Skipped unlocks

By sleeping on a new NFS Unlock-On-Close waitqueue, rpc tasks may wait for a lock context's iocounter to reach zero. The rpc waitqueue is only woken when the open_context has the NFS_CONTEXT_UNLOCK flag set in order to mitigate spurious wake-ups for any iocounter reaching zero.

Signed-off-by Benjamin Coddington <[email protected]>

---
 fs/nfs/client.c           |  1 +
 fs/nfs/pagelist.c         | 34 +++++++++++++++++++++++++++++++++-
 include/linux/nfs_fs.h    |  1 +
 include/linux/nfs_fs_sb.h |  1 +
 include/linux/nfs_page.h  |  1 +
 5 files changed, 37 insertions(+), 1 deletion(-)

fs/nfs/client.c +1 -0

index 91a8d610ba0f..c335c6dce285 100644
@@ -218,6 +218,7 @@ static void nfs_cb_idr_remove_locked(struct nfs_client *clp)
 static void pnfs_init_server(struct nfs_server *server)
 {
 	rpc_init_wait_queue(&server->roc_rpcwaitq, "pNFS ROC");
+	rpc_init_wait_queue(&server->uoc_rpcwaitq, "NFS UOC");
 }
 
 #else

fs/nfs/pagelist.c +33 -1

index 6e629b856a00..3487d215cee1 100644
@@ -115,6 +115,35 @@ nfs_iocounter_wait(struct nfs_lock_context *l_ctx)
 			TASK_KILLABLE);
 }
 
+/**
+ * nfs_async_iocounter_wait - wait on a rpc_waitqueue for I/O
+ * to complete
+ * @task: the rpc_task that should wait
+ * @l_ctx: nfs_lock_context with io_counter to check
+ *
+ * Returns true if there is outstanding I/O to wait on and the
+ * task has been put to sleep.
+ */
+bool
+nfs_async_iocounter_wait(struct rpc_task *task, struct nfs_lock_context *l_ctx)
+{
+	struct inode *inode = d_inode(l_ctx->open_context->dentry);
+	bool ret = false;
+
+	if (atomic_read(&l_ctx->io_count) > 0) {
+		rpc_sleep_on(&NFS_SERVER(inode)->uoc_rpcwaitq, task, NULL);
+		ret = true;
+	}
+
+	if (atomic_read(&l_ctx->io_count) == 0) {
+		rpc_wake_up_queued_task(&NFS_SERVER(inode)->uoc_rpcwaitq, task);
+		ret = false;
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(nfs_async_iocounter_wait);
+
 /*
  * nfs_page_group_lock - lock the head of the page group
  * @req - request in group that is to be locked

@@ -398,8 +427,11 @@ static void nfs_clear_request(struct nfs_page *req)
 		req->wb_page = NULL;
 	}
 	if (l_ctx != NULL) {
-		if (atomic_dec_and_test(&l_ctx->io_count))
+		if (atomic_dec_and_test(&l_ctx->io_count)) {
 			wake_up_atomic_t(&l_ctx->io_count);
+			if (test_bit(NFS_CONTEXT_UNLOCK, &ctx->flags))
+				rpc_wake_up(&NFS_SERVER(d_inode(ctx->dentry))->uoc_rpcwaitq);
+		}
 		nfs_put_lock_context(l_ctx);
 		req->wb_lock_context = NULL;
 	}

include/linux/nfs_fs.h +1 -0

index f1da8c8dd473..3ce3e42beead 100644
@@ -76,6 +76,7 @@ struct nfs_open_context {
 #define NFS_CONTEXT_ERROR_WRITE		(0)
 #define NFS_CONTEXT_RESEND_WRITES	(1)
 #define NFS_CONTEXT_BAD			(2)
+#define NFS_CONTEXT_UNLOCK	(3)
 	int error;
 
 	struct list_head list;

include/linux/nfs_fs_sb.h +1 -0

index b34097c67848..2a70f34dffe8 100644
@@ -222,6 +222,7 @@ struct nfs_server {
 	u32			mountd_version;
 	unsigned short		mountd_port;
 	unsigned short		mountd_protocol;
+	struct rpc_wait_queue	uoc_rpcwaitq;
 };
 
 /* Server capabilities */

include/linux/nfs_page.h +0 -0

index 957049f72290..81105e473750 100644

NFS would enjoy the ability to modify the behavior of the NLM client's unlock RPC task in order to delay the transmission of the unlock until IO that was submitted under that lock has completed. This ability can ensure that the NLM client will always complete the transmission of an unlock even if the waiting caller has been interrupted with fatal signal.

