With gcc-15 and gcc-16 with UBSAN_ALIGNMENT enabled the compiler fails to inline and optimize __scoped_seqlock_bug() away on s390: s390x-16.1.0-ld: kernel/sched/build_policy.o: in function `__scoped_seqlock_next': /.../seqlock.h:1286:(.text+0x22030): undefined reference to `__scoped_seqlock_bug' Fix this by adding UBSAN_ALIGNMENT to the list of config options where a not inlined empty __scoped_seqlock_bug() is allowed. Closes: https://lore.kernel.org/r/20260515092057.810542-1-arnd@kernel.org/ Reported-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Heiko Carstens <hca@linux.ibm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://patch.msgid.link/20260519110315.1385307-1-hca@linux.ibm.com
Remove __assume_ctx_lock() from lock initializers. Implicitly asserting an active context during initialization caused false-positive double-lock errors when acquiring a lock immediately after its initialization. Moving forward, guarded member initialization must either: 1. Use guard(type_init)(&lock) or scoped_guard(type_init, ...). 2. Use context_unsafe() for simple initialization. Reported-by: Bart Van Assche <bvanassche@acm.org> Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/all/57062131-e79e-42c2-aa0b-8f931cb8cac2@acm.org/ Link: https://patch.msgid.link/20260119094029.1344361-7-elver@google.com
Add scoped init guard definitions for common synchronization primitives supported by context analysis. The scoped init guards treat the context as active within initialization scope of the underlying context lock, given initialization implies exclusive access to the underlying object. This allows initialization of guarded members without disabling context analysis, while documenting initialization from subsequent usage. The documentation is updated with the new recommendation. Where scoped init guards are not provided or cannot be implemented (ww_mutex omitted for lack of multi-arg guard initializers), the alternative is to just disable context analysis where guarded members are initialized. Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/all/20251212095943.GM3911114@noisy.programming.kicks-ass.net/ Link: https://patch.msgid.link/20260119094029.1344361-3-elver@google.com
Eliminate all kernel-doc warnings in seqlock.h:
- correct the macro to have "()" immediately following the macro name
- don't include the macro parameters in the short description (first line)
- make the parameter names in the comments match the actual macro
parameter names.
- use "::" for the Example
WARNING: include/linux/seqlock.h:1341 This comment starts with '/**', but isn't a kernel-doc comment.
* scoped_seqlock_read (lock, ss_state) - execute the read side critical
Documentation/locking/seqlock:242: include/linux/seqlock.h:1351: WARNING:
Definition list ends without a blank line; unexpected unindent. [docutils]
Warning: include/linux/seqlock.h:1357 function parameter '_seqlock' not described in 'scoped_seqlock_read'
Warning: include/linux/seqlock.h:1357 function parameter '_target' not described in 'scoped_seqlock_read'
Fixes: cc39f3872c08 ("seqlock: Introduce scoped_seqlock_read()")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260123183749.3997533-1-rdunlap@infradead.org
Add support for Clang's context analysis for seqlock_t. Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://patch.msgid.link/20251219154418.3592607-12-elver@google.com
Arnd reported an x86 randconfig using gcc-15 tripped over __scoped_seqlock_bug(). Turns out GCC chose not to inline the scoped_seqlock helper functions and as such was not able to optimize properly. [ mingo: Clang fails the build too in some circumstances. ] Reported-by: Arnd Bergmann <arnd@arndb.de> Tested-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com> Link: https://patch.msgid.link/20251204104332.GG2528459@noisy.programming.kicks-ass.net
Some KASAN builds are failing to properly optimize this code -- luckily we don't care about core quality for KASAN builds, so just exclude it. Reported-by: kernel test robot <lkp@intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Closes: https://lore.kernel.org/oe-kbuild-all/202510251641.idrNXhv5-lkp@intel.com/
The read_seqbegin/need_seqretry/done_seqretry API is cumbersome and
error prone. With the new helper the "typical" code like
int seq, nextseq;
unsigned long flags;
nextseq = 0;
do {
seq = nextseq;
flags = read_seqbegin_or_lock_irqsave(&seqlock, &seq);
// read-side critical section
nextseq = 1;
} while (need_seqretry(&seqlock, seq));
done_seqretry_irqrestore(&seqlock, seq, flags);
can be rewritten as
scoped_seqlock_read (&seqlock, ss_lock_irqsave) {
// read-side critical section
}
Original idea by Oleg Nesterov; with contributions from Linus.
