate.c.

Fixes these build errors:

  ERROR: modpost: "dfltcc_inflate" [lib/zlib_inflate/zlib_inflate.ko] undefined!
  ERROR: modpost: "dfltcc_can_inflate" [lib/zlib_inflate/zlib_inflate.ko] undefined!

Fixes: 12619610 ("lib/zlib: add s390 hardware support for kernel zlib_inflate")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Ilya Leoshkevich <iii@linux.ibm.com>
Cc: Mikhail Zaslonko <zaslonko@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Link: https://lkml.kernel.org/r/20201123191712.4882-1-rdunlap@infradead.orgSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

"xargs echo" is not a safe way to remove line breaks because the input
may exceed the command line limit and xargs may break it up into
multiple invocations of echo. This should never happen because
scripts/gen_autoksyms.sh expects all undefined symbols are placed in
the second line of .mod files.

One possible way is to replace "xargs echo" with
"sed ':x;N;$!bx;s/\n/ /g'" or something, but I rewrote the code by
using awk because it is more readable.

This issue was reported by Sami Tolvanen; in his Clang LTO patch set,
$(multi-used-m) is no longer an ELF object, but a thin archive that
contains LLVM bitcode files. llvm-nm prints out symbols for each
archive member separately, which results a lot of dupications, in some
places, beyond the system-defined limit.

This problem must be fixed irrespective of LTO, and we must ensure
zero possibility of having this issue.

Link: https://lkml.org/lkml/2020/12/1/1658Reported-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>

This reverts commit d162219c.

The device uses a VIRTIO device ID out of a not-for-production range.
Releasing Linux using an ID out of this range will make it conflict with
development setups. An official request to reserve an ID for an MEI
device is yet to be submitted to the virtio TC, thus there's no chance
it will be reserved and fixed in time before the next release.

Once requested it usually takes 2-3 weeks to land in the spec, which
means the device can be supported with the official ID in the next Linux
version if contributors act quickly.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Cc: Tomas Winkler <tomas.winkler@intel.com>
Cc: Alexander Usyskin <alexander.usyskin@intel.com>
Cc: Wang Yu <yu1.wang@intel.com>
Cc: Liu Shuo <shuo.a.liu@intel.com>
Link: https://lore.kernel.org/r/20201205193625.469773-1-mst@redhat.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Since insn.prefixes.nbytes can be bigger than the size of
insn.prefixes.bytes[] when a prefix is repeated, the proper
check must be:

  insn.prefixes.bytes[i] != 0 and i < 4

instead of using insn.prefixes.nbytes. Use the new
for_each_insn_prefix() macro which does it correctly.

Debugged by Kees Cook <keescook@chromium.org>.

 [ bp: Massage commit message. ]

Fixes: 25189d08 ("x86/sev-es: Add support for handling IOIO exceptions")
Reported-by: syzbot+9b64b619f10f19d19a7c@syzkaller.appspotmail.com
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/160697106089.3146288.2052422845039649176.stgit@devnote2

Since insn.prefixes.nbytes can be bigger than the size of
insn.prefixes.bytes[] when a prefix is repeated, the proper check must
be

  insn.prefixes.bytes[i] != 0 and i < 4

instead of using insn.prefixes.nbytes. Use the new
for_each_insn_prefix() macro which does it correctly.

Debugged by Kees Cook <keescook@chromium.org>.

 [ bp: Massage commit message. ]

Fixes: 32d0b953 ("x86/insn-eval: Add utility functions to get segment selector")
Reported-by: syzbot+9b64b619f10f19d19a7c@syzkaller.appspotmail.com
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/160697104969.3146288.16329307586428270032.stgit@devnote2

Since insn.prefixes.nbytes can be bigger than the size of
insn.prefixes.bytes[] when a prefix is repeated, the proper check must
be

  insn.prefixes.bytes[i] != 0 and i < 4

instead of using insn.prefixes.nbytes.

Introduce a for_each_insn_prefix() macro for this purpose. Debugged by
Kees Cook <keescook@chromium.org>.

 [ bp: Massage commit message, sync with the respective header in tools/
   and drop "we". ]

Fixes: 2b144498 ("uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints")
Reported-by: syzbot+9b64b619f10f19d19a7c@syzkaller.appspotmail.com
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/160697103739.3146288.7437620795200799020.stgit@devnote2

Pull input fixes from Dmitry Torokhov:
 "A fix for 'RETRIGEN' handling in Atmel touch controllers that was
  causing lost interrupts on systems using edge-triggered interrupts, a
  quirk for i8042 driver, and a couple more fixes."

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input:
  Input: atmel_mxt_ts - fix lost interrupts
  Input: xpad - support Ardwiino Controllers
  Input: i8042 - add ByteSpeed touchpad to noloop table
  Input: i8042 - fix error return code in i8042_setup_aux()
  Input: soc_button_array - add missing include

Pull i2c fixes from Wolfram Sang:
 "Some more I2C driver updates. IMX updates are a tad bigger, but not
  exceptionally big"

* 'i2c/for-current' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux:
  i2c: mlxbf: Fix the return check of devm_ioremap and ioremap
  i2c: mlxbf: select CONFIG_I2C_SLAVE
  i2c: imx: Don't generate STOP condition if arbitration has been lost
  i2c: imx: Check for I2SR_IAL after every byte
  i2c: imx: Fix reset of I2SR_IAL flag
  i2c: qcom: Fix IRQ error misassignement
  i2c: qup: Fix error return code in qup_i2c_bam_schedule_desc()

Pull block fix from Jens Axboe:
 "Single fix for an issue with chunk_sectors and stacked devices"

* tag 'block-5.10-2020-12-05' of git://git.kernel.dk/linux-block:
  block: use gcd() to fix chunk_sectors limit stacking

Pull io_uring fix from Jens Axboe:
 "Just a small fix this time, for an issue with 32-bit compat apps and
  buffer selection with recvmsg"

* tag 'io_uring-5.10-2020-12-05' of git://git.kernel.dk/linux-block:
  io_uring: fix recvmsg setup with compat buf-select