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Konstantin Khlebnikov 605ca5ede7 mm/huge_memory.c: reorder operations in __split_huge_page_tail() 
THP split makes non-atomic change of tail page flags.  This is almost ok
because tail pages are locked and isolated but this breaks recent
changes in page locking: non-atomic operation could clear bit
PG_waiters.

As a result concurrent sequence get_page_unless_zero() -> lock_page()
might block forever.  Especially if this page was truncated later.

Fix is trivial: clone flags before unfreezing page reference counter.

This race exists since commit 6290602709 ("mm: add PageWaiters
indicating tasks are waiting for a page bit") while unsave unfreeze
itself was added in commit 8df651c705 ("thp: cleanup
split_huge_page()").

clear_compound_head() also must be called before unfreezing page
reference because after successful get_page_unless_zero() might follow
put_page() which needs correct compound_head().

And replace page_ref_inc()/page_ref_add() with page_ref_unfreeze() which
is made especially for that and has semantic of smp_store_release().

Link: http://lkml.kernel.org/r/151844393341.210639.13162088407980624477.stgit@buzz
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-04-05 21:36:25 -07:00
arch x86/mm/memory_hotplug: determine block size based on the end of boot memory 2018-04-05 21:36:25 -07:00
block Char/Misc patches for 4.17-rc1 2018-04-04 20:07:20 -07:00
certs certs/blacklist_nohashes.c: fix const confusion in certs blacklist 2018-02-21 15:35:43 -08:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2018-04-04 17:11:08 -07:00
Documentation mm, page_alloc: extend kernelcore and movablecore for percent 2018-04-05 21:36:25 -07:00
drivers mm/memory_hotplug: optimize memory hotplug 2018-04-05 21:36:25 -07:00
firmware kbuild: remove all dummy assignments to obj- 2017-11-18 11:46:06 +09:00
fs fs: don't flush pagecache when expanding block device 2018-04-05 21:36:23 -07:00
include mm/page_ref: use atomic_set_release in page_ref_unfreeze 2018-04-05 21:36:25 -07:00
init Merge branch 'syscalls-next' of git://git.kernel.org/pub/scm/linux/kernel/git/brodo/linux 2018-04-02 21:22:12 -07:00
ipc Merge branch 'userns-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2018-04-03 19:15:32 -07:00
kernel Driver core patches for 4.17-rc1 2018-04-04 19:41:45 -07:00
lib lib: fix stall in __bitmap_parselist() 2018-04-05 21:36:21 -07:00
LICENSES LICENSES: Add MPL-1.1 license 2018-01-06 10:59:44 -07:00
mm mm/huge_memory.c: reorder operations in __split_huge_page_tail() 2018-04-05 21:36:25 -07:00
net net/9p/client.c: fix potential refcnt problem of trans module 2018-04-05 21:36:23 -07:00
samples Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2018-04-03 14:04:18 -07:00
scripts scripts/faddr2line: show the code context 2018-04-05 21:36:21 -07:00
security Merge branch 'userns-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2018-04-03 19:15:32 -07:00
sound Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2018-04-03 14:04:18 -07:00
tools Char/Misc patches for 4.17-rc1 2018-04-04 20:07:20 -07:00
usr kbuild: rename built-in.o to built-in.a 2018-03-26 02:01:19 +09:00
virt kvm/arm fixes for 4.16, take 2 2018-03-15 21:45:37 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore kbuild: move include/config/ksym/* to include/ksym/* 2018-03-26 02:01:23 +09:00
.mailmap Merge remote-tracking branch 'spi/topic/samsung' into spi-next 2018-04-02 15:56:32 +01:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS/CREDITS: Drop METAG ARCHITECTURE 2018-03-05 16:34:24 +00:00
Kbuild Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
MAINTAINERS Char/Misc patches for 4.17-rc1 2018-04-04 20:07:20 -07:00
Makefile Kconfig updates for v4.17 2018-04-03 16:28:01 -07:00
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.