There's no flag in the delay accounting structure indicates that the task
is waiting on IO since commit 1193829da1 ("delayacct: cleanup flags in
struct task_delay_info and functions use it"). So remove the comment.
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Put cgroup_tryget_css() inside CONFIG_CGROUP_SCHED to fix the warning
of 'cgroup_tryget_css' defined but not used [-Wunused-function] when
CONFIG_CGROUP_SCHED is disabled.
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Kamalesh Babulal <kamalesh.babulal@oracle.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
A single partition setup and tear-down operation can lead to
multiple rebuild_sched_domains_locked() calls which is a waste of
effort. This can partly be mitigated by adding a flag to suppress the
rebuild_sched_domains_locked() call in update_cpumasks_hier(). Since
a Boolean flag has already been passed as the 3rd argument to
update_cpumasks_hier(), we can extend that to a full flag word.
The sched domain rebuild suppression is now enabled in
update_sibling_cpumasks() as all it callers will do the sched domain
rebuild after its return later on anyway.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
The limitation that update_parent_subparts_cpumask() can only use
addmask & delmask in the given tmp cpumasks is fragile and may lead to
unexpected error.
Fix this problem by allocating/freeing a struct tmpmasks in
update_cpumask() to avoid reusing the cpumasks in trial_cs.
With this change, we can move the update_tasks_cpumask() for the
parent and update_sibling_cpumasks() for the sibling to inside
update_parent_subparts_cpumask().
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Extract out the setting of CS_CPU_EXCLUSIVE and CS_SCHED_LOAD_BALANCE
flags as well as the rebuilding of scheduling domains into the new
update_partition_exclusive() and update_partition_sd_lb() helper
functions to simplify the logic. The update_partition_exclusive()
helper is called mainly at the beginning of the caller, but it may be
called at the end too. The update_partition_sd_lb() helper is called
at the end of the caller.
This patch should reduce the chance that cpuset partition will end up
in an incorrect state.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Since commit f28e22441f ("cgroup/cpuset: Add a new isolated
cpus.partition type"), the CS_SCHED_LOAD_BALANCE bit of a v2 cpuset
can be on or off. The child cpusets of a partition root must have the
same setting as its parent or it may screw up the rebuilding of sched
domains. Fix this problem by making sure the a child v2 cpuset will
follows its parent cpuset load balance state unless the child cpuset
is a new partition root itself.
Fixes: f28e22441f ("cgroup/cpuset: Add a new isolated cpus.partition type")
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Add a separate testfile to verify treating permissions when tasks are
migrated on cgroup v2 hierarchy between cpuset cgroups.
In accordance with v2 design, migration should be allowed based on
delegation boundaries (i.e. cgroup.procs permissions) and does not
depend on the migrated object (i.e. unprivileged process can migrate
another process (even privileged) as long as it remains in the original
dedicated scope).
Signed-off-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
No functional change intended, these small changes are merged into one
commit and they serve as a preparation for an upcoming new testcase.
Signed-off-by: Michal Koutný <mkoutny@suse.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
When we migrate a task between two cgroups, one of the checks is a
verification whether we can modify task's scheduler settings
(cap_task_setscheduler()).
An implicit migration occurs also when enabling a controller on the
unified hierarchy (think of parent to child migration). The
aforementioned check may be problematic if the caller of the migration
(enabling a controller) has no permissions over migrated tasks.
For instance, a user's cgroup that ends up running a process of a
different user. Although cgroup permissions are configured favorably,
the enablement fails due to the foreign process [1].
Change the behavior by relaxing the permissions check on the unified
hierarchy when no effective change would happen.
This is in accordance with unified hierarchy attachment behavior when
permissions of the source to target cgroups are decisive whereas the
migrated task is opaque (as opposed to more restrictive check in
__cgroup1_procs_write()).
Notice that foreign task's affinity may still be modified if the user
can modify destination cgroup's cpuset attributes
(update_tasks_cpumask() does no permissions check). The permissions
check could thus be skipped on v2 even when affinity changes. Stay
conservative in this patch though.
