Re: [RFC 01/26] mm, slub: allocate private object map for sysfs listings

[Christoph Lameter]

On Tue, 25 May 2021, Vlastimil Babka wrote:

> Slub has a static spinlock protected bitmap for marking which objects are on
> freelist when it wants to list them, for situations where dynamically
> allocating such map can lead to recursion or locking issues, and on-stack
> bitmap would be too large.
>
> The handlers of sysfs files alloc_calls and free_calls also currently use this
> shared bitmap, but their syscall context makes it straightforward to allocate a
> private map before entering locked sections, so switch these processing paths
> to use a private bitmap.

Right in that case a GFP_KERNEL allocation is fine and you can avoid the
static map.

Acked-by: Christoph Lameter <cl@xxxxxxxxx>