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From: NeilBrown <neilb@suse.com>
To: "J. Bruce Fields" <bfields@fieldses.org>,
	Chuck Lever <chuck.lever@oracle.com>,
	Jeff Layton <jlayton@kernel.org>,
	Trond Myklebust <trond.myklebust@hammerspace.com>,
	Anna Schumaker <anna.schumaker@netapp.com>
Cc: Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
	linux-kernel@vger.kernel.org
Subject: [PATCH 02/23] cred: add get_cred_rcu()
Date: Wed, 07 Nov 2018 15:12:30 +1100	[thread overview]
Message-ID: <154156395078.24086.348735293443892342.stgit@noble> (raw)
In-Reply-To: <154156285766.24086.14262073575778354276.stgit@noble>

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>
---
 include/linux/cred.h |   11 +++++++++++
 kernel/cred.c        |    2 +-
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/include/linux/cred.h b/include/linux/cred.h
index f1085767e1b3..48979fcb95cf 100644
--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -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
diff --git a/kernel/cred.c b/kernel/cred.c
index 0b3ac72bd717..ba60162249e8 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -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;



  parent reply	other threads:[~2018-11-07  4:13 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-07  4:12 [PATCH 00/23 - V4] NFS: Remove generic RPC credentials NeilBrown
2018-11-07  4:12 ` [PATCH 06/23] SUNRPC: remove groupinfo from struct auth_cred NeilBrown
2018-11-07  4:12 ` [PATCH 03/23] cred: export get_task_cred() NeilBrown
2018-11-07  4:12 ` [PATCH 04/23] cred: allow get_cred() and put_cred() to be given NULL NeilBrown
2018-11-07  4:12 ` [PATCH 05/23] SUNRPC: add 'struct cred *' to auth_cred and rpc_cred NeilBrown
2018-11-07  4:12 ` [PATCH 01/23] cred: add cred_fscmp() for comparing creds NeilBrown
2018-11-07  4:12 ` NeilBrown [this message]
2018-11-07  4:12 ` [PATCH 21/23] SUNRPC: remove crbind rpc_cred operation NeilBrown
2018-11-07  4:12 ` [PATCH 11/23] SUNRPC: discard RPC_DO_ROOTOVERRIDE() NeilBrown
2018-11-07  4:12 ` [PATCH 22/23] SUNRPC: simplify auth_unix NeilBrown
2018-11-07 15:19   ` Chuck Lever
2018-11-08  1:41     ` NeilBrown
2018-11-08 15:54       ` Chuck Lever
2018-11-09  0:45         ` NeilBrown
2018-11-07  4:12 ` [PATCH 18/23] NFS: struct nfs_open_dir_context: convert rpc_cred pointer to cred NeilBrown
2018-11-07  4:12 ` [PATCH 20/23] SUNRPC: remove generic cred code NeilBrown
2018-11-07  4:12 ` [PATCH 23/23] SUNRPC discard cr_uid from struct rpc_cred NeilBrown
2018-11-07  4:12 ` [PATCH 10/23] NFSv4: don't require lock for get_renew_cred or get_machine_cred NeilBrown
2018-11-07  4:12 ` [PATCH 19/23] NFS/NFSD/SUNRPC: replace generic creds with 'struct cred' NeilBrown
2018-11-07  4:12 ` [PATCH 12/23] NFS/SUNRPC: don't lookup machine credential until rpcauth_bindcred() NeilBrown
2018-11-07  4:12 ` [PATCH 17/23] NFS: change access cache to use 'struct cred' NeilBrown
2018-11-07  4:12 ` [PATCH 07/23] SUNRPC: remove uid and gid from struct auth_cred NeilBrown
2018-11-07  4:12 ` [PATCH 16/23] SUNRPC: remove RPCAUTH_AUTH_NO_CRKEY_TIMEOUT NeilBrown
2018-11-07  4:12 ` [PATCH 09/23] NFSv4: add cl_root_cred for use when machine cred is not available NeilBrown
2018-11-07  4:12 ` [PATCH 14/23] SUNRPC: add side channel to use non-generic cred for rpc call NeilBrown
2018-11-07  4:12 ` [PATCH 13/23] SUNRPC: introduce RPC_TASK_NULLCREDS to request auth_none NeilBrown
2018-11-07  4:12 ` [PATCH 08/23] SUNRPC: remove machine_cred field from struct auth_cred NeilBrown
2018-11-07  4:12 ` [PATCH 15/23] NFS: move credential expiry tracking out of SUNRPC into NFS NeilBrown
2018-11-29 23:19 ` [PATCH 00/23 - V4] NFS: Remove generic RPC credentials NeilBrown
2018-11-30 19:39   ` Schumaker, Anna
2018-12-03  0:30 [PATCH 00/23 - V5] " NeilBrown
2018-12-03  0:30 ` [PATCH 02/23] cred: add get_cred_rcu() NeilBrown

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