From: Kazuhito Hagio <k-hagio-ab(a)nec.com&gt; Kernel commit 5ba6bc27b1f9 ("slab: decouple pointer to barn from kmem_cache_node") changed kmem_cache.node array into struct kmem_cache_per_node_ptrs kmem_cache.per_node array. Without the patch, "kmem <slab address>" and "kmem -s" option fail with the following error. crash> kmem -s kmem: invalid structure member offset: kmem_cache_local_node FILE: memory.c LINE: 19563 FUNCTION: get_kmem_cache_slub_data() Signed-off-by: Kazuhito Hagio <k-hagio-ab(a)nec.com&gt; --- This patch needs to be applied on the top of the patch [1], so 2/2. [1] [PATCH] Fix compound_head() and "bt -F" option on Linux 7.1 and later https://www.mail-archive.com/devel@lists.crash-utility.osci.io/msg02256.html defs.h | 3 +++ memory.c | 19 +++++++++++++++---- symbols.c | 4 ++++ 3 files changed, 22 insertions(+), 4 deletions(-) diff --git a/defs.h b/defs.h index 88b7bbeb2372..ef34db90113f 100644 --- a/defs.h +++ b/defs.h @@ -2296,6 +2296,8 @@ struct offset_table { /* stash of commonly-used offsets */ long folio__folio_order; long folio__flags_1; long page_compound_info; + long kmem_cache_per_node; + long kmem_cache_per_node_ptrs_node; }; struct size_table { /* stash of commonly-used sizes */ @@ -2478,6 +2480,7 @@ struct size_table { /* stash of commonly-used sizes */ long page_compound_order; long folio__folio_order; long folio__flags_1; + long kmem_cache_per_node_ptrs; }; struct array_table { diff --git a/memory.c b/memory.c index 7102e951f1d5..7c3ab506217a 100644 --- a/memory.c +++ b/memory.c @@ -871,6 +871,8 @@ vm_init(void) MEMBER_OFFSET_INIT(kmem_cache_inuse, "kmem_cache", "inuse"); MEMBER_OFFSET_INIT(kmem_cache_align, "kmem_cache", "align"); MEMBER_OFFSET_INIT(kmem_cache_node, "kmem_cache", "node"); + if (INVALID_MEMBER(kmem_cache_node)) + MEMBER_OFFSET_INIT(kmem_cache_per_node, "kmem_cache", "per_node"); MEMBER_OFFSET_INIT(kmem_cache_cpu_slab, "kmem_cache", "cpu_slab"); MEMBER_OFFSET_INIT(kmem_cache_list, "kmem_cache", "list"); MEMBER_OFFSET_INIT(kmem_cache_red_left_pad, "kmem_cache", "red_left_pad"); @@ -922,7 +924,12 @@ vm_init(void) if (INVALID_MEMBER(page_objects)) ANON_MEMBER_OFFSET_INIT(page_objects, "slab", "objects"); } - if (VALID_MEMBER(kmem_cache_node)) { + if (VALID_MEMBER(kmem_cache_per_node)) { /* Linux 7.1 and later */ + MEMBER_OFFSET_INIT(kmem_cache_per_node_ptrs_node, + "kmem_cache_per_node_ptrs", "node"); + STRUCT_SIZE_INIT(kmem_cache_per_node_ptrs, "kmem_cache_per_node_ptrs"); + vt->flags |= CONFIG_NUMA; + } else if (VALID_MEMBER(kmem_cache_node)) { ARRAY_LENGTH_INIT(len, NULL, "kmem_cache.node", NULL, 0); vt->flags |= CONFIG_NUMA; } @@ -19555,9 +19562,13 @@ get_kmem_cache_slub_data(long cmd, struct meminfo *si) for (n = 0; n < vt->numnodes; n++) { if (vt->flags & CONFIG_NUMA) { nt = &vt->node_table[n]; - node_ptr = ULONG(si->cache_buf + - OFFSET(kmem_cache_node) + - (sizeof(void *) * nt->node_id)); + if (VALID_MEMBER(kmem_cache_per_node)) /* Linux 7.1 and later */ + node_ptr = ULONG(si->cache_buf + OFFSET(kmem_cache_per_node) + + (SIZE(kmem_cache_per_node_ptrs) * nt->node_id) + + OFFSET(kmem_cache_per_node_ptrs_node)); + else + node_ptr = ULONG(si->cache_buf + OFFSET(kmem_cache_node) + + (sizeof(void *) * nt->node_id)); } else node_ptr = si->cache + OFFSET(kmem_cache_local_node); diff --git a/symbols.c b/symbols.c index 2071bdf77819..ae7fa7b416a4 100644 --- a/symbols.c +++ b/symbols.c @@ -10932,6 +10932,9 @@ dump_offset_table(char *spec, ulong makestruct) OFFSET(kmem_cache_oo)); fprintf(fp, " kmem_cache_random: %ld\n", OFFSET(kmem_cache_random)); + fprintf(fp, " kmem_cache_per_node: %ld\n", OFFSET(kmem_cache_per_node)); + + fprintf(fp, " kmem_cache_per_node_ptrs_node: %ld\n", OFFSET(kmem_cache_per_node_ptrs_node)); fprintf(fp, " kmem_cache_node_nr_partial: %ld\n", OFFSET(kmem_cache_node_nr_partial)); @@ -12043,6 +12046,7 @@ dump_offset_table(char *spec, ulong makestruct) fprintf(fp, " kmem_cache: %ld\n", SIZE(kmem_cache)); fprintf(fp, " kmem_cache_node: %ld\n", SIZE(kmem_cache_node)); fprintf(fp, " kmem_cache_cpu: %ld\n", SIZE(kmem_cache_cpu)); + fprintf(fp, " kmem_cache_per_node_ptrs: %ld\n", SIZE(kmem_cache_per_node_ptrs)); fprintf(fp, " swap_info_struct: %ld\n", SIZE(swap_info_struct));

