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David Hildenbrand 4bf6a4ebc5 selftests: mm: cow: flag vmsplice() hugetlb tests as XFAIL 
Patch series "selftests: mm: cow: flag vmsplice() hugetlb tests as XFAIL".

The failing hugetlb vmsplice() COW tests keep confusing people, and having
tests that have been failing for years and likely will keep failing for
years to come because nobody cares enough is rather suboptimal.  Let's
mark them as XFAIL and document why fixing them is not that easy as it
would appear at first sight.

More details can be found in [1], especially around how hugetlb pages
cannot really be overcommitted, and why we don't particularly care about
these vmsplice() leaks for hugetlb -- in contrast to ordinary memory.

[1] https://lore.kernel.org/all/8b42a24d-caf0-46ef-9e15-0f88d47d2f21@redhat.com/


This patch (of 2):

The vmsplice() hugetlb tests have been failing right from the start, and
we documented that in the introducing commit 7dad331be7 ("selftests/vm:
anon_cow: hugetlb tests"):

	Note that some tests cases still fail. This will, for example, be
	fixed once vmsplice properly uses FOLL_PIN instead of FOLL_GET for
	pinning. With 2 MiB and 1 GiB hugetlb on x86_64, the expected
	failures are:

Until vmsplice() is changed, these tests will likely keep failing: hugetlb
COW reuse logic is harder to change, because using the same COW reuse
logic as we use for !hugetlb could harm other (sane) users when running
out of free hugetlb pages.

More details can be found in [1], especially around how hugetlb pages
cannot really be overcommitted, and why we don't particularly care about
these vmsplice() leaks for hugetlb -- in contrast to ordinary memory.

These (expected) failures keep confusing people, so flag them accordingly.

Before:
	$ ./cow
	[...]
	Bail out! 8 out of 778 tests failed
	# Totals: pass:769 fail:8 xfail:0 xpass:0 skip:1 error:0
	$ echo $?
	1

After:
	$ ./cow
	[...]
	# Totals: pass:769 fail:0 xfail:8 xpass:0 skip:1 error:0
	$ echo $?
	0

[1] https://lore.kernel.org/all/8b42a24d-caf0-46ef-9e15-0f88d47d2f21@redhat.com/

Link: https://lkml.kernel.org/r/20240502085259.103784-1-david@redhat.com
Link: https://lkml.kernel.org/r/20240502085259.103784-2-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Peter Xu <peterx@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-05-07 10:36:58 -07:00
arch mm/arm64: override clear_young_dirty_ptes() batch helper 2024-05-05 17:53:42 -07:00
block block-6.9-20240412 2024-04-12 10:22:33 -07:00
certs This update includes the following changes: 2023-11-02 16:15:30 -10:00
crypto This push fixes a regression that broke iwd as well as a divide by 2024-03-25 10:48:23 -07:00
Documentation Docs/ABI/damon: update for 'youg page' type DAMOS filter 2024-05-05 17:53:56 -07:00
drivers mm: pass VMA instead of MM to follow_pte() 2024-05-05 17:53:27 -07:00
fs mm: simplify thp_vma_allowable_order 2024-05-05 17:53:53 -07:00
include mm/pagemap: make trylock_page return bool 2024-05-05 17:53:56 -07:00
init mm: introduce slabobj_ext to support slab object extensions 2024-04-25 20:55:51 -07:00
io_uring mm: switch mm->get_unmapped_area() to a flag 2024-04-25 20:56:25 -07:00
ipc sysctl changes for v6.9-rc1 2024-03-18 14:59:13 -07:00
kernel mm/treewide: rename CONFIG_HAVE_FAST_GUP to CONFIG_HAVE_GUP_FAST 2024-04-25 20:56:41 -07:00
lib xarray: inline xas_descend to improve performance 2024-05-05 17:53:38 -07:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm mm/swapfile: mark racy access on si->highest_bit 2024-05-05 17:53:57 -07:00
net mm: change inlined allocation helpers to account at the call site 2024-04-25 20:55:59 -07:00
rust rust: add a rust helper for krealloc() 2024-04-25 20:55:55 -07:00
samples Tracing updates for 6.9: 2024-03-18 15:11:44 -07:00
scripts lib: add allocation tagging support for memory allocation profiling 2024-04-25 20:55:52 -07:00
security mm: init_mlocked_on_free_v3 2024-04-25 20:56:29 -07:00
sound fix missing vmalloc.h includes 2024-04-25 20:55:49 -07:00
tools selftests: mm: cow: flag vmsplice() hugetlb tests as XFAIL 2024-05-07 10:36:58 -07:00
usr Kbuild updates for v6.8 2024-01-18 17:57:07 -08:00
virt mm: pass VMA instead of MM to follow_pte() 2024-05-05 17:53:27 -07:00
.clang-format clang-format: Update with v6.7-rc4's for_each macro list 2023-12-08 23:54:38 +01:00
.cocciconfig
.editorconfig Add .editorconfig file for basic formatting 2023-12-28 16:22:47 +09:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: create a list of all built DTB files 2024-02-19 18:20:39 +09:00
.mailmap MAINTAINERS: update Naoya Horiguchi's email address 2024-04-16 15:39:51 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Drop Gustavo Pimentel as PCI DWC Maintainer 2024-03-27 13:41:02 -05:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS MAINTAINERS: add entries for code tagging and memory allocation profiling 2024-04-25 20:55:58 -07:00
Makefile Linux 6.9-rc4 2024-04-14 13:38:39 -07:00
README README: Fix spelling 2024-03-18 03:36:32 -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 reStructuredText markup notation.

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.