On Mon, Aug 01, 2022 at 03:51:49PM +0200, Vlastimil Babka wrote: > On 7/31/22 10:44, Hyeonggon Yoo wrote: > > On Wed, Jul 27, 2022 at 08:29:09PM +0200, Vlastimil Babka wrote: > > Also all issues (as far as I know) related to validate attribute > > as gone after this patch. > > As you (And Rongwei) were able to trigger/reproduce the issues, does your > testing also no longer reproduce them? Yes. I was no longer able to reproduce them. And it would be better if we could get Rongwei's Tested-by: too. > > Silly question: > > Do we want to apply on stable trees? > > I'd prefer not to, it's too intrusive for stable. > > > I doubt someone would use validate attribute when not debugging. > > I doubt as well. Also it requires root, and even if somebody hits the issue, > it's just spurious warnings, nothing fatal. So that doesn't warrant the > intrusive stable backport IMHO. Agreed. > > >> [1] https://lore.kernel.org/all/69462916-2d1c-dd50-2e64-b31c2b61690e@xxxxxxx/ > >> > >> mm/slub.c | 322 +++++++++++++++++++++++++++++++++++++++--------------- > >> 1 file changed, 231 insertions(+), 91 deletions(-) > >> > >> diff --git a/mm/slub.c b/mm/slub.c > >> index b1281b8654bd..01e5228809d7 100644 > >> --- a/mm/slub.c > >> +++ b/mm/slub.c > >> @@ -1324,17 +1324,14 @@ static inline int alloc_consistency_checks(struct kmem_cache *s, > >> } > > > > [...] > > > >> +/* > >> + * Called only for kmem_cache_debug() caches instead of acquire_slab(), with a > >> + * slab from the n->partial list. Removes only a single object from the slab > >> + * under slab_lock(), does the alloc_debug_processing() checks and leaves the > >> + * slab on the list, or moves it to full list if it was the last object. > >> + */ > >> +static void *alloc_single_from_partial(struct kmem_cache *s, > >> + struct kmem_cache_node *n, struct slab *slab) > >> +{ > >> + void *object; > >> + unsigned long flags; > >> + > >> + lockdep_assert_held(&n->list_lock); > >> + > >> + slab_lock(slab, &flags); > >> + > >> + object = slab->freelist; > >> + slab->freelist = get_freepointer(s, object); > >> + slab->inuse++; > >> + > >> + if (!alloc_debug_processing(s, slab, object)) { > >> + remove_partial(n, slab); > >> + slab_unlock(slab, &flags); > >> + return NULL; > >> + } > >> + > >> + if (slab->inuse == slab->objects) { > >> + remove_partial(n, slab); > >> + add_full(s, n, slab); > >> + } > >> + > >> + slab_unlock(slab, &flags); > > > > AFAIK add_full/remove_full/add_partial/remove_partial > > can be called outside slab_lock but inside list_lock. > > Right, I will adjust, thanks. > > >> + return object; > >> +} > >> + > >> +/* > >> + * Called only for kmem_cache_debug() caches to allocate from a freshly > >> + * allocated slab. Allocates a single object instead of whole freelist > >> + * and puts the slab to the partial (or full) list. > >> + */ > >> +static void *alloc_single_from_new_slab(struct kmem_cache *s, > >> + struct slab *slab) > >> +{ > >> + int nid = slab_nid(slab); > >> + struct kmem_cache_node *n = get_node(s, nid); > >> + unsigned long flags, flags2; > >> + void *object; > >> + > >> + spin_lock_irqsave(&n->list_lock, flags); > >> + slab_lock(slab, &flags2); > >> + > >> + object = slab->freelist; > >> + slab->freelist = get_freepointer(s, object); > >> + /* Undo what allocate_slab() did */ > >> + slab->frozen = 0; > >> + slab->inuse = 1; > > > > Maybe do it in allocate_slab()? > > Hmm yeah, I guess we could stop doing that pre-freezing and inuse = objects > in allocate_slab(), and do it in __slab_alloc(), which thus won't add any > overhead. Then we won't have to unfreeze in early_kmem_cache_node_alloc() as > well. Sounds good. > > >> + if (!alloc_debug_processing(s, slab, object)) { > >> + /* > >> + * It's not really expected that this would fail on a > >> + * freshly allocated slab, but a concurrent memory > >> + * corruption in theory could cause that. > >> + */ > >> + slab_unlock(slab, &flags2); > >> + spin_unlock_irqrestore(&n->list_lock, flags); > >> + return NULL; > >> + } > >> + > >> + if (slab->inuse == slab->objects) > >> + add_full(s, n, slab); > >> + else > >> + add_partial(n, slab, DEACTIVATE_TO_HEAD); > >> + > >> + slab_unlock(slab, &flags2); > >> + inc_slabs_node(s, nid, slab->objects); > >> + spin_unlock_irqrestore(&n->list_lock, flags); > >> + > >> + return object; > >> +} > > > > [...] > > > >> #endif /* CONFIG_SLUB_DEBUG */ > >> > >> #if defined(CONFIG_SLUB_DEBUG) || defined(CONFIG_SYSFS) > >> @@ -3036,6 +3165,20 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, > >> return NULL; > >> } > >> > >> + stat(s, ALLOC_SLAB); > >> + > >> + if (kmem_cache_debug(s)) { > >> + freelist = alloc_single_from_new_slab(s, slab); > >> + > >> + if (unlikely(!freelist)) > >> + goto new_objects; > >> + > >> + if (s->flags & SLAB_STORE_USER) > >> + set_track(s, freelist, TRACK_ALLOC, addr); > >> + > >> + return freelist; > >> + } > >> + > >> /* > >> * No other reference to the slab yet so we can > >> * muck around with it freely without cmpxchg > >> @@ -3043,29 +3186,29 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, > >> freelist = slab->freelist; > >> slab->freelist = NULL; > >> > >> - stat(s, ALLOC_SLAB); > >> + inc_slabs_node(s, slab_nid(slab), slab->objects); > >> > >> check_new_slab: > >> > >> if (kmem_cache_debug(s)) { > >> - if (!alloc_debug_processing(s, slab, freelist, addr)) { > >> - /* Slab failed checks. Next slab needed */ > >> - goto new_slab; > >> - } else { > >> - /* > >> - * For debug case, we don't load freelist so that all > >> - * allocations go through alloc_debug_processing() > >> - */ > >> - goto return_single; > >> - } > >> + /* > >> + * For debug caches here we had to go through > >> + * alloc_single_from_partial() so just store the tracking info > >> + * and return the object > >> + */ > >> + if (s->flags & SLAB_STORE_USER) > >> + set_track(s, freelist, TRACK_ALLOC, addr); > >> + return freelist; > >> } > >> > >> - if (unlikely(!pfmemalloc_match(slab, gfpflags))) > >> + if (unlikely(!pfmemalloc_match(slab, gfpflags))) { > >> /* > >> * For !pfmemalloc_match() case we don't load freelist so that > >> * we don't make further mismatched allocations easier. > >> */ > >> - goto return_single; > >> + deactivate_slab(s, slab, get_freepointer(s, freelist)); > >> + return freelist; > >> + } > > > > > > > >> > >> retry_load_slab: > >> > >> @@ -3089,11 +3232,6 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, > >> c->slab = slab; > >> > >> goto load_freelist; > >> - > >> -return_single: > >> - > >> - deactivate_slab(s, slab, get_freepointer(s, freelist)); > >> - return freelist; > >> } > >> > >> /* > >> @@ -3341,9 +3479,10 @@ static void __slab_free(struct kmem_cache *s, struct slab *slab, > >> if (kfence_free(head)) > >> return; > >> > >> - if (kmem_cache_debug(s) && > >> - !free_debug_processing(s, slab, head, tail, cnt, addr)) > >> + if (kmem_cache_debug(s)) { > >> + free_debug_processing(s, slab, head, tail, cnt, addr); > >> return; > >> + } > > > > Oh, now debugging caches does not share free path with non-debugging > > caches. > > > > Now free_debug_processing's return type can be void? > > Right. Thanks! > > >> > >> do { > >> if (unlikely(n)) { > >> @@ -3958,6 +4097,7 @@ static void early_kmem_cache_node_alloc(int node) > >> slab = new_slab(kmem_cache_node, GFP_NOWAIT, node); > >> > >> BUG_ON(!slab); > >> + inc_slabs_node(kmem_cache_node, slab_nid(slab), slab->objects); > >> if (slab_nid(slab) != node) { > >> pr_err("SLUB: Unable to allocate memory from node %d\n", node); > >> pr_err("SLUB: Allocating a useless per node structure in order to be able to continue\n"); > >> @@ -5625,7 +5765,7 @@ static ssize_t validate_store(struct kmem_cache *s, > >> { > >> int ret = -EINVAL; > >> > >> - if (buf[0] == '1') { > >> + if (buf[0] == '1' && kmem_cache_debug(s)) { > >> ret = validate_slab_cache(s); > >> if (ret >= 0) > >> ret = length; > > > > Yeah definitely this is what it should be, > > instead of serializing inc_slabs_node()/dec_slabs_node() > > for non-debugging caches. > > > >> -- > >> 2.37.1 > >> > > > -- Thanks, Hyeonggon