For this purpose, a pointer to a struct nlmclnt_operations can be assigned in a nfs_module's nfs_rpc_ops that will install those nlmclnt_operations on the nlm_host. The struct nlmclnt_operations defines three callback operations that will be used in a following patch:

nlmclnt_alloc_call - used to call back after a successful allocation of
a struct nlm_rqst in nlmclnt_proc().

nlmclnt_unlock_prepare - used to call back during NLM unlock's
rpc_call_prepare. The NLM client defers calling rpc_call_start() until this callback returns false.

nlmclnt_release_call - used to call back when the NLM client's struct
nlm_rqst is freed.

Signed-off-by Benjamin Coddington <[email protected]>

---
 fs/lockd/clntlock.c         |  1 +
 fs/lockd/clntproc.c         | 26 +++++++++++++++++++++++++-
 fs/nfs/client.c             |  1 +
 fs/nfs/nfs3proc.c           |  2 +-
 fs/nfs/proc.c               |  2 +-
 include/linux/lockd/bind.h  | 24 ++++++++++++++++++++++--
 include/linux/lockd/lockd.h |  2 ++
 include/linux/nfs_xdr.h     |  1 +
 8 files changed, 54 insertions(+), 5 deletions(-)

fs/lockd/clntlock.c +1 -0

index 41e491b8e5d7..27d577dbe51a 100644
@@ -69,6 +69,7 @@ struct nlm_host *nlmclnt_init(const struct nlmclnt_initdata *nlm_init)
 	if (host->h_rpcclnt == NULL && nlm_bind_host(host) == NULL)
 		goto out_nobind;
 
+	host->h_nlmclnt_ops = nlm_init->nlmclnt_ops;
 	return host;
 out_nobind:
 	nlmclnt_release_host(host);

fs/lockd/clntproc.c +25 -1

index 112952037933..066ac313ae5c 100644
@@ -150,17 +150,22 @@ static void nlmclnt_release_lockargs(struct nlm_rqst *req)
  * @host: address of a valid nlm_host context representing the NLM server
  * @cmd: fcntl-style file lock operation to perform
  * @fl: address of arguments for the lock operation
+ * @data: address of data to be sent to callback operations
  *
  */
-int nlmclnt_proc(struct nlm_host *host, int cmd, struct file_lock *fl)
+int nlmclnt_proc(struct nlm_host *host, int cmd, struct file_lock *fl, void *data)
 {
 	struct nlm_rqst		*call;
 	int			status;
+	const struct nlmclnt_operations *nlmclnt_ops = host->h_nlmclnt_ops;
 
 	call = nlm_alloc_call(host);
 	if (call == NULL)
 		return -ENOMEM;
 
+	if (nlmclnt_ops && nlmclnt_ops->nlmclnt_alloc_call)
+		nlmclnt_ops->nlmclnt_alloc_call(data);
+
 	nlmclnt_locks_init_private(fl, host);
 	if (!fl->fl_u.nfs_fl.owner) {
 		/* lockowner allocation has failed */

@@ -169,6 +174,7 @@ int nlmclnt_proc(struct nlm_host *host, int cmd, struct file_lock *fl)
 	}
 	/* Set up the argument struct */
 	nlmclnt_setlockargs(call, fl);
+	call->a_callback_data = data;
 
 	if (IS_SETLK(cmd) || IS_SETLKW(cmd)) {
 		if (fl->fl_type != F_UNLCK) {

@@ -214,8 +220,12 @@ struct nlm_rqst *nlm_alloc_call(struct nlm_host *host)
 
 void nlmclnt_release_call(struct nlm_rqst *call)
 {
+	const struct nlmclnt_operations *nlmclnt_ops = call->a_host->h_nlmclnt_ops;
+
 	if (!atomic_dec_and_test(&call->a_count))
 		return;
+	if (nlmclnt_ops && nlmclnt_ops->nlmclnt_release_call)
+		nlmclnt_ops->nlmclnt_release_call(call->a_callback_data);
 	nlmclnt_release_host(call->a_host);
 	nlmclnt_release_lockargs(call);
 	kfree(call);

@@ -687,6 +697,19 @@ nlmclnt_unlock(struct nlm_rqst *req, struct file_lock *fl)
 	return status;
 }
 
