On 6/3/2021 6:32 PM, Vlastimil Babka wrote: > On 6/3/21 1:48 PM, Faiyaz Mohammed wrote: >> alloc_calls and free_calls implementation in sysfs have two issues, >> one is PAGE_SIZE limitiation of sysfs and other is it does not adhere >> to "one value per file" rule. >> >> To overcome this issues, move the alloc_calls and free_calls implemeation >> to debugfs. >> >> Debugfs cache will be created if SLAB_STORE_USER flag is set. >> >> Rename the alloc_calls/free_calls to alloc_traces/free_traces, >> to be inline with what it does. >> >> Signed-off-by: Faiyaz Mohammed <faiyazm@xxxxxxxxxxxxxx> >> --- >> changes in v9: >> - Move the debugfs_slab_release to mm/slab.h. >> - Remove the global loc_track variable and using seq_file private. >> >> changes in v8: >> - https://lore.kernel.org/linux-mm/1622542057-14632-1-git-send-email-faiyazm@xxxxxxxxxxxxxx/ >> >> changes in V7: >> - https://lore.kernel.org/linux-mm/1621928285-751-1-git-send-email-faiyazm@xxxxxxxxxxxxxx/ >> >> changes in v6: >> - https://lore.kernel.org/linux-mm/1621341949-26762-1-git-send-email-faiyazm@xxxxxxxxxxxxxx/ >> >> changes in v5: >> - https://lore.kernel.org/linux-mm/1620296523-21922-1-git-send-email-faiyazm@xxxxxxxxxxxxxx/ >> >> changes in v4: >> - https://lore.kernel.org/linux-mm/1618583239-18124-1-git-send-email-faiyazm@xxxxxxxxxxxxxx/ >> >> changes in v3: >> - https://lore.kernel.org/linux-mm/1617712064-12264-1-git-send-email-faiyazm@xxxxxxxxxxxxxx/ >> >> changes in v2: >> - https://lore.kernel.org/linux-mm/3ac1d3e6-6207-96ad-16a1-0f5139d8b2b5@xxxxxxxxxxxxxx/ >> >> changes in v1 >> - https://lore.kernel.org/linux-mm/1610443287-23933-1-git-send-email-faiyazm@xxxxxxxxxxxxxx/ >> >> mm/slab.h | 8 ++ >> mm/slab_common.c | 2 + >> mm/slub.c | 312 ++++++++++++++++++++++++++++++++++++++----------------- >> 3 files changed, 229 insertions(+), 93 deletions(-) >> >> diff --git a/mm/slab.h b/mm/slab.h >> index 18c1927..3b60925 100644 >> --- a/mm/slab.h >> +++ b/mm/slab.h >> @@ -630,6 +630,14 @@ static inline bool slab_want_init_on_free(struct kmem_cache *c) >> return false; >> } >> >> +#if defined(CONFIG_DEBUG_FS) && defined(CONFIG_SLUB_DEBUG) >> +void debugfs_slab_release(struct kmem_cache *); >> +#else >> +static inline void debugfs_slab_release(struct kmem_cache *s) >> +{ >> +} >> +#endif >> + >> #ifdef CONFIG_PRINTK >> #define KS_ADDRS_COUNT 16 >> struct kmem_obj_info { >> diff --git a/mm/slab_common.c b/mm/slab_common.c >> index a4a5714..bca69b6 100644 >> --- a/mm/slab_common.c >> +++ b/mm/slab_common.c >> @@ -469,6 +469,7 @@ static int shutdown_cache(struct kmem_cache *s) >> list_del(&s->list); >> >> if (s->flags & SLAB_TYPESAFE_BY_RCU) { >> + debugfs_slab_release(s); >> #ifdef SLAB_SUPPORTS_SYSFS >> sysfs_slab_unlink(s); >> #endif >> @@ -476,6 +477,7 @@ static int shutdown_cache(struct kmem_cache *s) >> schedule_work(&slab_caches_to_rcu_destroy_work); >> } else { >> kfence_shutdown_cache(s); >> + debugfs_slab_release(s); >> #ifdef SLAB_SUPPORTS_SYSFS >> sysfs_slab_unlink(s); >> sysfs_slab_release(s); >> diff --git a/mm/slub.c b/mm/slub.c >> index 3f96e09..c00c9d5 100644 >> --- a/mm/slub.c >> +++ b/mm/slub.c >> @@ -36,6 +36,7 @@ >> #include <linux/memcontrol.h> >> #include <linux/random.h> >> >> +#include <linux/debugfs.h> >> #include <trace/events/kmem.h> >> >> #include "internal.h" >> @@ -225,6 +226,12 @@ static inline int sysfs_slab_alias(struct kmem_cache *s, const char *p) >> { return 0; } >> #endif >> >> +#if defined(CONFIG_DEBUG_FS) && defined(CONFIG_SLUB_DEBUG) >> +static void debugfs_slab_add(struct kmem_cache *); >> +#else >> +static inline void debugfs_slab_add(struct kmem_cache *s) { } >> +#endif >> + >> static inline void stat(const struct kmem_cache *s, enum stat_item si) >> { >> #ifdef CONFIG_SLUB_STATS >> @@ -4546,6 +4553,9 @@ int __kmem_cache_create(struct kmem_cache *s, slab_flags_t flags) >> if (err) >> __kmem_cache_release(s); >> >> + if (s->flags & SLAB_STORE_USER) >> + debugfs_slab_add(s); >> + >> return err; >> } >> >> @@ -4686,6 +4696,8 @@ static long validate_slab_cache(struct kmem_cache *s) >> >> return count; >> } >> + >> +#ifdef CONFIG_DEBUG_FS >> /* >> * Generate lists of code addresses where slabcache objects are allocated >> * and freed. >> @@ -4709,6 +4721,8 @@ struct loc_track { >> struct location *loc; >> }; >> >> +static struct dentry *slab_debugfs_root; >> + >> static void free_loc_track(struct loc_track *t) >> { >> if (t->max) >> @@ -4825,82 +4839,7 @@ static void process_slab(struct loc_track *t, struct kmem_cache *s, >> add_location(t, s, get_track(s, p, alloc)); >> put_map(map); >> } >> - >> -static int list_locations(struct kmem_cache *s, char *buf, >> - enum track_item alloc) >> -{ >> - int len = 0; >> - unsigned long i; >> - struct loc_track t = { 0, 0, NULL }; >> - int node; >> - struct kmem_cache_node *n; >> - >> - if (!alloc_loc_track(&t, PAGE_SIZE / sizeof(struct location), >> - GFP_KERNEL)) { >> - return sysfs_emit(buf, "Out of memory\n"); >> - } >> - /* Push back cpu slabs */ >> - flush_all(s); >> - >> - for_each_kmem_cache_node(s, node, n) { >> - unsigned long flags; >> - struct page *page; >> - >> - if (!atomic_long_read(&n->nr_slabs)) >> - continue; >> - >> - spin_lock_irqsave(&n->list_lock, flags); >> - list_for_each_entry(page, &n->partial, slab_list) >> - process_slab(&t, s, page, alloc); >> - list_for_each_entry(page, &n->full, slab_list) >> - process_slab(&t, s, page, alloc); >> - spin_unlock_irqrestore(&n->list_lock, flags); >> - } >> - >> - for (i = 0; i < t.count; i++) { >> - struct location *l = &t.loc[i]; >> - >> - len += sysfs_emit_at(buf, len, "%7ld ", l->count); >> - >> - if (l->addr) >> - len += sysfs_emit_at(buf, len, "%pS", (void *)l->addr); >> - else >> - len += sysfs_emit_at(buf, len, "<not-available>"); >> - >> - if (l->sum_time != l->min_time) >> - len += sysfs_emit_at(buf, len, " age=%ld/%ld/%ld", >> - l->min_time, >> - (long)div_u64(l->sum_time, >> - l->count), >> - l->max_time); >> - else >> - len += sysfs_emit_at(buf, len, " age=%ld", l->min_time); >> - >> - if (l->min_pid != l->max_pid) >> - len += sysfs_emit_at(buf, len, " pid=%ld-%ld", >> - l->min_pid, l->max_pid); >> - else >> - len += sysfs_emit_at(buf, len, " pid=%ld", >> - l->min_pid); >> - >> - if (num_online_cpus() > 1 && >> - !cpumask_empty(to_cpumask(l->cpus))) >> - len += sysfs_emit_at(buf, len, " cpus=%*pbl", >> - cpumask_pr_args(to_cpumask(l->cpus))); >> - >> - if (nr_online_nodes > 1 && !nodes_empty(l->nodes)) >> - len += sysfs_emit_at(buf, len, " nodes=%*pbl", >> - nodemask_pr_args(&l->nodes)); >> - >> - len += sysfs_emit_at(buf, len, "\n"); >> - } >> - >> - free_loc_track(&t); >> - if (!t.count) >> - len += sysfs_emit_at(buf, len, "No data\n"); >> - >> - return len; >> -} >> +#endif /* CONFIG_DEBUG_FS */ >> #endif /* CONFIG_SLUB_DEBUG */ >> >> #ifdef SLUB_RESILIENCY_TEST >> @@ -5350,21 +5289,6 @@ static ssize_t validate_store(struct kmem_cache *s, >> } >> SLAB_ATTR(validate); >> >> -static ssize_t alloc_calls_show(struct kmem_cache *s, char *buf) >> -{ >> - if (!(s->flags & SLAB_STORE_USER)) >> - return -ENOSYS; >> - return list_locations(s, buf, TRACK_ALLOC); >> -} >> -SLAB_ATTR_RO(alloc_calls); >> - >> -static ssize_t free_calls_show(struct kmem_cache *s, char *buf) >> -{ >> - if (!(s->flags & SLAB_STORE_USER)) >> - return -ENOSYS; >> - return list_locations(s, buf, TRACK_FREE); >> -} >> -SLAB_ATTR_RO(free_calls); >> #endif /* CONFIG_SLUB_DEBUG */ >> >> #ifdef CONFIG_FAILSLAB >> @@ -5528,8 +5452,6 @@ static struct attribute *slab_attrs[] = { >> &poison_attr.attr, >> &store_user_attr.attr, >> &validate_attr.attr, >> - &alloc_calls_attr.attr, >> - &free_calls_attr.attr, >> #endif >> #ifdef CONFIG_ZONE_DMA >> &cache_dma_attr.attr, >> @@ -5818,6 +5740,210 @@ static int __init slab_sysfs_init(void) >> __initcall(slab_sysfs_init); >> #endif /* CONFIG_SYSFS */ >> >> +#if defined(CONFIG_SLUB_DEBUG) && defined(CONFIG_DEBUG_FS) >> +static int slab_debugfs_show(struct seq_file *seq, void *v) >> +{ >> + >> + struct location *l; >> + unsigned int idx = *(unsigned int *)v; >> + struct loc_track *t = seq->private; >> + >> + if (idx < t->count) { >> + l = &t->loc[idx]; >> + >> + seq_printf(seq, "%7ld ", l->count); >> + >> + if (l->addr) >> + seq_printf(seq, "%pS", (void *)l->addr); >> + else >> + seq_puts(seq, "<not-available>"); >> + >> + if (l->sum_time != l->min_time) { >> + seq_printf(seq, " age=%ld/%ld/%ld", >> + l->min_time, >> + (long)div_u64(l->sum_time, l->count), >> + l->max_time); >> + } else >> + seq_printf(seq, " age=%ld", >> + l->min_time); >> + >> + if (l->min_pid != l->max_pid) >> + seq_printf(seq, " pid=%ld-%ld", >> + l->min_pid, l->max_pid); >> + else >> + seq_printf(seq, " pid=%ld", >> + l->min_pid); >> + >> + if (num_online_cpus() > 1 && >> + !cpumask_empty(to_cpumask(l->cpus))) >> + seq_printf(seq, " cpus=%*pbl", >> + cpumask_pr_args(to_cpumask(l->cpus))); >> + >> + if (nr_online_nodes > 1 && !nodes_empty(l->nodes)) >> + seq_printf(seq, " nodes=%*pbl", >> + nodemask_pr_args(&l->nodes)); >> + >> + seq_puts(seq, "\n"); >> + } >> + >> + if (!t->count) >> + seq_puts(seq, "No data\n"); >> + >> + return 0; >> +} >> + >> +static void slab_debugfs_stop(struct seq_file *seq, void *v) >> +{ >> + if ((!v) && >> + ((struct loc_track *)seq->private)->count == (seq->index - 1)) >> + free_loc_track((struct loc_track *)seq->private); > > Please use a local "loc_track *t" variable as elsewhere to avoid these multiple > inline casts. > Okay, will update in next patch version. > I don't think this code ever executes anything as !v is most likely never true? > It will execute when slab_debugfs_next() return NULL (v will be NULL) and slab_debugfs_next() will return NULLL, when it will completed the t->count reading. Still, I will update in next patch version. > Also I don't understand why the count == seq->index - 1 comparison. > The count == seq->index - 1 comparision is to avoid the calling of free_loc_track() multiple time. Still, I will update in next patch version. > I think this function should do simply: > > kfree(v); > hmm, yes we can do that but when ever seq_has_overflowed() happen it will call the ->stop(), so to avoiding that returning NULL from slab_debugfs_next() and doing !v check in slab_debugfs_stop. Still, I will update in next patch version. > More on the loc_track and seq->private lifecycle below. > >> +} >> + >> +static void *slab_debugfs_next(struct seq_file *seq, void *v, loff_t *ppos) >> +{ >> + loff_t *spos = v; >> + struct loc_track *t = seq->private; >> + >> + if (*ppos < t->count) { >> + *spos = *spos + 1; >> + *ppos = *spos; >> + return spos; >> + } >> + >> + *spos = *spos + 1; >> + *ppos = *spos; >> + return NULL; >> +} >> + >> +static void *slab_debugfs_start(struct seq_file *seq, loff_t *ppos) >> +{ >> + struct kmem_cache_node *n; >> + struct kmem_cache *s; >> + enum track_item alloc; >> + int node; >> + loff_t *spos = kmalloc(sizeof(loff_t), GFP_KERNEL); >> + >> + s = seq->file->f_inode->i_private; >> + >> + if (!spos) >> + return NULL; >> + >> + if (*ppos == 0) { > > Hm I think it's wrong to put all this behind the *ppos = 0 condition. Somebody > might open the file, then do a lseek() and then read. The condition should be > "did we fill lock_track info yet?". >>> + if (strcmp(seq->file->f_path.dentry->d_name.name, "alloc_traces") == 0) >> + alloc = TRACK_ALLOC; >> + else >> + alloc = TRACK_FREE; >> + >> + seq->private = kmalloc(sizeof(struct loc_track), GFP_KERNEL); > > This should be better allocated during open(). > >> + memset(seq->private, 0, sizeof(struct loc_track)); >> + >> + if (!alloc_loc_track((struct loc_track *)seq->private, > > Again, please define a local variable for this at the top of the function. > >> + PAGE_SIZE / sizeof(struct location), GFP_KERNEL)) { >> + seq_puts(seq, "Out of memory\n"); > > Hmm I don't think we can should to seq from a .start function. > Maybe just return the -ENOMEM. > >> + kfree(spos); >> + return ERR_PTR(-ENOMEM); >> + } >> + /* Push back cpu slabs */ >> + flush_all(s); >> + >> + for_each_kmem_cache_node(s, node, n) { >> + unsigned long flags; >> + struct page *page; >> + >> + if (!atomic_long_read(&n->nr_slabs)) >> + continue; >> + >> + spin_lock_irqsave(&n->list_lock, flags); >> + list_for_each_entry(page, &n->partial, slab_list) >> + process_slab((struct