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Kernel sources for Moto G9 (Play) (Guamp)
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Mel Gorman 26e871af46 mm/page_alloc: fix race condition between build_all_zonelists and page allocation 
commit 3d36424b3b5850bd92f3e89b953a430d7cfc88ef upstream.

Patrick Daly reported the following problem;

	NODE_DATA(nid)->node_zonelists[ZONELIST_FALLBACK] - before offline operation
	[0] - ZONE_MOVABLE
	[1] - ZONE_NORMAL
	[2] - NULL

	For a GFP_KERNEL allocation, alloc_pages_slowpath() will save the
	offset of ZONE_NORMAL in ac->preferred_zoneref. If a concurrent
	memory_offline operation removes the last page from ZONE_MOVABLE,
	build_all_zonelists() & build_zonerefs_node() will update
	node_zonelists as shown below. Only populated zones are added.

	NODE_DATA(nid)->node_zonelists[ZONELIST_FALLBACK] - after offline operation
	[0] - ZONE_NORMAL
	[1] - NULL
	[2] - NULL

The race is simple -- page allocation could be in progress when a memory
hot-remove operation triggers a zonelist rebuild that removes zones.  The
allocation request will still have a valid ac->preferred_zoneref that is
now pointing to NULL and triggers an OOM kill.

This problem probably always existed but may be slightly easier to trigger
due to 6aa303defb ("mm, vmscan: only allocate and reclaim from zones
with pages managed by the buddy allocator") which distinguishes between
zones that are completely unpopulated versus zones that have valid pages
not managed by the buddy allocator (e.g.  reserved, memblock, ballooning
etc).  Memory hotplug had multiple stages with timing considerations
around managed/present page updates, the zonelist rebuild and the zone
span updates.  As David Hildenbrand puts it

	memory offlining adjusts managed+present pages of the zone
	essentially in one go. If after the adjustments, the zone is no
	longer populated (present==0), we rebuild the zone lists.

	Once that's done, we try shrinking the zone (start+spanned
	pages) -- which results in zone_start_pfn == 0 if there are no
	more pages. That happens *after* rebuilding the zonelists via
	remove_pfn_range_from_zone().

The only requirement to fix the race is that a page allocation request
identifies when a zonelist rebuild has happened since the allocation
request started and no page has yet been allocated.  Use a seqlock_t to
track zonelist updates with a lockless read-side of the zonelist and
protecting the rebuild and update of the counter with a spinlock.

[akpm@linux-foundation.org: make zonelist_update_seq static]
Link: https://lkml.kernel.org/r/20220824110900.vh674ltxmzb3proq@techsingularity.net
Fixes: 6aa303defb ("mm, vmscan: only allocate and reclaim from zones with pages managed by the buddy allocator")
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Reported-by: Patrick Daly <quic_pdaly@quicinc.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: <stable@vger.kernel.org>	[4.9+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-10-05 10:36:44 +02:00
arch ARM: dts: integrator: Tag PCI host with device_type 2022-10-05 10:36:44 +02:00
block blk-iolatency: Fix inflight count imbalances and IO hangs on offline 2022-06-14 16:59:30 +02:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-25 11:49:16 +02:00
crypto crypto: drbg - make reseeding from get_random_bytes() synchronous 2022-06-25 11:49:13 +02:00
Documentation Input: iforce - add support for Boeder Force Feedback Wheel 2022-09-20 12:26:48 +02:00
drivers mmc: moxart: fix 4-bit bus width and remove 8-bit bus width 2022-10-05 10:36:44 +02:00
firmware Fix built-in early-load Intel microcode alignment 2020-01-23 08:21:29 +01:00
fs ntfs: fix BUG_ON in ntfs_lookup_inode_by_name() 2022-10-05 10:36:44 +02:00
include serial: Create uart_xmit_advance() 2022-09-28 11:02:57 +02:00
init random: handle latent entropy and command line from random_init() 2022-06-25 11:49:11 +02:00
ipc shm: extend forced shm destroy to support objects from several IPC nses 2021-12-08 08:50:11 +01:00
kernel workqueue: don't skip lockdep work dependency in cancel_work_sync() 2022-09-28 11:02:58 +02:00
lib ratelimit: Fix data-races in ___ratelimit(). 2022-09-05 10:26:30 +02:00
LICENSES
mm mm/page_alloc: fix race condition between build_all_zonelists and page allocation 2022-10-05 10:36:44 +02:00
net netfilter: ebtables: fix memory leak when blob is malformed 2022-09-28 11:02:56 +02:00
samples samples/kretprobes: Fix return value if register_kretprobe() failed 2021-11-26 11:36:11 +01:00
scripts mksysmap: Fix the mismatch of 'L0' symbols in System.map 2022-09-28 11:02:53 +02:00
security apparmor: Fix memleak in aa_simple_write_to_buffer() 2022-08-25 11:15:36 +02:00
sound ALSA: hda/realtek: Enable 4-speaker output Dell Precision 5530 laptop 2022-09-28 11:02:55 +02:00
tools perf kcore_copy: Do not check /proc/modules is unchanged 2022-09-28 11:02:57 +02:00
usr initramfs: restore default compression behavior 2020-04-13 10:44:59 +02:00
virt KVM: Add infrastructure and macro to mark VM as bugged 2022-08-25 11:15:31 +02:00
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MAINTAINERS MAINTAINERS: co-maintain random.c 2022-06-25 11:49:01 +02:00
Makefile Linux 4.19.260 2022-09-28 11:02:58 +02:00
README

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.