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none X-Spamd-Result: default: False [1.90 / 50.00]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; R_MISSING_CHARSET(2.50)[]; MIME_GOOD(-0.10)[text/plain]; TO_MATCH_ENVRCPT_ALL(0.00)[]; BROKEN_CONTENT_TYPE(1.50)[]; RCVD_COUNT_THREE(0.00)[3]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; RCPT_COUNT_SEVEN(0.00)[9]; MID_CONTAINS_FROM(1.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:email]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; FREEMAIL_CC(0.00)[vger.kernel.org,kvack.org,suse.com,suse.cz,google.com,gmail.com,suse.de]; RCVD_TLS_ALL(0.00)[]; BAYES_HAM(-3.00)[100.00%] X-Spam-Level: * X-Spam-Score: 1.90 X-Spam-Flag: NO X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1790377905213618678 X-GMAIL-MSGID: 1790377905213618678 This patch adds a new file called 'page_owner_stacks', which will show all stacks that were added by page_owner followed by their counting, giving us a clear overview of stack <-> count relationship. E.g: prep_new_page+0xa9/0x120 get_page_from_freelist+0x801/0x2210 __alloc_pages+0x18b/0x350 alloc_pages_mpol+0x91/0x1f0 folio_alloc+0x14/0x50 filemap_alloc_folio+0xb2/0x100 __filemap_get_folio+0x14a/0x490 ext4_write_begin+0xbd/0x4b0 [ext4] generic_perform_write+0xc1/0x1e0 ext4_buffered_write_iter+0x68/0xe0 [ext4] ext4_file_write_iter+0x70/0x740 [ext4] vfs_write+0x33d/0x420 ksys_write+0xa5/0xe0 do_syscall_64+0x80/0x160 entry_SYSCALL_64_after_hwframe+0x6e/0x76 stack_count: 4578 In order to show all the stacks, we implement stack_depot_get_next_stack(), which walks all buckets while retrieving the stacks stored in them. stack_depot_get_next_stack() will return all stacks, one at a time, by first finding a non-empty bucket, and then retrieving all the stacks stored in that bucket. Once we have completely gone through it, we get the next non-empty bucket and repeat the same steps, and so on until we have completely checked all buckets. Signed-off-by: Oscar Salvador --- include/linux/stackdepot.h | 20 +++++++++ lib/stackdepot.c | 46 +++++++++++++++++++++ mm/page_owner.c | 85 ++++++++++++++++++++++++++++++++++++++ 3 files changed, 151 insertions(+) diff --git a/include/linux/stackdepot.h b/include/linux/stackdepot.h index ac62de4d4999..d851ec821e6f 100644 --- a/include/linux/stackdepot.h +++ b/include/linux/stackdepot.h @@ -183,6 +183,26 @@ depot_stack_handle_t stack_depot_save(unsigned long *entries, */ struct stack_record *stack_depot_get_stack(depot_stack_handle_t handle); +/** + * stack_depot_get_next_stack - Returns all stacks, one at a time + * + * @table: Current table we are checking + * @bucket: Current bucket we are checking + * @last_found: Last stack that was found + * + * This function finds first a non-empty bucket and returns the first stack + * stored in it. On consequent calls, it walks the bucket to see whether + * it contains more stacks. + * Once we have walked all the stacks in a bucket, we check + * the next one, and we repeat the same steps until we have checked all of them + * + * Return: A pointer a to stack_record struct, or NULL when we have walked all + * buckets. + */ +struct stack_record *stack_depot_get_next_stack(unsigned long *table, + struct list_head **bucket, + struct stack_record **last_found); + /** * stack_depot_fetch - Fetch a stack trace from stack depot * diff --git a/lib/stackdepot.c b/lib/stackdepot.c index 197c355601f9..107bd0174cd6 100644 --- a/lib/stackdepot.c +++ b/lib/stackdepot.c @@ -782,6 +782,52 @@ unsigned int stack_depot_get_extra_bits(depot_stack_handle_t handle) } EXPORT_SYMBOL(stack_depot_get_extra_bits); +struct