On Mon, Sep 14, 2026 at 11:59 PM Hao Ge <[email protected]> wrote: > > After shutdown_mem_profiling() clears mem_profiling_support, > needs_section_mem() returns false, so later modules have their codetag > section placed as regular data and never enter the alloc_tag maple tree. > codetag_load_module() still called load_module(), which allocated a percpu > counter for every tag; release_module_tags() could not find these modules > on unload, so the counters leaked. > > Return -EOPNOTSUPP from load_module() when profiling is off: > codetag_module_init() drops the module's cmod, no counters are allocated > and the module loads without its tags. codetag_unload_module() now always > calls free_section_mem(), since a module whose module_load() returned > -EOPNOTSUPP is not in the idr but may still hold a reserved section. > > Reported-by: Sashiko <[email protected]> > Fixes: 4835f747d3ed ("alloc_tag: support for page allocation tag compression") > Cc: [email protected] > Suggested-by: Suren Baghdasaryan <[email protected]> > Acked-by: Suren Baghdasaryan <[email protected]>
Yeah, I guess I didn't think about alternatives... When mem_profiling_support=false, why can't load_module() skip allocating percpu counters, zero out the whole area between start_tag and stop_tag and return 0 as success (mem_profiling_support is not enabled, so we acted accordingly)? Module will be added into maple tree and later codetag_unload_module() will find the module, call release_module_tags() (which is a NOOP because tag->counter==NULL) and finally call free_section_mem(). This seems more natural than special-casing with EOPNOTSUPP. WDYT? > Signed-off-by: Hao Ge <[email protected]> > --- > lib/codetag.c | 10 ++++++++-- > mm/alloc_tag.c | 4 ++++ > 2 files changed, 12 insertions(+), 2 deletions(-) > > diff --git a/lib/codetag.c b/lib/codetag.c > index a9cda4c962a3..a0b600720afc 100644 > --- a/lib/codetag.c > +++ b/lib/codetag.c > @@ -240,7 +240,9 @@ static int codetag_module_init(struct codetag_type > *cttype, struct module *mod) > > if (err < 0) { > kfree(cmod); > - return err; > + /* -EOPNOTSUPP means we can load the module without its tag. > */ > + if (err != -EOPNOTSUPP) > + return err; > } > > return 0; > @@ -388,7 +390,11 @@ void codetag_unload_module(struct module *mod) > ++cttype->content_id; > } > up_write(&cttype->mod_lock); > - if (found && cttype->desc.free_section_mem) > + /* > + * A module whose module_load() returned -EOPNOTSUPP is not > + * in the idr but may still hold reserved section memory. > + */ > + if (cttype->desc.free_section_mem) > cttype->desc.free_section_mem(mod, true); > } > mutex_unlock(&codetag_lock); > diff --git a/mm/alloc_tag.c b/mm/alloc_tag.c > index 5836803898ad..1ca0409b492b 100644 > --- a/mm/alloc_tag.c > +++ b/mm/alloc_tag.c > @@ -988,6 +988,10 @@ static int load_module(struct module *mod, struct > codetag *start, struct codetag > struct alloc_tag *stop_tag; > struct alloc_tag *tag; > > + /* Profiling disabled: load the module without its tags. */ > + if (!mem_profiling_support) > + return -EOPNOTSUPP; > + > /* percpu counters for core allocations are already statically > allocated */ > if (!mod) > return 0; > -- > 2.25.1 >
