053c095a82
Contrary to common expectations for an "int" return, these functions
return only a positive value -- if used correctly they cannot even
return 0 because the message header will necessarily be in the skb.
This makes the very common pattern of
if (genlmsg_end(...) < 0) { ... }
be a whole bunch of dead code. Many places also simply do
return nlmsg_end(...);
and the caller is expected to deal with it.
This also commonly (at least for me) causes errors, because it is very
common to write
if (my_function(...))
/* error condition */
and if my_function() does "return nlmsg_end()" this is of course wrong.
Additionally, there's not a single place in the kernel that actually
needs the message length returned, and if anyone needs it later then
it'll be very easy to just use skb->len there.
Remove this, and make the functions void. This removes a bunch of dead
code as described above. The patch adds lines because I did
- return nlmsg_end(...);
+ nlmsg_end(...);
+ return 0;
I could have preserved all the function's return values by returning
skb->len, but instead I've audited all the places calling the affected
functions and found that none cared. A few places actually compared
the return value with <= 0 in dump functionality, but that could just
be changed to < 0 with no change in behaviour, so I opted for the more
efficient version.
One instance of the error I've made numerous times now is also present
in net/phonet/pn_netlink.c in the route_dumpit() function - it didn't
check for <0 or <=0 and thus broke out of the loop every single time.
I've preserved this since it will (I think) have caused the messages to
userspace to be formatted differently with just a single message for
every SKB returned to userspace. It's possible that this isn't needed
for the tools that actually use this, but I don't even know what they
are so couldn't test that changing this behaviour would be acceptable.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
136 lines
2.8 KiB
C
136 lines
2.8 KiB
C
/*
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* Copyright (C) 2007 Red Hat, Inc. All rights reserved.
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*
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* This copyrighted material is made available to anyone wishing to use,
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* modify, copy, or redistribute it subject to the terms and conditions
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* of the GNU General Public License v.2.
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*/
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#include <net/genetlink.h>
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#include <linux/dlm.h>
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#include <linux/dlm_netlink.h>
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#include <linux/gfp.h>
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#include "dlm_internal.h"
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static uint32_t dlm_nl_seqnum;
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static uint32_t listener_nlportid;
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static struct genl_family family = {
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.id = GENL_ID_GENERATE,
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.name = DLM_GENL_NAME,
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.version = DLM_GENL_VERSION,
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};
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static int prepare_data(u8 cmd, struct sk_buff **skbp, size_t size)
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{
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struct sk_buff *skb;
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void *data;
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skb = genlmsg_new(size, GFP_NOFS);
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if (!skb)
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return -ENOMEM;
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/* add the message headers */
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data = genlmsg_put(skb, 0, dlm_nl_seqnum++, &family, 0, cmd);
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if (!data) {
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nlmsg_free(skb);
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return -EINVAL;
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}
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*skbp = skb;
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return 0;
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}
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static struct dlm_lock_data *mk_data(struct sk_buff *skb)
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{
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struct nlattr *ret;
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ret = nla_reserve(skb, DLM_TYPE_LOCK, sizeof(struct dlm_lock_data));
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if (!ret)
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return NULL;
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return nla_data(ret);
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}
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static int send_data(struct sk_buff *skb)
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{
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struct genlmsghdr *genlhdr = nlmsg_data((struct nlmsghdr *)skb->data);
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void *data = genlmsg_data(genlhdr);
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genlmsg_end(skb, data);
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return genlmsg_unicast(&init_net, skb, listener_nlportid);
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}
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static int user_cmd(struct sk_buff *skb, struct genl_info *info)
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{
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listener_nlportid = info->snd_portid;
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printk("user_cmd nlpid %u\n", listener_nlportid);
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return 0;
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}
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static struct genl_ops dlm_nl_ops[] = {
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{
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.cmd = DLM_CMD_HELLO,
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.doit = user_cmd,
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},
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};
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int __init dlm_netlink_init(void)
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{
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return genl_register_family_with_ops(&family, dlm_nl_ops);
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}
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void dlm_netlink_exit(void)
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{
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genl_unregister_family(&family);
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}
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static void fill_data(struct dlm_lock_data *data, struct dlm_lkb *lkb)
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{
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struct dlm_rsb *r = lkb->lkb_resource;
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memset(data, 0, sizeof(struct dlm_lock_data));
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data->version = DLM_LOCK_DATA_VERSION;
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data->nodeid = lkb->lkb_nodeid;
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data->ownpid = lkb->lkb_ownpid;
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data->id = lkb->lkb_id;
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data->remid = lkb->lkb_remid;
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data->status = lkb->lkb_status;
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data->grmode = lkb->lkb_grmode;
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data->rqmode = lkb->lkb_rqmode;
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if (lkb->lkb_ua)
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data->xid = lkb->lkb_ua->xid;
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if (r) {
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data->lockspace_id = r->res_ls->ls_global_id;
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data->resource_namelen = r->res_length;
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memcpy(data->resource_name, r->res_name, r->res_length);
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}
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}
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void dlm_timeout_warn(struct dlm_lkb *lkb)
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{
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struct sk_buff *uninitialized_var(send_skb);
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struct dlm_lock_data *data;
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size_t size;
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int rv;
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size = nla_total_size(sizeof(struct dlm_lock_data)) +
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nla_total_size(0); /* why this? */
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rv = prepare_data(DLM_CMD_TIMEOUT, &send_skb, size);
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if (rv < 0)
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return;
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data = mk_data(send_skb);
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if (!data) {
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nlmsg_free(send_skb);
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return;
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}
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fill_data(data, lkb);
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send_data(send_skb);
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}
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