stack_record *stack_depot_get_next_stack(unsigned long *table, + struct list_head **curr_bucket, + struct stack_record **last_found) +{ + struct list_head *bucket = *curr_bucket; + unsigned long nr_table = *table; + struct stack_record *found = NULL; + unsigned long stack_table_entries = stack_hash_mask + 1; + + rcu_read_lock_sched_notrace(); + if (!bucket) { + /* + * Find a non-empty bucket. Once we have found it, + * we will use list_for_each_entry_continue_rcu() on the next + * call to keep walking the bucket. + */ +new_table: + bucket = &stack_table[nr_table]; + list_for_each_entry_rcu(found, bucket, hash_list) { + goto out; + } + } else { + /* Check whether we have more stacks in this bucket */ + found = *last_found; + list_for_each_entry_continue_rcu(found, bucket, hash_list) { + goto out; + } + } + + /* No more stacks in this bucket, check the next one */ + nr_table++; + if (nr_table < stack_table_entries) + goto new_table; + + /* We are done walking all buckets */ + found = NULL; + +out: + *table = nr_table; + *curr_bucket = bucket; + *last_found = found; + rcu_read_unlock_sched_notrace(); + + return found; +} + static int stats_show(struct seq_file *seq, void *v) { /* diff --git a/mm/page_owner.c b/mm/page_owner.c index 0adf41702b9d..aea212734557 100644 --- a/mm/page_owner.c +++ b/mm/page_owner.c @@ -749,6 +749,89 @@ static const struct file_operations proc_page_owner_operations = { .llseek = lseek_page_owner, }; +struct stack_iterator { + unsigned long nr_table; + struct list_head *bucket; + struct stack_record *last_stack; +}; + +static void *stack_start(struct seq_file *m, loff_t *ppos) +{ + struct stack_iterator *iter = m->private; + + if (*ppos == -1UL) + return NULL; + + return stack_depot_get_next_stack(&iter->nr_table, + &iter->bucket, + &iter->last_stack); +} + +static void *stack_next(struct seq_file *m, void *v, loff_t *ppos) +{ + struct stack_iterator *iter = m->private; + struct stack_record *stack; + + stack = stack_depot_get_next_stack(&iter->nr_table, + &iter->bucket, + &iter->last_stack); + *ppos = stack ? *ppos + 1 : -1UL; + + return stack; +} + +static int stack_print(struct seq_file *m, void *v) +{ + char *buf; + int ret = 0; + struct stack_iterator *iter = m->private; + struct stack_record *stack = iter->last_stack; + + if (!stack->size || stack->size < 0 || refcount_read(&stack->count) < 2) + return 0; + + buf = kzalloc(PAGE_SIZE, GFP_KERNEL); + + ret += stack_trace_snprint(buf, PAGE_SIZE, stack->entries, stack->size, + 0); + if (!ret) + goto out; + + scnprintf(buf + ret, PAGE_SIZE - ret, "stack_count: %d\n\n", + refcount_read(&stack->count)); + + seq_printf(m, buf); + seq_puts(m, "\n\n"); +out: + kfree(buf); + + return 0; +} + +static void stack_stop(struct seq_file *m, void *v) +{ +} + +static const struct seq_operations page_owner_stack_op = { + .start = stack_start, + .next = stack_next, + .stop = stack_stop, + .show = stack_print +}; + +static int page_owner_stack_open(struct inode *inode, struct file *file) +{ + return seq_open_private(file, &page_owner_stack_op, + sizeof(struct stack_iterator)); +} + +const struct file_operations page_owner_stack_operations = { + .open = page_owner_stack_open, + .read = seq_read, + .llseek = seq_lseek, + .release = seq_release, +}; + static int __init pageowner_init(void) { if (!static_branch_unlikely(&page_owner_inited)) { @@ -758,6 +841,8 @@ static int __init pageowner_init(void) debugfs_create_file("page_owner", 0400, NULL, NULL, &proc_page_owner_operations); + debugfs_create_file("page_owner_stacks", 0400, NULL, NULL, + &page_owner_stack_operations); return 0; }