From: Andrew Morton <akpm@linux-foundation.org>
To: mm-commits@vger.kernel.org,ziy@nvidia.com,vbabka@kernel.org,surenb@google.com,kernel.org,stable@vger,mhocko@suse.com,jackmanb@google.com,hannes@cmpxchg.org,hao.ge@linux.dev,akpm@linux-foundation.org
Subject: [to-be-updated] mm-alloc_tag-clear-codetag-for-pages-allocated-before-page_ext-initialization.patch removed from -mm tree
Date: Thu, 26 Mar 2026 18:34:50 -0700 [thread overview]
Message-ID: <20260327013450.916B5C116C6@smtp.kernel.org> (raw)
The quilt patch titled
Subject: mm/alloc_tag: clear codetag for pages allocated before page_ext initialization
has been removed from the -mm tree. Its filename was
mm-alloc_tag-clear-codetag-for-pages-allocated-before-page_ext-initialization.patch
This patch was dropped because an updated version will be issued
------------------------------------------------------
From: Hao Ge <hao.ge@linux.dev>
Subject: mm/alloc_tag: clear codetag for pages allocated before page_ext initialization
Date: Thu, 26 Mar 2026 22:05:54 +0800
Due to initialization ordering, page_ext is allocated and initialized
relatively late during boot. Some pages have already been allocated and
freed before page_ext becomes available, leaving their codetag
uninitialized.
A clear example is in init_section_page_ext(): alloc_page_ext() calls
kmemleak_alloc(). 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, which causes
the warning to trigger when they are freed because their codetag ref is
still empty.
Use a global array to track pages allocated before page_ext is fully
initialized. The array size is fixed at 8192 entries, and will emit a
warning if this limit is exceeded. When page_ext initialization
completes, set their codetag to empty to avoid warnings when they are
freed later.
The following warning is observed when this issue occurs:
[ 9.582133] ------------[ cut here ]------------
[ 9.582137] alloc_tag was not set
[ 9.582139] WARNING: ./include/linux/alloc_tag.h:164 at __pgalloc_tag_sub+0x40f/0x550, CPU#5: systemd/1
[ 9.582190] CPU: 5 UID: 0 PID: 1 Comm: systemd Not tainted 7.0.0-rc4 #1 PREEMPT(lazy)
[ 9.582192] Hardware name: Red Hat KVM, BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[ 9.582194] RIP: 0010:__pgalloc_tag_sub+0x40f/0x550
[ 9.582196] Code: 00 00 4c 29 e5 48 8b 05 1f 88 56 05 48 8d 4c ad 00 48 8d 2c c8 e9 87 fd ff ff 0f 0b 0f 0b e9 f3 fe ff ff 48 8d 3d 61 2f ed 03 <67> 48 0f b9 3a e9 b3 fd ff ff 0f 0b eb e4 e8 5e cd 14 02 4c 89 c7
[ 9.582197] RSP: 0018:ffffc9000001f940 EFLAGS: 00010246
[ 9.582200] RAX: dffffc0000000000 RBX: 1ffff92000003f2b RCX: 1ffff110200d806c
[ 9.582201] RDX: ffff8881006c0360 RSI: 0000000000000004 RDI: ffffffff9bc7b460
[ 9.582202] RBP: 0000000000000000 R08: 0000000000000000 R09: fffffbfff3a62324
[ 9.582203] R10: ffffffff9d311923 R11: 0000000000000000 R12: ffffea0004001b00
[ 9.582204] R13: 0000000000002000 R14: ffffea0000000000 R15: ffff8881006c0360
[ 9.582206] FS: 00007ffbbcf2d940(0000) GS:ffff888450479000(0000) knlGS:0000000000000000
[ 9.582208] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 9.582210] CR2: 000055ee3aa260d0 CR3: 0000000148b67005 CR4: 0000000000770ef0
[ 9.582211] PKRU: 55555554
[ 9.582212] Call Trace:
[ 9.582213] <TASK>
[ 9.582214] ? __pfx___pgalloc_tag_sub+0x10/0x10
[ 9.582216] ? check_bytes_and_report+0x68/0x140
[ 9.582219] __free_frozen_pages+0x2e4/0x1150
[ 9.582221] ? __free_slab+0xc2/0x2b0
[ 9.582224] qlist_free_all+0x4c/0xf0
[ 9.582227] kasan_quarantine_reduce+0x15d/0x180
[ 9.582229] __kasan_slab_alloc+0x69/0x90
[ 9.582232] kmem_cache_alloc_noprof+0x14a/0x500