[1] https://github.com/systemd/systemd/issues/18293#issuecomment-831205649
Signed-off-by: Michal Koutný <mkoutny@suse.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
cpuset_mutex unlock and lock pair is only needed when transferring tasks
out of empty cpuset. Avoid unneeded cpuset_mutex re-lock when !is_empty
to save cpu cycles.
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
kthread_is_per_cpu() can be called directly without checking whether
PF_KTHREAD is set in task->flags. So remove PF_KTHREAD check to make
code more concise.
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Make it under CONFIG_CGROUP_SCHED to rid of __maybe_unused annotation.
And further fetch cgrp inside cgroup_extra_stat_show() directly to rid
of __maybe_unused annotation of cgrp. No functional change intended.
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
The return value of cgroup_rm_cftypes_locked() is always 0. So remove
it to simplify the code. No functional change intended.
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Pull crypto fixes from Herbert Xu:
"Fix a couple of regressions in af_alg and incorrect return values in
crypto/asymmetric_keys/public_key"
* tag 'v6.5-p2' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6:
crypto: algif_hash - Fix race between MORE and non-MORE sends
KEYS: asymmetric: Fix error codes
crypto: af_alg - Fix merging of written data into spliced pages
We just sorted the entries and fields last release, so just out of a
perverse sense of curiosity, I decided to see if we can keep things
ordered for even just one release.
The answer is "No. No we cannot".
I suggest that all kernel developers will need weekly training sessions,
involving a lot of Big Bird and Sesame Street. And at the yearly
maintainer summit, we will all sing the alphabet song together.
I doubt I will keep doing this. At some point "perverse sense of
curiosity" turns into just a cold dark place filled with sadness and
despair.
Repeats: 80e62bc848 ("MAINTAINERS: re-sort all entries and fields")
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull dma-mapping fixes from Christoph Hellwig:
- swiotlb area sizing fixes (Petr Tesarik)
* tag 'dma-mapping-6.5-2023-07-09' of git://git.infradead.org/users/hch/dma-mapping:
swiotlb: reduce the number of areas to match actual memory pool size
swiotlb: always set the number of areas before allocating the pool
Pull irq update from Borislav Petkov:
- Optimize IRQ domain's name assignment
* tag 'irq_urgent_for_v6.5_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
irqdomain: Use return value of strreplace()
Pull x86 fpu fix from Borislav Petkov:
- Do FPU AP initialization on Xen PV too which got missed by the recent
boot reordering work
* tag 'x86_urgent_for_v6.5_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/xen: Fix secondary processors' FPU initialization
Pull x86 fix from Thomas Gleixner:
"A single fix for the mechanism to park CPUs with an INIT IPI.
On shutdown or kexec, the kernel tries to park the non-boot CPUs with
an INIT IPI. But the same code path is also used by the crash utility.
If the CPU which panics is not the boot CPU then it sends an INIT IPI
to the boot CPU which resets the machine.
Prevent this by validating that the CPU which runs the stop mechanism
is the boot CPU. If not, leave the other CPUs in HLT"
* tag 'x86-core-2023-07-09' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/smp: Don't send INIT to boot CPU
Pull MIPS fixes from Thomas Bogendoerfer:
- fixes for KVM
- fix for loongson build and cpu probing
- DT fixes
* tag 'mips_6.5_1' of git://git.kernel.org/pub/scm/linux/kernel/git/mips/linux:
MIPS: kvm: Fix build error with KVM_MIPS_DEBUG_COP0_COUNTERS enabled
MIPS: dts: add missing space before {
MIPS: Loongson: Fix build error when make modules_install
MIPS: KVM: Fix NULL pointer dereference
MIPS: Loongson: Fix cpu_probe_loongson() again
Pull xfs fix from Darrick Wong:
"Nothing exciting here, just getting rid of a gcc warning that I got
tired of seeing when I turn on gcov"
* tag 'xfs-6.5-merge-6' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux:
xfs: fix uninit warning in xfs_growfs_data
Pull more smb client updates from Steve French:
- fix potential use after free in unmount
- minor cleanup
- add worker to cleanup stale directory leases
* tag '6.5-rc-smb3-client-fixes-part2' of git://git.samba.org/sfrench/cifs-2.6:
cifs: Add a laundromat thread for cached directories
smb: client: remove redundant pointer 'server'
cifs: fix session state transition to avoid use-after-free issue
Lockdep is certainly right to complain about
(&vma->vm_lock->lock){++++}-{3:3}, at: vma_start_write+0x2d/0x3f
but task is already holding lock:
(&mapping->i_mmap_rwsem){+.+.}-{3:3}, at: mmap_region+0x4dc/0x6db
Invert those to the usual ordering.