Hi Kazu, While testing crash with recent mainline kernel, I applied your two patches. It does emit the errors mentioned, but crash failed to start, it failed in the task init path, I suspect below log with "crash -d 8": read_diskdump: paddr/pfn: 7b39d4c0/7b39d -> physical page is cached: 7b39d000 <read_diskdump: addr: ffff88807b39e000 paddr: 7b39e000 cnt: 192> read_diskdump: paddr/pfn: 7b39e000/7b39e -> physical page is cached: 7b39e000 task 1 0x8df932 please wait... (gathering task table data)<readmem: ffffffff81c25948, KVADDR, "xarray xa_head", 8, (FOE), 7ffcd7a168d0> <read_diskdump: addr: ffffffff81c25948 paddr: 2225948 cnt: 8> read_diskdump: paddr/pfn: 2225948/2225 -> cache physical page: 2225000 <readmem: ffff888003241b60, KVADDR, "xa_node shift", 1, (FOE), 7ffcd7a168cf> <read_diskdump: addr: ffff888003241b60 paddr: 3241b60 cnt: 1> read_diskdump: PAGE_EXCLUDED: paddr/pfn: 3241b60/3241 crash: page excluded: kernel virtual address: ffff888003241b60 type: "xa_node shift" And then I tried 6.19.0 kernel, crash works fine. Bisect finished with below result: bash-5.3$ git bisect bad Bisecting: 1 revision left to test after this (roughly 1 step) [d50569612c29215c5d1c64f47a65604ed265d2e9] mm: rename the 'compound_head' field in the 'struct page' to 'compound_info' bash-5.3$ git bisect view --oneline 8c846c879e22 mm: rework compound_head() for power-of-2 sizeof(struct page) 2969b42c8f99 LoongArch/mm: align vmemmap to maximal folio size 476849b0fba4 riscv/mm: align vmemmap to maximal folio size 67c79a5af051 mm: move set/clear_compound_head() next to compound_head() d50569612c29 (HEAD) mm: rename the 'compound_head' field in the 'struct page' to 'compound_info' bash-5.3$ git bisect skip There are only 'skip'ped commits left to test. The first bad commit could be any of: 476849b0fba4450f5adf22196bcff9c24c673bc4 67c79a5af051f57339ecf383d3f67e200741ce20 2969b42c8f994330fc020ec0d235aeb43bce317c d50569612c29215c5d1c64f47a65604ed265d2e9 8c846c879e226c312c2c7a7bc1e323779903530f We cannot bisect more! Bisect skipped a few commits due to kernel can not compile, but the issue seems related to those commits. Any thoughts? I suspect your fixes are not enough? Attached the kernel config, it is a very small config I tuned for testing with a kvm guest. If you need more info just let me know. On 8/2/26 1:15 PM, Dave Young wrote: > Add Kairui and Baoquan who could help to review the patch > > On 7/24/26 9:27 AM, HAGIO KAZUHITO(萩尾 一仁) wrote: >> From: Kazuhito Hagio <k-hagio-ab(a)nec.com&gt; >> >> Kernel commit 5ba6bc27b1f9 ("slab: decouple pointer to barn from >> kmem_cache_node") changed kmem_cache.node array into struct >> kmem_cache_per_node_ptrs kmem_cache.per_node array. >> >> Without the patch, "kmem <slab address>" and "kmem -s" option fail with >> the following error. >> >> crash> kmem -s >> >> kmem: invalid structure member offset: kmem_cache_local_node >> FILE: memory.c LINE: 19563 FUNCTION: get_kmem_cache_slub_data() >> >> Signed-off-by: Kazuhito Hagio <k-hagio-ab(a)nec.com&gt; >> --- >> This patch needs to be applied on the top of the patch [1], so 2/2. >> [1] [PATCH] Fix compound_head() and "bt -F" option on Linux 7.1 and later >> https://www.mail-archive.com/devel@lists.crash-utility.osci.io/msg02256.html >> >> defs.h | 3 +++ >> memory.c | 19 +++++++++++++++---- >> symbols.c | 4 ++++ >> 3 files changed, 22 insertions(+), 4 deletions(-) >> >> diff --git a/defs.h b/defs.h >> index 88b7bbeb2372..ef34db90113f 100644 >> --- a/defs.h >> +++ b/defs.h >> @@ -2296,6 +2296,8 @@ struct offset_table { /* stash of commonly-used offsets */ >> long folio__folio_order; >> long folio__flags_1; >> long page_compound_info; >> + long kmem_cache_per_node; >> + long kmem_cache_per_node_ptrs_node; >> }; >> >> struct size_table { /* stash of commonly-used sizes */ >> @@ -2478,6 +2480,7 @@ struct size_table { /* stash of commonly-used sizes */ >> long page_compound_order; >> long