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NFS Force Unmounting

RFC Superseded Joshua Watt 2 participants 11 messages Nov 10, 2017 – Nov 13, 2017

Subsystems (3)
Networking NFS client NFS server

v2 of 4 Superseded Latest is v4 →

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Joshua Watt

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#0 lore raw

v2 cover NFS Force Unmounting

Reworked patch set in response to Neil's comments. This patchset requires his patch as a prerequisite:

    http://www.spinics.net/lists/linux-nfs/msg66341.html

These patches implements behavior that allows a failed server to be "cut off" (e.g. all RPC tasks fail with -EIO) with the following sequence of operations:

mount -o remount,serverfailed
umount -f

In the event you want to try and recover the server, you can remount to remove the serverfailed status:

mount -o remount,noserverfailed

Although, I'm not sure what implications that might have for data loss.

For the most part I think it is pretty straight forward, the only thing I am unsure about is the last two patches. This behavior is really useful in my use case (where the server disappears) as it prevents the umount -f from blocking while trying to send some DESTROY_SESSION messages to the client (as long as you mounted with nosharecache).

Version 1 can be found at:

    http://www.spinics.net/lists/linux-nfs/msg66348.html

Thanks in advance for the reviews and comments

Joshua Watt (7):
SUNRPC: Add flag to kill new tasks
SUNRPC: Expose kill_new_tasks in debugfs
SUNRPC: Simplify client shutdown
NFS: Add mount flags mask
NFS: Add serverfailed mount option
NFS: Propagate NFS_MOUNT_UNSHARED to clients
NFS: Propagate operations to unshared clients

 fs/nfs/client.c                |  9 +++-
 fs/nfs/inode.c                 |  6 +++
 fs/nfs/internal.h              |  1 +
 fs/nfs/nfs3client.c            |  2 +
 fs/nfs/nfs4client.c            |  4 ++
 fs/nfs/super.c                 | 98 ++++++++++++++++++++++++++----------------
 include/linux/nfs_fs_sb.h      |  1 +
 include/linux/sunrpc/clnt.h    |  1 +
 include/uapi/linux/nfs_mount.h |  1 +
 net/sunrpc/clnt.c              | 11 ++---
 net/sunrpc/debugfs.c           |  4 ++
 net/sunrpc/sched.c             |  3 ++
 12 files changed, 95 insertions(+), 46 deletions(-)
Signature · 1 line
2.13.6
author
#1 lore raw

RFC v2 1/7 SUNRPC: Add flag to kill new tasks

The flag causes any new tasks that are queued to exit immediately with -EIO instead of executing. This will allow clients (particularly NFS) to prevents these task from delaying shutdown of the RPC session longer than necessary.

Signed-off-by Joshua Watt <[email protected]>
---
 include/linux/sunrpc/clnt.h | 1 +
 net/sunrpc/clnt.c           | 3 ---
 net/sunrpc/sched.c          | 3 +++
 3 files changed, 4 insertions(+), 3 deletions(-)
include/linux/sunrpc/clnt.h +1 -0
index 71c237e8240e..94f4e464de1b 100644
@@ -54,6 +54,7 @@ struct rpc_clnt {
 				cl_noretranstimeo: 1,/* No retransmit timeouts */
 				cl_autobind : 1,/* use getport() */
 				cl_chatty   : 1;/* be verbose */
+	bool			cl_kill_new_tasks;	/* Kill all new tasks */
 
 	struct rpc_rtt *	cl_rtt;		/* RTO estimator data */
 	const struct rpc_timeout *cl_timeout;	/* Timeout strategy */
net/sunrpc/clnt.c +0 -3
index df4ecb042ebe..aa64cd667696 100644
@@ -818,9 +818,6 @@ void rpc_killall_tasks(struct rpc_clnt *clnt)
 {
 	struct rpc_task	*rovr;
 
-
-	if (list_empty(&clnt->cl_tasks))
-		return;
 	dprintk("RPC:       killing all tasks for client %p\n", clnt);
 	/*
 	 * Spin lock all_tasks to prevent changes...
net/sunrpc/sched.c +3 -0
index 0cc83839c13c..2c9fe5c0319b 100644
@@ -748,6 +748,9 @@ static void __rpc_execute(struct rpc_task *task)
 	dprintk("RPC: %5u __rpc_execute flags=0x%x\n",
 			task->tk_pid, task->tk_flags);
 
