slab_debugfs_init() creates the slab debugfs root at device initcall time, while slab_sysfs_init() moves slab_state to FULL at late initcall time. SLAB_STORE_USER caches created in this window miss their debugfs entries because do_kmem_cache_create() skips debugfs_slab_add() when slab_state <= UP. This was observed with MPTCP's request_sock_subflow_v6 cache, whose slab debugfs directory was missing. The affected window is: slab_debugfs_init() slab_debugfs_root = debugfs_create_dir(...) list_for_each_entry(s, &slab_caches, list) debugfs_slab_add(s) kmem_cache_create(..., SLAB_STORE_USER, ...) do_kmem_cache_create() if (slab_state <= UP) return without debugfs entries slab_sysfs_init() slab_state = FULL Initialize the debugfs root and add debugfs entries while holding slab_mutex, walking slab_caches exactly once and handling both sysfs and debugfs entries in the same pass. This gives the sysfs and debugfs initialization an explicit order and prevents caches from being created between the debugfs scan and slab_state reaching FULL. Gate the new slab_late_init() on either sysfs or debugfs being enabled, with the slab_kset creation and alias_list processing factored into helpers that have empty no-sysfs variants, as suggested by Vlastimil Babka. On slab_kset_init() failure, slab_state stays below FULL so kmem_cache_create() keeps taking the early-boot path, matching prior behavior. Guard debugfs_slab_release() against an uninitialized debugfs root, since the root is now created later and a cache may be released before it exists. Fixes: 1a5ad30b89b4 ("mm: slub: make slab_sysfs_init() a late_initcall") Cc: stable@vger.kernel.org Suggested-by: Vlastimil Babka Signed-off-by: Li Xiasong --- Changes in v3: - Introduce a generic slab_late_init() that runs when either sysfs or SLUB debugfs support is enabled. - Factor slab_kset initialization and saved alias processing into sysfs-specific helpers with empty no-sysfs variants. Changes in v2: - Move debugfs root and cache entry initialization into slab_sysfs_init() so both use the same mutex-protected cache walk. - Guard debugfs_slab_release() against an uninitialized debugfs root. - Update the commit message accordingly. v2: https://lore.kernel.org/linux-mm/20260723115532.761920-1-lixiasong1@huawei.com/ v1: https://lore.kernel.org/linux-mm/20260720145124.3684976-1-lixiasong1@huawei.com/ --- mm/slub.c | 76 +++++++++++++++++++++++++++++++++++-------------------- 1 file changed, 48 insertions(+), 28 deletions(-) diff --git a/mm/slub.c b/mm/slub.c index 0337e60db5ac..4ef84de4f3d7 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -333,14 +333,20 @@ enum track_item { TRACK_ALLOC, TRACK_FREE }; #ifdef SLAB_SUPPORTS_SYSFS static int sysfs_slab_add(struct kmem_cache *); +static int __init slab_kset_init(void); +static void __init slab_sysfs_process_aliases(void); #else static inline int sysfs_slab_add(struct kmem_cache *s) { return 0; } +static inline int slab_kset_init(void) { return 0; } +static inline void slab_sysfs_process_aliases(void) { } #endif #if defined(CONFIG_DEBUG_FS) && defined(CONFIG_SLUB_DEBUG) static void debugfs_slab_add(struct kmem_cache *); +static void __init slab_debugfs_root_init(void); #else static inline void debugfs_slab_add(struct kmem_cache *s) { } +static inline void slab_debugfs_root_init(void) { } #endif enum add_mode { @@ -9734,28 +9740,20 @@ int sysfs_slab_alias(struct kmem_cache *s, const char *name) return 0; } -static int __init slab_sysfs_init(void) +static int __init slab_kset_init(void) { - struct kmem_cache *s; - int err; - - mutex_lock(&slab_mutex); - slab_kset = kset_create_and_add("slab", NULL, kernel_kobj); if (!slab_kset) { - mutex_unlock(&slab_mutex); pr_err("Cannot register slab subsystem.\n"); return -ENOMEM; } - slab_state = FULL; + return 0; +} - list_for_each_entry(s, &slab_caches, list) { - err = sysfs_slab_add(s); - if (err) - pr_err("SLUB: Unable to add boot slab %s to sysfs\n", - s->name); - } +static void __init slab_sysfs_process_aliases(void) +{ + int err; while (alias_list) { struct saved_alias *al = alias_list; @@ -9767,12 +9765,41 @@ static int __init slab_sysfs_init(void) al->name); kfree(al); } +} +#endif /* SLAB_SUPPORTS_SYSFS */ + +#if defined(SLAB_SUPPORTS_SYSFS) || \ + (defined(CONFIG_SLUB_DEBUG) && defined(CONFIG_DEBUG_FS)) +static int __init slab_late_init(void) +{ + struct kmem_cache *s; + int err; + mutex_lock(&slab_mutex); + + err = slab_kset_init(); + if (err) + goto out; + + slab_debugfs_root_init(); + slab_state = FULL; + + list_for_each_entry(s, &slab_caches, list) { + if (sysfs_slab_add(s)) + pr_err("SLUB: Unable to add boot slab %s to sysfs\n", + s->name); + + if (s->flags & SLAB_STORE_USER) + debugfs_slab_add(s); + } + + slab_sysfs_process_aliases(); +out: mutex_unlock(&slab_mutex); - return 0; + return err; } -late_initcall(slab_sysfs_init); -#endif /* SLAB_SUPPORTS_SYSFS */ +late_initcall(slab_late_init); +#endif #if defined(CONFIG_SLUB_DEBUG) && defined(CONFIG_DEBUG_FS) static int slab_debugfs_show(struct seq_file *seq, void *v) @@ -9964,23 +9991,16 @@ static void debugfs_slab_add(struct kmem_cache *s) void debugfs_slab_release(struct kmem_cache *s) { + if (unlikely(!slab_debugfs_root)) + return; + debugfs_lookup_and_remove(s->name, slab_debugfs_root); } -static int __init slab_debugfs_init(void) +static void __init slab_debugfs_root_init(void) { - struct kmem_cache *s; - slab_debugfs_root = debugfs_create_dir("slab", NULL); - - list_for_each_entry(s, &slab_caches, list) - if (s->flags & SLAB_STORE_USER) - debugfs_slab_add(s); - - return 0; - } -__initcall(slab_debugfs_init); #endif /* * The /proc/slabinfo ABI -- 2.34.1