On Mon, Aug 10, 2026 at 8:52 PM Andrew Morton <[email protected]> wrote: > > On Mon, 10 Aug 2026 17:39:53 +0800 Hao Ge <[email protected]> wrote: > > > v3 was a single patch. After discussion with Suren and Andrew we went > > for a more graceful approach: rather than failing the module load on > > overflow, let it load without profiling. Once profiling is disabled, > > codetag_needs_module_section() returns false, so on retry the codetag > > section is placed as regular module data. > > > > A new patch (1/2) is added to move release_module_tags() above > > reserve_module_tags(), since the overflow path now has to call it and > > the helper sits below it. > > Thing is, [2/2] has cc:stable but it requires [1/2] to be able to be > compiled. [1/2] doesn't have cc:stable so we're asking -stable folks > to backport a patch which doesn't compile. > > Resolve this by using the same Fixes: and cc:stable in both patches. > > > release_module_tags() is what module unload calls to drop a module's > > reservation from the maple tree. By the time reserve_module_tags() > > detects the overflow it has already stored that reservation, and the > > -EAGAIN return skips vm_module_tags_populate(), so the backing pages > > never get mapped. If reserve_module_tags() returns without calling > > release_module_tags(), the stale entry keeps pointing at that unmapped > > range; when the module is later unloaded, release_module_tags() walks > > it and panics. > > AI review had a lot to say about this patchset. Some pre-existing, some > not: > > https://sashiko.dev/#/patchset/[email protected]
Yeah, some of them are not related to this change but at least one does. I need to address the unrelated ones. Will do that as a separate patchset. > > > > offtopic: alloc_tag isn't getting allmodconfig build coverage at this > time because: > > 1: MEM_ALLOC_PROFILING depends on !DEBUG_FORCE_WEAK_PER_CPU (why? I > can't figure that out) DEBUG_FORCE_WEAK_PER_CPU forces weak percpu definitions everywhere, even in the core kernel. This introduces the restriction of [1]: 2. Static percpu variables cannot be defined inside a function. Memory allocation profiling relies on percpu variables inside a function in DEFINE_ALLOC_TAG(). For CONFIG_ARCH_MODULE_NEEDS_WEAK_PER_CPU we comporomise by accounting all module allocations to a statically defined _shared_alloc_tag (see [2]) but we can't do that for all kernel allocations because profiling becomes quite meaningless at that point (all allocations being accounted in the same counter is not useful). [1] https://elixir.bootlin.com/linux/v7.2-rc6/source/include/linux/percpu-defs.h#L64 [2] https://elixir.bootlin.com/linux/v7.2-rc6/source/include/linux/alloc_tag.h#L91 > > 2: x86_64 allmodconfig enables DEBUG_FORCE_WEAK_PER_CPU, despite it > being for s390 and alpha. In fact it might be alpha-only. > > Adding > > depends on ALPHA || S390 > > in there fixes this.