Fixes: 33313a747e ("mm: lock newly mapped VMA which can be modified after it becomes visible")
Cc: stable@vger.kernel.org
Signed-off-by: Hugh Dickins <hughd@google.com>
Tested-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull hotfixes from Andrew Morton:
"16 hotfixes. Six are cc:stable and the remainder address post-6.4
issues"
The merge undoes the disabling of the CONFIG_PER_VMA_LOCK feature, since
it was all hopefully fixed in mainline.
* tag 'mm-hotfixes-stable-2023-07-08-10-43' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm:
lib: dhry: fix sleeping allocations inside non-preemptable section
kasan, slub: fix HW_TAGS zeroing with slub_debug
kasan: fix type cast in memory_is_poisoned_n
mailmap: add entries for Heiko Stuebner
mailmap: update manpage link
bootmem: remove the vmemmap pages from kmemleak in free_bootmem_page
MAINTAINERS: add linux-next info
mailmap: add Markus Schneider-Pargmann
writeback: account the number of pages written back
mm: call arch_swap_restore() from do_swap_page()
squashfs: fix cache race with migration
mm/hugetlb.c: fix a bug within a BUG(): inconsistent pte comparison
docs: update ocfs2-devel mailing list address
MAINTAINERS: update ocfs2-devel mailing list address
mm: disable CONFIG_PER_VMA_LOCK until its fixed
fork: lock VMAs of the parent process when forking
When forking a child process, the parent write-protects anonymous pages
and COW-shares them with the child being forked using copy_present_pte().
We must not take any concurrent page faults on the source vma's as they
are being processed, as we expect both the vma and the pte's behind it
to be stable. For example, the anon_vma_fork() expects the parents
vma->anon_vma to not change during the vma copy.
A concurrent page fault on a page newly marked read-only by the page
copy might trigger wp_page_copy() and a anon_vma_prepare(vma) on the
source vma, defeating the anon_vma_clone() that wasn't done because the
parent vma originally didn't have an anon_vma, but we now might end up
copying a pte entry for a page that has one.
Before the per-vma lock based changes, the mmap_lock guaranteed
exclusion with concurrent page faults. But now we need to do a
vma_start_write() to make sure no concurrent faults happen on this vma
while it is being processed.
This fix can potentially regress some fork-heavy workloads. Kernel
build time did not show noticeable regression on a 56-core machine while
a stress test mapping 10000 VMAs and forking 5000 times in a tight loop
shows ~5% regression. If such fork time regression is unacceptable,
disabling CONFIG_PER_VMA_LOCK should restore its performance. Further
optimizations are possible if this regression proves to be problematic.
Suggested-by: David Hildenbrand <david@redhat.com>
Reported-by: Jiri Slaby <jirislaby@kernel.org>
Closes: https://lore.kernel.org/all/dbdef34c-3a07-5951-e1ae-e9c6e3cdf51b@kernel.org/
Reported-by: Holger Hoffstätte <holger@applied-asynchrony.com>
Closes: https://lore.kernel.org/all/b198d649-f4bf-b971-31d0-e8433ec2a34c@applied-asynchrony.com/
Reported-by: Jacob Young <jacobly.alt@gmail.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217624
Fixes: 0bff0aaea0 ("x86/mm: try VMA lock-based page fault handling first")
Cc: stable@vger.kernel.org
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mmap_region adds a newly created VMA into VMA tree and might modify it
afterwards before dropping the mmap_lock. This poses a problem for page
faults handled under per-VMA locks because they don't take the mmap_lock
and can stumble on this VMA while it's still being modified. Currently
this does not pose a problem since post-addition modifications are done
only for file-backed VMAs, which are not handled under per-VMA lock.
However, once support for handling file-backed page faults with per-VMA
locks is added, this will become a race.
