The quilt patch titled Subject: mm/memory-failure: fix deadlock when hugetlb_optimize_vmemmap is enabled has been removed from the -mm tree. Its filename was mm-memory-failure-fix-deadlock-when-hugetlb_optimize_vmemmap-is-enabled.patch
This patch was dropped because it was merged into the mm-hotfixes-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------ From: Miaohe Lin linmiaohe@huawei.com Subject: mm/memory-failure: fix deadlock when hugetlb_optimize_vmemmap is enabled Date: Sun, 7 Apr 2024 16:54:56 +0800
When I did hard offline test with hugetlb pages, below deadlock occurs:
====================================================== WARNING: possible circular locking dependency detected 6.8.0-11409-gf6cef5f8c37f #1 Not tainted ------------------------------------------------------ bash/46904 is trying to acquire lock: ffffffffabe68910 (cpu_hotplug_lock){++++}-{0:0}, at: static_key_slow_dec+0x16/0x60
but task is already holding lock: ffffffffabf92ea8 (pcp_batch_high_lock){+.+.}-{3:3}, at: zone_pcp_disable+0x16/0x40
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (pcp_batch_high_lock){+.+.}-{3:3}: __mutex_lock+0x6c/0x770 page_alloc_cpu_online+0x3c/0x70 cpuhp_invoke_callback+0x397/0x5f0 __cpuhp_invoke_callback_range+0x71/0xe0 _cpu_up+0xeb/0x210 cpu_up+0x91/0xe0 cpuhp_bringup_mask+0x49/0xb0 bringup_nonboot_cpus+0xb7/0xe0 smp_init+0x25/0xa0 kernel_init_freeable+0x15f/0x3e0 kernel_init+0x15/0x1b0 ret_from_fork+0x2f/0x50 ret_from_fork_asm+0x1a/0x30
-> #0 (cpu_hotplug_lock){++++}-{0:0}: __lock_acquire+0x1298/0x1cd0 lock_acquire+0xc0/0x2b0 cpus_read_lock+0x2a/0xc0 static_key_slow_dec+0x16/0x60 __hugetlb_vmemmap_restore_folio+0x1b9/0x200 dissolve_free_huge_page+0x211/0x260 __page_handle_poison+0x45/0xc0 memory_failure+0x65e/0xc70 hard_offline_page_store+0x55/0xa0 kernfs_fop_write_iter+0x12c/0x1d0 vfs_write+0x387/0x550 ksys_write+0x64/0xe0 do_syscall_64+0xca/0x1e0 entry_SYSCALL_64_after_hwframe+0x6d/0x75
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1 ---- ---- lock(pcp_batch_high_lock); lock(cpu_hotplug_lock); lock(pcp_batch_high_lock); rlock(cpu_hotplug_lock);
*** DEADLOCK ***
5 locks held by bash/46904: #0: ffff98f6c3bb23f0 (sb_writers#5){.+.+}-{0:0}, at: ksys_write+0x64/0xe0 #1: ffff98f6c328e488 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0xf8/0x1d0 #2: ffff98ef83b31890 (kn->active#113){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x100/0x1d0 #3: ffffffffabf9db48 (mf_mutex){+.+.}-{3:3}, at: memory_failure+0x44/0xc70 #4: ffffffffabf92ea8 (pcp_batch_high_lock){+.+.}-{3:3}, at: zone_pcp_disable+0x16/0x40
stack backtrace: CPU: 10 PID: 46904 Comm: bash Kdump: loaded Not tainted 6.8.0-11409-gf6cef5f8c37f #1 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 check_noncircular+0x129/0x140 __lock_acquire+0x1298/0x1cd0 lock_acquire+0xc0/0x2b0 cpus_read_lock+0x2a/0xc0 static_key_slow_dec+0x16/0x60 __hugetlb_vmemmap_restore_folio+0x1b9/0x200 dissolve_free_huge_page+0x211/0x260 __page_handle_poison+0x45/0xc0 memory_failure+0x65e/0xc70 hard_offline_page_store+0x55/0xa0 kernfs_fop_write_iter+0x12c/0x1d0 vfs_write+0x387/0x550 ksys_write+0x64/0xe0 do_syscall_64+0xca/0x1e0 entry_SYSCALL_64_after_hwframe+0x6d/0x75 RIP: 0033:0x7fc862314887 Code: 10 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 51 c3 48 83 ec 28 48 89 54 24 18 48 89 74 24 RSP: 002b:00007fff19311268 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 000000000000000c RCX: 00007fc862314887 RDX: 000000000000000c RSI: 000056405645fe10 RDI: 0000000000000001 RBP: 000056405645fe10 R08: 00007fc8623d1460 R09: 000000007fffffff R10: 0000000000000000 R11: 0000000000000246 R12: 000000000000000c R13: 00007fc86241b780 R14: 00007fc862417600 R15: 00007fc862416a00
In short, below scene breaks the lock dependency chain:
memory_failure __page_handle_poison zone_pcp_disable -- lock(pcp_batch_high_lock) dissolve_free_huge_page __hugetlb_vmemmap_restore_folio static_key_slow_dec cpus_read_lock -- rlock(cpu_hotplug_lock)
Fix this by calling drain_all_pages() instead.
This issue won't occur until commit a6b40850c442 ("mm: hugetlb: replace hugetlb_free_vmemmap_enabled with a static_key"). As it introduced rlock(cpu_hotplug_lock) in dissolve_free_huge_page() code path while lock(pcp_batch_high_lock) is already in the __page_handle_poison().
[linmiaohe@huawei.com: extend comment per Oscar] [akpm@linux-foundation.org: reflow block comment] Link: https://lkml.kernel.org/r/20240407085456.2798193-1-linmiaohe@huawei.com Fixes: a6b40850c442 ("mm: hugetlb: replace hugetlb_free_vmemmap_enabled with a static_key") Signed-off-by: Miaohe Lin linmiaohe@huawei.com Acked-by: Oscar Salvador osalvador@suse.de Reviewed-by: Jane Chu jane.chu@oracle.com Cc: Naoya Horiguchi nao.horiguchi@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
mm/memory-failure.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-)
--- a/mm/memory-failure.c~mm-memory-failure-fix-deadlock-when-hugetlb_optimize_vmemmap-is-enabled +++ a/mm/memory-failure.c @@ -154,11 +154,23 @@ static int __page_handle_poison(struct p { int ret;
- zone_pcp_disable(page_zone(page)); + /* + * zone_pcp_disable() can't be used here. It will + * hold pcp_batch_high_lock and dissolve_free_huge_page() might hold + * cpu_hotplug_lock via static_key_slow_dec() when hugetlb vmemmap + * optimization is enabled. This will break current lock dependency + * chain and leads to deadlock. + * Disabling pcp before dissolving the page was a deterministic + * approach because we made sure that those pages cannot end up in any + * PCP list. Draining PCP lists expels those pages to the buddy system, + * but nothing guarantees that those pages do not get back to a PCP + * queue if we need to refill those. + */ ret = dissolve_free_huge_page(page); - if (!ret) + if (!ret) { + drain_all_pages(page_zone(page)); ret = take_page_off_buddy(page); - zone_pcp_enable(page_zone(page)); + }
return ret; } _
Patches currently in -mm which might be from linmiaohe@huawei.com are