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Hugh Dickins 629ee482e0 mm/thp: fix __split_huge_pmd_locked() on shmem migration entry 
[ Upstream commit 99fa8a4820 ]

Patch series "mm/thp: fix THP splitting unmap BUGs and related", v10.

Here is v2 batch of long-standing THP bug fixes that I had not got
around to sending before, but prompted now by Wang Yugui's report
https://lore.kernel.org/linux-mm/20210412180659.B9E3.409509F4@e16-tech.com/

Wang Yugui has tested a rollup of these fixes applied to 5.10.39, and
they have done no harm, but have *not* fixed that issue: something more
is needed and I have no idea of what.

This patch (of 7):

Stressing huge tmpfs page migration racing hole punch often crashed on
the VM_BUG_ON(!pmd_present) in pmdp_huge_clear_flush(), with DEBUG_VM=y
kernel; or shortly afterwards, on a bad dereference in
__split_huge_pmd_locked() when DEBUG_VM=n.  They forgot to allow for pmd
migration entries in the non-anonymous case.

Full disclosure: those particular experiments were on a kernel with more
relaxed mmap_lock and i_mmap_rwsem locking, and were not repeated on the
vanilla kernel: it is conceivable that stricter locking happens to avoid
those cases, or makes them less likely; but __split_huge_pmd_locked()
already allowed for pmd migration entries when handling anonymous THPs,
so this commit brings the shmem and file THP handling into line.

And while there: use old_pmd rather than _pmd, as in the following
blocks; and make it clearer to the eye that the !vma_is_anonymous()
block is self-contained, making an early return after accounting for
unmapping.

Link: https://lkml.kernel.org/r/af88612-1473-2eaa-903-8d1a448b26@google.com
Link: https://lkml.kernel.org/r/dd221a99-efb3-cd1d-6256-7e646af29314@google.com
Fixes: e71769ae52 ("mm: enable thp migration for shmem thp")
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Wang Yugui <wangyugui@e16-tech.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Jue Wang <juew@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Note on stable backport: this commit made intervening cleanups in
pmdp_huge_clear_flush() redundant: here it's rediffed to skip them.

Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-07-11 12:49:27 +02:00
arch PCI: Add AMD RS690 quirk to enable 64-bit DMA 2021-06-30 08:48:33 -04:00
block blk-mq: Swap two calls in blk_mq_exit_queue() 2021-05-22 10:59:46 +02:00
certs certs: Fix blacklist flag type confusion 2021-03-04 09:39:44 +01:00
crypto crypto: api - check for ERR pointers in crypto_destroy_tfm() 2021-05-22 10:59:14 +02:00
Documentation mm/slub: clarify verification reporting 2021-06-30 08:48:26 -04:00
drivers i2c: robotfuzz-osif: fix control-request directions 2021-06-30 08:48:34 -04:00
firmware Fix built-in early-load Intel microcode alignment 2020-01-23 08:21:29 +01:00
fs nilfs2: fix memory leak in nilfs_sysfs_delete_device_group 2021-06-30 08:48:34 -04:00
include mm: add VM_WARN_ON_ONCE_PAGE() macro 2021-07-11 12:49:26 +02:00
init pid: take a reference when initializing cad_pid 2021-06-10 13:24:06 +02:00
ipc ipc/util.c: sysvipc_find_ipc() incorrectly updates position index 2020-05-20 08:18:40 +02:00
kernel module: limit enabling module.sig_enforce 2021-06-30 08:48:28 -04:00
lib lib: stackdepot: turn depot_lock spinlock to raw_spinlock 2021-05-22 10:59:49 +02:00
LICENSES LICENSES: Remove CC-BY-SA-4.0 license text 2018-10-18 11:28:50 +02:00
mm mm/thp: fix __split_huge_pmd_locked() on shmem migration entry 2021-07-11 12:49:27 +02:00
net net/packet: annotate accesses to po->ifindex 2021-06-30 08:48:31 -04:00
samples samples: vfio-mdev: fix error handing in mdpy_fb_probe() 2021-06-10 13:24:04 +02:00
scripts scripts: switch explicitly to Python 3 2021-05-22 10:59:50 +02:00
security security: commoncap: fix -Wstringop-overread warning 2021-05-22 10:59:21 +02:00
sound ASoC: rt5659: Fix the lost powers for the HDA header 2021-06-30 08:48:21 -04:00
tools KVM: selftests: Fix kvm_check_cap() assertion 2021-06-30 08:48:32 -04:00
usr initramfs: restore default compression behavior 2020-04-13 10:44:59 +02:00
virt KVM: arm/arm64: Fix KVM_VGIC_V3_ADDR_TYPE_REDIST read 2021-06-30 08:48:27 -04:00
.clang-format clang-format: Set IndentWrappedFunctionNames false 2018-08-01 18:38:51 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Kbuild updates for v4.17 (2nd) 2018-04-15 17:21:30 -07:00
.mailmap libnvdimm-for-4.19_misc 2018-08-25 18:13:10 -07:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS 9p: remove Ron Minnich from MAINTAINERS 2018-08-17 16:20:26 -07:00
Kbuild Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS Documentation/llvm: add documentation on building w/ Clang/LLVM 2020-09-26 18:01:31 +02:00
Makefile Linux 4.19.196 2021-06-30 09:18:40 -04:00
README Docs: Added a pointer to the formatted docs to README 2018-03-21 09:02:53 -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.
See Documentation/00-INDEX for a list of what is contained in each file.

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.