mm/slub: use stackdepot to save stack trace in objects

Many stack traces are similar so there are many similar arrays.
Stackdepot saves each unique stack only once.

Replace field addrs in struct track with depot_stack_handle_t handle.  Use
stackdepot to save stack trace.

The benefits are smaller memory overhead and possibility to aggregate
per-cache statistics in the following patch using the stackdepot handle
instead of matching stacks manually.

[ vbabka@suse.cz: rebase to 5.17-rc1 and adjust accordingly ]

This was initially merged as commit 788691464c29 and reverted by commit
ae14c63a9f20 due to several issues, that should now be fixed.
The problem of unconditional memory overhead by stackdepot has been
addressed by commit 2dba5eb1c73b ("lib/stackdepot: allow optional init
and stack_table allocation by kvmalloc()"), so the dependency on
stackdepot will result in extra memory usage only when a slab cache
tracking is actually enabled, and not for all CONFIG_SLUB_DEBUG builds.
The build failures on some architectures were also addressed, and the
reported issue with xfs/433 test did not reproduce on 5.17-rc1 with this
patch.

Signed-off-by: Oliver Glitta <glittao@gmail.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-and-tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>

diff --git a/init/Kconfig b/init/Kconfig
index ddcbefe535e9e784d170bf2dd765dc0ad3e81652..adc57f989d8795fe6b20722bcd948a82559e2b85 100644 (file)
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1875,6 +1875,7 @@ config SLUB_DEBUG
        default y
        bool "Enable SLUB debugging support" if EXPERT
        depends on SLUB && SYSFS
+       select STACKDEPOT if STACKTRACE_SUPPORT
        help
          SLUB has extensive debug support features. Disabling these can
          result in significant savings in code size. This also disables

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 075cd25363ac38ea7cc126dac79c9c0b40145bf8..78d6139111cd9cc8f909d57e500962a66ef77770 100644 (file)
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -709,6 +709,7 @@ config DEBUG_SLAB
 config SLUB_DEBUG_ON
        bool "SLUB debugging on by default"
        depends on SLUB && SLUB_DEBUG
+       select STACKDEPOT_ALWAYS_INIT if STACKTRACE_SUPPORT
        default n
        help
          Boot with debugging on by default. SLUB boots by default with

diff --git a/mm/slab_common.c b/mm/slab_common.c
index 6ee64d6208b395980d346d8bf4518bd77eec3f60..73943479a2b767702514011e82c0d3623453253c 100644 (file)
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -24,6 +24,7 @@
 #include <asm/tlbflush.h>
 #include <asm/page.h>
 #include <linux/memcontrol.h>
+#include <linux/stackdepot.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/kmem.h>
@@ -314,9 +315,13 @@ kmem_cache_create_usercopy(const char *name,
         * If no slub_debug was enabled globally, the static key is not yet
         * enabled by setup_slub_debug(). Enable it if the cache is being
         * created with any of the debugging flags passed explicitly.
+        * It's also possible that this is the first cache created with
+        * SLAB_STORE_USER and we should init stack_depot for it.
         */
        if (flags & SLAB_DEBUG_FLAGS)
                static_branch_enable(&slub_debug_enabled);
+       if (flags & SLAB_STORE_USER)
+               stack_depot_init();
 #endif
 
        mutex_lock(&slab_mutex);

diff --git a/mm/slub.c b/mm/slub.c
index cd4fd0159911a026a8ccba855d80e4c50c3466a7..98c1450c23f0ba4abdac6f583ef6fa500f56d0fb 100644 (file)
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -26,6 +26,7 @@
 #include <linux/cpuset.h>
 #include <linux/mempolicy.h>
 #include <linux/ctype.h>
+#include <linux/stackdepot.h>
 #include <linux/debugobjects.h>
 #include <linux/kallsyms.h>
 #include <linux/kfence.h>
@@ -264,8 +265,8 @@ static inline bool kmem_cache_has_cpu_partial(struct kmem_cache *s)
 #define TRACK_ADDRS_COUNT 16
 struct track {
        unsigned long addr;     /* Called from address */
-#ifdef CONFIG_STACKTRACE
-       unsigned long addrs[TRACK_ADDRS_COUNT]; /* Called from address */
+#ifdef CONFIG_STACKDEPOT
+       depot_stack_handle_t handle;
 #endif
        int cpu;                /* Was running on cpu */
        int pid;                /* Pid context */
@@ -724,22 +725,19 @@ static struct track *get_track(struct kmem_cache *s, void *object,
        return kasan_reset_tag(p + alloc);
 }
 