folio__folio_order; >> long folio__flags_1; >> + long kmem_cache_per_node_ptrs; >> }; >> >> struct array_table { >> diff --git a/memory.c b/memory.c >> index 7102e951f1d5..7c3ab506217a 100644 >> --- a/memory.c >> +++ b/memory.c >> @@ -871,6 +871,8 @@ vm_init(void) >> MEMBER_OFFSET_INIT(kmem_cache_inuse, "kmem_cache", "inuse"); >> MEMBER_OFFSET_INIT(kmem_cache_align, "kmem_cache", "align"); >> MEMBER_OFFSET_INIT(kmem_cache_node, "kmem_cache", "node"); >> + if (INVALID_MEMBER(kmem_cache_node)) >> + MEMBER_OFFSET_INIT(kmem_cache_per_node, "kmem_cache", "per_node"); >> MEMBER_OFFSET_INIT(kmem_cache_cpu_slab, "kmem_cache", "cpu_slab"); >> MEMBER_OFFSET_INIT(kmem_cache_list, "kmem_cache", "list"); >> MEMBER_OFFSET_INIT(kmem_cache_red_left_pad, "kmem_cache", "red_left_pad"); >> @@ -922,7 +924,12 @@ vm_init(void) >> if (INVALID_MEMBER(page_objects)) >> ANON_MEMBER_OFFSET_INIT(page_objects, "slab", "objects"); >> } >> - if (VALID_MEMBER(kmem_cache_node)) { >> + if (VALID_MEMBER(kmem_cache_per_node)) { /* Linux 7.1 and later */ >> + MEMBER_OFFSET_INIT(kmem_cache_per_node_ptrs_node, >> + "kmem_cache_per_node_ptrs", "node"); >> + STRUCT_SIZE_INIT(kmem_cache_per_node_ptrs, "kmem_cache_per_node_ptrs"); >> + vt->flags |= CONFIG_NUMA; >> + } else if (VALID_MEMBER(kmem_cache_node)) { >> ARRAY_LENGTH_INIT(len, NULL, "kmem_cache.node", NULL, 0); >> vt->flags |= CONFIG_NUMA; >> } >> @@ -19555,9 +19562,13 @@ get_kmem_cache_slub_data(long cmd, struct meminfo *si) >> for (n = 0; n < vt->numnodes; n++) { >> if (vt->flags & CONFIG_NUMA) { >> nt = &vt->node_table[n]; >> - node_ptr = ULONG(si->cache_buf + >> - OFFSET(kmem_cache_node) + >> - (sizeof(void *) * nt->node_id)); >> + if (VALID_MEMBER(kmem_cache_per_node)) /* Linux 7.1 and later */ >> + node_ptr = ULONG(si->cache_buf + OFFSET(kmem_cache_per_node) + >> + (SIZE(kmem_cache_per_node_ptrs) * nt->node_id) + >> + OFFSET(kmem_cache_per_node_ptrs_node)); >> + else >> + node_ptr = ULONG(si->cache_buf + OFFSET(kmem_cache_node) + >> + (sizeof(void *) * nt->node_id)); >> } else >> node_ptr = si->cache + >> OFFSET(kmem_cache_local_node); >> diff --git a/symbols.c b/symbols.c >> index 2071bdf77819..ae7fa7b416a4 100644 >> --- a/symbols.c >> +++ b/symbols.c >> @@ -10932,6 +10932,9 @@ dump_offset_table(char *spec, ulong makestruct) >> OFFSET(kmem_cache_oo)); >> fprintf(fp, " kmem_cache_random: %ld\n", >> OFFSET(kmem_cache_random)); >> + fprintf(fp, " kmem_cache_per_node: %ld\n", OFFSET(kmem_cache_per_node)); >> + >> + fprintf(fp, " kmem_cache_per_node_ptrs_node: %ld\n", OFFSET(kmem_cache_per_node_ptrs_node)); >> >> fprintf(fp, " kmem_cache_node_nr_partial: %ld\n", >> OFFSET(kmem_cache_node_nr_partial)); >> @@ -12043,6 +12046,7 @@ dump_offset_table(char *spec, ulong makestruct) >> fprintf(fp, " kmem_cache: %ld\n", SIZE(kmem_cache)); >> fprintf(fp, " kmem_cache_node: %ld\n", SIZE(kmem_cache_node)); >> fprintf(fp, " kmem_cache_cpu: %ld\n", SIZE(kmem_cache_cpu)); >> + fprintf(fp, " kmem_cache_per_node_ptrs: %ld\n", SIZE(kmem_cache_per_node_ptrs)); >> >> fprintf(fp, " swap_info_struct: %ld\n", >> SIZE(swap_info_struct)); > -- > Crash-utility mailing list -- devel(a)lists.crash-utility.osci.io > To unsubscribe send an email to devel-leave(a)lists.crash-utility.osci.io > https://${domain_name}/admin/lists/devel.lists.crash-utility.osci.io/ > Contribution Guidelines: https://github.com/crash-utility/crash/wiki > > -- > Crash-utility mailing list -- devel(a)lists.crash-utility.osci.io > To unsubscribe send an email to devel-leave(a)lists.crash-utility.osci.io > https://${domain_name}/admin/lists/devel.lists.crash-utility.osci.io/ > Contribution Guidelines: https://github.com/crash-utility/crash/wiki

