Re: [PATCH RFC 5/6] net: Generic resolver backend

On Wed, Sep 14, 2016 at 2:49 AM, Thomas Graf [off-list ref] wrote:

On 09/09/16 at 04:19pm, Tom Herbert wrote:

quoted

diff --git a/net/core/resolver.c b/net/core/resolver.c
new file mode 100644
index 0000000..61b36c5
--- /dev/null
+++ b/net/core/resolver.c

@@ -0,0 +1,267 @@
+#include <linux/errno.h>
+#include <linux/ip.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/netlink.h>
+#include <linux/skbuff.h>
+#include <linux/socket.h>
+#include <linux/types.h>
+#include <linux/vmalloc.h>
+#include <net/checksum.h>
+#include <net/ip.h>
+#include <net/ip6_fib.h>
+#include <net/lwtunnel.h>
+#include <net/protocol.h>
+#include <net/resolver.h>
+#include <uapi/linux/ila.h>

This include list could be stripped down a bit. ila, lwt, fib, ...

quoted

+
+static struct net_rslv_ent *net_rslv_new_ent(struct net_rslv *nrslv,
+                                          void *key)

Comment above that net_rslv_get_lock() must be held?

quoted

+{
+     struct net_rslv_ent *nrent;
+     int err;
+
+     nrent = kzalloc(sizeof(*nrent) + nrslv->obj_size, GFP_KERNEL);

GFP_ATOMIC since you typically hold net_rslv_get_lock() spinlock?

quoted

+     if (!nrent)
+             return ERR_PTR(-EAGAIN);
+
+     /* Key is always at beginning of object data */
+     memcpy(nrent->object, key, nrslv->params.key_len);
+
+     /* Initialize user data */
+     if (nrslv->rslv_init)
+             nrslv->rslv_init(nrslv, nrent);
+
+     /* Put in hash table */
+     err = rhashtable_lookup_insert_fast(&nrslv->rhash_table,
+                                         &nrent->node, nrslv->params);
+     if (err)
+             return ERR_PTR(err);
+
+     if (nrslv->timeout) {
+             /* Schedule timeout for resolver */
+             INIT_DELAYED_WORK(&nrent->timeout_work, net_rslv_delayed_work);

Should this be done before inserting into rhashtable?

Adding to the table and setting delayed work are done under a lock so
I think it should be okay. I'll add a comment to the function that the
lock is held.

quoted

+             schedule_delayed_work(&nrent->timeout_work, nrslv->timeout);
+     }
+
+     nrent->nrslv = nrslv;

Same here.  net_rslv_cancel_all_delayed_work() walking the rhashtable could
see ->nrslv as NULL.

I'll move it up, but net_rslv_cancel_all_delayed_work is only called
when we're destroying the table so it would be a bug in the higher
layer if it is both destroying the table and adding entries at the
same time.

Thanks,
Tom