-static void set_track(struct kmem_cache *s, void *object,
+static void noinline set_track(struct kmem_cache *s, void *object,
                        enum track_item alloc, unsigned long addr)
 {
        struct track *p = get_track(s, object, alloc);
 
-#ifdef CONFIG_STACKTRACE
+#ifdef CONFIG_STACKDEPOT
+       unsigned long entries[TRACK_ADDRS_COUNT];
        unsigned int nr_entries;
 
-       metadata_access_enable();
-       nr_entries = stack_trace_save(kasan_reset_tag(p->addrs),
-                                     TRACK_ADDRS_COUNT, 3);
-       metadata_access_disable();
-
-       if (nr_entries < TRACK_ADDRS_COUNT)
-               p->addrs[nr_entries] = 0;
+       nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 3);
+       p->handle = stack_depot_save(entries, nr_entries, GFP_NOWAIT);
 #endif
+
        p->addr = addr;
        p->cpu = smp_processor_id();
        p->pid = current->pid;
@@ -759,20 +757,19 @@ static void init_tracking(struct kmem_cache *s, void *object)
 
 static void print_track(const char *s, struct track *t, unsigned long pr_time)
 {
+       depot_stack_handle_t handle __maybe_unused;
+
        if (!t->addr)
                return;
 
        pr_err("%s in %pS age=%lu cpu=%u pid=%d\n",
               s, (void *)t->addr, pr_time - t->when, t->cpu, t->pid);
-#ifdef CONFIG_STACKTRACE
-       {
-               int i;
-               for (i = 0; i < TRACK_ADDRS_COUNT; i++)
-                       if (t->addrs[i])
-                               pr_err("\t%pS\n", (void *)t->addrs[i]);
-                       else
-                               break;
-       }
+#ifdef CONFIG_STACKDEPOT
+       handle = READ_ONCE(t->handle);
+       if (handle)
+               stack_depot_print(handle);
+       else
+               pr_err("object allocation/free stack trace missing\n");
 #endif
 }
 
@@ -1532,6 +1529,8 @@ static int __init setup_slub_debug(char *str)
                        global_slub_debug_changed = true;
                } else {
                        slab_list_specified = true;
+                       if (flags & SLAB_STORE_USER)
+                               stack_depot_want_early_init();
                }
        }
 
@@ -1549,6 +1548,8 @@ static int __init setup_slub_debug(char *str)
        }
 out:
        slub_debug = global_flags;
+       if (slub_debug & SLAB_STORE_USER)
+               stack_depot_want_early_init();
        if (slub_debug != 0 || slub_debug_string)
                static_branch_enable(&slub_debug_enabled);
        else
@@ -4342,18 +4343,26 @@ void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *slab)
        objp = fixup_red_left(s, objp);
        trackp = get_track(s, objp, TRACK_ALLOC);
        kpp->kp_ret = (void *)trackp->addr;
-#ifdef CONFIG_STACKTRACE
-       for (i = 0; i < KS_ADDRS_COUNT && i < TRACK_ADDRS_COUNT; i++) {
-               kpp->kp_stack[i] = (void *)trackp->addrs[i];
-               if (!kpp->kp_stack[i])
-                       break;
-       }
+#ifdef CONFIG_STACKDEPOT
+       {
+               depot_stack_handle_t handle;
+               unsigned long *entries;
+               unsigned int nr_entries;
+
+               handle = READ_ONCE(trackp->handle);
+               if (handle) {
+                       nr_entries = stack_depot_fetch(handle, &entries);
+                       for (i = 0; i < KS_ADDRS_COUNT && i < nr_entries; i++)
+                               kpp->kp_stack[i] = (void *)entries[i];
+               }
 
-       trackp = get_track(s, objp, TRACK_FREE);
-       for (i = 0; i < KS_ADDRS_COUNT && i < TRACK_ADDRS_COUNT; i++) {
-               kpp->kp_free_stack[i] = (void *)trackp->addrs[i];
-               if (!kpp->kp_free_stack[i])
-                       break;
+               trackp = get_track(s, objp, TRACK_FREE);
+               handle = READ_ONCE(trackp->handle);
+               if (handle) {
+                       nr_entries = stack_depot_fetch(handle, &entries);
+                       for (i = 0; i < KS_ADDRS_COUNT && i < nr_entries; i++)
+                               kpp->kp_free_stack[i] = (void *)entries[i];
+               }
        }
 #endif
 #endif