+static void nlmclnt_unlock_prepare(struct rpc_task *task, void *data)
+{
+	struct nlm_rqst	*req = data;
+	const struct nlmclnt_operations *nlmclnt_ops = req->a_host->h_nlmclnt_ops;
+	bool defer_call = false;
+
+	if (nlmclnt_ops && nlmclnt_ops->nlmclnt_unlock_prepare)
+		defer_call = nlmclnt_ops->nlmclnt_unlock_prepare(task, req->a_callback_data);
+
+	if (!defer_call)
+		rpc_call_start(task);
+}
+
 static void nlmclnt_unlock_callback(struct rpc_task *task, void *data)
 {
 	struct nlm_rqst	*req = data;

@@ -720,6 +743,7 @@ static void nlmclnt_unlock_callback(struct rpc_task *task, void *data)
 }
 
 static const struct rpc_call_ops nlmclnt_unlock_ops = {
+	.rpc_call_prepare = nlmclnt_unlock_prepare,
 	.rpc_call_done = nlmclnt_unlock_callback,
 	.rpc_release = nlmclnt_rpc_release,
 };

fs/nfs/client.c +1 -0

index c335c6dce285..f4c022e57541 100644
@@ -536,6 +536,7 @@ static int nfs_start_lockd(struct nfs_server *server)
 		.noresvport	= server->flags & NFS_MOUNT_NORESVPORT ?
 					1 : 0,
 		.net		= clp->cl_net,
+		.nlmclnt_ops 	= clp->cl_nfs_mod->rpc_ops->nlmclnt_ops,
 	};
 
 	if (nlm_init.nfs_version > 3)

fs/nfs/nfs3proc.c +1 -1

index dc925b531f32..03b3c3de28f1 100644
@@ -870,7 +870,7 @@ nfs3_proc_lock(struct file *filp, int cmd, struct file_lock *fl)
 {
 	struct inode *inode = file_inode(filp);
 
-	return nlmclnt_proc(NFS_SERVER(inode)->nlm_host, cmd, fl);
+	return nlmclnt_proc(NFS_SERVER(inode)->nlm_host, cmd, fl, NULL);
 }
 
 static int nfs3_have_delegation(struct inode *inode, fmode_t flags)

fs/nfs/proc.c +1 -1

index b7bca8303989..9872cf676a50 100644
@@ -638,7 +638,7 @@ nfs_proc_lock(struct file *filp, int cmd, struct file_lock *fl)
 {
 	struct inode *inode = file_inode(filp);
 
-	return nlmclnt_proc(NFS_SERVER(inode)->nlm_host, cmd, fl);
+	return nlmclnt_proc(NFS_SERVER(inode)->nlm_host, cmd, fl, NULL);
 }
 
 /* Helper functions for NFS lock bounds checking */

include/linux/lockd/bind.h +22 -2

index 140edab64446..05728396a1a1 100644
@@ -18,6 +18,7 @@
 
 /* Dummy declarations */
 struct svc_rqst;
+struct rpc_task;
 
 /*
  * This is the set of functions for lockd->nfsd communication

@@ -43,6 +44,7 @@ struct nlmclnt_initdata {
 	u32			nfs_version;
 	int			noresvport;
 	struct net		*net;
+	const struct nlmclnt_operations	*nlmclnt_ops;
 };
 
 /*

@@ -52,8 +54,26 @@ struct nlmclnt_initdata {
 extern struct nlm_host *nlmclnt_init(const struct nlmclnt_initdata *nlm_init);
 extern void	nlmclnt_done(struct nlm_host *host);
 
-extern int	nlmclnt_proc(struct nlm_host *host, int cmd,
-					struct file_lock *fl);
+/*
+ * NLM client operations provide a means to modify RPC processing of NLM
+ * requests.  Callbacks receive a pointer to data passed into the call to
+ * nlmclnt_proc().
+ */
+struct nlmclnt_operations {
+	/* Called on successful allocation of nlm_rqst, use for allocation or
+	 * reference counting. */
+	void (*nlmclnt_alloc_call)(void *);
+
+	/* Called in rpc_task_prepare for unlock.  A return value of true
+	 * indicates the callback has put the task to sleep on a waitqueue
+	 * and NLM should not call rpc_call_start(). */
+	bool (*nlmclnt_unlock_prepare)(struct rpc_task*, void *);
+
+	/* Called when the nlm_rqst is freed, callbacks should clean up here */
+	void (*nlmclnt_release_call)(void *);
+};
+
+extern int	nlmclnt_proc(struct nlm_host *host, int cmd, struct file_lock *fl, void *data);
 extern int	lockd_up(struct net *net);
 extern void	lockd_down(struct net *net);
 

include/linux/lockd/lockd.h +2 -0

index c15373894a42..01c38992150d 100644
@@ -69,6 +69,7 @@ struct nlm_host {
 	char			*h_addrbuf;	/* address eyecatcher */
 	struct net		*net;		/* host net */
 	char			nodename[UNX_MAXNODENAME + 1];
+	const struct nlmclnt_operations	*h_nlmclnt_ops;	/* Callback ops for NLM users */
 };
 
