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Vlastimil Babka a7526fe8b9 mm, slab: put should_failslab() back behind CONFIG_SHOULD_FAILSLAB 
Patch series "revert unconditional slab and page allocator fault injection
calls".

These two patches largely revert commits that added function call overhead
into slab and page allocation hotpaths and that cannot be currently
disabled even though related CONFIG_ options do exist.

A much more involved solution that can keep the callsites always existing
but hidden behind a static key if unused, is possible [1] and can be
pursued by anyone who believes it's necessary.  Meanwhile the fact the
should_failslab() error injection is already not functional on kernels
built with current gcc without anyone noticing [2], and lukewarm response
to [1] suggests the need is not there.  I believe it will be more fair to
have the state after this series as a baseline for possible further
optimisation, instead of the unconditional overhead.

For example a possible compromise for anyone who's fine with an empty
function call overhead but not the full CONFIG_FAILSLAB /
CONFIG_FAIL_PAGE_ALLOC overhead is to reuse patch 1 from [1] but insert a
static key check only inside should_failslab() and
should_fail_alloc_page() before performing the more expensive checks.

[1] https://lore.kernel.org/all/20240620-fault-injection-statickeys-v2-0-e23947d3d84b@suse.cz/#t
[2] https://github.com/bpftrace/bpftrace/issues/3258


This patch (of 2):

This mostly reverts commit 4f6923fbb3 ("mm: make should_failslab always
available for fault injection").  The commit made should_failslab() a
noinline function that's always called from the slab allocation hotpath,
even if it's empty because CONFIG_SHOULD_FAILSLAB is not enabled, and
there is no option to disable that call.  This is visible in profiles and
the function call overhead can be noticeable especially with cpu
mitigations.

Meanwhile the bpftrace program example in the commit silently does not
work without CONFIG_SHOULD_FAILSLAB anyway with a recent gcc, because the
empty function gets a .constprop clone that is actually being called
(uselessly) from the slab hotpath, while the error injection is hooked to
the original function that's not being called at all [1].

Thus put the whole should_failslab() function back behind
CONFIG_SHOULD_FAILSLAB.  It's not a complete revert of 4f6923fbb3 - the
int return type that returns -ENOMEM on failure is preserved, as well
ALLOW_ERROR_INJECTION annotation.  The BTF_ID() record that was meanwhile
added is also guarded by CONFIG_SHOULD_FAILSLAB.

[1] https://github.com/bpftrace/bpftrace/issues/3258

Link: https://lkml.kernel.org/r/20240711-b4-fault-injection-reverts-v1-0-9e2651945d68@suse.cz
Link: https://lkml.kernel.org/r/20240711-b4-fault-injection-reverts-v1-1-9e2651945d68@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: David Rientjes <rientjes@google.com>
Cc: Eduard Zingerman <eddyz87@gmail.com>
Cc: Hao Luo <haoluo@google.com>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: KP Singh <kpsingh@kernel.org>
Cc: Martin KaFai Lau <martin.lau@linux.dev>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Song Liu <song@kernel.org>
Cc: Stanislav Fomichev <sdf@fomichev.me>
Cc: Yonghong Song <yonghong.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-07-17 21:05:18 -07:00
arch powerpc/mm: remove hugepd leftovers 2024-07-12 15:52:19 -07:00
block block: unmap and free user mapped integrity via submitter 2024-06-12 11:00:50 -06:00
certs kbuild: use $(src) instead of $(srctree)/$(src) for source directory 2024-05-10 04:34:52 +09:00
crypto This push fixes a bug in the new ecc P521 code as well as a buggy 2024-05-20 08:47:54 -07:00
Documentation mm: shmem: rename mTHP shmem counters 2024-07-12 15:52:23 -07:00
drivers memory tier: consolidate the initialization of memory tiers 2024-07-12 15:52:20 -07:00
fs hugetlbfs: ensure generic_hugetlb_get_unmapped_area() returns higher address than mmap_min_addr 2024-07-17 21:05:18 -07:00
include mm, slab: put should_failslab() back behind CONFIG_SHOULD_FAILSLAB 2024-07-17 21:05:18 -07:00
init mm: remove CONFIG_MEMCG_KMEM 2024-07-10 12:14:54 -07:00
io_uring io_uring: signal SQPOLL task_work with TWA_SIGNAL_NO_IPI 2024-06-24 19:46:15 -06:00
ipc Mainly singleton patches, documented in their respective changelogs. 2024-05-19 14:02:03 -07:00
kernel mm, slab: put should_failslab() back behind CONFIG_SHOULD_FAILSLAB 2024-07-17 21:05:18 -07:00
lib Merge branch 'mm-hotfixes-stable' into mm-stable to pick up "mm: fix 2024-07-06 11:44:41 -07:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm mm, slab: put should_failslab() back behind CONFIG_SHOULD_FAILSLAB 2024-07-17 21:05:18 -07:00
net NFS client bugfixes for Linux 6.10 2024-06-29 13:48:24 -07:00
rust rust: avoid unused import warning in rusttest 2024-06-11 23:33:28 +02:00
samples kmemleak-test: add missing MODULE_DESCRIPTION() macro 2024-07-03 19:30:04 -07:00
scripts kbuild: scripts/gdb: bring the "abspath" back 2024-06-27 04:20:32 +09:00
security lsm/stable-6.10 PR 20240617 2024-06-17 18:35:12 -07:00
sound ASoC: Fixes for v6.10 2024-06-26 22:02:55 +02:00
tools selftests/proc: add PROCMAP_QUERY ioctl tests 2024-07-12 15:52:12 -07:00
usr kbuild: use $(src) instead of $(srctree)/$(src) for source directory 2024-05-10 04:34:52 +09:00
virt KVM fixes for 6.10 2024-06-21 08:03:55 -04:00
.clang-format clang-format: Update with v6.7-rc4's for_each macro list 2023-12-08 23:54:38 +01:00
.cocciconfig
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.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: mailmap: update Lorenzo Stoakes's email address 2024-07-06 11:39:51 -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 Merge branch 'mm-hotfixes-stable' into mm-stable to pick up "mm: fix 2024-07-06 11:44:41 -07:00
Makefile Linux 6.10-rc6 2024-06-30 14:40:44 -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.