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Filename Latest commit message Latest commit date
Michal Hocko 06ad276ac1 mm, oom: do not enforce OOM killer for __GFP_NOFAIL automatically
__alloc_pages_may_oom makes sure to skip the OOM killer depending on the
allocation request.  This includes lowmem requests, costly high order
requests and others.  For a long time __GFP_NOFAIL acted as an override
for all those rules.  This is not documented and it can be quite
surprising as well.  E.g.  GFP_NOFS requests are not invoking the OOM
killer but GFP_NOFS|__GFP_NOFAIL does so if we try to convert some of
the existing open coded loops around allocator to nofail request (and we
have done that in the past) then such a change would have a non trivial
side effect which is far from obvious.  Note that the primary motivation
for skipping the OOM killer is to prevent from pre-mature invocation.

The exception has been added by commit 82553a937f ("oom: invoke oom
killer for __GFP_NOFAIL").  The changelog points out that the oom killer
has to be invoked otherwise the request would be looping for ever.  But
this argument is rather weak because the OOM killer doesn't really
guarantee a forward progress for those exceptional cases:

- it will hardly help to form costly order which in turn can result in
  the system panic because of no oom killable task in the end - I believe
  we certainly do not want to put the system down just because there is a
  nasty driver asking for order-9 page with GFP_NOFAIL not realizing all
  the consequences.  It is much better this request would loop for ever
  than the massive system disruption

- lowmem is also highly unlikely to be freed during OOM killer

- GFP_NOFS request could trigger while there is still a lot of memory
  pinned by filesystems.

This patch simply removes the __GFP_NOFAIL special case in order to have a
more clear semantic without surprising side effects.

Signed-off-by: Michal Hocko <mhocko@suse.com>
Reported-by: Nils Holland <nholland@tisys.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-02-22 16:41:30 -08:00
arch lib/show_mem.c: teach show_mem to work with the given nodemask 2017-02-22 16:41:30 -08:00
block block: use for_each_thread() in sys_ioprio_set()/sys_ioprio_get() 2017-02-22 16:41:27 -08:00
certs
crypto
Documentation mm, thp: add new defer+madvise defrag option 2017-02-22 16:41:30 -08:00
drivers lib/show_mem.c: teach show_mem to work with the given nodemask 2017-02-22 16:41:30 -08:00
firmware
fs powerpc: do not make the entire heap executable 2017-02-22 16:41:29 -08:00
include lib/show_mem.c: teach show_mem to work with the given nodemask 2017-02-22 16:41:30 -08:00
init slub: make sysfs directories for memcg sub-caches optional 2017-02-22 16:41:27 -08:00
ipc
kernel userfaultfd: non-cooperative: Add fork() event 2017-02-22 16:41:28 -08:00
lib lib/show_mem.c: teach show_mem to work with the given nodemask 2017-02-22 16:41:30 -08:00
mm mm, oom: do not enforce OOM killer for __GFP_NOFAIL automatically 2017-02-22 16:41:30 -08:00
net
samples
scripts scripts/tags.sh: include arch/Kconfig* for tags generation 2017-02-22 16:41:26 -08:00
security driver core patches for 4.11-rc1 2017-02-22 11:44:32 -08:00
sound
tools userfaultfd: selftest: test UFFDIO_ZEROPAGE on all memory types 2017-02-22 16:41:29 -08:00
usr
virt
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS dax: update MAINTAINERS entries for FS DAX 2017-02-22 16:41:26 -08:00
Makefile
README

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

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

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.