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Wed, 25 Mar 2026 00:35:54 -0700 (PDT) MIME-Version: 1.0 References: <20260319083153.2488005-1-hao.ge@linux.dev> <20260319152808.fce61386fdf2934d7a3b0edb@linux-foundation.org> <9ef1c798-a30f-4458-9684-900136ae8b7d@linux.dev> <575e727e-cd47-41df-966a-142425aa8a8b@linux.dev> <35d274d9-ed52-4325-80fb-c374e8af3169@linux.dev> <88c6ac9d-d966-4c25-b16d-6808f9e8c43a@linux.dev> In-Reply-To: From: Suren Baghdasaryan Date: Wed, 25 Mar 2026 00:35:42 -0700 X-Gm-Features: AQROBzAx1ve-sHzZz65Ou5Mg0qCXwRb7aCmCa1-QCJdBQlyAHH46Vlu8p4iWkSU Message-ID: Subject: Re: [PATCH] mm/alloc_tag: clear codetag for pages allocated before page_ext initialization To: Hao Ge Cc: Andrew Morton , Kent Overstreet , linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: DEA8B20003 X-Stat-Signature: ic4iueorsdtj5k7x5j7zu5of1f6zztfg X-Rspam-User: X-HE-Tag: 1774424155-897108 X-HE-Meta: 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 h7B1bKmJ vqs6cCwNCrYmkcQ/G/HGpiiENEYzBVHlcbbW6o7eBZhEqQplhAP4ncZoFRZKllZBVM2VxAUBBQY1Akyc7BKyIIe71DDsxbfjmJWcIJvAg17mtF+cgZKweDofL2H2FuLUiaDbb+LJ3LGBh3Q0VJAW5YWyAHIfYOQbDsP9q0e6Uyo0EAg7CkbuLgzMV+s/e69cqxccSsTyAw132TRKNb6W522CuLMsKVZy/0a8jO+znZ7XAPXzNWZdL56t3StlrQZM9k5WwnvMlNytRnoofWKH5m+ZJy8YN0KBwp3G5lpyS8n7D0jbm8HIu3GdDYNeHmvmvrMcwFZMFyNLLGIEhfhDVTvx5FVvB4+aAwO9P0j9gV0zpbBeIXjRvSeubckOSM/B3Qo0+QBBjoOFQrc6K+PhAii0d9Jq+ipP22PoZPywN+3NL/nucaV+cHqQA9aK8DDETU/4ffBUqxzUw0p8ucBOBHLz88dPdQkNGQjZX57nil31V2Mk= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Mar 24, 2026 at 11:25=E2=80=AFPM Suren Baghdasaryan wrote: > > On Tue, Mar 24, 2026 at 7:08=E2=80=AFPM Hao Ge wrote: > > > > > > On 2026/3/25 08:21, Suren Baghdasaryan wrote: > > > On Tue, Mar 24, 2026 at 2:43=E2=80=AFAM Hao Ge wro= te: > > >> > > >> On 2026/3/24 06:47, Suren Baghdasaryan wrote: > > >>> On Mon, Mar 23, 2026 at 2:16=E2=80=AFAM Hao Ge w= rote: > > >>>> On 2026/3/20 10:14, Suren Baghdasaryan wrote: > > >>>>> On Thu, Mar 19, 2026 at 6:58=E2=80=AFPM Hao Ge = wrote: > > >>>>>> On 2026/3/20 07:48, Suren Baghdasaryan wrote: > > >>>>>>> On Thu, Mar 19, 2026 at 4:44=E2=80=AFPM Suren Baghdasaryan wrote: > > >>>>>>>> On Thu, Mar 19, 2026 at 3:28=E2=80=AFPM Andrew Morton wrote: > > >>>>>>>>> On Thu, 19 Mar 2026 16:31:53 +0800 Hao Ge = wrote: > > >>>>>>>>> > > >>>>>>>>>> Due to initialization ordering, page_ext is allocated and in= itialized > > >>>>>>>>>> relatively late during boot. Some pages have already been al= located > > >>>>>>>>>> and freed before page_ext becomes available, leaving their c= odetag > > >>>>>>>>>> uninitialized. > > >>>>>>>> Hi Hao, > > >>>>>>>> Thanks for the report. > > >>>>>>>> Hmm. So, we are allocating pages before page_ext is initialize= d... > > >>>>>>>> > > >>>>>>>>>> A clear example is in init_section_page_ext(): alloc_page_ex= t() calls > > >>>>>>>>>> kmemleak_alloc(). > > >>>>>>> Forgot to ask. The example you are using here is for page_ext > > >>>>>>> allocation itself. Do you have any other examples where page > > >>>>>>> allocation happens before page_ext initialization? If that's th= e only > > >>>>>>> place, then we might be able to fix this in a simpler way by do= ing > > >>>>>>> something special for alloc_page_ext(). > > >>>>>> Hi Suren > > >>>>>> > > >>>>>> To help illustrate the point, here's the debug log I added: > > >>>>>> > > >>>>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > >>>>>> index 2d4b6f1a554e..ebfe636f5b07 100644 > > >>>>>> --- a/mm/page_alloc.c > > >>>>>> +++ b/mm/page_alloc.c > > >>>>>> @@ -1293,6 +1293,9 @@ void __pgalloc_tag_add(struct page *page, = struct > > >>>>>> task_struct *task, > > >>>>>> alloc_tag_add(&ref, task->alloc_tag, PAGE_SI= ZE * nr); > > >>>>>> update_page_tag_ref(handle, &ref); > > >>>>>> put_page_tag_ref(handle); > > >>>>>> + } else { > > >>>>>> + pr_warn("__pgalloc_tag_add: get_page_tag_ref fai= led! > > >>>>>> page=3D%p pfn=3D%lu nr=3D%u\n", page, page_to_pfn(page), nr); > > >>>>>> + dump_stack(); > > >>>>>> } > > >>>>>> } > > >>>>>> > > >>>>>> > > >>>>>> And I caught the following logs: > > >>>>>> > > >>>>>> [ 0.296399] __pgalloc_tag_add: get_page_tag_ref failed! > > >>>>>> page=3Dffffea000400c700 pfn=3D1049372 nr=3D1 > > >>>>>> [ 0.296400] CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted > > >>>>>> 7.0.0-rc4-dirty #12 PREEMPT(lazy) > > >>>>>> [ 0.296402] Hardware name: Red Hat KVM, BIOS > > >>>>>> rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 > > >>>>>> [ 0.296402] Call Trace: > > >>>>>> [ 0.296403] > > >>>>>> [ 0.296403] dump_stack_lvl+0x53/0x70 > > >>>>>> [ 0.296405] __pgalloc_tag_add+0x3a3/0x6e0 > > >>>>>> [ 0.296406] ? __pfx___pgalloc_tag_add+0x10/0x10 > > >>>>>> [ 0.296407] ? kasan_unpoison+0x27/0x60 > > >>>>>> [ 0.296409] ? __kasan_unpoison_pages+0x2c/0x40 > > >>>>>> [ 0.296411] get_page_from_freelist+0xa54/0x1310 > > >>>>>> [ 0.296413] __alloc_frozen_pages_noprof+0x206/0x4c0 > > >>>>>> [ 