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flowcache: Avoid OOM condition under preasure 

We can hit an OOM condition if we are under presure because
we can not free the entries in gc_list fast enough. So add
a counter for the not yet freed entries in the gc_list and
refuse new allocations if the value is too high.

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
This commit is contained in:
Steffen Klassert 2016-02-22 10:40:07 +01:00
parent aac8d3c282
commit 6ad3122a08
2 changed files with 14 additions and 1 deletions
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1
include/net/netns/xfrm.h
View File

@ -80,6 +80,7 @@ struct netns_xfrm {
struct flow_cache flow_cache_global;
atomic_t flow_cache_genid;
struct list_head flow_cache_gc_list;
atomic_t flow_cache_gc_count;
spinlock_t flow_cache_gc_lock;
struct work_struct flow_cache_gc_work;
struct work_struct flow_cache_flush_work;

14
net/core/flow.c
View File

@ -92,8 +92,11 @@ static void flow_cache_gc_task(struct work_struct *work)
list_splice_tail_init(&xfrm->flow_cache_gc_list, &gc_list);
spin_unlock_bh(&xfrm->flow_cache_gc_lock);
list_for_each_entry_safe(fce, n, &gc_list, u.gc_list)
list_for_each_entry_safe(fce, n, &gc_list, u.gc_list) {
flow_entry_kill(fce, xfrm);
atomic_dec(&xfrm->flow_cache_gc_count);
WARN_ON(atomic_read(&xfrm->flow_cache_gc_count) < 0);
}
}
static void flow_cache_queue_garbage(struct flow_cache_percpu *fcp,
@ -101,6 +104,7 @@ static void flow_cache_queue_garbage(struct flow_cache_percpu *fcp,
struct netns_xfrm *xfrm)
{
if (deleted) {
atomic_add(deleted, &xfrm->flow_cache_gc_count);
fcp->hash_count -= deleted;
spin_lock_bh(&xfrm->flow_cache_gc_lock);
list_splice_tail(gc_list, &xfrm->flow_cache_gc_list);
@ -232,6 +236,13 @@ flow_cache_lookup(struct net *net, const struct flowi *key, u16 family, u8 dir,
if (fcp->hash_count > fc->high_watermark)
flow_cache_shrink(fc, fcp);
if (fcp->hash_count > 2 * fc->high_watermark ||
atomic_read(&net->xfrm.flow_cache_gc_count) > fc->high_watermark) {
atomic_inc(&net->xfrm.flow_cache_genid);
flo = ERR_PTR(-ENOBUFS);
goto ret_object;
}
fle = kmem_cache_alloc(flow_cachep, GFP_ATOMIC);
if (fle) {
fle->net = net;
@ -446,6 +457,7 @@ int flow_cache_init(struct net *net)
INIT_WORK(&net->xfrm.flow_cache_gc_work, flow_cache_gc_task);
INIT_WORK(&net->xfrm.flow_cache_flush_work, flow_cache_flush_task);
mutex_init(&net->xfrm.flow_flush_sem);
atomic_set(&net->xfrm.flow_cache_gc_count, 0);
fc->hash_shift = 10;
fc->low_watermark = 2 * flow_cache_hash_size(fc);