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SubjectRe: [PATCH] mm: convert three more cases to kvmalloc
On Wed 28-06-17 23:24:10, Mikulas Patocka wrote:
[...]
> From: Mikulas Patocka <mpatocka@redhat.com>
>
> The patch a7c3e901 ("mm: introduce kv[mz]alloc helpers") converted a lot
> of kernel code to kvmalloc. This patch converts three more forgotten
> cases.

Thanks! I have two remarks below but other than that feel free to add

> Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

Acked-by: Michal Hocko <mhocko@suse.com>
[...]
> Index: linux-2.6/kernel/bpf/syscall.c
> ===================================================================
> --- linux-2.6.orig/kernel/bpf/syscall.c
> +++ linux-2.6/kernel/bpf/syscall.c
> @@ -58,16 +58,7 @@ void *bpf_map_area_alloc(size_t size)
> * trigger under memory pressure as we really just want to
> * fail instead.
> */
> - const gfp_t flags = __GFP_NOWARN | __GFP_NORETRY | __GFP_ZERO;
> - void *area;
> -
> - if (size <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER)) {
> - area = kmalloc(size, GFP_USER | flags);
> - if (area != NULL)
> - return area;
> - }
> -
> - return __vmalloc(size, GFP_KERNEL | flags, PAGE_KERNEL);
> + return kvmalloc(size, GFP_USER | __GFP_NOWARN | __GFP_NORETRY | __GFP_ZERO);

kvzalloc without additional flags would be more appropriate.
__GFP_NORETRY is explicitly documented as non-supported and NOWARN
wouldn't be applied everywhere in the vmalloc path.

> }
>
> void bpf_map_area_free(void *area)
> Index: linux-2.6/kernel/cgroup/cgroup-v1.c
> ===================================================================
> --- linux-2.6.orig/kernel/cgroup/cgroup-v1.c
> +++ linux-2.6/kernel/cgroup/cgroup-v1.c
> @@ -184,15 +184,10 @@ struct cgroup_pidlist {
> /*
> * The following two functions "fix" the issue where there are more pids
> * than kmalloc will give memory for; in such cases, we use vmalloc/vfree.
> - * TODO: replace with a kernel-wide solution to this problem
> */
> -#define PIDLIST_TOO_LARGE(c) ((c) * sizeof(pid_t) > (PAGE_SIZE * 2))
> static void *pidlist_allocate(int count)
> {
> - if (PIDLIST_TOO_LARGE(count))
> - return vmalloc(count * sizeof(pid_t));
> - else
> - return kmalloc(count * sizeof(pid_t), GFP_KERNEL);
> + return kvmalloc(count * sizeof(pid_t), GFP_KERNEL);
> }

I would rather use kvmalloc_array to have an overflow protection as
well.

>
> static void pidlist_free(void *p)

--
Michal Hocko
SUSE Labs

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