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Filename Latest commit message Latest commit date
Linus Torvalds cb59d054a9 UPSTREAM: mm: don't try to NUMA-migrate COW pages that have other uses
Oded Gabbay reports that enabling NUMA balancing causes corruption with
his Gaudi accelerator test load:

 "All the details are in the bug, but the bottom line is that somehow,
  this patch causes corruption when the numa balancing feature is
  enabled AND we don't use process affinity AND we use GUP to pin pages
  so our accelerator can DMA to/from system memory.

  Either disabling numa balancing, using process affinity to bind to
  specific numa-node or reverting this patch causes the bug to
  disappear"

and Oded bisected the issue to commit 09854ba94c6a ("mm: do_wp_page()
simplification").

Now, the NUMA balancing shouldn't actually be changing the writability
of a page, and as such shouldn't matter for COW.  But it appears it
does.  Suspicious.

However, regardless of that, the condition for enabling NUMA faults in
change_pte_range() is nonsensical.  It uses "page_mapcount(page)" to
decide if a COW page should be NUMA-protected or not, and that makes
absolutely no sense.

The number of mappings a page has is irrelevant: not only does GUP get a
reference to a page as in Oded's case, but the other mappings migth be
paged out and the only reference to them would be in the page count.

Since we should never try to NUMA-balance a page that we can't move
anyway due to other references, just fix the code to use 'page_count()'.
Oded confirms that that fixes his issue.

Now, this does imply that something in NUMA balancing ends up changing
page protections (other than the obvious one of making the page
inaccessible to get the NUMA faulting information).  Otherwise the COW
simplification wouldn't matter - since doing the GUP on the page would
make sure it's writable.

The cause of that permission change would be good to figure out too,
since it clearly results in spurious COW events - but fixing the
nonsensical test that just happened to work before is obviously the
CorrectThing(tm) to do regardless.

Bug: 254441685
Fixes: 09854ba94c6a ("mm: do_wp_page() simplification")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=215616
Link: https://lore.kernel.org/all/CAFCwf10eNmwq2wD71xjUhqkvv5+_pJMR1nPug2RqNDcFT4H86Q@mail.gmail.com/
Reported-and-tested-by: Oded Gabbay <oded.gabbay@gmail.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit 80d47f5de5e311cbc0d01ebb6ee684e8f4c196c6)
Signed-off-by: Lee Jones <joneslee@google.com>
Change-Id: I490544efe86c2c8bc9d297135bad7d2ceab4686e
2022-11-22 07:58:43 +00:00
android ANDROID: GKI: Update FCNT KMI symbol list 2022-10-24 15:54:15 +00:00
arch BACKPORT: ARM: 9039/1: assembler: generalize byte swapping macro into rev_l 2022-11-09 18:51:41 +00:00
block This is the 5.4.198 stable release 2022-06-21 14:58:56 +02:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:11:22 +02:00
crypto This is the 5.4.200 stable release 2022-06-23 15:04:40 +02:00
Documentation BACKPORT: fscrypt: rename FS_KEY_DERIVATION_NONCE_SIZE 2022-11-22 07:58:42 +00:00
drivers UPSTREAM: usb: raw-gadget: fix handling of dual-direction-capable endpoints 2022-11-22 07:58:43 +00:00
fs UPSTREAM: fscrypt: fix derivation of SipHash keys on big endian CPUs 2022-11-22 07:58:42 +00:00
include BACKPORT: fs: align IOCB_* flags with RWF_* flags 2022-11-18 14:31:11 +00:00
init This is the 5.4.200 stable release 2022-06-23 15:04:40 +02:00
ipc ipc/mqueue: use get_tree_nodev() in mqueue_get_tree() 2022-06-14 18:11:41 +02:00
kernel ANDROID: Fix kenelci build-break for !CONFIG_PERF_EVENTS 2022-10-13 19:47:26 +00:00
lib ANDROID: restore some removed refcount functions 2022-07-30 15:19:41 +02:00
LICENSES
mm UPSTREAM: mm: don't try to NUMA-migrate COW pages that have other uses 2022-11-22 07:58:43 +00:00
net UPSTREAM: af_key: Do not call xfrm_probe_algs in parallel 2022-11-02 15:04:14 +00:00
samples This is the 5.4.160 stable release 2021-11-17 10:19:21 +01:00
scripts This is the 5.4.202 stable release 2022-06-29 09:05:51 +02:00
security UPSTREAM: selinux: check return value of sel_make_avc_files 2022-11-22 07:58:43 +00:00
sound This is the 5.4.208 stable release 2022-07-30 14:33:25 +02:00
tools This is the 5.4.210 stable release 2022-08-11 14:59:05 +02:00
usr
virt KVM: Don't null dereference ops->destroy 2022-08-11 12:57:52 +02:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
build.config.aarch64 ANDROID: distribute Module.symvers 2021-10-14 13:14:46 +08:00
build.config.allmodconfig
build.config.allmodconfig.aarch64
build.config.allmodconfig.arm
build.config.allmodconfig.x86_64
build.config.arm
build.config.common ANDROID: fix KCFLAGS override by __ANDROID_COMMON_KERNEL__ 2022-04-29 17:53:05 +00:00
build.config.db845c
build.config.gki
build.config.gki-debug.aarch64
build.config.gki-debug.x86_64
build.config.gki.aarch64 ANDROID: GKI: Add symbol list for Zebra 2022-03-23 15:27:27 +00:00
build.config.gki.x86_64
build.config.gki_kasan
build.config.gki_kasan.aarch64
build.config.gki_kasan.x86_64
build.config.gki_kprobes
build.config.gki_kprobes.aarch64
build.config.gki_kprobes.x86_64
build.config.hikey960
build.config.x86_64 ANDROID: distribute Module.symvers 2021-10-14 13:14:46 +08:00
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS This is the 5.4.200 stable release 2022-06-23 15:04:40 +02:00
Makefile UPSTREAM: hardening: Remove Clang's enable flag for -ftrivial-auto-var-init=zero 2022-10-24 19:35:42 +00:00
OWNERS
README
README.md

