[PATCH net-next v2 3/5] bpf: consolidate bpf_prog_put{,_rcu} dismantle paths

From: Daniel Borkmann
Date: Thu Oct 29 2015 - 09:59:37 EST


We currently have duplicated cleanup code in bpf_prog_put() and
bpf_prog_put_rcu() cleanup paths. Back then we decided that it was
not worth it to make it a common helper called by both, but with
the recent addition of resource charging, we could have avoided
the fix in commit ac00737f4e81 ("bpf: Need to call bpf_prog_uncharge_memlock
from bpf_prog_put") if we would have had only a single, common path.
We can simplify it further by assigning aux->prog only once during
allocation time.

Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Acked-by: Alexei Starovoitov <ast@xxxxxxxxxx>
---
kernel/bpf/core.c | 3 ++-
kernel/bpf/syscall.c | 15 +++++----------
2 files changed, 7 insertions(+), 11 deletions(-)

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 8086471..334b1bd 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -92,6 +92,7 @@ struct bpf_prog *bpf_prog_alloc(unsigned int size, gfp_t gfp_extra_flags)

fp->pages = size / PAGE_SIZE;
fp->aux = aux;
+ fp->aux->prog = fp;

return fp;
}
@@ -116,6 +117,7 @@ struct bpf_prog *bpf_prog_realloc(struct bpf_prog *fp_old, unsigned int size,

memcpy(fp, fp_old, fp_old->pages * PAGE_SIZE);
fp->pages = size / PAGE_SIZE;
+ fp->aux->prog = fp;

/* We keep fp->aux from fp_old around in the new
* reallocated structure.
@@ -726,7 +728,6 @@ void bpf_prog_free(struct bpf_prog *fp)
struct bpf_prog_aux *aux = fp->aux;

INIT_WORK(&aux->work, bpf_prog_free_deferred);
- aux->prog = fp;
schedule_work(&aux->work);
}
EXPORT_SYMBOL_GPL(bpf_prog_free);
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 3fff82c..d7783cb 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -513,7 +513,7 @@ static void bpf_prog_uncharge_memlock(struct bpf_prog *prog)
free_uid(user);
}

-static void __prog_put_rcu(struct rcu_head *rcu)
+static void __prog_put_common(struct rcu_head *rcu)
{
struct bpf_prog_aux *aux = container_of(rcu, struct bpf_prog_aux, rcu);

@@ -525,19 +525,14 @@ static void __prog_put_rcu(struct rcu_head *rcu)
/* version of bpf_prog_put() that is called after a grace period */
void bpf_prog_put_rcu(struct bpf_prog *prog)
{
- if (atomic_dec_and_test(&prog->aux->refcnt)) {
- prog->aux->prog = prog;
- call_rcu(&prog->aux->rcu, __prog_put_rcu);
- }
+ if (atomic_dec_and_test(&prog->aux->refcnt))
+ call_rcu(&prog->aux->rcu, __prog_put_common);
}

void bpf_prog_put(struct bpf_prog *prog)
{
- if (atomic_dec_and_test(&prog->aux->refcnt)) {
- free_used_maps(prog->aux);
- bpf_prog_uncharge_memlock(prog);
- bpf_prog_free(prog);
- }
+ if (atomic_dec_and_test(&prog->aux->refcnt))
+ __prog_put_common(&prog->aux->rcu);
}
EXPORT_SYMBOL_GPL(bpf_prog_put);

--
1.9.3

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