The patch titled Subject: mm/hugetlb: fix possible recursive locking detected warning has been added to the -mm mm-unstable branch. Its filename is mm-hugetlb-fix-possible-recursive-locking-detected-warning.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Miaohe Lin linmiaohe@huawei.com Subject: mm/hugetlb: fix possible recursive locking detected warning Date: Fri, 12 Jul 2024 11:13:14 +0800

When tries to demote 1G hugetlb folios, a lockdep warning is observed:

============================================ WARNING: possible recursive locking detected 6.10.0-rc6-00452-ga4d0275fa660-dirty #79 Not tainted -------------------------------------------- bash/710 is trying to acquire lock: ffffffff8f0a7850 (&h->resize_lock){+.+.}-{3:3}, at: demote_store+0x244/0x460

but task is already holding lock: ffffffff8f0a6f48 (&h->resize_lock){+.+.}-{3:3}, at: demote_store+0xae/0x460

other info that might help us debug this: Possible unsafe locking scenario:

CPU0 ---- lock(&h->resize_lock); lock(&h->resize_lock);

*** DEADLOCK ***

May be due to missing lock nesting notation

4 locks held by bash/710: #0: ffff8f118439c3f0 (sb_writers#5){.+.+}-{0:0}, at: ksys_write+0x64/0xe0 #1: ffff8f11893b9e88 (&of->mutex#2){+.+.}-{3:3}, at: kernfs_fop_write_iter+0xf8/0x1d0 #2: ffff8f1183dc4428 (kn->active#98){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x100/0x1d0 #3: ffffffff8f0a6f48 (&h->resize_lock){+.+.}-{3:3}, at: demote_store+0xae/0x460

stack backtrace: CPU: 3 PID: 710 Comm: bash Not tainted 6.10.0-rc6-00452-ga4d0275fa660-dirty #79 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0x68/0xa0 __lock_acquire+0x10f2/0x1ca0 lock_acquire+0xbe/0x2d0 __mutex_lock+0x6d/0x400 demote_store+0x244/0x460 kernfs_fop_write_iter+0x12c/0x1d0 vfs_write+0x380/0x540 ksys_write+0x64/0xe0 do_syscall_64+0xb9/0x1d0 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fa61db14887 RSP: 002b:00007ffc56c48358 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007fa61db14887 RDX: 0000000000000002 RSI: 000055a030050220 RDI: 0000000000000001 RBP: 000055a030050220 R08: 00007fa61dbd1460 R09: 000000007fffffff R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002 R13: 00007fa61dc1b780 R14: 00007fa61dc17600 R15: 00007fa61dc16a00 </TASK>

Lockdep considers this an AA deadlock because the different resize_lock mutexes reside in the same lockdep class, but this is a false positive. Place them in distinct classes to avoid these warnings.

Link: https://lkml.kernel.org/r/20240712031314.2570452-1-linmiaohe@huawei.com Fixes: 8531fc6f52f5 ("hugetlb: add hugetlb demote page support") Signed-off-by: Miaohe Lin linmiaohe@huawei.com Acked-by: Muchun Song muchun.song@linux.dev Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

include/linux/hugetlb.h | 1 + mm/hugetlb.c | 2 +- 2 files changed, 2 insertions(+), 1 deletion(-)

--- a/include/linux/hugetlb.h~mm-hugetlb-fix-possible-recursive-locking-detected-warning +++ a/include/linux/hugetlb.h @@ -663,6 +663,7 @@ HPAGEFLAG(RawHwpUnreliable, raw_hwp_unre /* Defines one hugetlb page size */ struct hstate { struct mutex resize_lock; + struct lock_class_key resize_key; int next_nid_to_alloc; int next_nid_to_free; unsigned int order; --- a/mm/hugetlb.c~mm-hugetlb-fix-possible-recursive-locking-detected-warning +++ a/mm/hugetlb.c @@ -4645,7 +4645,7 @@ void __init hugetlb_add_hstate(unsigned BUG_ON(hugetlb_max_hstate >= HUGE_MAX_HSTATE); BUG_ON(order < order_base_2(__NR_USED_SUBPAGE)); h = &hstates[hugetlb_max_hstate++]; - mutex_init(&h->resize_lock); + __mutex_init(&h->resize_lock, "resize mutex", &h->resize_key); h->order = order; h->mask = ~(huge_page_size(h) - 1); for (i = 0; i < MAX_NUMNODES; ++i) _

Patches currently in -mm which might be from linmiaohe@huawei.com are

mm-memory-failure-remove-obsolete-mf_msg_different_compound.patch mm-hugetlb-fix-potential-race-with-try_memory_failure_hugetlb.patch mm-memory-failure-fix-vm_bug_on_pagepagepoisonedpage-when-unpoison-memory.patch mm-hugetlb-fix-possible-recursive-locking-detected-warning.patch