0.296415] ? __pfx___alloc_frozen_pages_noprof+0x10/0x10 > > >>>>>> [ 0.296417] ? stack_depot_save_flags+0x3f/0x680 > > >>>>>> [ 0.296418] ? ___slab_alloc+0x518/0x530 > > >>>>>> [ 0.296420] alloc_pages_mpol+0x13a/0x3f0 > > >>>>>> [ 0.296421] ? __pfx_alloc_pages_mpol+0x10/0x10 > > >>>>>> [ 0.296423] ? _raw_spin_lock_irqsave+0x8a/0xf0 > > >>>>>> [ 0.296424] ? __pfx__raw_spin_lock_irqsave+0x10/0x10 > > >>>>>> [ 0.296426] alloc_slab_page+0xc2/0x130 > > >>>>>> [ 0.296427] allocate_slab+0x77/0x2c0 > > >>>>>> [ 0.296429] ? syscall_enter_define_fields+0x3bb/0x5f0 > > >>>>>> [ 0.296430] ___slab_alloc+0x125/0x530 > > >>>>>> [ 0.296432] ? __trace_define_field+0x252/0x3d0 > > >>>>>> [ 0.296433] __kmalloc_noprof+0x329/0x630 > > >>>>>> [ 0.296435] ? syscall_enter_define_fields+0x3bb/0x5f0 > > >>>>>> [ 0.296436] syscall_enter_define_fields+0x3bb/0x5f0 > > >>>>>> [ 0.296438] ? __pfx_syscall_enter_define_fields+0x10/0x10 > > >>>>>> [ 0.296440] event_define_fields+0x326/0x540 > > >>>>>> [ 0.296441] __trace_early_add_events+0xac/0x3c0 > > >>>>>> [ 0.296443] trace_event_init+0x24c/0x460 > > >>>>>> [ 0.296445] trace_init+0x9/0x20 > > >>>>>> [ 0.296446] start_kernel+0x199/0x3c0 > > >>>>>> [ 0.296448] x86_64_start_reservations+0x18/0x30 > > >>>>>> [ 0.296449] x86_64_start_kernel+0xe2/0xf0 > > >>>>>> [ 0.296451] common_startup_64+0x13e/0x141 > > >>>>>> [ 0.296453] > > >>>>>> > > >>>>>> > > >>>>>> [ 0.312234] __pgalloc_tag_add: get_page_tag_ref failed! > > >>>>>> page=3Dffffea000400f900 pfn=3D1049572 nr=3D1 > > >>>>>> [ 0.312234] CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted > > >>>>>> 7.0.0-rc4-dirty #12 PREEMPT(lazy) > > >>>>>> [ 0.312236] Hardware name: Red Hat KVM, BIOS > > >>>>>> rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 > > >>>>>> [ 0.312236] Call Trace: > > >>>>>> [ 0.312237] > > >>>>>> [ 0.312237] dump_stack_lvl+0x53/0x70 > > >>>>>> [ 0.312239] __pgalloc_tag_add+0x3a3/0x6e0 > > >>>>>> [ 0.312240] ? __pfx___pgalloc_tag_add+0x10/0x10 > > >>>>>> [ 0.312241] ? rmqueue.constprop.0+0x4fc/0x1ce0 > > >>>>>> [ 0.312243] ? kasan_unpoison+0x27/0x60 > > >>>>>> [ 0.312244] ? __kasan_unpoison_pages+0x2c/0x40 > > >>>>>> [ 0.312246] get_page_from_freelist+0xa54/0x1310 > > >>>>>> [ 0.312248] __alloc_frozen_pages_noprof+0x206/0x4c0 > > >>>>>> [ 0.312250] ? __pfx___alloc_frozen_pages_noprof+0x10/0x10 > > >>>>>> [ 0.312253] alloc_slab_page+0x39/0x130 > > >>>>>> [ 0.312254] allocate_slab+0x77/0x2c0 > > >>>>>> [ 0.312255] ? alloc_cpumask_var_node+0xc7/0x230 > > >>>>>> [ 0.312257] ___slab_alloc+0x46d/0x530 > > >>>>>> [ 0.312259] __kmalloc_node_noprof+0x2fa/0x680 > > >>>>>> [ 0.312261] ? alloc_cpumask_var_node+0xc7/0x230 > > >>>>>> [ 0.312263] alloc_cpumask_var_node+0xc7/0x230 > > >>>>>> [ 0.312264] init_desc+0x141/0x6b0 > > >>>>>> [ 0.312266] alloc_desc+0x108/0x1b0 > > >>>>>> [ 0.312267] early_irq_init+0xee/0x1c0 > > >>>>>> [ 0.312268] ? __pfx_early_irq_init+0x10/0x10 > > >>>>>> [ 0.312271] start_kernel+0x1ab/0x3c0 > > >>>>>> [ 0.312272] x86_64_start_reservations+0x18/0x30 > > >>>>>> [ 0.312274] x86_64_start_kernel+0xe2/0xf0 > > >>>>>> [ 0.312275] common_startup_64+0x13e/0x141 > > >>>>>> [ 0.312277] > > >>>>>> > > >>>>>> [ 0.312834] __pgalloc_tag_add: get_page_tag_ref failed! > > >>>>>> page=3Dffffea000400fc00 pfn=3D1049584 nr=3D1 > > >>>>>> [ 0.312835] CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted > > >>>>>> 7.0.0-rc4-dirty #12 PREEMPT(lazy) > > >>>>>> [ 0.312836] Hardware name: Red Hat KVM, BIOS > > >>>>>> rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 > > >>>>>> [ 0.312837] Call Trace: > > >>>>>> [ 0.312837] > > >>>>>> [ 0.312838] dump_stack_lvl+0x53/0x70 > > >>>>>> [ 0.312840] __pgalloc_tag_add+0x3a3/0x6e0 > > >>>>>> [ 0.312841] ? __pfx___pgalloc_tag_add+0x10/0x10 > > >>>>>> [ 0.312842] ? rmqueue.constprop.0+0x4fc/0x1ce0 > > >>>>>> [ 0.312844] ? kasan_unpoison+0x27/0x60 > > >>>>>> [ 0.312845] ? __kasan_unpoison_pages+0x2c/0x40 > > >>>>>> [ 0.312847] get_page_from_freelist+0xa54/0x1310 > > >>>>>> [ 0.312849] __alloc_frozen_pages_noprof+0x206/0x4c0 > > >>>>>> [ 0.312851] ? __pfx___alloc_frozen_pages_noprof+0x10/0x10 > > >>>>>> [ 0.312853] alloc_pages_mpol+0x13a/0x3f0 > > >>>>>> [ 0.312855] ? __pfx_alloc_pages_mpol+0x10/0x10 > > >>>>>> [ 0.312856] ? xas_find+0x2d8/0x450 > > >>>>>> [ 0.312858] ? _raw_spin_lock+0x84/0xe0 > > >>>>>> [ 0.312859] ? __pfx__raw_spin_lock+0x10/0x10 > > >>>>>> [ 0.312861] alloc_pages_noprof+0xf6/0x2b0 > > >>>>>> [ 0.312862] __change_page_attr+0x293/0x850 > > >>>>>> [ 0.312864] ? __pfx___change_page_attr+0x10/0x10 > > >>>>>> [ 0.312865] ? _vm_unmap_aliases+0x2d0/0x650 > > >>>>>> [ 0.312868] ? __pfx__vm_unmap_aliases+0x10/0x10 > > >>>>>> [ 0.312869] __change_page_attr_set_clr+0x16c/0x360 > > >>>>>> [ 0.312871] ? spp_getpage+0xbb/0x1e0 > > >>>>>> [ 0.312872] change_page_attr_set_clr+0x220/0x3c0 > > >>>>>> [ 0.312873] ? flush_tlb_one_kernel+0xf/0x30 > > >>>>>> [ 