[PATCH bpf-next v7 02/11] bpf: convert cgroup_bpf.progs to hlist

From: Stanislav Fomichev <hidden>
Date: 2022-05-18 22:57:11
Also in: bpf
Subsystem: bpf [core], bpf [general] (safe dynamic programs and tools), bpf [storage & cgroups], the rest · Maintainers: Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Martin KaFai Lau, Linus Torvalds

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>
Signed-off-by: Stanislav Fomichev <redacted>
---
 include/linux/bpf-cgroup-defs.h |  4 +-
 include/linux/bpf-cgroup.h      |  2 +-
 kernel/bpf/cgroup.c             | 72 +++++++++++++++++++--------------
 3 files changed, 45 insertions(+), 33 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 afb414b26d01..134785ab487c 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 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;
 	int err;

@@ -766,9 +777,10 @@ static int __cgroup_bpf_detach(struct cgroup *cgrp, struct bpf_prog *prog,
 		goto cleanup;
 
 	/* 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)

@@ -802,7 +814,7 @@ 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;

@@ -841,7 +853,7 @@ 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)))

-- 
2.36.1.124.g0e6072fb45-goog

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