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bpf: Simplify __cgroup_bpf_attach

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__cgroup_bpf_attach has a lot of identical code to handle two scenarios:
BPF_F_ALLOW_MULTI is set and unset.

Simplify it by splitting the two main steps:

* First, the decision is made whether a new bpf_prog_list entry should
  be allocated or existing entry should be reused for the new program.
  This decision is saved in replace_pl pointer;

* Next, replace_pl pointer is used to handle both possible states of
  BPF_F_ALLOW_MULTI flag (set / unset) instead of doing similar work for
  them separately.

This splitting, in turn, allows to make further simplifications:

* The check for attaching same program twice in BPF_F_ALLOW_MULTI mode
  can be done before allocating cgroup storage, so that if user tries to
  attach same program twice no alloc/free happens as it was before;

* pl_was_allocated becomes redundant so it's removed.

Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/c6193db6fe630797110b0d3ff06c125d093b834c.1576741281.git.rdna@fb.com
This commit is contained in:
Andrey Ignatov 2019-12-18 23:44:33 -08:00 committed by Alexei Starovoitov
parent c92bbaa0fd
commit 1020c1f24a
1 changed files with 23 additions and 39 deletions
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62
kernel/bpf/cgroup.c
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@ -295,9 +295,8 @@ int __cgroup_bpf_attach(struct cgroup *cgrp, struct bpf_prog *prog,
struct bpf_prog *old_prog = NULL;
struct bpf_cgroup_storage *storage[MAX_BPF_CGROUP_STORAGE_TYPE],
*old_storage[MAX_BPF_CGROUP_STORAGE_TYPE] = {NULL};
struct bpf_prog_list *pl, *replace_pl = NULL;
enum bpf_cgroup_storage_type stype;
struct bpf_prog_list *pl;
bool pl_was_allocated;
int err;
if ((flags & BPF_F_ALLOW_OVERRIDE) && (flags & BPF_F_ALLOW_MULTI))
@ -317,6 +316,16 @@ int __cgroup_bpf_attach(struct cgroup *cgrp, struct bpf_prog *prog,
if (prog_list_length(progs) >= BPF_CGROUP_MAX_PROGS)
return -E2BIG;
if (flags & BPF_F_ALLOW_MULTI) {
list_for_each_entry(pl, progs, node) {
if (pl->prog == prog)
/* disallow attaching the same prog twice */
return -EINVAL;
}
} else if (!list_empty(progs)) {
replace_pl = list_first_entry(progs, typeof(*pl), node);
}
for_each_cgroup_storage_type(stype) {
storage[stype] = bpf_cgroup_storage_alloc(prog, stype);
if (IS_ERR(storage[stype])) {
@ -327,52 +336,27 @@ int __cgroup_bpf_attach(struct cgroup *cgrp, struct bpf_prog *prog,
}
}
if (flags & BPF_F_ALLOW_MULTI) {
list_for_each_entry(pl, progs, node) {
if (pl->prog == prog) {
/* disallow attaching the same prog twice */
for_each_cgroup_storage_type(stype)
bpf_cgroup_storage_free(storage[stype]);
return -EINVAL;
}
if (replace_pl) {
pl = replace_pl;
old_prog = pl->prog;
for_each_cgroup_storage_type(stype) {
old_storage[stype] = pl->storage[stype];
bpf_cgroup_storage_unlink(old_storage[stype]);
}
} else {
pl = kmalloc(sizeof(*pl), GFP_KERNEL);
if (!pl) {
for_each_cgroup_storage_type(stype)
bpf_cgroup_storage_free(storage[stype]);
return -ENOMEM;
}
pl_was_allocated = true;
pl->prog = prog;
for_each_cgroup_storage_type(stype)
pl->storage[stype] = storage[stype];
list_add_tail(&pl->node, progs);
} else {
if (list_empty(progs)) {
pl = kmalloc(sizeof(*pl), GFP_KERNEL);
if (!pl) {
for_each_cgroup_storage_type(stype)
bpf_cgroup_storage_free(storage[stype]);
return -ENOMEM;
}
pl_was_allocated = true;
list_add_tail(&pl->node, progs);
} else {
pl = list_first_entry(progs, typeof(*pl), node);
old_prog = pl->prog;
for_each_cgroup_storage_type(stype) {
old_storage[stype] = pl->storage[stype];
bpf_cgroup_storage_unlink(old_storage[stype]);
}
pl_was_allocated = false;
}
pl->prog = prog;
for_each_cgroup_storage_type(stype)
pl->storage[stype] = storage[stype];
}
pl->prog = prog;
for_each_cgroup_storage_type(stype)
pl->storage[stype] = storage[stype];
cgrp->bpf.flags[type] = flags;
err = update_effective_progs(cgrp, type);
@ -401,7 +385,7 @@ int __cgroup_bpf_attach(struct cgroup *cgrp, struct bpf_prog *prog,
pl->storage[stype] = old_storage[stype];
bpf_cgroup_storage_link(old_storage[stype], cgrp, type);
}
if (pl_was_allocated) {
if (!replace_pl) {
list_del(&pl->node);
kfree(pl);
}