Fix this by write-locking the VMA before inserting it into the VMA tree.
Other places where a new VMA is added into VMA tree do not modify it
after the insertion, so do not need the same locking.
Cc: stable@vger.kernel.org
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
With recent changes necessitating mmap_lock to be held for write while
expanding a stack, per-VMA locks should follow the same rules and be
write-locked to prevent page faults into the VMA being expanded. Add
the necessary locking.
Cc: stable@vger.kernel.org
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull more SCSI updates from James Bottomley:
"A few late arriving patches that missed the initial pull request. It's
mostly bug fixes (the dt-bindings is a fix for the initial pull)"
* tag 'scsi-misc' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi:
scsi: ufs: core: Remove unused function declaration
scsi: target: docs: Remove tcm_mod_builder.py
scsi: target: iblock: Quiet bool conversion warning with pr_preempt use
scsi: dt-bindings: ufs: qcom: Fix ICE phandle
scsi: core: Simplify scsi_cdl_check_cmd()
scsi: isci: Fix comment typo
scsi: smartpqi: Replace one-element arrays with flexible-array members
scsi: target: tcmu: Replace strlcpy() with strscpy()
scsi: ncr53c8xx: Replace strlcpy() with strscpy()
scsi: lpfc: Fix lpfc_name struct packing
Pull more i2c updates from Wolfram Sang:
- xiic patch should have been in the original pull but slipped through
- mpc patch fixes a build regression
- nomadik cleanup
* tag 'i2c-for-6.5-rc1-part2' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux:
i2c: mpc: Drop unused variable
i2c: nomadik: Remove a useless call in the remove function
i2c: xiic: Don't try to handle more interrupt events after error
The debugfs_create_dir function returns ERR_PTR in case of error, and the
only correct way to check if an error occurred is 'IS_ERR' inline function.
This patch will replace the null-comparison with IS_ERR.
Signed-off-by: Anup Sharma <anupnewsmail@gmail.com>
Suggested-by: Ivan Orlov <ivan.orlov0322@gmail.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>
Pull more perf tools updates from Namhyung Kim:
"These are remaining changes and fixes for this cycle.
Build:
- Allow generating vmlinux.h from BTF using `make GEN_VMLINUX_H=1`
and skip if the vmlinux has no BTF.
- Replace deprecated clang -target xxx option by --target=xxx.
perf record:
- Print event attributes with well known type and config symbols in
the debug output like below:
# perf record -e cycles,cpu-clock -C0 -vv true
<SNIP>
------------------------------------------------------------
perf_event_attr:
type 0 (PERF_TYPE_HARDWARE)
size 136
config 0 (PERF_COUNT_HW_CPU_CYCLES)
{ sample_period, sample_freq } 4000
sample_type IP|TID|TIME|CPU|PERIOD|IDENTIFIER
read_format ID
disabled 1
inherit 1
freq 1
sample_id_all 1
exclude_guest 1
------------------------------------------------------------
sys_perf_event_open: pid -1 cpu 0 group_fd -1 flags 0x8 = 5
------------------------------------------------------------
perf_event_attr:
type 1 (PERF_TYPE_SOFTWARE)
size 136
config 0 (PERF_COUNT_SW_CPU_CLOCK)
{ sample_period, sample_freq } 4000
sample_type IP|TID|TIME|CPU|PERIOD|IDENTIFIER
read_format ID
disabled 1
inherit 1
freq 1
sample_id_all 1
exclude_guest 1
- Update AMD IBS event error message since it now support per-process
profiling but no priviledge filters.
$ sudo perf record -e ibs_op//k -C 0
Error:
AMD IBS doesn't support privilege filtering. Try again without
the privilege modifiers (like 'k') at the end.
perf lock contention:
- Support CSV style output using -x option
$ sudo perf lock con -ab -x, sleep 1
# output: contended, total wait, max wait, avg wait, type, caller
19, 194232, 21415, 10222, spinlock, process_one_work+0x1f0
15, 162748, 23843, 10849, rwsem:R, do_user_addr_fault+0x40e
4, 86740, 23415, 21685, rwlock:R, ep_poll_callback+0x2d
1, 84281, 84281, 84281, mutex, iwl_mvm_async_handlers_wk+0x135
8, 67608, 27404, 8451, spinlock, __queue_work+0x174
3, 58616, 31125, 19538, rwsem:W, do_mprotect_pkey+0xff
3, 52953, 21172, 17651, rwlock:W, do_epoll_wait+0x248
2, 30324, 19704, 15162, rwsem:R, do_madvise+0x3ad
1, 24619, 24619, 24619, spinlock, rcu_core+0xd4
- Add --output option to save the data to a file not to be interfered
by other debug messages.