 /*

@@ -142,6 +143,7 @@ struct nlm_rqst {
 	struct nlm_block *	a_block;
 	unsigned int		a_retries;	/* Retry count */
 	u8			a_owner[NLMCLNT_OHSIZE];
+	void *	a_callback_data; /* sent to nlmclnt_operations callbacks */
 };
 
 /*

include/linux/nfs_xdr.h +0 -0

index 348f7c158084..3279ab2e1fee 100644

NFS attempts to wait for read and write completion before unlocking in order to ensure that the data returned was protected by the lock. When this waiting is interrupted by a signal, the unlock may be skipped, and messages similar to the following are seen in the kernel ring buffer:

[20.167876] Leaked locks on dev=0x0:0x2b ino=0x8dd4c3:
[20.168286] POSIX: fl_owner=ffff880078b06940 fl_flags=0x1 fl_type=0x0 fl_pid=20183
[20.168727] POSIX: fl_owner=ffff880078b06680 fl_flags=0x1 fl_type=0x0 fl_pid=20185

For NFSv3, the missing unlock will cause the server to refuse conflicting locks indefinitely. For NFSv4, the leftover lock will be removed by the server after the lease timeout.

This patch fixes this issue by skipping the usual wait in nfs_iocounter_wait if the FL_CLOSE flag is set when signaled. Instead, the wait happens in the unlock RPC task on the NFS UOC rpc_waitqueue.

For NFSv3, use lockd's new nlmclnt_operations along with nfs_async_iocounter_wait to defer NLM's unlock task until the lock context's iocounter reaches zero.

For NFSv4, call nfs_async_iocounter_wait() directly from unlock's current rpc_call_prepare.

Signed-off-by Benjamin Coddington <[email protected]>

---
 fs/nfs/file.c     | 10 +++++-----
 fs/nfs/nfs3proc.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++++++++-
 fs/nfs/nfs4proc.c |  9 +++++++++
 3 files changed, 67 insertions(+), 6 deletions(-)

fs/nfs/file.c +5 -5

index a490f45df4db..df695f52bb9d 100644
@@ -697,14 +697,14 @@ do_unlk(struct file *filp, int cmd, struct file_lock *fl, int is_local)
 	if (!IS_ERR(l_ctx)) {
 		status = nfs_iocounter_wait(l_ctx);
 		nfs_put_lock_context(l_ctx);
-		if (status < 0)
+		/*  NOTE: special case
+		 * 	If we're signalled while cleaning up locks on process exit, we
+		 * 	still need to complete the unlock.
+		 */
+		if (status < 0 && !(fl->fl_flags & FL_CLOSE))
 			return status;
 	}
 
-	/* NOTE: special case
-	 * 	If we're signalled while cleaning up locks on process exit, we
-	 * 	still need to complete the unlock.
-	 */
 	/*
 	 * Use local locking if mounted with "-onolock" or with appropriate
 	 * "-olocal_lock="

fs/nfs/nfs3proc.c +53 -1

index 03b3c3de28f1..ce06ae0a25cf 100644
@@ -865,12 +865,63 @@ static void nfs3_proc_commit_setup(struct nfs_commit_data *data, struct rpc_mess
 	msg->rpc_proc = &nfs3_procedures[NFS3PROC_COMMIT];
 }
 
