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sunrpc: add a get_rpccred_rcu inline 

Sometimes we might have a RCU managed credential pointer and don't want
to use locking to handle it. Add a function that will take a reference
to the cred iff the refcount is not already zero. Callers can dereference
the pointer under the rcu_read_lock and use that function to take a
reference only if the cred is not on its way to destruction.

Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
This commit is contained in:
Jeff Layton 2016-04-21 20:51:56 -04:00 committed by Anna Schumaker
parent c065d229e3
commit 62dbef2ae4
1 changed files with 18 additions and 0 deletions
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18
include/linux/sunrpc/auth.h
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@ -206,5 +206,23 @@ struct rpc_cred * get_rpccred(struct rpc_cred *cred)
return cred;
}
/**
* get_rpccred_rcu - get a reference to a cred using rcu-protected pointer
* @cred: cred of which to take a reference
*
* In some cases, we may have a pointer to a credential to which we
* want to take a reference, but don't already have one. Because these
* objects are freed using RCU, we can access the cr_count while its
* on its way to destruction and only take a reference if it's not already
* zero.
*/
static inline struct rpc_cred *
get_rpccred_rcu(struct rpc_cred *cred)
{
if (atomic_inc_not_zero(&cred->cr_count))
return cred;
return NULL;
}
#endif /* __KERNEL__ */
#endif /* _LINUX_SUNRPC_AUTH_H */