Originally-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Pull MM updates from Andrew Morton:
"The various patchsets are summarized below. Plus of course many
indivudual patches which are described in their changelogs.
- "Allocate and free frozen pages" from Matthew Wilcox reorganizes
the page allocator so we end up with the ability to allocate and
free zero-refcount pages. So that callers (ie, slab) can avoid a
refcount inc & dec
- "Support large folios for tmpfs" from Baolin Wang teaches tmpfs to
use large folios other than PMD-sized ones
- "Fix mm/rodata_test" from Petr Tesarik performs some maintenance
and fixes for this small built-in kernel selftest
- "mas_anode_descend() related cleanup" from Wei Yang tidies up part
of the mapletree code
- "mm: fix format issues and param types" from Keren Sun implements a
few minor code cleanups
- "simplify split calculation" from Wei Yang provides a few fixes and
a test for the mapletree code
- "mm/vma: make more mmap logic userland testable" from Lorenzo
Stoakes continues the work of moving vma-related code into the
(relatively) new mm/vma.c
- "mm/page_alloc: gfp flags cleanups for alloc_contig_*()" from David
Hildenbrand cleans up and rationalizes handling of gfp flags in the
page allocator
- "readahead: Reintroduce fix for improper RA window sizing" from Jan
Kara is a second attempt at fixing a readahead window sizing issue.
It should reduce the amount of unnecessary reading
- "synchronously scan and reclaim empty user PTE pages" from Qi Zheng
addresses an issue where "huge" amounts of pte pagetables are
accumulated:
https://lore.kernel.org/lkml/cover.1718267194.git.zhengqi.arch@bytedance.com/
Qi's series addresses this windup by synchronously freeing PTE
memory within the context of madvise(MADV_DONTNEED)
- "selftest/mm: Remove warnings found by adding compiler flags" from
Muhammad Usama Anjum fixes some build warnings in the selftests
code when optional compiler warnings are enabled
- "mm: don't use __GFP_HARDWALL when migrating remote pages" from
David Hildenbrand tightens the allocator's observance of
__GFP_HARDWALL
- "pkeys kselftests improvements" from Kevin Brodsky implements
various fixes and cleanups in the MM selftests code, mainly
pertaining to the pkeys tests
- "mm/damon: add sample modules" from SeongJae Park enhances DAMON to
estimate application working set size
- "memcg/hugetlb: Rework memcg hugetlb charging" from Joshua Hahn
provides some cleanups to memcg's hugetlb charging logic
- "mm/swap_cgroup: remove global swap cgroup lock" from Kairui Song
removes the global swap cgroup lock. A speedup of 10% for a
tmpfs-based kernel build was demonstrated
- "zram: split page type read/write handling" from Sergey Senozhatsky
has several fixes and cleaups for zram in the area of
zram_write_page(). A watchdog softlockup warning was eliminated
- "move pagetable_*_dtor() to __tlb_remove_table()" from Kevin
Brodsky cleans up the pagetable destructor implementations. A rare
use-after-free race is fixed
- "mm/debug: introduce and use VM_WARN_ON_VMG()" from Lorenzo Stoakes
simplifies and cleans up the debugging code in the VMA merging
logic
- "Account page tables at all levels" from Kevin Brodsky cleans up
and regularizes the pagetable ctor/dtor handling. This results in
improvements in accounting accuracy
- "mm/damon: replace most damon_callback usages in sysfs with new
core functions" from SeongJae Park cleans up and generalizes
DAMON's sysfs file interface logic
- "mm/damon: enable page level properties based monitoring" from
SeongJae Park increases the amount of information which is
presented in response to DAMOS actions
- "mm/damon: remove DAMON debugfs interface" from SeongJae Park
removes DAMON's long-deprecated debugfs interfaces. Thus the