0.312875] ? set_pte_vaddr_p4d+0x110/0x180 > > >>>>>> [ 0.312877] ? __pfx_change_page_attr_set_clr+0x10/0x10 > > >>>>>> [ 0.312878] ? __pfx_set_pte_vaddr_p4d+0x10/0x10 > > >>>>>> [ 0.312881] ? __pfx_mtree_load+0x10/0x10 > > >>>>>> [ 0.312883] ? __pfx_mtree_load+0x10/0x10 > > >>>>>> [ 0.312884] ? __asan_memcpy+0x3c/0x60 > > >>>>>> [ 0.312886] ? set_intr_gate+0x10c/0x150 > > >>>>>> [ 0.312888] set_memory_ro+0x76/0xa0 > > >>>>>> [ 0.312889] ? __pfx_set_memory_ro+0x10/0x10 > > >>>>>> [ 0.312891] idt_setup_apic_and_irq_gates+0x2c1/0x390 > > >>>>>> > > >>>>>> and more. > > >>>>> Ok, it's not the only place. Got your point. > > >>>>> > > >>>>>> off topic - if we were to handle only alloc_page_ext() specific= ally, > > >>>>>> what would be the most straightforward > > >>>>>> > > >>>>>> solution in your mind? I'd really appreciate your insight. > > >>>>> I was thinking if it's the only special case maybe we can handle = it > > >>>>> somehow differently, like we do when we allocate obj_ext vectors = for > > >>>>> slabs using __GFP_NO_OBJ_EXT. I haven't found a good solution yet= but > > >>>>> since it's not a special case we would not be able to use it even= if I > > >>>>> came up with something... > > >>>>> I think your way is the most straight-forward but please try my > > >>>>> suggestion to see if we can avoid extra overhead. > > >>>>> Thanks, > > >>>>> Suren. > > Hi Suren > > >> Hi Suren > > >> > > >> > > >>> Hi Hao, > > >>> > > >>>> Hi Suren > > >>>> > > >>>> Thank you for your feedback. After re-examining this issue, > > >>>> > > >>>> I realize my previous focus was misplaced. > > >>>> > > >>>> Upon deeper consideration, I understand that this is not merely a = bug, > > >>>> > > >>>> but rather a warning that indicates a gap in our memory profiling = mechanism. > > >>>> > > >>>> Specifically, the current implementation appears to be missing mem= ory > > >>>> allocation > > >>>> > > >>>> tracking during the period between the buddy system allocation and= page_ext > > >>>> > > >>>> initialization. > > >>>> > > >>>> This profiling gap means we may not be capturing all relevant memo= ry > > >>>> allocation > > >>>> > > >>>> events during this critical transition phase. > > >>> Correct, this limitation exists because memory profiling relies on > > >>> some kernel facilities (page_ext, objj_ext) which might not be > > >>> initialized yet at the time of allocation. > > >>> > > >>>> My approach is to dynamically allocate codetag_ref when get_page_t= ag_ref > > >>>> fails, > > >>>> > > >>>> and maintain a linked list to track all buddy system allocations t= hat > > >>>> occur prior to page_ext initialization. > > >>>> > > >>>> However, this introduces performance concerns: > > >>>> > > >>>> 1. Free Path Overhead: When freeing these pages, we would need to > > >>>> traverse the entire linked list to locate > > >>>> > > >>>> the corresponding codetag_ref, resulting in O(n) lookup co= mplexity > > >>>> per free operation. > > >>>> > > >>>> 2. Initialization Overhead: During init_page_alloc_tagging, iterat= ing > > >>>> through the linked list to assign codetag_ref to > > >>>> > > >>>> page_ext would introduce additional traversal cost. > > >>>> > > >>>> If the number of pages is substantial, this could incur significan= t > > >>>> overhead. What are your thoughts on this? I look forward to your > > >>>> suggestions. > > >>> My thinking is that these early allocations comprise a small portio= n > > >>> of overall memory consumed by the system. So, instead of trying to > > >>> record and handle them in some alternative way, we just accept that > > >>> some counters might not be exactly accurate and ignore those early > > >>> allocations. See how the early slab allocations are marked with the > > >>> CODETAG_FLAG_INACCURATE flag and later reported as inaccurate. I th= ink > > >>> that's an acceptable alternative to introducing extra complexity an= d > > >>> performance overhead. IOW, the benefits of accounting for these ear= ly > > >>> allocations are low compared to the effort required to account for > > >>> them. Unless you found a simple and performant way to do that... > > >> > > >> I have been exploring possible solutions to this issue over the past= few > > >> days, > > >> > > >> but so far I have not come up with a good approach. > > >> > > >> I have counted the number of memory allocations that occur earlier t= han the > > >> > > >> allocation and initialization of our page_ext, and found that there = are > > >> actually > > >> > > >> quite a lot of them. > > > Interesting... I wonder it's because deferred_struct_pages defers > > > page_ext initialization. Can you check if setting early_page_ext > > > reduces or eliminates these allocations before page_ext init cases? > > > > Yes, you are correct. In my 8-core 16GB virtual machine, I used a globa= l > > counter > > > > to record these allocations. With early_page_ext