[Crash-utility] Re: [PATCH] memory: Handle crash failure in linux-next caused by struct kmem_cache changes

Hi Tao, On 11-Feb-26 10:21, Tao Liu wrote: > Hi Mikhail, > > Thanks for your fix on this! > > On Tue, Jan 27, 2026 at 8:40 PM Mikhail Zaslonko <zaslonko(a)linux.ibm.com&gt; wrote: >> >> Since kernel commit cf338283652f ("slab: remove struct kmem_cache_cpu") >> in linux-next we have no more 'cpu_slab' member in struct kmem_cache. >> Pick 'cpu_sheaves' as an alternative kmem_cache member for kernel-next to >> identify the SLUB case. >> >> Without the patch, crash fails to start on kernel-next with the error >> message: >> >> crash: invalid structure member offset: kmem_cache_s_num >> FILE: memory.c LINE: 9988 FUNCTION: kmem_cache_init() >> >> This fix allows the crash to start with no errors. But kmap -s is no >> longer working for kernel-next since kmem_cache_cpu array is completely >> missing. >> >> Signed-off-by: Mikhail Zaslonko <zaslonko(a)linux.ibm.com&gt; >> --- >> memory.c | 3 ++- >> 1 file changed, 2 insertions(+), 1 deletion(-) >> >> diff --git a/memory.c b/memory.c >> index cbc8d2f..3373fdb 100644 >> --- a/memory.c >> +++ b/memory.c >> @@ -672,6 +672,7 @@ vm_init(void) >> } else if (!VALID_STRUCT(kmem_slab_s) && >> !VALID_STRUCT(slab_s) && >> !MEMBER_EXISTS("kmem_cache", "cpu_slab") && >> + !MEMBER_EXISTS("kmem_cache", "cpu_sheaves") && >> (VALID_STRUCT(slab) || (vt->flags & SLAB_OVERLOAD_PAGE))) { >> vt->flags |= PERCPU_KMALLOC_V2; >> >> @@ -816,7 +817,7 @@ vm_init(void) >> if (INVALID_MEMBER(page_first_page)) >> ANON_MEMBER_OFFSET_INIT(page_first_page, "page", "first_page"); >> >> - } else if (MEMBER_EXISTS("kmem_cache", "cpu_slab") && >> + } else if ((MEMBER_EXISTS("kmem_cache", "cpu_slab") || MEMBER_EXISTS("kmem_cache", "cpu_sheaves")) && >> STRUCT_EXISTS("kmem_cache_node")) { >> vt->flags |= KMALLOC_SLUB; >> > > I tested your patch and find "kmem -s/-S" both not work: > > crash> kmem -s > CACHE OBJSIZE ALLOCATED TOTAL SLABS SSIZE NAME > kmem: cannot determine location of kmem_cache.cpu_slab page > crash> kmem -S > CACHE OBJSIZE ALLOCATED TOTAL SLABS SSIZE NAME > kmem: cannot determine location of kmem_cache.cpu_slab page > > And I add the following change upon your patch, to 1) let "kmem -s" > work and 2) "kmem -S" output error info. > > @@ -5270,6 +5272,9 @@ cmd_kmem(void) > if (sflag || Sflag || rflag || !(vt->flags & KMEM_CACHE_INIT)) > kmem_cache_init(); > > + if (Sflag && MEMBER_EXISTS("kmem_cache", "cpu_sheaves")) > + error(FATAL, "-S not supported for this kernel\n"); > + Shouldn't it be: if (Sflag && !MEMBER_EXISTS("kmem_cache", "cpu_slab")) Otherwise kmem -S is 'not supported' on all kernels starting 6.18 ('cpu_sheaves' belongs to struct kmem_cache since kernel v.6.18)

> while (args[optind]) { > if (hexadecimal(args[optind], 0)) { > value[spec_addr++] = > @@ -20401,7 +20406,6 @@ get_cpu_slab_ptr(struct meminfo *si, int cpu, > ulong *cpu_freelist) > > default: > cpu_slab_ptr = 0; > - error(FATAL, "cannot determine location of indeed, 'kmem -s' works again on kernel-next after this trick :) > > Thanks, > Tao Liu > >> -- >> 2.52.0 >> >