mm/page_owner: add struct stack_print_ctx.flags

Add the flags field to stack_print_ctx, and define two flags for current
behavior (printing stack traces and their number of base pages).

The plumbing of flags is debugfs_create_file(data) -> inode.i_private ->
page_owner_stack_open() -> stack_print_ctx.flags -> stack_print().

No behavior change intended.

Link: https://lkml.kernel.org/r/20251001175611.575861-3-mfo@igalia.com
Signed-off-by: Mauricio Faria de Oliveira <mfo@igalia.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/page_owner.c b/mm/page_owner.c
index 05e26c9d43efc4a3dceccb7d07567b8614eda033..2f6f99d60ba7eaad5fa90140785bd9fc73acfb14 100644 (file)
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -45,8 +45,12 @@ static struct stack failure_stack;
 static struct stack *stack_list;
 static DEFINE_SPINLOCK(stack_list_lock);
 
+#define STACK_PRINT_FLAG_STACK         0x1
+#define STACK_PRINT_FLAG_PAGES         0x2
+
 struct stack_print_ctx {
        struct stack *stack;
+       u8 flags;
 };
 
 static bool page_owner_enabled __initdata;
@@ -904,20 +908,24 @@ static int stack_print(struct seq_file *m, void *v)
        unsigned long *entries;
        unsigned long nr_entries;
        struct stack_record *stack_record = stack->stack_record;
+       struct stack_print_ctx *ctx = m->private;
 
        if (!stack->stack_record)
                return 0;
 
-       nr_entries = stack_record->size;
-       entries = stack_record->entries;
        nr_base_pages = refcount_read(&stack_record->count) - 1;
 
        if (nr_base_pages < 1 || nr_base_pages < page_owner_pages_threshold)
                return 0;
 
-       for (i = 0; i < nr_entries; i++)
-               seq_printf(m, " %pS\n", (void *)entries[i]);
-       seq_printf(m, "nr_base_pages: %d\n\n", nr_base_pages);
+       if (ctx->flags & STACK_PRINT_FLAG_STACK) {
+               nr_entries = stack_record->size;
+               entries = stack_record->entries;
+               for (i = 0; i < nr_entries; i++)
+                       seq_printf(m, " %pS\n", (void *)entries[i]);
+       }
+       if (ctx->flags & STACK_PRINT_FLAG_PAGES)
+               seq_printf(m, "nr_base_pages: %d\n\n", nr_base_pages);
 
        return 0;
 }
@@ -938,6 +946,13 @@ static int page_owner_stack_open(struct inode *inode, struct file *file)
        int ret = seq_open_private(file, &page_owner_stack_op,
                                   sizeof(struct stack_print_ctx));
 
+       if (!ret) {
+               struct seq_file *m = file->private_data;
+               struct stack_print_ctx *ctx = m->private;
+
+               ctx->flags = (uintptr_t) inode->i_private;
+       }
+
        return ret;
 }
 
@@ -976,7 +991,9 @@ static int __init pageowner_init(void)
        debugfs_create_file("page_owner", 0400, NULL, NULL,
                            &proc_page_owner_operations);
        dir = debugfs_create_dir("page_owner_stacks", NULL);
-       debugfs_create_file("show_stacks", 0400, dir, NULL,
+       debugfs_create_file("show_stacks", 0400, dir,
+                           (void *)(STACK_PRINT_FLAG_STACK |
+                                    STACK_PRINT_FLAG_PAGES),
                            &page_owner_stack_operations);
        debugfs_create_file("count_threshold", 0600, dir, NULL,
                            &proc_page_owner_threshold);