enabled, there were 13= 0 > > allocations > > > > before page_ext initialization. Without early_page_ext, there were 802 > > allocations > > > > before page_ext initialization. > > > > > > > > > >> Similarly, I have made the following changes and collected the > > >> corresponding logs. > > >> > > >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > >> index 2d4b6f1a554e..6db65b3d52d3 100644 > > >> --- a/mm/page_alloc.c > > >> +++ b/mm/page_alloc.c > > >> @@ -1293,6 +1293,8 @@ void __pgalloc_tag_add(struct page *page, stru= ct > > >> task_struct *task, > > >> alloc_tag_add(&ref, task->alloc_tag, PAGE_SIZE * n= r); > > >> update_page_tag_ref(handle, &ref); > > >> put_page_tag_ref(handle); > > >> + } else{ > > >> + pr_warn("__pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3D%p pfn=3D%lu nr=3D%u\n", page, page_to_pfn(page), nr); > > >> } > > >> } > > >> > > >> @@ -1314,6 +1316,8 @@ void __pgalloc_tag_sub(struct page *page, unsi= gned > > >> int nr) > > >> alloc_tag_sub(&ref, PAGE_SIZE * nr); > > >> update_page_tag_ref(handle, &ref); > > >> put_page_tag_ref(handle); > > >> + } else{ > > >> + pr_warn("__pgalloc_tag_sub: get_page_tag_ref failed= ! > > >> page=3D%p pfn=3D%lu nr=3D%u\n", page, page_to_pfn(page), nr); > > >> } > > >> } > > >> > > >> [ 0.261699] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001000 pfn=3D1048640 nr=3D2 > > >> [ 0.261711] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001100 pfn=3D1048644 nr=3D4 > > >> [ 0.261717] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001200 pfn=3D1048648 nr=3D4 > > >> [ 0.261721] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001300 pfn=3D1048652 nr=3D4 > > >> [ 0.261893] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001080 pfn=3D1048642 nr=3D2 > > >> [ 0.261917] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001400 pfn=3D1048656 nr=3D4 > > >> [ 0.262018] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001500 pfn=3D1048660 nr=3D2 > > >> [ 0.262024] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001600 pfn=3D1048664 nr=3D8 > > >> [ 0.262040] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001580 pfn=3D1048662 nr=3D1 > > >> [ 0.262048] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea00040015c0 pfn=3D1048663 nr=3D1 > > >> [ 0.262056] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001800 pfn=3D1048672 nr=3D2 > > >> [ 0.262064] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001880 pfn=3D1048674 nr=3D2 > > >> [ 0.262078] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001900 pfn=3D1048676 nr=3D2 > > >> [ 0.262196] SLUB: HWalign=3D64, Order=3D0-3, MinObjects=3D0, CPUs= =3D8, Nodes=3D1 > > >> [ 0.262213] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001980 pfn=3D1048678 nr=3D2 > > >> [ 0.262220] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001a00 pfn=3D1048680 nr=3D4 > > >> [ 0.262246] ODEBUG: selftest passed > > >> [ 0.262268] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001b00 pfn=3D1048684 nr=3D1 > > >> [ 0.262318] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001b40 pfn=3D1048685 nr=3D1 > > >> [ 0.262368] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001b80 pfn=3D1048686 nr=3D1 > > >> [ 0.262418] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001bc0 pfn=3D1048687 nr=3D1 > > >> [ 0.262469] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001c00 pfn=3D1048688 nr=3D1 > > >> [ 0.262519] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001c40 pfn=3D1048689 nr=3D1 > > >> [ 0.262569] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001c80 pfn=3D1048690 nr=3D1 > > >> [ 0.262620] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001cc0 pfn=3D1048691 nr=3D1 > > >> [ 0.262670] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001d00 pfn=3D1048692 nr=3D1 > > >> [ 0.262721] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001d40 pfn=3D1048693 nr=3D1 > > >> [ 0.262771] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001d80 pfn=3D1048694 nr=3D1 > > >> [ 0.262821] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001dc0 pfn=3D1048695 nr=3D1 > > >> [ 0.262871] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001e00 pfn=3D1048696 nr=3D1 > > >> [ 0.262923] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001e40 pfn=3D1048697 nr=3D1 > > >> [ 0.262974] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001e80 pfn=3D1048698 nr=3D1 > > >> [ 0.263024] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001ec0 pfn=3D1048699 nr=3D1 > > >> [ 0.263074] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001f00 pfn=3D1048700 nr=3D1 > > >> [ 0.263124] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001f40 pfn=3D1048701 nr=3D1 > > >> [ 0.263174] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001f80 pfn=3D1048702 nr=3D1 > > >> [ 0.263224] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004001fc0 pfn=3D1048703 nr=3D1 > > >> [ 