Test:
- Fix event parsing test on ARM where there's no raw PMU nor supports
PERF_PMU_CAP_EXTENDED_HW_TYPE.
- Update the lock contention test case for CSV output.
- Fix a segfault in the daemon command test.
Vendor events (JSON):
- Add has_event() to check if the given event is available on system
at runtime. On Intel machines, some transaction events may not be
present when TSC extensions are disabled.
- Update Intel event metrics.
Misc:
- Sort symbols by name using an external array of pointers instead of
a rbtree node in the symbol. This will save 16-bytes or 24-bytes
per symbol whether the sorting is actually requested or not.
- Fix unwinding DWARF callstacks using libdw when --symfs option is
used"
* tag 'perf-tools-for-v6.5-2-2023-07-06' of git://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next: (38 commits)
perf test: Fix event parsing test when PERF_PMU_CAP_EXTENDED_HW_TYPE isn't supported.
perf test: Fix event parsing test on Arm
perf evsel amd: Fix IBS error message
perf: unwind: Fix symfs with libdw
perf symbol: Fix uninitialized return value in symbols__find_by_name()
perf test: Test perf lock contention CSV output
perf lock contention: Add --output option
perf lock contention: Add -x option for CSV style output
perf lock: Remove stale comments
perf vendor events intel: Update tigerlake to 1.13
perf vendor events intel: Update skylakex to 1.31
perf vendor events intel: Update skylake to 57
perf vendor events intel: Update sapphirerapids to 1.14
perf vendor events intel: Update icelakex to 1.21
perf vendor events intel: Update icelake to 1.19
perf vendor events intel: Update cascadelakex to 1.19
perf vendor events intel: Update meteorlake to 1.03
perf vendor events intel: Add rocketlake events/metrics
perf vendor metrics intel: Make transaction metrics conditional
perf jevents: Support for has_event function
...
Pull bitmap updates from Yury Norov:
"Fixes for different bitmap pieces:
- lib/test_bitmap: increment failure counter properly
The tests that don't use expect_eq() macro to determine that a test
is failured must increment failed_tests explicitly.
- lib/bitmap: drop optimization of bitmap_{from,to}_arr64
bitmap_{from,to}_arr64() optimization is overly optimistic
on 32-bit LE architectures when it's wired to
bitmap_copy_clear_tail().
- nodemask: Drop duplicate check in for_each_node_mask()
As the return value type of first_node() became unsigned, the node
>= 0 became unnecessary.
- cpumask: fix function description kernel-doc notation
- MAINTAINERS: Add bits.h and bitfield.h to the BITMAP API record
Add linux/bits.h and linux/bitfield.h for visibility"
* tag 'bitmap-6.5-rc1' of https://github.com/norov/linux:
MAINTAINERS: Add bitfield.h to the BITMAP API record
MAINTAINERS: Add bits.h to the BITMAP API record
cpumask: fix function description kernel-doc notation
nodemask: Drop duplicate check in for_each_node_mask()
lib/bitmap: drop optimization of bitmap_{from,to}_arr64
lib/test_bitmap: increment failure counter properly
Patch series "Update .mailmap for my work address and fix manpage".
While updating mailmap for the going-away address, I also found that on
current systems the manpage linked from the header comment changed.
And in fact it looks like the git mailmap feature got its own manpage.
This patch (of 2):
On recent systems the git-shortlog manpage only tells people to
See gitmailmap(5)
So instead of sending people on a scavenger hunt, put that info into the
header directly. Though keep the old reference around for older systems.