loc_track *)seq->private, s, page, alloc); >> + list_for_each_entry(page, &n->full, slab_list) >> + process_slab((struct loc_track *)seq->private, s, page, alloc); >> + spin_unlock_irqrestore(&n->list_lock, flags); >> + } >> + } >> + >> + if (seq->private) { >> + struct loc_track *t = seq->private; >> + >> + if (*ppos < t->count) { >> + *spos = *ppos; >> + return spos; >> + } >> + } >> + >> + kfree(spos); >> + kfree(seq->private); >> + return NULL; >> +} >> + >> +static const struct seq_operations slab_debugfs_sops = { >> + .start = slab_debugfs_start, >> + .next = slab_debugfs_next, >> + .stop = slab_debugfs_stop, >> + .show = slab_debugfs_show >> +}; > > So I think the seq->private lifecycle should be tied to open()/close(), not > start()/stop() where the latter is AFAIK performed as part of each read() syscall. > > So like in > https://lore.kernel.org/linux-mm/20210521121127.24653-3-glittao@xxxxxxxxx/ > we'll need a "struct file_operations" too, with an .open function that > __seq_open_private() to allocate seq->private and then do the initial > alloc_loc_track(). > > Then we'll also need a .release function that does free_loc_track() and then > seq_release_private(). > > The filling of loc_track with data could happen either in open() or in start(), > but only once after open() and not depending on *ppos == 0 (as I mentioned above). > > The next/stop should take care only of the spos object. > >> +DEFINE_SEQ_ATTRIBUTE(slab_debugfs); >> + >> +static void debugfs_slab_add(struct kmem_cache *s) >> +{ >> + const char *name; >> + struct dentry *slab_cache_dir; >> + int unmergeable = slab_unmergeable(s); >> + >> + if (unlikely(!slab_debugfs_root)) >> + return; >> + >> + if (!unmergeable && disable_higher_order_debug && >> + (slub_debug & DEBUG_METADATA_FLAGS)) >> + unmergeable = 1; >> + >> + if (unmergeable) { >> + /* >> + * Slabcache can never be merged so we can use the name proper. >> + * This is typically the case for debug situations. In that >> + * case we can catch duplicate names easily. >> + */ >> + slab_cache_dir = debugfs_lookup(s->name, slab_debugfs_root); >> + debugfs_remove_recursive(slab_cache_dir); >> + name = s->name; >> + } else { >> + /* >> + * Create a unique name for the slab as a target >> + * for the symlinks. >> + */ >> + name = create_unique_id(s); >> + } > > I think here we can rely on the fact that SLAB_STORE_USER cache will return > slab_unmergeable(s) as 1, and greatly simplify the code above. > >> + slab_cache_dir = debugfs_create_dir(name, slab_debugfs_root); >> + >> + debugfs_create_file("alloc_traces", 0400, >> + slab_cache_dir, s, &slab_debugfs_fops); >> + >> + debugfs_create_file("free_traces", 0400, >> + slab_cache_dir, s, &slab_debugfs_fops); >> +} >> + >> +void debugfs_slab_release(struct kmem_cache *s) >> +{ >> + debugfs_remove_recursive(debugfs_lookup(s->name, >> + slab_debugfs_root)); >> +} >> + >> +static int __init slab_debugfs_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 >> */ >> > I will update in next patch version.
