Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Mon,  1 May 2023 09:54:49 -0700
In-Reply-To: <20230501165450.15352-1-surenb@google.com>
Mime-Version: 1.0
References: <20230501165450.15352-1-surenb@google.com>
Message-ID: <20230501165450.15352-40-surenb@google.com>
Subject: [PATCH 39/40] codetag: debug: introduce OBJEXTS_ALLOC_FAIL to mark
 failed slab_ext allocations
From:   Suren Baghdasaryan <surenb@google.com>
To:     akpm@linux-foundation.org
Cc:     kent.overstreet@linux.dev, mhocko@suse.com, vbabka@suse.cz,
        hannes@cmpxchg.org, roman.gushchin@linux.dev, mgorman@suse.de,
        dave@stgolabs.net, willy@infradead.org, liam.howlett@oracle.com,
        corbet@lwn.net, void@manifault.com, peterz@infradead.org,
        juri.lelli@redhat.com, ldufour@linux.ibm.com,
        catalin.marinas@arm.com, will@kernel.org, arnd@arndb.de,
        tglx@linutronix.de, mingo@redhat.com, dave.hansen@linux.intel.com,
        x86@kernel.org, peterx@redhat.com, david@redhat.com,
        axboe@kernel.dk, mcgrof@kernel.org, masahiroy@kernel.org,
        nathan@kernel.org, dennis@kernel.org, tj@kernel.org,
        muchun.song@linux.dev, rppt@kernel.org, paulmck@kernel.org,
        pasha.tatashin@soleen.com, yosryahmed@google.com,
        yuzhao@google.com, dhowells@redhat.com, hughd@google.com,
        andreyknvl@gmail.com, keescook@chromium.org,
        ndesaulniers@google.com, gregkh@linuxfoundation.org,
        ebiggers@google.com, ytcoode@gmail.com, vincent.guittot@linaro.org,
        dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com,
        bristot@redhat.com, vschneid@redhat.com, cl@linux.com,
        penberg@kernel.org, iamjoonsoo.kim@lge.com, 42.hyeyoo@gmail.com,
        glider@google.com, elver@google.com, dvyukov@google.com,
        shakeelb@google.com, songmuchun@bytedance.com, jbaron@akamai.com,
        rientjes@google.com, minchan@google.com, kaleshsingh@google.com,
        surenb@google.com, kernel-team@android.com,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        iommu@lists.linux.dev, linux-arch@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
        linux-modules@vger.kernel.org, kasan-dev@googlegroups.com,
        cgroups@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

If slabobj_ext vector allocation for a slab object fails and later on it
succeeds for another object in the same slab, the slabobj_ext for the
original object will be NULL and will be flagged in case when
CONFIG_MEM_ALLOC_PROFILING_DEBUG is enabled.
Mark failed slabobj_ext vector allocations using a new objext_flags flag
stored in the lower bits of slab->obj_exts. When new allocation succeeds
it marks all tag references in the same slabobj_ext vector as empty to
avoid warnings implemented by CONFIG_MEM_ALLOC_PROFILING_DEBUG checks.

Signed-off-by: Suren Baghdasaryan <surenb@google.com>
---
 include/linux/memcontrol.h |  4 +++-
 mm/slab_common.c           | 27 +++++++++++++++++++++++++--
 2 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index c7f21b15b540..3eb8975c1462 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -356,8 +356,10 @@ enum page_memcg_data_flags {
 #endif /* CONFIG_MEMCG */
 
 enum objext_flags {
+	/* slabobj_ext vector failed to allocate */
+	OBJEXTS_ALLOC_FAIL = __FIRST_OBJEXT_FLAG,
 	/* the next bit after the last actual flag */
-	__NR_OBJEXTS_FLAGS  = __FIRST_OBJEXT_FLAG,
+	__NR_OBJEXTS_FLAGS  = (__FIRST_OBJEXT_FLAG << 1),
 };
 
 #define OBJEXTS_FLAGS_MASK (__NR_OBJEXTS_FLAGS - 1)
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 89265f825c43..5b7e096b70a5 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -217,21 +217,44 @@ int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,
 {
 	unsigned int objects = objs_per_slab(s, slab);
 	unsigned long obj_exts;
-	void *vec;
+	struct slabobj_ext *vec;
 
 	gfp &= ~OBJCGS_CLEAR_MASK;
 	/* Prevent recursive extension vector allocation */
 	gfp |= __GFP_NO_OBJ_EXT;
 	vec = kcalloc_node(objects, sizeof(struct slabobj_ext), gfp,
 			   slab_nid(slab));
-	if (!vec)
+	if (!vec) {
+#ifdef CONFIG_MEM_ALLOC_PROFILING_DEBUG
+		if (new_slab) {
+			/* Mark vectors which failed to allocate */
+			slab->obj_exts = OBJEXTS_ALLOC_FAIL;
+#ifdef CONFIG_MEMCG
+			slab->obj_exts |= MEMCG_DATA_OBJEXTS;
+#endif
+		}
+#endif
 		return -ENOMEM;
+	}
 
 	obj_exts = (unsigned long)vec;
 #ifdef CONFIG_MEMCG
 	obj_exts |= MEMCG_DATA_OBJEXTS;
 #endif
 	if (new_slab) {
+#ifdef CONFIG_MEM_ALLOC_PROFILING_DEBUG
+		/*
+		 * If vector previously failed to allocate then we have live
+		 * objects with no tag reference. Mark all references in this
+		 * vector as empty to avoid warnings later on.
+		 */
+		if (slab->obj_exts & OBJEXTS_ALLOC_FAIL) {
+			unsigned int i;
+
+			for (i = 0; i < objects; i++)
+				set_codetag_empty(&vec[i].ref);
+		}
+#endif
 		/*
 		 * If the slab is brand new and nobody can yet access its
 		 * obj_exts, no synchronization is required and obj_exts can
-- 
2.40.1.495.gc816e09b53d-goog