+void nfs3_nlm_alloc_call(void *data)
+{
+	struct nfs_lock_context *l_ctx = data;
+	if (l_ctx && test_bit(NFS_CONTEXT_UNLOCK, &l_ctx->open_context->flags)) {
+		get_nfs_open_context(l_ctx->open_context);
+		nfs_get_lock_context(l_ctx->open_context);
+	}
+}
+
+bool nfs3_nlm_unlock_prepare(struct rpc_task *task, void *data)
+{
+	struct nfs_lock_context *l_ctx = data;
+	if (l_ctx && test_bit(NFS_CONTEXT_UNLOCK, &l_ctx->open_context->flags))
+		return nfs_async_iocounter_wait(task, l_ctx);
+	return false;
+
+}
+
+void nfs3_nlm_release_call(void *data)
+{
+	struct nfs_lock_context *l_ctx = data;
+	struct nfs_open_context *ctx;
+	if (l_ctx && test_bit(NFS_CONTEXT_UNLOCK, &l_ctx->open_context->flags)) {
+		ctx = l_ctx->open_context;
+		nfs_put_lock_context(l_ctx);
+		put_nfs_open_context(ctx);
+	}
+}
+
+const struct nlmclnt_operations nlmclnt_fl_close_lock_ops = {
+	.nlmclnt_alloc_call = nfs3_nlm_alloc_call,
+	.nlmclnt_unlock_prepare = nfs3_nlm_unlock_prepare,
+	.nlmclnt_release_call = nfs3_nlm_release_call,
+};
+
 static int
 nfs3_proc_lock(struct file *filp, int cmd, struct file_lock *fl)
 {
 	struct inode *inode = file_inode(filp);
+	struct nfs_lock_context *l_ctx = NULL;
+	struct nfs_open_context *ctx = nfs_file_open_context(filp);
+	int status;
 
-	return nlmclnt_proc(NFS_SERVER(inode)->nlm_host, cmd, fl, NULL);
+	if (fl->fl_flags & FL_CLOSE) {
+		l_ctx = nfs_get_lock_context(ctx);
+		if (IS_ERR(l_ctx))
+			l_ctx = NULL;
+		else
+			set_bit(NFS_CONTEXT_UNLOCK, &ctx->flags);
+	}
+
+	status = nlmclnt_proc(NFS_SERVER(inode)->nlm_host, cmd, fl, l_ctx);
+
+	if (l_ctx)
+		nfs_put_lock_context(l_ctx);
+
+	return status;
 }
 
 static int nfs3_have_delegation(struct inode *inode, fmode_t flags)

@@ -921,6 +972,7 @@ const struct nfs_rpc_ops nfs_v3_clientops = {
 	.dir_inode_ops	= &nfs3_dir_inode_operations,
 	.file_inode_ops	= &nfs3_file_inode_operations,
 	.file_ops	= &nfs_file_operations,
+	.nlmclnt_ops	= &nlmclnt_fl_close_lock_ops,
 	.getroot	= nfs3_proc_get_root,
 	.submount	= nfs_submount,
 	.try_mount	= nfs_try_mount,

fs/nfs/nfs4proc.c +7 -0

index 91f88bfbbe79..171ed89d243f 100644
@@ -5906,6 +5906,7 @@ struct nfs4_unlockdata {
 	struct nfs_locku_res res;
 	struct nfs4_lock_state *lsp;
 	struct nfs_open_context *ctx;
+	struct nfs_lock_context *l_ctx;
 	struct file_lock fl;
 	struct nfs_server *server;
 	unsigned long timestamp;

@@ -5930,6 +5931,7 @@ static struct nfs4_unlockdata *nfs4_alloc_unlockdata(struct file_lock *fl,
 	atomic_inc(&lsp->ls_count);
 	/* Ensure we don't close file until we're done freeing locks! */
 	p->ctx = get_nfs_open_context(ctx);
+	p->l_ctx = nfs_get_lock_context(ctx);
 	memcpy(&p->fl, fl, sizeof(p->fl));
 	p->server = NFS_SERVER(inode);
 	return p;

@@ -5940,6 +5942,7 @@ static void nfs4_locku_release_calldata(void *data)
 	struct nfs4_unlockdata *calldata = data;
 	nfs_free_seqid(calldata->arg.seqid);
 	nfs4_put_lock_state(calldata->lsp);
+	nfs_put_lock_context(calldata->l_ctx);
 	put_nfs_open_context(calldata->ctx);
 	kfree(calldata);
 }

@@ -5981,6 +5984,10 @@ static void nfs4_locku_prepare(struct rpc_task *task, void *data)
 {
 	struct nfs4_unlockdata *calldata = data;
 
+	if (test_bit(NFS_CONTEXT_UNLOCK, &calldata->l_ctx->open_context->flags) &&
+		nfs_async_iocounter_wait(task, calldata->l_ctx))
+		return;
+
 	if (nfs_wait_on_sequence(calldata->arg.seqid, task) != 0)
 		goto out_wait;
 	nfs4_stateid_copy(&calldata->arg.stateid, &calldata->lsp->ls_stateid);