Add Kairui and Baoquan who could help to review this patch On 7/23/26 1:09 PM, HAGIO KAZUHITO(萩尾 一仁) wrote: > From: Kazuhito Hagio <k-hagio-ab(a)nec.com&gt; > > Kernel commit d50569612c29 ("mm: rename the 'compound_head' field in the > 'struct page' to 'compound_info'") and related patches [1] changed the > field name and its value. > > Without the patch, crash prints the following warning during startup, > > WARNING: SLUB: cannot determine how compound pages are linked > > and "bt -F" option fails with the following error. > > crash> bt -F > > bt: invalid structure member offset: page_first_page > FILE: memory.c LINE: 20238 FUNCTION: compound_head() > > [1] https://lore.kernel.org/all/20260227194302.274384-1-kas@kernel.org/ > > Signed-off-by: Kazuhito Hagio <k-hagio-ab(a)nec.com&gt; > --- > defs.h | 1 + > memory.c | 44 ++++++++++++++++++++++++++++++++++++-------- > symbols.c | 1 + > 3 files changed, 38 insertions(+), 8 deletions(-) > > diff --git a/defs.h b/defs.h > index e3027e2b9141..88b7bbeb2372 100644 > --- a/defs.h > +++ b/defs.h > @@ -2295,6 +2295,7 @@ struct offset_table { /* stash of commonly-used offsets */ > long page_compound_order; > long folio__folio_order; > long folio__flags_1; > + long page_compound_info; > }; > > struct size_table { /* stash of commonly-used sizes */ > diff --git a/memory.c b/memory.c > index 3f3aa274ab5a..7102e951f1d5 100644 > --- a/memory.c > +++ b/memory.c > @@ -414,6 +414,7 @@ mem_init(void) > #define FOLIO_ORDER_V2 2 > #define FOLIO_ORDER_V3 3 > static int folio_order_version; > +static int compound_info_has_mask = FALSE; > > /* > * Stash a few popular offsets and some basic kernel virtual memory > @@ -547,6 +548,7 @@ vm_init(void) > MEMBER_OFFSET_INIT(page_compound_head, "page", "compound_head"); > if (INVALID_MEMBER(page_compound_head)) > ANON_MEMBER_OFFSET_INIT(page_compound_head, "page", "compound_head"); > + MEMBER_OFFSET_INIT(page_compound_info, "page", "compound_info"); > MEMBER_OFFSET_INIT(page_private, "page", "private"); > MEMBER_OFFSET_INIT(page_freelist, "page", "freelist"); > MEMBER_OFFSET_INIT(page_page_type, "page", "page_type"); > @@ -1352,6 +1354,17 @@ vm_init(void) > } else if (CRASHDEBUG(1)) > error(NOTE, "page_hash_table does not exist in this kernel\n"); > > + /* > + * on Linux 7.1 and later, zone.vmemmap_tails is defined only when > + * CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP is enabled. > + */ > +#define is_power_of_2(n) (n - 1 < (n ^ (n - 1))) > + if (VALID_MEMBER(page_compound_info) && > + is_power_of_2(SIZE(page)) && MEMBER_EXISTS("zone", "vmemmap_tails")) > + compound_info_has_mask = TRUE; > + if (CRASHDEBUG(1)) > + error(NOTE, "compound_info_has_mask = %d\n", compound_info_has_mask); > + > kmem_cache_init(); > > page_flags_init(); > @@ -5642,10 +5655,11 @@ PG_slab_flag_init(void) > } > } > > - if (VALID_MEMBER(page_compound_head)) { > + if (VALID_MEMBER(page_compound_head) || VALID_MEMBER(page_compound_info)) { > if (CRASHDEBUG(2)) > fprintf(fp, > - "PG_head_tail_mask: (UNUSED): page.compound_head exists!\n"); > + "PG_head_tail_mask: (UNUSED): page.compound_head or " > + "page.compound_info exists!\n"); > } else if (vt->flags & KMALLOC_SLUB) { > /* > * PG_slab and the following are hardwired for > @@ -9858,7 +9872,8 @@ vaddr_to_kmem_cache(ulong vaddr, char *buf, int verbose) > &page_flags, sizeof(ulong), "page.flags", > FAULT_ON_ERROR); > if (!page_slab(page, page_flags)) { > - if (((vt->flags & KMALLOC_SLUB) || VALID_MEMBER(page_compound_head)) || > + if (((vt->flags & KMALLOC_SLUB) || VALID_MEMBER(page_compound_head) || > + VALID_MEMBER(page_compound_info)) || > ((vt->flags & KMALLOC_COMMON) && > VALID_MEMBER(page_slab) && VALID_MEMBER(page_first_page))) { > readmem(compound_head(page)+OFFSET(page_flags), KVADDR, > @@ -9873,7 +9888,8 @@ vaddr_to_kmem_cache(ulong vaddr, char *buf, int verbose) > > if ((vt->flags & KMALLOC_SLUB) || > ((vt->flags & KMALLOC_COMMON) && VALID_MEMBER(page_slab) && > - (VALID_MEMBER(page_compound_head) || VALID_MEMBER(page_first_page)))) { > + (VALID_MEMBER(page_compound_head) || VALID_MEMBER(page_compound_info) || > + VALID_MEMBER(page_first_page)))) { > readmem(compound_head(page)+OFFSET(page_slab), > KVADDR, &cache, sizeof(void *), > "page.slab", FAULT_ON_ERROR); > @@ -9904,7 +9920,8 @@ is_slab_overload_page(ulong vaddr, ulong *page_head, char *buf) > > if ((vt->flags & SLAB_OVERLOAD_PAGE) && > is_page_ptr(vaddr, NULL) && VALID_MEMBER(page_slab) && > - (VALID_MEMBER(page_compound_head) || VALID_MEMBER(page_first_page))) { > + (VALID_MEMBER(page_compound_head) || VALID_MEMBER(page_compound_info) || > + VALID_MEMBER(page_first_page))) { > readmem(compound_head(vaddr)+OFFSET(page_slab), > KVADDR, &cache, sizeof(void *), > "page.slab", FAULT_ON_ERROR); > @@ -9944,7 +9961,8 @@ vaddr_to_slab(ulong vaddr) > > slab = 0; > > - if ((vt->flags & KMALLOC_SLUB) || VALID_MEMBER(page_compound_head)) > + if ((vt->flags & KMALLOC_SLUB) || VALID_MEMBER(page_compound_head) || > + VALID_MEMBER(page_compound_info)) > slab = compound_head(page); > else if (vt->flags & SLAB_OVERLOAD_PAGE) > slab = compound_head(page); > @@ -20222,11 +20240,21 @@ get_kmem_cache_child_list(ulong **cache_buf, ulong root) > static ulong > compound_head(ulong page) > { > - ulong flags, first_page, compound_head; > + ulong flags, first_page, compound_head, info, mask; > > first_page = page; > > - if (VALID_MEMBER(page_compound_head)) { > + if (VALID_MEMBER(page_compound_info)) { > + if (readmem(page + OFFSET(page_compound_info), KVADDR, &info, > + sizeof(ulong), "page.compound_info", RETURN_ON_ERROR)) { > + if (compound_info_has_mask) { > + mask = (info & 1) - 1; > + mask |= info; > + first_page = page & mask; > + } else if (info & 1) > + first_page = info - 1; > + } > + } else if (VALID_MEMBER(page_compound_head)) { > if (readmem(page+OFFSET(page_compound_head), KVADDR, &compound_head, > sizeof(ulong), "page.compound_head", RETURN_ON_ERROR)) { > if (compound_head & 1) > diff --git a/symbols.c b/symbols.c > index 03511c8cbe8c..2071bdf77819 100644 > --- a/symbols.c > +++ b/symbols.c > @@ -10504,6 +10504,7 @@ dump_offset_table(char *spec, ulong makestruct) > OFFSET(page_active)); > fprintf(fp, " page_compound_head: %ld\n", > OFFSET(page_compound_head)); > + fprintf(fp, " page_compound_info: %ld\n", OFFSET(page_compound_info)); > fprintf(fp, " page_private: %ld\n", OFFSET(page_private)); > fprintf(fp, " page_page_type: %ld\n", > OFFSET(page_page_type)); -- Crash-utility mailing list -- devel(a)lists.crash-utility.osci.io To unsubscribe send an email to devel-leave(a)lists.crash-utility.osci.io https://${domain_name}/admin/lists/devel.lists.crash-utility.osci.io/ Contribution Guidelines: https://github.com/crash-utility/crash/wiki

On 7/23/26 1:09 PM, HAGIO KAZUHITO(萩尾 一仁) wrote: > From: Kazuhito Hagio <k-hagio-ab(a)nec.com&gt; > > Kernel commit d50569612c29 ("mm: rename the 'compound_head' field in the > 'struct page' to 'compound_info'") and related patches [1] changed the > field name and its value. > > Without the patch, crash prints the following warning during startup, > > WARNING: SLUB: cannot determine how compound pages are linked > > and "bt -F" option fails with the following error. > > crash> bt -F > > bt: invalid structure member offset: page_first_page > FILE: memory.c LINE: 20238 FUNCTION: compound_head() > > [1] https://lore.kernel.org/all/20260227194302.274384-1-kas@kernel.org/ > > Signed-off-by: Kazuhito Hagio <k-hagio-ab(a)nec.com&gt; > --- > defs.h | 1 + > memory.c | 44 ++++++++++++++++++++++++++++++++++++-------- > symbols.c | 1 + > 3 files changed, 38 insertions(+), 8 deletions(-) > > diff --git a/defs.h b/defs.h > index e3027e2b9141..88b7bbeb2372 100644 > --- a/defs.h > +++ b/defs.h > @@ -2295,6 +2295,7 @@ struct offset_table { /* stash of commonly-used offsets */ > long page_compound_order; > long folio__folio_order; > long folio__flags_1; > + long page_compound_info; > }; > > struct size_table { /* stash of commonly-used sizes */ > diff --git a/memory.c b/memory.c > index 3f3aa274ab5a..7102e951f1d5 100644 > --- a/memory.c > +++ b/memory.c > @@ -414,6 +414,7 @@ mem_init(void) > #define FOLIO_ORDER_V2 2 > #define FOLIO_ORDER_V3 3 > static int folio_order_version; > +static int compound_info_has_mask = FALSE; > > /* > * Stash a few popular offsets and some basic kernel virtual memory > @@ -547,6 +548,7 @@ vm_init(void) > MEMBER_OFFSET_INIT(page_compound_head, "page", "compound_head"); > if (INVALID_MEMBER(page_compound_head)) > ANON_MEMBER_OFFSET_INIT(page_compound_head, "page", "compound_head"); > + MEMBER_OFFSET_INIT(page_compound_info, "page", "compound_info"); > MEMBER_OFFSET_INIT(page_private, "page", "private"); > MEMBER_OFFSET_INIT(page_freelist, "page", "freelist"); > MEMBER_OFFSET_INIT(page_page_type, "page", "page_type"); > @@ -1352,6 +1354,17 @@ vm_init(void) > } else if (CRASHDEBUG(1)) > error(NOTE, "page_hash_table does not exist in this kernel\n"); > > + /* > + * on Linux 7.1 and later, zone.vmemmap_tails is defined only when > + * CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP is enabled. > + */ > +#define is_power_of_2(n) (n - 1 < (n ^ (n - 1))) Hi Kazu, BTW, there is one nitpick found by AI, it would be better to improve the above macro as below or just use the kernel inline function: #define IS_POWER_OF_TWO(n) ((n) > 0 && ((n) & ((n) - 1)) == 0)

Feel free to take my Tested-by

On 8/12/26 3:13 PM, HAGIO KAZUHITO(萩尾 一仁) wrote: > On 2026/08/12 11:33, Dave Young wrote: >> >> >> On 7/23/26 1:09 PM, HAGIO KAZUHITO(萩尾 一仁) wrote: >>> From: Kazuhito Hagio <k-hagio-ab(a)nec.com&gt; >>> >>> Kernel commit d50569612c29 ("mm: rename the 'compound_head' field in the >>> 'struct page' to 'compound_info'") and related patches [1] changed the >>> field name and its value. >>> >>> Without the patch, crash prints the following warning during startup, >>> >>> WARNING: SLUB: cannot determine how compound pages are linked >>> >>> and "bt -F" option fails with the following error. >>> >>> crash> bt -F >>> >>> bt: invalid structure member offset: page_first_page >>> FILE: memory.c LINE: 20238 FUNCTION: compound_head() >>> >>> [1] https://lore.kernel.org/all/20260227194302.274384-1-kas@kernel.org/ >>> >>> Signed-off-by: Kazuhito Hagio <k-hagio-ab(a)nec.com&gt; >>> --- >>> defs.h | 1 + >>> memory.c | 44 ++++++++++++++++++++++++++++++++++++-------- >>> symbols.c | 1 + >>> 3 files changed, 38 insertions(+), 8 deletions(-) >>> >>> diff --git a/defs.h b/defs.h >>> index e3027e2b9141..88b7bbeb2372 100644 >>> --- a/defs.h >>> +++ b/defs.h >>> @@ -2295,6 +2295,7 @@ struct offset_table { /* stash of commonly-used offsets */ >>> long page_compound_order; >>> long folio__folio_order; >>> long folio__flags_1; >>> + long page_compound_info; >>> }; >>> >>> struct size_table { /* stash of commonly-used sizes */ >>> diff --git a/memory.c b/memory.c >>> index 3f3aa274ab5a..7102e951f1d5 100644 >>> --- a/memory.c >>> +++ b/memory.c >>> @@ -414,6 +414,7 @@ mem_init(void) >>> #define FOLIO_ORDER_V2 2 >>> #define FOLIO_ORDER_V3 3 >>> static int folio_order_version; >>> +static int compound_info_has_mask = FALSE; >>> >>> /* >>> * Stash a few popular offsets and some basic kernel virtual memory >>> @@ -547,6 +548,7 @@ vm_init(void) >>> MEMBER_OFFSET_INIT(page_compound_head, "page", "compound_head"); >>> if (INVALID_MEMBER(page_compound_head)) >>> ANON_MEMBER_OFFSET_INIT(page_compound_head, "page", "compound_head"); >>> + MEMBER_OFFSET_INIT(page_compound_info, "page", "compound_info"); >>> MEMBER_OFFSET_INIT(page_private, "page", "private"); >>> MEMBER_OFFSET_INIT(page_freelist, "page", "freelist"); >>> MEMBER_OFFSET_INIT(page_page_type, "page", "page_type"); >>> @@ -1352,6 +1354,17 @@ vm_init(void) >>> } else if (CRASHDEBUG(1)) >>> error(NOTE, "page_hash_table does not exist in this kernel\n"); >>> >>> + /* >>> + * on Linux 7.1 and later, zone.vmemmap_tails is defined only when >>> + * CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP is enabled. >>> + */ >>> +#define is_power_of_2(n) (n - 1 < (n ^ (n - 1))) >> >> Hi Kazu, BTW, there is one nitpick found by AI, it would be better to improve the above macro as below or just use the kernel inline function: >> #define IS_POWER_OF_TWO(n) ((n) > 0 && ((n) & ((n) - 1)) == 0) > > Either is fine, but I think the former is the current is_power_of_2() > used in compound_info_has_mask(), and I used the same one as kernel. Hi Kazu, I agree with you it should work here, but the suggested one is more robust as it checks the edge value and adds parentheses around 'n' to avoid side effect of multiple expansion in some cases. Anyway up to Tao to handle it or not.

