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Mike Kravetz 302b9e1899 cma: don't quit at first error when activating reserved areas 
[ Upstream commit 3a5139f1c5 ]

The routine cma_init_reserved_areas is designed to activate all
reserved cma areas.  It quits when it first encounters an error.
This can leave some areas in a state where they are reserved but
not activated.  There is no feedback to code which performed the
reservation.  Attempting to allocate memory from areas in such a
state will result in a BUG.

Modify cma_init_reserved_areas to always attempt to activate all
areas.  The called routine, cma_activate_area is responsible for
leaving the area in a valid state.  No one is making active use
of returned error codes, so change the routine to void.

How to reproduce:  This example uses kernelcore, hugetlb and cma
as an easy way to reproduce.  However, this is a more general cma
issue.

Two node x86 VM 16GB total, 8GB per node
Kernel command line parameters, kernelcore=4G hugetlb_cma=8G
Related boot time messages,
  hugetlb_cma: reserve 8192 MiB, up to 4096 MiB per node
  cma: Reserved 4096 MiB at 0x0000000100000000
  hugetlb_cma: reserved 4096 MiB on node 0
  cma: Reserved 4096 MiB at 0x0000000300000000
  hugetlb_cma: reserved 4096 MiB on node 1
  cma: CMA area hugetlb could not be activated

 # echo 8 > /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages

  BUG: kernel NULL pointer dereference, address: 0000000000000000
  #PF: supervisor read access in kernel mode
  #PF: error_code(0x0000) - not-present page
  PGD 0 P4D 0
  Oops: 0000 [#1] SMP PTI
  ...
  Call Trace:
    bitmap_find_next_zero_area_off+0x51/0x90
    cma_alloc+0x1a5/0x310
    alloc_fresh_huge_page+0x78/0x1a0
    alloc_pool_huge_page+0x6f/0xf0
    set_max_huge_pages+0x10c/0x250
    nr_hugepages_store_common+0x92/0x120
    ? __kmalloc+0x171/0x270
    kernfs_fop_write+0xc1/0x1a0
    vfs_write+0xc7/0x1f0
    ksys_write+0x5f/0xe0
    do_syscall_64+0x4d/0x90
    entry_SYSCALL_64_after_hwframe+0x44/0xa9

Fixes: c64be2bb1c ("drivers: add Contiguous Memory Allocator")
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Roman Gushchin <guro@fb.com>
Acked-by: Barry Song <song.bao.hua@hisilicon.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/20200730163123.6451-1-mike.kravetz@oracle.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
 		2020-09-03 11:26:51 +02:00
Documentation kbuild: support LLVM=1 to switch the default tools to Clang/LLVM 2020-08-26 10:40:47 +02:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
arch s390/numa: set node distance to LOCAL_DISTANCE 2020-09-03 11:26:50 +02:00
block iocost: Fix check condition of iocg abs_vdebt 2020-08-19 08:15:58 +02:00
certs PKCS#7: Refactor verify_pkcs7_signature() 2019-08-05 18:40:18 -04:00
crypto crypto: algif_aead - fix uninitialized ctx->init 2020-08-21 13:05:38 +02:00
drivers drm/xen-front: Fix misused IS_ERR_OR_NULL checks 2020-09-03 11:26:50 +02:00
fs btrfs: only commit delayed items at fsync if we are logging a directory 2020-09-03 11:26:51 +02:00
include efi: provide empty efi_enter_virtual_mode implementation 2020-09-03 11:26:49 +02:00
init x86: Fix early boot crash on gcc-10, third try 2020-05-20 08:20:34 +02:00
ipc ipc/util.c: sysvipc_find_ipc() incorrectly updates position index 2020-05-20 08:20:16 +02:00
kernel sched/uclamp: Fix a deadlock when enabling uclamp static key 2020-09-03 11:26:49 +02:00
lib test_kmod: avoid potential double free in trigger_config_run_type() 2020-08-21 13:05:37 +02:00
mm cma: don't quit at first error when activating reserved areas 2020-09-03 11:26:51 +02:00
net net/sched: act_ct: Fix skb double-free in tcf_ct_handle_fragments() error flow 2020-09-03 11:26:40 +02:00
samples bpf: Fix fds_example SIGSEGV error 2020-08-19 08:16:03 +02:00
scripts kconfig: qconf: fix signal connection to invalid slots 2020-08-26 10:41:04 +02:00
security Smack: prevent underflow in smk_set_cipso() 2020-08-19 08:16:16 +02:00
sound ALSA: hda: Add support for Loongson 7A1000 controller 2020-09-03 11:26:45 +02:00
tools selftests/powerpc: Purge extra count_pmc() calls of ebb selftests 2020-09-03 11:26:44 +02:00
usr initramfs: restore default compression behavior 2020-04-08 09:08:38 +02:00
virt KVM: arm64: Only reschedule if MMU_NOTIFIER_RANGE_BLOCKABLE is not set 2020-08-26 10:41:08 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Modules updates for v5.4 2019-09-22 10:34:46 -07:00
.mailmap ARM: SoC fixes 2019-11-10 13:41:59 -08:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS: Remove Simon as Renesas SoC Co-Maintainer 2019-10-10 08:12:51 -07:00
Kbuild kbuild: do not descend to ./Kbuild when cleaning 2019-08-21 21:03:58 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS Documentation/llvm: add documentation on building w/ Clang/LLVM 2020-08-26 10:40:46 +02:00
Makefile Linux 5.4.61 2020-08-26 10:41:08 +02:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.