[PATCH 5.19 203/717] bpf: convert cgroup_bpf.progs to hlist

Greg Kroah-Hartman
2022-10-22T07:55:03Z

From: Stanislav Fomichev <sdf@google.com>

[ Upstream commit 00442143a2ab7f1da46fbf4d2a99c85df767d49a ]

This lets us reclaim some space to be used by new cgroup lsm slots.

Before:
struct cgroup_bpf {
struct bpf_prog_array * effective[23]; /* 0 184 */
/* --- cacheline 2 boundary (128 bytes) was 56 bytes ago --- */
struct list_head progs[23]; /* 184 368 */
/* --- cacheline 8 boundary (512 bytes) was 40 bytes ago --- */
u32 flags[23]; /* 552 92 */

/* XXX 4 bytes hole, try to pack */

/* --- cacheline 10 boundary (640 bytes) was 8 bytes ago --- */
struct list_head storages; /* 648 16 */
struct bpf_prog_array * inactive; /* 664 8 */
struct percpu_ref refcnt; /* 672 16 */
struct work_struct release_work; /* 688 32 */

/* size: 720, cachelines: 12, members: 7 */
/* sum members: 716, holes: 1, sum holes: 4 */
/* last cacheline: 16 bytes */
};

After:
struct cgroup_bpf {
struct bpf_prog_array * effective[23]; /* 0 184 */
/* --- cacheline 2 boundary (128 bytes) was 56 bytes ago --- */
struct hlist_head progs[23]; /* 184 184 */
/* --- cacheline 5 boundary (320 bytes) was 48 bytes ago --- */
u8 flags[23]; /* 368 23 */

/* XXX 1 byte hole, try to pack */

/* --- cacheline 6 boundary (384 bytes) was 8 bytes ago --- */
struct list_head storages; /* 392 16 */
struct bpf_prog_array * inactive; /* 408 8 */
struct percpu_ref refcnt; /* 416 16 */
struct work_struct release_work; /* 432 72 */

/* size: 504, cachelines: 8, members: 7 */
/* sum members: 503, holes: 1, sum holes: 1 */
/* last cacheline: 56 bytes */
};

Suggested-by: Jakub Sitnicki <jakub@cloudflare.com>
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Reviewed-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/r/20220628174314.1216643-3-sdf@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Stable-dep-of: 883743422ced ("bpf: Fix ref_obj_id for dynptr data slices in verifier")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/linux/bpf-cgroup-defs.h | 4 +-
include/linux/bpf-cgroup.h | 2 +-
kernel/bpf/cgroup.c | 76 +++++++++++++++++++--------------
3 files changed, 47 insertions(+), 35 deletions(-)

diff --git a/include/linux/bpf-cgroup-defs.h b/include/linux/bpf-cgroup-defs.h
index 695d1224a71b..5d268e76d8e6 100644
--- a/include/linux/bpf-cgroup-defs.h
+++ b/include/linux/bpf-cgroup-defs.h
@@ -47,8 +47,8 @@ struct cgroup_bpf {
* have either zero or one element
* when BPF_F_ALLOW_MULTI the list can have up to BPF_CGROUP_MAX_PROGS
*/
- struct list_head progs[MAX_CGROUP_BPF_ATTACH_TYPE];
- u32 flags[MAX_CGROUP_BPF_ATTACH_TYPE];
+ struct hlist_head progs[MAX_CGROUP_BPF_ATTACH_TYPE];
+ u8 flags[MAX_CGROUP_BPF_ATTACH_TYPE];

/* list of cgroup shared storages */
struct list_head storages;
diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h
index 669d96d074ad..6673acfbf2ef 100644
--- a/include/linux/bpf-cgroup.h
+++ b/include/linux/bpf-cgroup.h
@@ -95,7 +95,7 @@ struct bpf_cgroup_link {
};

struct bpf_prog_list {
- struct list_head node;
+ struct hlist_node node;
struct bpf_prog *prog;
struct bpf_cgroup_link *link;
struct bpf_cgroup_storage *storage[MAX_BPF_CGROUP_STORAGE_TYPE];
diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index 34dfa45ef4f3..13526b01f1fd 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -157,11 +157,12 @@ static void cgroup_bpf_release(struct work_struct *work)
mutex_lock(&cgroup_mutex);

for (atype = 0; atype < ARRAY_SIZE(cgrp->bpf.progs); atype++) {
- struct list_head *progs = &cgrp->bpf.progs[atype];
- struct bpf_prog_list *pl, *pltmp;
+ struct hlist_head *progs = &cgrp->bpf.progs[atype];
+ struct bpf_prog_list *pl;
+ struct hlist_node *pltmp;

- list_for_each_entry_safe(pl, pltmp, progs, node) {
- list_del(&pl->node);
+ hlist_for_each_entry_safe(pl, pltmp, progs, node) {
+ hlist_del(&pl->node);
if (pl->prog)
bpf_prog_put(pl->prog);
if (pl->link)
@@ -217,12 +218,12 @@ static struct bpf_prog *prog_list_prog(struct bpf_prog_list *pl)
/* count number of elements in the list.
* it's slow but the list cannot be long
*/
-static u32 prog_list_length(struct list_head *head)
+static u32 prog_list_length(struct hlist_head *head)
{
struct bpf_prog_list *pl;
u32 cnt = 0;