> > https://github.com/torvalds/linux/commit/4cc67b048459bebb7a60b693044ec83f... > https://github.com/torvalds/linux/blob/master/include/linux/page-flags.h#... > >> >> Feel free to take my Tested-by > > Thank you for your help! > > Thanks, > Kazu > >> >> >>> + if (VALID_MEMBER(page_compound_info) && >>> + is_power_of_2(SIZE(page)) && MEMBER_EXISTS("zone", "vmemmap_tails")) >>> + compound_info_has_mask = TRUE; >>> + if (CRASHDEBUG(1)) >>> + error(NOTE, "compound_info_has_mask = %d\n", compound_info_has_mask); >>> + >>> kmem_cache_init(); >>> >>> page_flags_init(); >>> @@ -5642,10 +5655,11 @@ PG_slab_flag_init(void) >>> } >>> } >>> >>> - if (VALID_MEMBER(page_compound_head)) { >>> + if (VALID_MEMBER(page_compound_head) || VALID_MEMBER(page_compound_info)) { >>> if (CRASHDEBUG(2)) >>> fprintf(fp, >>> - "PG_head_tail_mask: (UNUSED): page.compound_head exists!\n"); >>> + "PG_head_tail_mask: (UNUSED): page.compound_head or " >>> + "page.compound_info exists!\n"); >>> } else if (vt->flags & KMALLOC_SLUB) { >>> /* >>> * PG_slab and the following are hardwired for >>> @@ -9858,7 +9872,8 @@ vaddr_to_kmem_cache(ulong vaddr, char *buf, int verbose) >>> &page_flags, sizeof(ulong), "page.flags", >>> FAULT_ON_ERROR); >>> if (!page_slab(page, page_flags)) { >>> - if (((vt->flags & KMALLOC_SLUB) || VALID_MEMBER(page_compound_head)) || >>> + if (((vt->flags & KMALLOC_SLUB) || VALID_MEMBER(page_compound_head) || >>> + VALID_MEMBER(page_compound_info)) || >>> ((vt->flags & KMALLOC_COMMON) && >>> VALID_MEMBER(page_slab) && VALID_MEMBER(page_first_page))) { >>> readmem(compound_head(page)+OFFSET(page_flags), KVADDR, >>> @@ -9873,7 +9888,8 @@ vaddr_to_kmem_cache(ulong vaddr, char *buf, int verbose) >>> >>> if ((vt->flags & KMALLOC_SLUB) || >>> ((vt->flags & KMALLOC_COMMON) && VALID_MEMBER(page_slab) && >>> - (VALID_MEMBER(page_compound_head) || VALID_MEMBER(page_first_page)))) { >>> + (VALID_MEMBER(page_compound_head) || VALID_MEMBER(page_compound_info) || >>> + VALID_MEMBER(page_first_page)))) { >>> readmem(compound_head(page)+OFFSET(page_slab), >>> KVADDR, &cache, sizeof(void *), >>> "page.slab", FAULT_ON_ERROR); >>> @@ -9904,7 +9920,8 @@ is_slab_overload_page(ulong vaddr, ulong *page_head, char *buf) >>> >>> if ((vt->flags & SLAB_OVERLOAD_PAGE) && >>> is_page_ptr(vaddr, NULL) && VALID_MEMBER(page_slab) && >>> - (VALID_MEMBER(page_compound_head) || VALID_MEMBER(page_first_page))) { >>> + (VALID_MEMBER(page_compound_head) || VALID_MEMBER(page_compound_info) || >>> + VALID_MEMBER(page_first_page))) { >>> readmem(compound_head(vaddr)+OFFSET(page_slab), >>> KVADDR, &cache, sizeof(void *), >>> "page.slab", FAULT_ON_ERROR); >>> @@ -9944,7 +9961,8 @@ vaddr_to_slab(ulong vaddr) >>> >>> slab = 0; >>> >>> - if ((vt->flags & KMALLOC_SLUB) || VALID_MEMBER(page_compound_head)) >>> + if ((vt->flags & KMALLOC_SLUB) || VALID_MEMBER(page_compound_head) || >>> + VALID_MEMBER(page_compound_info)) >>> slab = compound_head(page); >>> else if (vt->flags & SLAB_OVERLOAD_PAGE) >>> slab = compound_head(page); >>> @@ -20222,11 +20240,21 @@ get_kmem_cache_child_list(ulong **cache_buf, ulong root) >>> static ulong >>> compound_head(ulong page) >>> { >>> - ulong flags, first_page, compound_head; >>> + ulong flags, first_page, compound_head, info, mask; >>> >>> first_page = page; >>> >>> - if (VALID_MEMBER(page_compound_head)) { >>> + if (VALID_MEMBER(page_compound_info)) { >>> + if (readmem(page + OFFSET(page_compound_info), KVADDR, &info, >>> + sizeof(ulong), "page.compound_info", RETURN_ON_ERROR)) { >>> + if (compound_info_has_mask) { >>> + mask = (info & 1) - 1; >>> + mask |= info; >>> + first_page = page & mask; >>> + } else if (info & 1) >>> + first_page = info - 1; >>> + } >>> + } else if (VALID_MEMBER(page_compound_head)) { >>> if (readmem(page+OFFSET(page_compound_head), KVADDR, &compound_head, >>> sizeof(ulong), "page.compound_head", RETURN_ON_ERROR)) { >>> if (compound_head & 1) >>> diff --git a/symbols.c b/symbols.c >>> index 03511c8cbe8c..2071bdf77819 100644 >>> --- a/symbols.c >>> +++ b/symbols.c >>> @@ -10504,6 +10504,7 @@ dump_offset_table(char *spec, ulong makestruct) >>> OFFSET(page_active)); >>> fprintf(fp, " page_compound_head: %ld\n", >>> OFFSET(page_compound_head)); >>> + fprintf(fp, " page_compound_info: %ld\n", OFFSET(page_compound_info)); >>> fprintf(fp, " page_private: %ld\n", OFFSET(page_private)); >>> fprintf(fp, " page_page_type: %ld\n", >>> OFFSET(page_page_type)); >> -- >> Crash-utility mailing list -- devel(a)lists.crash-utility.osci.io >> To unsubscribe send an email to