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. I don't think this code ever executes anything as !v is most likely never true? Also I don't understand why the count == seq->index - 1 comparison. I think this function should do simply: kfree(v); 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 > */ >