0.263275] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004002000 pfn=3D1048704 nr=3D1 > > >> [ 0.263325] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004002040 pfn=3D1048705 nr=3D1 > > >> [ 0.263375] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004002080 pfn=3D1048706 nr=3D1 > > >> [ 0.263427] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004002400 pfn=3D1048720 nr=3D16 > > >> [ 0.263437] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea00040020c0 pfn=3D1048707 nr=3D1 > > >> [ 0.263463] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004002100 pfn=3D1048708 nr=3D1 > > >> [ 0.263465] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004002140 pfn=3D1048709 nr=3D1 > > >> [ 0.263467] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004002180 pfn=3D1048710 nr=3D1 > > >> [ 0.263509] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004002200 pfn=3D1048712 nr=3D4 > > >> [ 0.263512] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004002800 pfn=3D1048736 nr=3D8 > > >> [ 0.263524] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea00040021c0 pfn=3D1048711 nr=3D1 > > >> [ 0.263536] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004002300 pfn=3D1048716 nr=3D1 > > >> [ 0.263537] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004002340 pfn=3D1048717 nr=3D1 > > >> [ 0.263539] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004002380 pfn=3D1048718 nr=3D1 > > >> [ 0.263604] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004004000 pfn=3D1048832 nr=3D128 > > >> [ 0.263638] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004003000 pfn=3D1048768 nr=3D64 > > >> [ 0.263650] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004002c00 pfn=3D1048752 nr=3D16 > > >> [ 0.263655] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea00040023c0 pfn=3D1048719 nr=3D1 > > >> [ 0.270582] __pgalloc_tag_sub: get_page_tag_ref failed! > > >> page=3Dffffea00040023c0 pfn=3D1048719 nr=3D1 > > >> [ 0.270591] ftrace: allocating 52717 entries in 208 pages > > >> [ 0.270592] ftrace: allocated 208 pages with 3 groups > > >> [ 0.270620] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004002a00 pfn=3D1048744 nr=3D8 > > >> [ 0.270636] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea00040023c0 pfn=3D1048719 nr=3D1 > > >> [ 0.270643] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004006000 pfn=3D1048960 nr=3D1 > > >> [ 0.270649] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004006040 pfn=3D1048961 nr=3D1 > > >> [ 0.270658] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004007000 pfn=3D1049024 nr=3D64 > > >> [ 0.270659] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004006080 pfn=3D1048962 nr=3D2 > > >> [ 0.270722] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004006100 pfn=3D1048964 nr=3D1 > > >> [ 0.270730] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004006140 pfn=3D1048965 nr=3D1 > > >> [ 0.270738] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004006180 pfn=3D1048966 nr=3D1 > > >> [ 0.270777] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea00040061c0 pfn=3D1048967 nr=3D1 > > >> [ 0.270786] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004006200 pfn=3D1048968 nr=3D1 > > >> [ 0.270792] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004006240 pfn=3D1048969 nr=3D1 > > >> [ 0.270833] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004006300 pfn=3D1048972 nr=3D4 > > >> [ 0.270891] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004006280 pfn=3D1048970 nr=3D1 > > >> [ 0.270980] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea00040062c0 pfn=3D1048971 nr=3D1 > > >> [ 0.271071] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004006400 pfn=3D1048976 nr=3D1 > > >> [ 0.271156] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004006440 pfn=3D1048977 nr=3D1 > > >> [ 0.271185] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004006480 pfn=3D1048978 nr=3D2 > > >> [ 0.271301] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004006500 pfn=3D1048980 nr=3D1 > > >> [ 0.271655] Dynamic Preempt: lazy > > >> [ 0.271662] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004006580 pfn=3D1048982 nr=3D2 > > >> [ 0.271752] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004006600 pfn=3D1048984 nr=3D4 > > >> [ 0.271762] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004010000 pfn=3D1049600 nr=3D4 > > >> [ 0.271824] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004006540 pfn=3D1048981 nr=3D1 > > >> [ 0.271916] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004006700 pfn=3D1048988 nr=3D2 > > >> [ 0.271964] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004006780 pfn=3D1048990 nr=3D1 > > >> [ 0.272099] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea00040067c0 pfn=3D1048991 nr=3D1 > > >> [ 0.272138] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004006800 pfn=3D1048992 nr=3D2 > > >> [ 