- list_for_each_entry(pl, head, node) {
+ hlist_for_each_entry(pl, head, node) {
if (!prog_list_prog(pl))
continue;
cnt++;
@@ -291,7 +292,7 @@ static int compute_effective_progs(struct cgroup *cgrp,
if (cnt > 0 && !(p->bpf.flags[atype] & BPF_F_ALLOW_MULTI))
continue;

- list_for_each_entry(pl, &p->bpf.progs[atype], node) {
+ hlist_for_each_entry(pl, &p->bpf.progs[atype], node) {
if (!prog_list_prog(pl))
continue;

@@ -342,7 +343,7 @@ int cgroup_bpf_inherit(struct cgroup *cgrp)
cgroup_bpf_get(p);

for (i = 0; i < NR; i++)
- INIT_LIST_HEAD(&cgrp->bpf.progs[i]);
+ INIT_HLIST_HEAD(&cgrp->bpf.progs[i]);

INIT_LIST_HEAD(&cgrp->bpf.storages);

@@ -418,7 +419,7 @@ static int update_effective_progs(struct cgroup *cgrp,

#define BPF_CGROUP_MAX_PROGS 64

-static struct bpf_prog_list *find_attach_entry(struct list_head *progs,
+static struct bpf_prog_list *find_attach_entry(struct hlist_head *progs,
struct bpf_prog *prog,
struct bpf_cgroup_link *link,
struct bpf_prog *replace_prog,
@@ -428,12 +429,12 @@ static struct bpf_prog_list *find_attach_entry(struct list_head *progs,

/* single-attach case */
if (!allow_multi) {
- if (list_empty(progs))
+ if (hlist_empty(progs))
return NULL;
- return list_first_entry(progs, typeof(*pl), node);
+ return hlist_entry(progs->first, typeof(*pl), node);
}

- list_for_each_entry(pl, progs, node) {
+ hlist_for_each_entry(pl, progs, node) {
if (prog && pl->prog == prog && prog != replace_prog)
/* disallow attaching the same prog twice */
return ERR_PTR(-EINVAL);
@@ -444,7 +445,7 @@ static struct bpf_prog_list *find_attach_entry(struct list_head *progs,

/* direct prog multi-attach w/ replacement case */
if (replace_prog) {
- list_for_each_entry(pl, progs, node) {
+ hlist_for_each_entry(pl, progs, node) {
if (pl->prog == replace_prog)
/* a match found */
return pl;
@@ -480,7 +481,7 @@ static int __cgroup_bpf_attach(struct cgroup *cgrp,
struct bpf_cgroup_storage *new_storage[MAX_BPF_CGROUP_STORAGE_TYPE] = {};
enum cgroup_bpf_attach_type atype;
struct bpf_prog_list *pl;
- struct list_head *progs;
+ struct hlist_head *progs;
int err;

if (((flags & BPF_F_ALLOW_OVERRIDE) && (flags & BPF_F_ALLOW_MULTI)) ||
@@ -503,7 +504,7 @@ static int __cgroup_bpf_attach(struct cgroup *cgrp,
if (!hierarchy_allows_attach(cgrp, atype))
return -EPERM;

- if (!list_empty(progs) && cgrp->bpf.flags[atype] != saved_flags)
+ if (!hlist_empty(progs) && cgrp->bpf.flags[atype] != saved_flags)
/* Disallow attaching non-overridable on top
* of existing overridable in this cgroup.
* Disallow attaching multi-prog if overridable or none
@@ -525,12 +526,22 @@ static int __cgroup_bpf_attach(struct cgroup *cgrp,
if (pl) {
old_prog = pl->prog;
} else {
+ struct hlist_node *last = NULL;
+
pl = kmalloc(sizeof(*pl), GFP_KERNEL);
if (!pl) {
bpf_cgroup_storages_free(new_storage);
return -ENOMEM;
}
- list_add_tail(&pl->node, progs);
+ if (hlist_empty(progs))
+ hlist_add_head(&pl->node, progs);
+ else
+ hlist_for_each(last, progs) {
+ if (last->next)
+ continue;
+ hlist_add_behind(&pl->node, last);
+ break;
+ }
}

pl->prog = prog;
@@ -556,7 +567,7 @@ static int __cgroup_bpf_attach(struct cgroup *cgrp,
}
bpf_cgroup_storages_free(new_storage);
if (!old_prog) {
- list_del(&pl->node);
+ hlist_del(&pl->node);
kfree(pl);
}
return err;
@@ -587,7 +598,7 @@ static void replace_effective_prog(struct cgroup *cgrp,
struct cgroup_subsys_state *css;
struct bpf_prog_array *progs;
struct bpf_prog_list *pl;
- struct list_head *head;
+ struct hlist_head *head;
struct cgroup *cg;
int pos;

