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Commit 97d0fb23 authored Dec 03, 2018 by NeilBrown Committed by Anna Schumaker Dec 19, 2018

cred: add get_cred_rcu()



Sometimes we want to opportunistically get a
ref to a cred in an rcu_read_lock protected section.
get_task_cred() does this, and NFS does as similar thing
with its own credential structures.
To prepare for NFS converting to use 'struct cred' more
uniformly, define get_cred_rcu(), and use it in
get_task_cred().

Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

parent d89b22d4

include/linux/cred.h

+11 −0

Original line number	Diff line number	Diff line
		@@ -252,6 +252,17 @@ static inline const struct cred get_cred(const struct cred cred)
		return get_new_cred(nonconst_cred);
		}

		static inline const struct cred get_cred_rcu(const struct cred cred)
		{
		struct cred nonconst_cred = (struct cred ) cred;
		if (!cred)
		return NULL;
		if (!atomic_inc_not_zero(&nonconst_cred->usage))
		return NULL;
		validate_creds(cred);
		return cred;
		}

		/**
		* put_cred - Release a reference to a set of credentials
		* @cred: The credentials to release

kernel/cred.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -195,7 +195,7 @@ const struct cred get_task_cred(struct task_struct task)
		do {
		cred = __task_cred((task));
		BUG_ON(!cred);
		} while (!atomic_inc_not_zero(&((struct cred *)cred)->usage));
		} while (!get_cred_rcu(cred));

		rcu_read_unlock();
		return cred;