Link: https://lkml.kernel.org/r/20230704163919.1136784-1-heiko@sntech.de
Link: https://lkml.kernel.org/r/20230704163919.1136784-2-heiko@sntech.de
Signed-off-by: Heiko Stuebner <heiko.stuebner@vrull.eu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
nr_to_write is a count of pages, so we need to decrease it by the number
of pages in the folio we just wrote, not by 1. Most callers specify
either LONG_MAX or 1, so are unaffected, but writeback_sb_inodes() might
end up writing 512x as many pages as it asked for.
Dave added:
: XFS is the only filesystem this would affect, right? AFAIA, nothing
: else enables large folios and uses writeback through
: write_cache_pages() at this point...
:
: In which case, I'd be surprised if much difference, if any, gets
: noticed by anyone.
Link: https://lkml.kernel.org/r/20230628185548.981888-1-willy@infradead.org
Fixes: 793917d997 ("mm/readahead: Add large folio readahead")
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Jan Kara <jack@suse.cz>
Cc: Dave Chinner <david@fromorbit.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The following crash happens for me when running the -mm selftests (below).
Specifically, it happens while running the uffd-stress subtests:
kernel BUG at mm/hugetlb.c:7249!
invalid opcode: 0000 [#1] PREEMPT SMP NOPTI
CPU: 0 PID: 3238 Comm: uffd-stress Not tainted 6.4.0-hubbard-github+ #109
Hardware name: ASUS X299-A/PRIME X299-A, BIOS 1503 08/03/2018
RIP: 0010:huge_pte_alloc+0x12c/0x1a0
...
Call Trace:
<TASK>
? __die_body+0x63/0xb0
? die+0x9f/0xc0
? do_trap+0xab/0x180
? huge_pte_alloc+0x12c/0x1a0
? do_error_trap+0xc6/0x110
? huge_pte_alloc+0x12c/0x1a0
? handle_invalid_op+0x2c/0x40
? huge_pte_alloc+0x12c/0x1a0
? exc_invalid_op+0x33/0x50
? asm_exc_invalid_op+0x16/0x20
? __pfx_put_prev_task_idle+0x10/0x10
? huge_pte_alloc+0x12c/0x1a0
hugetlb_fault+0x1a3/0x1120
? finish_task_switch+0xb3/0x2a0
? lock_is_held_type+0xdb/0x150
handle_mm_fault+0xb8a/0xd40
? find_vma+0x5d/0xa0
do_user_addr_fault+0x257/0x5d0
exc_page_fault+0x7b/0x1f0
asm_exc_page_fault+0x22/0x30
That happens because a BUG() statement in huge_pte_alloc() attempts to
check that a pte, if present, is a hugetlb pte, but it does so in a
non-lockless-safe manner that leads to a false BUG() report.
We got here due to a couple of bugs, each of which by itself was not quite
enough to cause a problem:
First of all, before commit c33c794828f2("mm: ptep_get() conversion"), the
BUG() statement in huge_pte_alloc() was itself fragile: it relied upon
compiler behavior to only read the pte once, despite using it twice in the
same conditional.
Next, commit c33c794828 ("mm: ptep_get() conversion") broke that
delicate situation, by causing all direct pte reads to be done via
READ_ONCE(). And so READ_ONCE() got called twice within the same BUG()
conditional, leading to comparing (potentially, occasionally) different
versions of the pte, and thus to false BUG() reports.
Fix this by taking a single snapshot of the pte before using it in the
BUG conditional.
Now, that commit is only partially to blame here but, people doing
bisections will invariably land there, so this will help them find a fix
for a real crash. And also, the previous behavior was unlikely to ever
expose this bug--it was fragile, yet not actually broken.
So that's why I chose this commit for the Fixes tag, rather than the
commit that created the original BUG() statement.
Link: https://lkml.kernel.org/r/20230701010442.2041858-1-jhubbard@nvidia.com
Fixes: c33c794828 ("mm: ptep_get() conversion")
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Acked-by: James Houghton <jthoughton@google.com>
Acked-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Acked-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Dave Airlie <airlied@gmail.com>
Cc: Dimitri Sivanich <dimitri.sivanich@hpe.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: SeongJae Park <sj@kernel.org>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Uladzislau Rezki (Sony) <urezki@gmail.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
