Re: [PATCH v2 sl-b 3/5] mm: Make mem_dump_obj() handle vmalloc() memory

Vlastimil Babka
2020-12-09T17:51:26Z

On 12/9/20 2:13 AM, paulmck@kernel.org wrote:
> From: "Paul E. McKenney" <paulmck@kernel.org>
>
> This commit adds vmalloc() support to mem_dump_obj(). Note that the
> vmalloc_dump_obj() function combines the checking and dumping, in
> contrast with the split between kmem_valid_obj() and kmem_dump_obj().
> The reason for the difference is that the checking in the vmalloc()
> case involves acquiring a global lock, and redundant acquisitions of
> global locks should be avoided, even on not-so-fast paths.
>
> Note that this change causes on-stack variables to be reported as
> vmalloc() storage from kernel_clone() or similar, depending on the degree
> of inlining that your compiler does. This is likely more helpful than
> the earlier "non-paged (local) memory".
>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> Cc: <linux-mm@kvack.org>
> Reported-by: Andrii Nakryiko <andrii@kernel.org>
> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

...

> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -3431,6 +3431,18 @@ void pcpu_free_vm_areas(struct vm_struct **vms, int nr_vms)
> }
> #endif /* CONFIG_SMP */
>
> +bool vmalloc_dump_obj(void *object)
> +{
> + struct vm_struct *vm;
> + void *objp = (void *)PAGE_ALIGN((unsigned long)object);
> +
> + vm = find_vm_area(objp);
> + if (!vm)
> + return false;
> + pr_cont(" vmalloc allocated at %pS\n", vm->caller);

Would it be useful to print the vm area boundaries too?

> + return true;
> +}
> +
> #ifdef CONFIG_PROC_FS
> static void *s_start(struct seq_file *m, loff_t *pos)
> __acquires(&vmap_purge_lock)
>