[ 9.582234] do_getname+0x96/0x310
[ 9.582237] do_readlinkat+0x91/0x2f0
[ 9.582239] ? __pfx_do_readlinkat+0x10/0x10
[ 9.582240] ? get_random_bytes_user+0x1df/0x2c0
[ 9.582244] __x64_sys_readlinkat+0x96/0x100
[ 9.582246] do_syscall_64+0xce/0x650
[ 9.582250] ? __x64_sys_getrandom+0x13a/0x1e0
[ 9.582252] ? __pfx___x64_sys_getrandom+0x10/0x10
[ 9.582254] ? do_syscall_64+0x114/0x650
[ 9.582255] ? ksys_read+0xfc/0x1d0
[ 9.582258] ? __pfx_ksys_read+0x10/0x10
[ 9.582260] ? do_syscall_64+0x114/0x650
[ 9.582262] ? do_syscall_64+0x114/0x650
[ 9.582264] ? __pfx_fput_close_sync+0x10/0x10
[ 9.582266] ? file_close_fd_locked+0x178/0x2a0
[ 9.582268] ? __x64_sys_faccessat2+0x96/0x100
[ 9.582269] ? __x64_sys_close+0x7d/0xd0
[ 9.582271] ? do_syscall_64+0x114/0x650
[ 9.582273] ? do_syscall_64+0x114/0x650
[ 9.582275] ? clear_bhb_loop+0x50/0xa0
[ 9.582277] ? clear_bhb_loop+0x50/0xa0
[ 9.582279] entry_SYSCALL_64_after_hwframe+0x76/0x7e
[ 9.582280] RIP: 0033:0x7ffbbda345ee
[ 9.582282] Code: 0f 1f 40 00 48 8b 15 29 38 0d 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff c3 0f 1f 40 00 f3 0f 1e fa 49 89 ca b8 0b 01 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d fa 37 0d 00 f7 d8 64 89 01 48
[ 9.582284] RSP: 002b:00007ffe2ad8de58 EFLAGS: 00000202 ORIG_RAX: 000000000000010b
[ 9.582286] RAX: ffffffffffffffda RBX: 000055ee3aa25570 RCX: 00007ffbbda345ee
[ 9.582287] RDX: 000055ee3aa25570 RSI: 00007ffe2ad8dee0 RDI: 00000000ffffff9c
[ 9.582288] RBP: 0000000000001000 R08: 0000000000000003 R09: 0000000000001001
[ 9.582289] R10: 0000000000001000 R11: 0000000000000202 R12: 0000000000000033
[ 9.582290] R13: 00007ffe2ad8dee0 R14: 00000000ffffff9c R15: 00007ffe2ad8deb0
[ 9.582292] </TASK>
[ 9.582293] ---[ end trace 0000000000000000 ]---
Link: https://lkml.kernel.org/r/20260326140554.191996-1-hao.ge@linux.dev
Fixes: 93d5440ece3c ("alloc_tag: uninline code gated by mem_alloc_profiling_key in page allocator")
Signed-off-by: Hao Ge <hao.ge@linux.dev>
Suggested-by: Suren Baghdasaryan <surenb@google.com>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
include/linux/alloc_tag.h | 2
include/linux/pgalloc_tag.h | 2
lib/alloc_tag.c | 92 ++++++++++++++++++++++++++++++++++
mm/page_alloc.c | 7 ++
4 files changed, 102 insertions(+), 1 deletion(-)
--- a/include/linux/alloc_tag.h~mm-alloc_tag-clear-codetag-for-pages-allocated-before-page_ext-initialization
+++ a/include/linux/alloc_tag.h
@@ -74,6 +74,8 @@ static inline void set_codetag_empty(uni
#ifdef CONFIG_MEM_ALLOC_PROFILING
+void alloc_tag_add_early_pfn(unsigned long pfn);
+
#define ALLOC_TAG_SECTION_NAME "alloc_tags"
struct codetag_bytes {
--- a/include/linux/pgalloc_tag.h~mm-alloc_tag-clear-codetag-for-pages-allocated-before-page_ext-initialization
+++ a/include/linux/pgalloc_tag.h
@@ -181,7 +181,7 @@ static inline struct alloc_tag *__pgallo
if (get_page_tag_ref(page, &ref, &handle)) {
alloc_tag_sub_check(&ref);
- if (ref.ct)
+ if (ref.ct && !is_codetag_empty(&ref))
tag = ct_to_alloc_tag(ref.ct);
put_page_tag_ref(handle);
}
--- a/lib/alloc_tag.c~mm-alloc_tag-clear-codetag-for-pages-allocated-before-page_ext-initialization
+++ a/lib/alloc_tag.c
@@ -6,6 +6,7 @@
#include <linux/kallsyms.h>
#include <linux/module.h>
#include <linux/page_ext.h>
+#include <linux/pgalloc_tag.h>
#include <linux/proc_fs.h>
#include <linux/seq_buf.h>
#include <linux/seq_file.h>
@@ -26,6 +27,96 @@ static bool mem_profiling_support;
static struct codetag_type *alloc_tag_cttype;
+#ifdef CONFIG_MEM_ALLOC_PROFILING_DEBUG
+
+/*
+ * Track page allocations before page_ext is initialized.