0.272144] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004006a00 pfn=3D1049000 nr=3D8 > > >> [ 0.272249] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004006c00 pfn=3D1049008 nr=3D8 > > >> [ 0.272319] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004006880 pfn=3D1048994 nr=3D2 > > >> [ 0.272351] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004006900 pfn=3D1048996 nr=3D4 > > >> [ 0.272424] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004006e00 pfn=3D1049016 nr=3D8 > > >> [ 0.272485] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004008000 pfn=3D1049088 nr=3D8 > > >> [ 0.272535] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004008200 pfn=3D1049096 nr=3D2 > > >> [ 0.272600] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004008400 pfn=3D1049104 nr=3D8 > > >> [ 0.272663] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004008300 pfn=3D1049100 nr=3D4 > > >> [ 0.272694] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004008280 pfn=3D1049098 nr=3D2 > > >> [ 0.272708] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004008600 pfn=3D1049112 nr=3D8 > > >> > > >> [ 0.272924] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004008880 pfn=3D1049122 nr=3D2 > > >> [ 0.272934] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004008900 pfn=3D1049124 nr=3D2 > > >> [ 0.272952] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004008c00 pfn=3D1049136 nr=3D4 > > >> [ 0.273035] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004008980 pfn=3D1049126 nr=3D2 > > >> [ 0.273062] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004008e00 pfn=3D1049144 nr=3D8 > > >> [ 0.273674] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004008d00 pfn=3D1049140 nr=3D1 > > >> [ 0.273884] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004008d80 pfn=3D1049142 nr=3D2 > > >> [ 0.273943] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004009000 pfn=3D1049152 nr=3D2 > > >> [ 0.274379] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004009080 pfn=3D1049154 nr=3D2 > > >> [ 0.274575] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004009200 pfn=3D1049160 nr=3D8 > > >> [ 0.274617] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004009100 pfn=3D1049156 nr=3D4 > > >> [ 0.274794] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004009400 pfn=3D1049168 nr=3D2 > > >> [ 0.274840] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004009480 pfn=3D1049170 nr=3D2 > > >> [ 0.275057] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004009500 pfn=3D1049172 nr=3D2 > > >> [ 0.275092] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004009580 pfn=3D1049174 nr=3D2 > > >> [ 0.275134] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004009600 pfn=3D1049176 nr=3D8 > > >> [ 0.275211] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004009800 pfn=3D1049184 nr=3D4 > > >> [ 0.275510] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004009900 pfn=3D1049188 nr=3D2 > > >> [ 0.275548] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004009980 pfn=3D1049190 nr=3D2 > > >> [ 0.275976] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004009a00 pfn=3D1049192 nr=3D8 > > >> [ 0.275987] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004009c00 pfn=3D1049200 nr=3D2 > > >> [ 0.276139] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004009c80 pfn=3D1049202 nr=3D2 > > >> [ 0.276152] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004008d40 pfn=3D1049141 nr=3D1 > > >> [ 0.276242] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004009d00 pfn=3D1049204 nr=3D1 > > >> [ 0.276358] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004009d40 pfn=3D1049205 nr=3D1 > > >> [ 0.276444] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004009d80 pfn=3D1049206 nr=3D1 > > >> [ 0.276526] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004009dc0 pfn=3D1049207 nr=3D1 > > >> [ 0.276615] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004009e00 pfn=3D1049208 nr=3D1 > > >> [ 0.276696] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004009e40 pfn=3D1049209 nr=3D1 > > >> [ 0.276792] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004009e80 pfn=3D1049210 nr=3D1 > > >> [ 0.276827] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004009f00 pfn=3D1049212 nr=3D2 > > >> [ 0.276891] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004009ec0 pfn=3D1049211 nr=3D1 > > >> [ 0.276999] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004009f80 pfn=3D1049214 nr=3D1 > > >> [ 0.277082] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea0004009fc0 pfn=3D1049215 nr=3D1 > > >> [ 0.277172] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea000400a000 pfn=3D1049216 nr=3D1 > > >> [ 0.277257] __pgalloc_tag_add: get_page_tag_ref failed! > > >> page=3Dffffea000400a040 pfn=3D1049217 nr=3D1 > > >> > > >> and so on. > > >> > > >> > > >>> I think your earlier patch can