redonkable/alistair23-linux
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netns: Remove __peernet2id_alloc()

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__peernet2id_alloc() was used for both plain lookups and for netns ID
allocations (depending the value of '*alloc'). Let's separate lookups
from allocations instead. That is, integrate the lookup code into
__peernet2id() and make peernet2id_alloc() responsible for allocating
new netns IDs when necessary.

This makes it clear that __peernet2id() doesn't modify the idr and
prepares the code for lockless lookups.

Also, mark the 'net' argument of __peernet2id() as 'const', since we're
modifying this line.

Signed-off-by: Guillaume Nault <gnault@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Guillaume Nault 2020-01-13 22:39:20 +01:00 committed by David S. Miller
parent 621400366b
commit 4905294162
1 changed files with 23 additions and 32 deletions
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55
net/core/net_namespace.c
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@ -211,16 +211,10 @@ static int net_eq_idr(int id, void *net, void *peer)
return 0;
}
/* Should be called with nsid_lock held. If a new id is assigned, the bool alloc
* is set to true, thus the caller knows that the new id must be notified via
* rtnl.
*/
static int __peernet2id_alloc(struct net *net, struct net *peer, bool *alloc)
/* Should be called with nsid_lock held. */
static int __peernet2id(const struct net *net, struct net *peer)
{
int id = idr_for_each(&net->netns_ids, net_eq_idr, peer);
bool alloc_it = *alloc;
*alloc = false;
/* Magic value for id 0. */
if (id == NET_ID_ZERO)
@ -228,23 +222,9 @@ static int __peernet2id_alloc(struct net *net, struct net *peer, bool *alloc)
if (id > 0)
return id;
if (alloc_it) {
id = alloc_netid(net, peer, -1);
*alloc = true;
return id >= 0 ? id : NETNSA_NSID_NOT_ASSIGNED;
}
return NETNSA_NSID_NOT_ASSIGNED;
}
/* should be called with nsid_lock held */
static int __peernet2id(struct net *net, struct net *peer)
{
bool no = false;
return __peernet2id_alloc(net, peer, &no);
}
static void rtnl_net_notifyid(struct net *net, int cmd, int id, u32 portid,
struct nlmsghdr *nlh, gfp_t gfp);
/* This function returns the id of a peer netns. If no id is assigned, one will
@ -252,26 +232,37 @@ static void rtnl_net_notifyid(struct net *net, int cmd, int id, u32 portid,
*/
int peernet2id_alloc(struct net *net, struct net *peer, gfp_t gfp)
{
bool alloc = false, alive = false;
int id;
if (refcount_read(&net->count) == 0)
return NETNSA_NSID_NOT_ASSIGNED;
spin_lock_bh(&net->nsid_lock);
/*
* When peer is obtained from RCU lists, we may race with
id = __peernet2id(net, peer);
if (id >= 0) {
spin_unlock_bh(&net->nsid_lock);
return id;
}
/* When peer is obtained from RCU lists, we may race with
* its cleanup. Check whether it's alive, and this guarantees
* we never hash a peer back to net->netns_ids, after it has
* just been idr_remove()'d from there in cleanup_net().
*/
if (maybe_get_net(peer))
alive = alloc = true;
id = __peernet2id_alloc(net, peer, &alloc);
if (!maybe_get_net(peer)) {
spin_unlock_bh(&net->nsid_lock);
return NETNSA_NSID_NOT_ASSIGNED;
}
id = alloc_netid(net, peer, -1);
spin_unlock_bh(&net->nsid_lock);
if (alloc && id >= 0)
rtnl_net_notifyid(net, RTM_NEWNSID, id, 0, NULL, gfp);
if (alive)
put_net(peer);
put_net(peer);
if (id < 0)
return NETNSA_NSID_NOT_ASSIGNED;
rtnl_net_notifyid(net, RTM_NEWNSID, id, 0, NULL, gfp);
return id;
}
EXPORT_SYMBOL_GPL(peernet2id_alloc);