@@ -603,7 +614,7 @@ static void replace_effective_prog(struct cgroup *cgrp,
continue;

head = &cg->bpf.progs[atype];
- list_for_each_entry(pl, head, node) {
+ hlist_for_each_entry(pl, head, node) {
if (!prog_list_prog(pl))
continue;
if (pl->link == link)
@@ -637,7 +648,7 @@ static int __cgroup_bpf_replace(struct cgroup *cgrp,
enum cgroup_bpf_attach_type atype;
struct bpf_prog *old_prog;
struct bpf_prog_list *pl;
- struct list_head *progs;
+ struct hlist_head *progs;
bool found = false;

atype = to_cgroup_bpf_attach_type(link->type);
@@ -649,7 +660,7 @@ static int __cgroup_bpf_replace(struct cgroup *cgrp,
if (link->link.prog->type != new_prog->type)
return -EINVAL;

- list_for_each_entry(pl, progs, node) {
+ hlist_for_each_entry(pl, progs, node) {
if (pl->link == link) {
found = true;
break;
@@ -688,7 +699,7 @@ static int cgroup_bpf_replace(struct bpf_link *link, struct bpf_prog *new_prog,
return ret;
}

-static struct bpf_prog_list *find_detach_entry(struct list_head *progs,
+static struct bpf_prog_list *find_detach_entry(struct hlist_head *progs,
struct bpf_prog *prog,
struct bpf_cgroup_link *link,
bool allow_multi)
@@ -696,14 +707,14 @@ static struct bpf_prog_list *find_detach_entry(struct list_head *progs,
struct bpf_prog_list *pl;

if (!allow_multi) {
- if (list_empty(progs))
+ if (hlist_empty(progs))
/* report error when trying to detach and nothing is attached */
return ERR_PTR(-ENOENT);

/* to maintain backward compatibility NONE and OVERRIDE cgroups
* allow detaching with invalid FD (prog==NULL) in legacy mode
*/
- return list_first_entry(progs, typeof(*pl), node);
+ return hlist_entry(progs->first, typeof(*pl), node);
}

if (!prog && !link)
@@ -713,7 +724,7 @@ static struct bpf_prog_list *find_detach_entry(struct list_head *progs,
return ERR_PTR(-EINVAL);

/* find the prog or link and detach it */
- list_for_each_entry(pl, progs, node) {
+ hlist_for_each_entry(pl, progs, node) {
if (pl->prog == prog && pl->link == link)
return pl;
}
@@ -737,7 +748,7 @@ static void purge_effective_progs(struct cgroup *cgrp, struct bpf_prog *prog,
struct cgroup_subsys_state *css;
struct bpf_prog_array *progs;
struct bpf_prog_list *pl;
- struct list_head *head;
+ struct hlist_head *head;
struct cgroup *cg;
int pos;

@@ -754,7 +765,7 @@ static void purge_effective_progs(struct cgroup *cgrp, struct bpf_prog *prog,
continue;

head = &cg->bpf.progs[atype];
- list_for_each_entry(pl, head, node) {
+ hlist_for_each_entry(pl, head, node) {
if (!prog_list_prog(pl))
continue;
if (pl->prog == prog && pl->link == link)
@@ -793,7 +804,7 @@ static int __cgroup_bpf_detach(struct cgroup *cgrp, struct bpf_prog *prog,
enum cgroup_bpf_attach_type atype;
struct bpf_prog *old_prog;
struct bpf_prog_list *pl;
- struct list_head *progs;
+ struct hlist_head *progs;
u32 flags;

atype = to_cgroup_bpf_attach_type(type);
@@ -824,9 +835,10 @@ static int __cgroup_bpf_detach(struct cgroup *cgrp, struct bpf_prog *prog,
}

/* now can actually delete it from this cgroup list */
- list_del(&pl->node);
+ hlist_del(&pl->node);
+
kfree(pl);
- if (list_empty(progs))
+ if (hlist_empty(progs))
/* last program was detached, reset flags to zero */
cgrp->bpf.flags[atype] = 0;
if (old_prog)
@@ -854,7 +866,7 @@ static int __cgroup_bpf_query(struct cgroup *cgrp, const union bpf_attr *attr,
enum bpf_attach_type type = attr->query.attach_type;
enum cgroup_bpf_attach_type atype;
struct bpf_prog_array *effective;
- struct list_head *progs;
+ struct hlist_head *progs;
struct bpf_prog *prog;
int cnt, ret = 0, i;
u32 flags;
@@ -893,7 +905,7 @@ static int __cgroup_bpf_query(struct cgroup *cgrp, const union bpf_attr *attr,
u32 id;

i = 0;
- list_for_each_entry(pl, progs, node) {
+ hlist_for_each_entry(pl, progs, node) {
prog = prog_list_prog(pl);
id = prog->aux->id;
if (copy_to_user(prog_ids + i, &id, sizeof(id)))
--
2.35.1