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Linus Torvalds 7800f13d93 minmax: avoid overly complicated constant expressions in VM code 
[ Upstream commit 3a7e02c040 ]

The minmax infrastructure is overkill for simple constants, and can
cause huge expansions because those simple constants are then used by
other things.

For example, 'pageblock_order' is a core VM constant, but because it was
implemented using 'min_t()' and all the type-checking that involves, it
actually expanded to something like 2.5kB of preprocessor noise.

And when that simple constant was then used inside other expansions:

  #define pageblock_nr_pages      (1UL << pageblock_order)
  #define pageblock_start_pfn(pfn)  ALIGN_DOWN((pfn), pageblock_nr_pages)

and we then use that inside a 'max()' macro:

	case ISOLATE_SUCCESS:
		update_cached = false;
		last_migrated_pfn = max(cc->zone->zone_start_pfn,
			pageblock_start_pfn(cc->migrate_pfn - 1));

the end result was that one statement expanding to 253kB in size.

There are probably other cases of this, but this one case certainly
stood out.

I've added 'MIN_T()' and 'MAX_T()' macros for this kind of "core simple
constant with specific type" use.  These macros skip the type checking,
and as such need to be very sparingly used only for obvious cases that
have active issues like this.

Reported-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Link: https://lore.kernel.org/all/36aa2cad-1db1-4abf-8dd2-fb20484aabc3@lucifer.local/
Cc: David Laight <David.Laight@aculab.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Eliav Farber <farbere@amazon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2025-10-02 13:40:42 +02:00
arch minmax: add in_range() macro 2025-10-02 13:40:41 +02:00
block block: reject invalid operation in submit_bio_noacct 2025-08-28 16:26:10 +02:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2025-04-25 10:44:04 +02:00
crypto crypto: af_alg - Disallow concurrent writes in af_alg_sendmsg 2025-09-25 10:58:55 +02:00
Documentation docs: networking: can: change bcm_msg_head frames member to support flexible array 2025-09-19 16:29:58 +02:00
drivers minmax: add in_range() macro 2025-10-02 13:40:41 +02:00
fs minmax: add in_range() macro 2025-10-02 13:40:41 +02:00
include minmax: avoid overly complicated constant expressions in VM code 2025-10-02 13:40:42 +02:00
init sched/isolation: Make CONFIG_CPU_ISOLATION depend on CONFIG_SMP 2025-05-02 07:47:04 +02:00
io_uring io_uring: include dying ring in task_work "should cancel" state 2025-09-25 10:58:53 +02:00
ipc ipc: fix to protect IPCS lookups using RCU 2025-06-27 11:07:30 +01:00
kernel tracing: dynevent: Add a missing lockdown check on dynevent 2025-10-02 13:40:40 +02:00
lib minmax: add in_range() macro 2025-10-02 13:40:41 +02:00
LICENSES
mm mm/migrate_device: don't add folio to be freed to LRU in migrate_device_finalize() 2025-10-02 13:40:41 +02:00
net minmax: add in_range() macro 2025-10-02 13:40:41 +02:00
rust rust: module: place cleanup_module() in .exit.text section 2025-07-06 10:57:54 +02:00
samples ftrace/samples: Fix function size computation 2025-09-19 16:29:56 +02:00
scripts kconfig: lxdialog: fix 'space' to (de)select options 2025-08-28 16:26:02 +02:00
security apparmor: use the condition in AA_BUG_FMT even with debug disabled 2025-08-28 16:26:01 +02:00
sound ALSA: usb-audio: Add mute TLV for playback volumes on more devices 2025-10-02 13:40:36 +02:00
tools minmax: add in_range() macro 2025-10-02 13:40:41 +02:00
usr kbuild: hdrcheck: fix cross build with clang 2025-06-27 11:07:25 +01:00
virt KVM: Fix a data race on last_boosted_vcpu in kvm_vcpu_on_spin() 2024-06-27 13:46:21 +02:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore Remove *.orig pattern from .gitignore 2024-10-17 15:21:15 +02:00
.mailmap
.rustfmt.toml
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS sign-file,extract-cert: move common SSL helper functions to a header 2025-04-25 10:44:04 +02:00
Makefile Linux 6.1.154 2025-09-25 10:58:55 +02:00
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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.

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.