effectively detect these early > > >>> allocations and suppress the warnings. We should also mark these > > >>> allocations with CODETAG_FLAG_INACCURATE. > > >> Thanks to an excellent AI review, I realized there are issues with > > >> > > >> my original patch. One problem is the 256-element array; another > > > Yes, if there are lots of such allocations, it's not appropriate. > > > > > >> is that it involves allocation and free operations =E2=80=94 meaning= we need > > >> > > >> to record entries at __pgalloc_tag_add and remove them at __pgalloc_= tag_sub, > > >> > > >> which introduces a noticeable overhead. I'm wondering if we can inst= ead > > >> set a flag > > >> > > >> bit in page flags during the early boot stage, which I'll refer to a= s > > >> EARLY_ALLOC_FLAGS. > > >> > > >> Then, in __pgalloc_tag_sub, we first check for EARLY_ALLOC_FLAGS. If > > >> set, we clear the > > >> > > >> flag and return immediately; otherwise, we perform the actual > > >> subtraction of the tag count. > > >> > > >> This approach seems somewhat similar to the idea behind > > >> mem_profiling_compressed. > > > That seems doable but let's first check if we can make page_ext > > > initialization happen before these allocations. That would be the > > > ideal path. If it's not possible then we can focus on alternatives > > > like the one you propose. > > > > > > Yes, the ideal scenario would be to have page_ext initialization > > complete before > > > > these allocations occur. I just did a code walkthrough and found that > > this resembles > > > > the FLATMEM implementation approach - FLATMEM allocates page_ext before > > the buddy > > > > system initialization, so it doesn't seem to encounter the issue we're > > facing now. > > > > https://elixir.bootlin.com/linux/v7.0-rc5/source/mm/mm_init.c#L2707 > > Yes, page_ext_init_flatmem() looks like an interesting option and it > would not work with sparsemem. TBH I would prefer to find a simple > solution that can identify early init allocations, mark them inaccuate > and suppress the warning rather than introduce some complex mechanism > to account for them which would work only is some cases (flatmem). > With your original approach I think the only real issue is the size of > the array that might be too small. The other issue you mentioned about > allocated page being freed and then re-allocated after page_ext is > inialized but before clear_page_tag_ref() is called is not really a > problem. Yes, we will lose that counter's value but it's similar to > other early allocations which we just treat as inaccurate. We can also > minimize the possibility of this happening by moving > clear_page_tag_ref() into init_page_alloc_tagging(). > > I don't like the pageflag option you mentioned because it adds an > extra condition check into __pgalloc_tag_sub() which will be executed > even after the init stage is over. > I'll look into this some more tomorrow as it's quite late now. Just though of something. Are all these pages allocated by slab? If so, I think slab does not use page->lru (need to double-check) and we could add all these pages allocated during early init into a list and then set their page_ext reference to CODETAG_EMPTY in init_page_alloc_tagging(). > Thanks, > Suren. > > > > > However, I'm not entirely certain whether SPARSEMEM can guarantee the > > same behavior. > > > > > > > > > >> I would appreciate your valuable feedback and any better suggestions= you > > >> might have. > > > Thanks for pursuing this! I'll help in any way I can. > > > Suren. > > > > Thank you so much for your patient guidance and assistance. > > > > I truly appreciate your willingness to share your knowledge and insight= s. > > > > Thanks, > > Hao > > > > >> Thanks > > >> > > >> Hao > > >> > > >>> Thanks, > > >>> Suren. > > >>> > > >>>> Thanks > > >>>> > > >>>> Hao > > >>>> > > >>>>>> Thanks. > > >>>>>> > > >>>>>> > > >>>>>>>>>> If the slab cache has no free objects, it falls back > > >>>>>>>>>> to the buddy allocator to allocate memory. However, at this = point page_ext > > >>>>>>>>>> is not yet fully initialized, so these newly allocated pages= have no > > >>>>>>>>>> codetag set. These pages may later be reclaimed by KASAN,whi= ch causes > > >>>>>>>>>> the warning to trigger when they are freed because their cod= etag ref is > > >>>>>>>>>> still empty. > > >>>>>>>>>> > > >>>>>>>>>> Use a global array to track pages allocated before page_ext = is fully > > >>>>>>>>>> initialized, similar to how kmemleak tracks early allocation= s. > > >>>>>>>>>> When page_ext initialization completes, set their codetag > > >>>>>>>>>> to empty to avoid warnings when they are freed later. > > >>>>>>>>>> > > >>>>>>>>>> ... > > >>>>>>>>>> > > >>>>>>>>>> --- a/include/linux/alloc_tag.h > > >>>>>>>>>> +++ b/include/linux/alloc_tag.h > > >>>>>>>>>> @@ -74,6 +74,9 @@ static inline void set_codetag_empty(union= codetag_ref *ref) > > >>>>>>>>>> > > >>>>>>>>>> #ifdef CONFIG_MEM_ALLOC_PROFILING > > >>>>>>>>>> > > >>>>>>>>>> +bool mem_profiling_is_available(void); > > >>>>>>>>>> +void alloc_tag_add_early_pfn(unsigned long pfn); > > >>>>>>>>>> + > > >>>>>>>>>> #define ALLOC_TAG_SECTION_NAME "alloc_tags" > > >>>>>>>>>> > > >>>>>>>>>> struct codetag_bytes { > > >>>>>>>>>> diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c > > >>>>>>>>>> index 58991ab09d84..a5bf4e72c154 100644 > > >>>>>>>>>> --- a/lib/alloc_tag.c > > >>>>>>>>>> +++ b/lib/alloc_tag.c > > >>>>>>>>>> @@ -6,6 +6,7 @@ > > >>>>>>>>>> #include > > >>>>>>>>>> #include > > >>>>>>>>>> #include > > >>>>>>>>>> +#include > > >>>>>>>>>> #include > > >>>>>>>>>> #include > > >>>>>>>>>> #include > > >>>>>>>>>> @@ -26,6 +27,82 @@ static bool mem_profiling_support; > > >>>>>>>>>> > > >>>>>>>>>> static struct codetag_type *alloc_tag_cttype; > > >>>>>>>>>> > > >>>>>>>>>> +/* > > >>>>>>>>>> + * State of the alloc_tag > > >>>>>>>>>> + * > > >>>>>>>>>> + * This is used to describe the states of the alloc_tag dur= ing bootup. > > >>>>>>>>>> + * > > >>>>>>>>>> + * When we need to allocate page_ext to store codetag, we f= ace an > > >>>>>>>>>> + * initialization timing problem: > > >>>>>>>>>> + * > > >>>>>>>>>> + * Due to initialization order, pages may be allocated via = buddy system > > >>>>>>>>>> + * before page_ext is fully allocated and initialized. Alth= ough these > > >>>>>>>>>> + * pages call the allocation hooks, the codetag will not be= set because > > >>>>>>>>>> + * page_ext is not yet available. > > >>>>>>>>>> + * > > >>>>>>>>>> + * When these pages are later free to the buddy system, it = triggers > > >>>>>>>>>> + * warnings because their codetag is actually empty if > > >>>>>>>>>> + * CONFIG_MEM_ALLOC_PROFILING_DEBUG is enabled. > > >>>>>>>>>> + * > > >>>>>>>>>> + * Additionally, in this situation, we cannot record detail= ed allocation > > >>>>>>>>>> + * information for these pages. > > >>>>>>>>>> + */ > > >>>>>>>>>> +enum mem_profiling_state { > > >>>>>>>>>> + DOWN, /* No mem_profiling functional= ity yet */ > > >>>>>>>>>> + UP /* Everything is working */ > > >>>>>>>>>> +}; > > >>>>>>>>>> + > > >>>>>>>>>> +static enum mem_profiling_state mem_profiling_state =3D DOW= N; > > >>>>>>>>>> + > > >>>>>>>>>> +bool mem_profiling_is_available(void) > > >>>>>>>>>> +{ > > >>>>>>>>>> + return mem_profiling_state =3D=3D UP; > > >>>>>>>>>> +} > > >>>>>>>>>> + > > >>>>>>>>>> +#ifdef CONFIG_MEM_ALLOC_PROFILING_DEBUG > > >>>>>>>>>> + > > >>>>>>>>>> +#define EARLY_ALLOC_PFN_MAX 256 > > >>>>>>>>>> + > > >>>>>>>>>> +static unsigned long early_pfns[EARLY_ALLOC_PFN_MAX]; > > >>>>>>>>> It's unfortunate that this isn't __initdata. > > >>>>>>>>> > > >>>>>>>>>> +static unsigned int early_pfn_count; > > >>>>>>>>>> +static DEFINE_SPINLOCK(early_pfn_lock); > > >>>>>>>>>> + > > >>>>>>>>>> > > >>>>>>>>>> ... > > >>>>>>>>>> > > >>>>>>>>>> --- a/mm/page_alloc.c > > >>>>>>>>>> +++ b/mm/page_alloc.c > > >>>>>>>>>> @@ -1293,6 +1293,13 @@ void __pgalloc_tag_add(struct page *p= age, struct task_struct *task, > > >>>>>>>>>> alloc_tag_add(&ref, task->alloc_tag, PAGE_= SIZE * nr); > > >>>>>>>>>> update_page_tag_ref(handle, &ref); > > >>>>>>>>>> put_page_tag_ref(handle); > > >>>>>>>>>> + } else { > > >>>>>>>> This branch can be marked as "unlikely". > > >>>>>>>> > > >>>>>>>>>> + /* > > >>>>>>>>>> + * page_ext is not available yet, record the p= fn so we can > > >>>>>>>>>> + * clear the tag ref later when page_ext is in= itialized. > > >>>>>>>>>> + */ > > >>>>>>>>>> + if (!mem_profiling_is_available()) > > >>>>>>>>>> + alloc_tag_add_early_pfn(page_to_pfn(pa= ge)); > > >>>>>>>>>> } > > >>>>>>>>>> } > > >>>>>>>>> All because of this, I believe. Is this fixable? > > >>>>>>>>> > > >>>>>>>>> If we take that `else', we know we're running in __init code,= yes? I > > >>>>>>>>> don't see how `__init pgalloc_tag_add_early()' could be made = to work. > > >>>>>>>>> hrm. Something clever, please. > > >>>>>>>> We can have a pointer to a function that is initialized to poi= nt to > > >>>>>>>> alloc_tag_add_early_pfn, which is defined as __init and uses > > >>>>>>>> early_pfns which now can be defined as __initdata. After > > >>>>>>>> clear_early_alloc_pfn_tag_refs() is done we reset that pointer= to > > >>>>>>>> NULL. __pgalloc_tag_add() instead of calling alloc_tag_add_ear= ly_pfn() > > >>>>>>>> directly checks that pointer and if it's not NULL then calls t= he > > >>>>>>>> function that it points to. This way __pgalloc_tag_add() which= is not > > >>>>>>>> an __init function will be invoking alloc_tag_add_early_pfn() = __init > > >>>>>>>> function only until we are done with initialization. I haven't= tried > > >>>>>>>> this but I think that should work. This also eliminates the ne= ed for > > >>>>>>>> mem_profiling_state variable since we can use this function po= inter > > >>>>>>>> instead. > > >>>>>>>> > > >>>>>>>>