devel-leave(a)lists.crash-utility.osci.io >> https://${domain_name}/admin/lists/devel.lists.crash-utility.osci.io/ >> Contribution Guidelines: https://github.com/crash-utility/crash/wiki > -- > Crash-utility mailing list -- devel(a)lists.crash-utility.osci.io > To unsubscribe send an email to devel-leave(a)lists.crash-utility.osci.io > https://${domain_name}/admin/lists/devel.lists.crash-utility.osci.io/ > Contribution Guidelines: https://github.com/crash-utility/crash/wiki -- Crash-utility mailing list -- devel(a)lists.crash-utility.osci.io To unsubscribe send an email to devel-leave(a)lists.crash-utility.osci.io https://${domain_name}/admin/lists/devel.lists.crash-utility.osci.io/ Contribution Guidelines: https://github.com/crash-utility/crash/wiki

Hi Dave & Kazu, On Thu, Aug 13, 2026 at 5:22 PM Dave Young <yangrr.2009(a)tsinghua.org.cn&gt; wrote: > > > > On 8/12/26 3:13 PM, HAGIO KAZUHITO(萩尾 一仁) wrote: > > On 2026/08/12 11:33, Dave Young wrote: > >> > >> > >> On 7/23/26 1:09 PM, HAGIO KAZUHITO(萩尾 一仁) wrote: > >>> From: Kazuhito Hagio <k-hagio-ab(a)nec.com&gt; > >>> > >>> Kernel commit d50569612c29 ("mm: rename the 'compound_head' field in the > >>> 'struct page' to 'compound_info'") and related patches [1] changed the > >>> field name and its value. > >>> > >>> Without the patch, crash prints the following warning during startup, > >>> > >>> WARNING: SLUB: cannot determine how compound pages are linked > >>> > >>> and "bt -F" option fails with the following error. > >>> > >>> crash> bt -F > >>> > >>> bt: invalid structure member offset: page_first_page > >>> FILE: memory.c LINE: 20238 FUNCTION: compound_head() > >>> > >>> [1] https://lore.kernel.org/all/20260227194302.274384-1-kas@kernel.org/ > >>> > >>> Signed-off-by: Kazuhito Hagio <k-hagio-ab(a)nec.com&gt; > >>> --- > >>> defs.h | 1 + > >>> memory.c | 44 ++++++++++++++++++++++++++++++++++++-------- > >>> symbols.c | 1 + > >>> 3 files changed, 38 insertions(+), 8 deletions(-) > >>> > >>> diff --git a/defs.h b/defs.h > >>> index e3027e2b9141..88b7bbeb2372 100644 > >>> --- a/defs.h > >>> +++ b/defs.h > >>> @@ -2295,6 +2295,7 @@ struct offset_table { /* stash of commonly-used offsets */ > >>> long page_compound_order; > >>> long folio__folio_order; > >>> long folio__flags_1; > >>> + long page_compound_info; > >>> }; > >>> > >>> struct size_table { /* stash of commonly-used sizes */ > >>> diff --git a/memory.c b/memory.c > >>> index 3f3aa274ab5a..7102e951f1d5 100644 > >>> --- a/memory.c > >>> +++ b/memory.c > >>> @@ -414,6 +414,7 @@ mem_init(void) > >>> #define FOLIO_ORDER_V2 2 > >>> #define FOLIO_ORDER_V3 3 > >>> static int folio_order_version; > >>> +static int compound_info_has_mask = FALSE; > >>> > >>> /* > >>> * Stash a few popular offsets and some basic kernel virtual memory > >>> @@ -547,6 +548,7 @@ vm_init(void) > >>> MEMBER_OFFSET_INIT(page_compound_head, "page", "compound_head"); > >>> if (INVALID_MEMBER(page_compound_head)) > >>> ANON_MEMBER_OFFSET_INIT(page_compound_head, "page", "compound_head"); > >>> + MEMBER_OFFSET_INIT(page_compound_info, "page", "compound_info"); > >>> MEMBER_OFFSET_INIT(page_private, "page", "private"); > >>> MEMBER_OFFSET_INIT(page_freelist, "page", "freelist"); > >>> MEMBER_OFFSET_INIT(page_page_type, "page", "page_type"); > >>> @@ -1352,6 +1354,17 @@ vm_init(void) > >>> } else if (CRASHDEBUG(1)) > >>> error(NOTE, "page_hash_table does not exist in this kernel\n"); > >>> > >>> + /* > >>> + * on Linux 7.1 and later, zone.vmemmap_tails is defined only when > >>> + * CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP is enabled. > >>> + */ > >>> +#define is_power_of_2(n) (n - 1 < (n ^ (n - 1))) > >> > >> Hi Kazu, BTW, there is one nitpick found by AI, it would be better to improve the above macro as below or just use the kernel inline function: > >> #define IS_POWER_OF_TWO(n) ((n) > 0 && ((n) & ((n) - 1)) == 0) > > > > Either is fine, but I think the former is the current is_power_of_2() > > used in compound_info_has_mask(), and I used the same one as kernel. > > Hi Kazu, I agree with you it should work here, but the suggested one is more robust as it checks the edge value and adds parentheses around 'n' to avoid side effect of multiple expansion in some cases. Anyway up to Tao to handle it or not. > Frankly I'd prefer the ((n) > 0 && ((n) & ((n) - 1)) == 0) one, because it is more easy to understand than (n - 1 < (n ^ (n - 1))). How about we use the former instead? If Kazu agrees, we can replace it when merge, so no need to send v2. For the patchset, LGTM, ack.