migration to sysfs is completed
- "mm/hugetlb: Refactor hugetlb allocation resv accounting" from
Peter Xu cleans up and generalizes the hugetlb reservation
accounting
- "mm: alloc_pages_bulk: small API refactor" from Luiz Capitulino
removes a never-used feature of the alloc_pages_bulk() interface
- "mm/damon: extend DAMOS filters for inclusion" from SeongJae Park
extends DAMOS filters to support not only exclusion (rejecting),
but also inclusion (allowing) behavior
- "Add zpdesc memory descriptor for zswap.zpool" from Alex Shi
introduces a new memory descriptor for zswap.zpool that currently
overlaps with struct page for now. This is part of the effort to
reduce the size of struct page and to enable dynamic allocation of
memory descriptors
- "mm, swap: rework of swap allocator locks" from Kairui Song redoes
and simplifies the swap allocator locking. A speedup of 400% was
demonstrated for one workload. As was a 35% reduction for kernel
build time with swap-on-zram
- "mm: update mips to use do_mmap(), make mmap_region() internal"
from Lorenzo Stoakes reworks MIPS's use of mmap_region() so that
mmap_region() can be made MM-internal
- "mm/mglru: performance optimizations" from Yu Zhao fixes a few
MGLRU regressions and otherwise improves MGLRU performance
- "Docs/mm/damon: add tuning guide and misc updates" from SeongJae
Park updates DAMON documentation
- "Cleanup for memfd_create()" from Isaac Manjarres does that thing
- "mm: hugetlb+THP folio and migration cleanups" from David
Hildenbrand provides various cleanups in the areas of hugetlb
folios, THP folios and migration
- "Uncached buffered IO" from Jens Axboe implements the new
RWF_DONTCACHE flag which provides synchronous dropbehind for
pagecache reading and writing. To permite userspace to address
issues with massive buildup of useless pagecache when
reading/writing fast devices
- "selftests/mm: virtual_address_range: Reduce memory" from Thomas
Weißschuh fixes and optimizes some of the MM selftests"
* tag 'mm-stable-2025-01-26-14-59' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (321 commits)
mm/compaction: fix UBSAN shift-out-of-bounds warning
s390/mm: add missing ctor/dtor on page table upgrade
kasan: sw_tags: use str_on_off() helper in kasan_init_sw_tags()
tools: add VM_WARN_ON_VMG definition
mm/damon/core: use str_high_low() helper in damos_wmark_wait_us()
seqlock: add missing parameter documentation for raw_seqcount_try_begin()
mm/page-writeback: consolidate wb_thresh bumping logic into __wb_calc_thresh
mm/page_alloc: remove the incorrect and misleading comment
zram: remove zcomp_stream_put() from write_incompressible_page()
mm: separate move/undo parts from migrate_pages_batch()
mm/kfence: use str_write_read() helper in get_access_type()
selftests/mm/mkdirty: fix memory leak in test_uffdio_copy()
kasan: hw_tags: Use str_on_off() helper in kasan_init_hw_tags()
selftests/mm: virtual_address_range: avoid reading from VM_IO mappings
selftests/mm: vm_util: split up /proc/self/smaps parsing
selftests/mm: virtual_address_range: unmap chunks after validation
selftests/mm: virtual_address_range: mmap() without PROT_WRITE
selftests/memfd/memfd_test: fix possible NULL pointer dereference
mm: add FGP_DONTCACHE folio creation flag
mm: call filemap_fdatawrite_range_kick() after IOCB_DONTCACHE issue
...
Add missing documentation for raw_seqcount_try_begin() start parameter.
Link: https://lkml.kernel.org/r/20250116182730.801497-1-surenb@google.com
Fixes: dba4761a3e40 ("seqlock: add raw_seqcount_try_begin")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Closes: https://lore.kernel.org/all/20250116170522.23e884d5@canb.auug.org.au/
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Acked-by: Waiman Long <longman@redhat.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>