How do I submit patches to Android Common Kernels

  1. BEST: Make all of your changes to upstream Linux. If appropriate, backport to the stable releases. These patches will be merged automatically in the corresponding common kernels. If the patch is already in upstream Linux, post a backport of the patch that conforms to the patch requirements below.

  2. LESS GOOD: Develop your patches out-of-tree (from an upstream Linux point-of-view). Unless these are fixing an Android-specific bug, these are very unlikely to be accepted unless they have been coordinated with kernel-team@android.com. If you want to proceed, post a patch that conforms to the patch requirements below.

Common Kernel patch requirements

  • All patches must conform to the Linux kernel coding standards and pass script/checkpatch.pl
  • Patches shall not break gki_defconfig or allmodconfig builds for arm, arm64, x86, x86_64 architectures (see https://source.android.com/setup/build/building-kernels)
  • If the patch is not merged from an upstream branch, the subject must be tagged with the type of patch: UPSTREAM:, BACKPORT:, FROMGIT:, FROMLIST:, or ANDROID:.
  • All patches must have a Change-Id: tag (see https://gerrit-review.googlesource.com/Documentation/user-changeid.html)
  • If an Android bug has been assigned, there must be a Bug: tag.
  • All patches must have a Signed-off-by: tag by the author and the submitter

Additional requirements are listed below based on patch type

Requirements for backports from mainline Linux: UPSTREAM:, BACKPORT:

  • If the patch is a cherry-pick from Linux mainline with no changes at all
    • tag the patch subject with UPSTREAM:.
    • add upstream commit information with a (cherry-picked from ...) line
    • Example:
      • if the upstream commit message is
        important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>
    - then Joe Smith would upload the patch for the common kernel as
        UPSTREAM: important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>

        Bug: 135791357
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        (cherry-picked from c31e73121f4c1ec41143423ac6ce3ce6dafdcec1)
        Signed-off-by: Joe Smith <joe.smith@foo.org>
  • If the patch requires any changes from the upstream version, tag the patch with BACKPORT: instead of UPSTREAM:.
    • use the same tags as UPSTREAM:
    • add comments about the changes under the (cherry-picked from ...) line
    • Example:
        BACKPORT: important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>

        Bug: 135791357
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        (cherry-picked from c31e73121f4c1ec41143423ac6ce3ce6dafdcec1)
        [ Resolved minor conflict in drivers/foo/bar.c ]
        Signed-off-by: Joe Smith <joe.smith@foo.org>

Requirements for other backports: FROMGIT:, FROMLIST:,

  • If the patch has been merged into an upstream maintainer tree, but has not yet been merged into Linux mainline
    • tag the patch subject with FROMGIT:
    • add info on where the patch came from as (cherry picked from commit <sha1> <repo> <branch>). This must be a stable maintainer branch (not rebased, so don't use linux-next for example).
    • if changes were required, use BACKPORT: FROMGIT:
    • Example:
      • if the commit message in the maintainer tree is
        important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>
    - then Joe Smith would upload the patch for the common kernel as
        FROMGIT: important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>

        Bug: 135791357
        (cherry picked from commit 878a2fd9de10b03d11d2f622250285c7e63deace
         https://git.kernel.org/pub/scm/linux/kernel/git/foo/bar.git test-branch)
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        Signed-off-by: Joe Smith <joe.smith@foo.org>
  • If the patch has been submitted to LKML, but not accepted into any maintainer tree
    • tag the patch subject with FROMLIST:
    • add a Link: tag with a link to the submittal on lore.kernel.org
    • if changes were required, use BACKPORT: FROMLIST:
    • Example:
        FROMLIST: important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>

        Bug: 135791357
        Link: https://lore.kernel.org/lkml/20190619171517.GA17557@someone.com/
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        Signed-off-by: Joe Smith <joe.smith@foo.org>

Requirements for Android-specific patches: ANDROID:

  • If the patch is fixing a bug to Android-specific code
    • tag the patch subject with ANDROID:
    • add a Fixes: tag that cites the patch with the bug
    • Example:
        ANDROID: fix android-specific bug in foobar.c

        This is the detailed description of the important fix

        Fixes: 1234abcd2468 ("foobar: add cool feature")
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        Signed-off-by: Joe Smith <joe.smith@foo.org>
  • If the patch is a new feature
    • tag the patch subject with ANDROID:
    • add a Bug: tag with the Android bug (required for android-specific features)