+ * Some pages are allocated before page_ext becomes available, leaving
+ * their codetag uninitialized. Track these early PFNs so we can clear
+ * their codetag refs later to avoid warnings when they are freed.
+ *
+ * Early allocations include:
+ * - Base allocations independent of CPU count
+ * - Per-CPU allocations (e.g., CPU hotplug callbacks during smp_init,
+ * such as trace ring buffers, scheduler per-cpu data)
+ *
+ * For simplicity, we fix the size to 8192.
+ * If insufficient, a warning will be triggered to alert the user.
+ */
+#define EARLY_ALLOC_PFN_MAX 8192
+
+static unsigned long early_pfns[EARLY_ALLOC_PFN_MAX] __initdata;
+static atomic_t early_pfn_count __initdata = ATOMIC_INIT(0);
+
+static void __init __alloc_tag_add_early_pfn(unsigned long pfn)
+{
+ int old_idx, new_idx;
+
+ do {
+ old_idx = atomic_read(&early_pfn_count);
+ if (old_idx >= EARLY_ALLOC_PFN_MAX) {
+ pr_warn_once("Early page allocations before page_ext init exceeded EARLY_ALLOC_PFN_MAX (%d)\n",
+ EARLY_ALLOC_PFN_MAX);
+ return;
+ }
+ new_idx = old_idx + 1;
+ } while (!atomic_try_cmpxchg(&early_pfn_count, &old_idx, new_idx));
+
+ early_pfns[old_idx] = pfn;
+}
+
+static void (*alloc_tag_add_early_pfn_ptr)(unsigned long pfn) __refdata =
+ __alloc_tag_add_early_pfn;
+
+void alloc_tag_add_early_pfn(unsigned long pfn)
+{
+ if (static_key_enabled(&mem_profiling_compressed))
+ return;
+
+ if (alloc_tag_add_early_pfn_ptr)
+ alloc_tag_add_early_pfn_ptr(pfn);
+}
+
+static void __init clear_early_alloc_pfn_tag_refs(void)
+{
+ unsigned int i;
+
+ for (i = 0; i < atomic_read(&early_pfn_count); i++) {
+ unsigned long pfn = early_pfns[i];
+
+ if (pfn_valid(pfn)) {
+ struct page *page = pfn_to_page(pfn);
+ union pgtag_ref_handle handle;
+ union codetag_ref ref;
+
+ if (get_page_tag_ref(page, &ref, &handle)) {
+ /*
+ * An early-allocated page could be freed and reallocated
+ * after its page_ext is initialized but before we clear it.
+ * In that case, it already has a valid tag set.
+ * We should not overwrite that valid tag with CODETAG_EMPTY.
+ */
+ if (ref.ct) {
+ put_page_tag_ref(handle);
+ continue;
+ }
+
+ set_codetag_empty(&ref);
+ update_page_tag_ref(handle, &ref);
+ put_page_tag_ref(handle);
+ }
+ }
+
+ }
+ atomic_set(&early_pfn_count, 0);
+
+ alloc_tag_add_early_pfn_ptr = NULL;
+}
+#else /* !CONFIG_MEM_ALLOC_PROFILING_DEBUG */
+inline void alloc_tag_add_early_pfn(unsigned long pfn) {}
+static inline void __init clear_early_alloc_pfn_tag_refs(void) {}
+#endif
+
#ifdef CONFIG_ARCH_MODULE_NEEDS_WEAK_PER_CPU
DEFINE_PER_CPU(struct alloc_tag_counters, _shared_alloc_tag);
EXPORT_SYMBOL(_shared_alloc_tag);
@@ -760,6 +851,7 @@ static __init bool need_page_alloc_taggi
static __init void init_page_alloc_tagging(void)
{
+ clear_early_alloc_pfn_tag_refs();
}
struct page_ext_operations page_alloc_tagging_ops = {
--- a/mm/page_alloc.c~mm-alloc_tag-clear-codetag-for-pages-allocated-before-page_ext-initialization
+++ a/mm/page_alloc.c
@@ -1256,6 +1256,13 @@ void __pgalloc_tag_add(struct page *page
alloc_tag_add(&ref, task->alloc_tag, PAGE_SIZE * nr);
update_page_tag_ref(handle, &ref);
put_page_tag_ref(handle);
+ } else {
+ /*
+ * page_ext is not available yet, record the pfn so we can
+ * clear the tag ref later when page_ext is initialized.
+ */
+ alloc_tag_add_early_pfn(page_to_pfn(page));
+ alloc_tag_set_inaccurate(current->alloc_tag);
}
}
_
Patches currently in -mm which might be from hao.ge@linux.dev are
next reply other threads:[~2026-03-27 1:34 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-27 1:34 Andrew Morton [this message]
-- strict thread matches above, loose matches on Subject: below --
2026-04-01 2:39 [to-be-updated] mm-alloc_tag-clear-codetag-for-pages-allocated-before-page_ext-initialization.patch removed from -mm tree Andrew Morton
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