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Tue, 08 Sep 2026 06:13:56 -0700 (PDT) From: Caleb Kan Date: Tue, 08 Sep 2026 14:13:39 +0100 Subject: [PATCH RFC v2 06/11] mm/slub: materialize trie-backed stack depot traces Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260908-stackdepot-trie-v2-6-1996d5cef732@cloudflare.com> References: <20260908-stackdepot-trie-v2-0-1996d5cef732@cloudflare.com> In-Reply-To: <20260908-stackdepot-trie-v2-0-1996d5cef732@cloudflare.com> To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, Vlastimil Babka , Alexander Potapenko , Marco Elver , Dmitry Vyukov , Andrey Konovalov , Oscar Salvador , Caleb Kan , kernel-team@cloudflare.com X-Mailer: b4 0.16.0 From: Caleb Kan SLUB owner tracking stores allocation and free stacks as persistent stack depot handles. Trie-backed handles do not expose contiguous stack-record entries, so __kmem_obj_info() and the alloc_traces and free_traces debugfs files cannot use stack_depot_fetch(). Use stack_depot_fetch_into() with TRACK_ADDRS_COUNT-sized local arrays. This matches the save-side limit. Keep the existing KS_ADDRS_COUNT copy limit and debugfs formatting unchanged for hash-backed handles. Continue to copy or print no frames when the fetch returns zero. Signed-off-by: Caleb Kan --- mm/slub.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/mm/slub.c b/mm/slub.c index f9b56cb439e7..4aa1c5a45718 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -8198,12 +8198,12 @@ void __kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *slab) #ifdef CONFIG_STACKDEPOT { depot_stack_handle_t handle; - unsigned long *entries; + unsigned long entries[TRACK_ADDRS_COUNT]; unsigned int nr_entries; handle = READ_ONCE(trackp->handle); if (handle) { - nr_entries = stack_depot_fetch(handle, &entries); + nr_entries = stack_depot_fetch_into(handle, entries, ARRAY_SIZE(entries)); for (i = 0; i < KS_ADDRS_COUNT && i < nr_entries; i++) kpp->kp_stack[i] = (void *)entries[i]; } @@ -8211,7 +8211,7 @@ void __kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *slab) trackp = get_track(s, objp, TRACK_FREE); handle = READ_ONCE(trackp->handle); if (handle) { - nr_entries = stack_depot_fetch(handle, &entries); + nr_entries = stack_depot_fetch_into(handle, entries, ARRAY_SIZE(entries)); for (i = 0; i < KS_ADDRS_COUNT && i < nr_entries; i++) kpp->kp_free_stack[i] = (void *)entries[i]; } @@ -9946,12 +9946,14 @@ static int slab_debugfs_show(struct seq_file *seq, void *v) #ifdef CONFIG_STACKDEPOT { depot_stack_handle_t handle; - unsigned long *entries; + unsigned long entries[TRACK_ADDRS_COUNT]; unsigned int nr_entries, j; handle = READ_ONCE(l->handle); if (handle) { - nr_entries = stack_depot_fetch(handle, &entries); + nr_entries = + stack_depot_fetch_into(handle, entries, + ARRAY_SIZE(entries)); seq_puts(seq, "\n"); for (j = 0; j < nr_entries; j++) seq_printf(seq, " %pS\n", (void *)entries[j]); -- Git-155)