+	if (task->tk_client->cl_kill_new_tasks)
+		rpc_exit(task, -EIO);
+
 	WARN_ON_ONCE(RPC_IS_QUEUED(task));
 	if (RPC_IS_QUEUED(task))
 		return;
Signature · 1 line
2.13.6
author
#2 lore raw

RFC v2 2/7 SUNRPC: Expose kill_new_tasks in debugfs

In reply to Joshua Watt
Signed-off-by Joshua Watt <[email protected]>
---
 net/sunrpc/debugfs.c | 4 ++++
 1 file changed, 4 insertions(+)
net/sunrpc/debugfs.c +4 -0
index e980d2a493de..2ca67b681c1e 100644
@@ -160,6 +160,10 @@ rpc_clnt_debugfs_register(struct rpc_clnt *clnt)
 	if (!debugfs_create_symlink("xprt", clnt->cl_debugfs, name))
 		goto out_err;
 
+	if (!debugfs_create_bool("kill_new_tasks", S_IRUSR | S_IWUSR,
+				 clnt->cl_debugfs, &clnt->cl_kill_new_tasks))
+		goto out_err;
+
 	return;
 out_err:
 	debugfs_remove_recursive(clnt->cl_debugfs);
Signature · 1 line
2.13.6
author
#3 lore raw

RFC v2 3/7 SUNRPC: Simplify client shutdown

In reply to Joshua Watt

Use the flag to kill all new tasks when shutting down instead of repeatedly killing all the pending tasks.

Signed-off-by Joshua Watt <[email protected]>
---
 net/sunrpc/clnt.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)
net/sunrpc/clnt.c +3 -5
index aa64cd667696..b00793c30518 100644
@@ -850,11 +850,9 @@ void rpc_shutdown_client(struct rpc_clnt *clnt)
 			clnt->cl_program->name,
 			rcu_dereference(clnt->cl_xprt)->servername);
 
-	while (!list_empty(&clnt->cl_tasks)) {
-		rpc_killall_tasks(clnt);
-		wait_event_timeout(destroy_wait,
-			list_empty(&clnt->cl_tasks), 1*HZ);
-	}
+	clnt->cl_kill_new_tasks = true;
+	rpc_killall_tasks(clnt);
+	wait_event(destroy_wait, list_empty(&clnt->cl_tasks));
 
 	rpc_release_client(clnt);
 }
Signature · 1 line
2.13.6
author
#4 lore raw

RFC v2 4/7 NFS: Add mount flags mask

In reply to Joshua Watt

Track which mount options were specified so that only the flags that actually changed will be updated when remounting.

Signed-off-by Joshua Watt <[email protected]>
---
 fs/nfs/internal.h |  1 +
 fs/nfs/super.c    | 58 ++++++++++++++++++++++++++-----------------------------
 2 files changed, 28 insertions(+), 31 deletions(-)
fs/nfs/internal.h +1 -0
index f9a4a5524bd5..f4308b730c1c 100644
@@ -90,6 +90,7 @@ struct nfs_client_initdata {
  */
 struct nfs_parsed_mount_data {
 	int			flags;
+	int			flags_mask;
 	unsigned int		rsize, wsize;
 	unsigned int		timeo, retrans;
 	unsigned int		acregmin, acregmax,
fs/nfs/super.c +27 -31

108 lines not on this page · raw message

Signature · 1 line
2.13.6
author
#5 lore raw

RFC v2 5/7 NFS: Add serverfailed mount option

In reply to Joshua Watt

Specifying the serverfailed mount option causes all subsequent RPC tasks that are queued to fail with -EIO instead of timing out. For example, if a server has disappeared, the sequence:

mount -o remount,serverfailed
umount -f

will ensure that all pending I/O requests are cancelled, and any new requests will also fail. In the event that the server returns, the flag can be removed with a remount:

mount -o remount,noserverfailed

Although bringing the server back may result in a loss of data

Signed-off-by Joshua Watt <[email protected]>
---
 fs/nfs/inode.c                 |  6 ++++++
 fs/nfs/super.c                 | 30 +++++++++++++++++++++++++-----
 include/uapi/linux/nfs_mount.h |  1 +
 3 files changed, 32 insertions(+), 5 deletions(-)
fs/nfs/inode.c +6 -0
index 134d9f560240..55b7cd40508d 100644
@@ -723,6 +723,12 @@ static void nfs_readdirplus_parent_cache_hit(struct dentry *dentry)
 
 static bool nfs_need_revalidate_inode(struct inode *inode)
 {
+	/* If the server has failed, it is not going to respond, so don't try
+	 * and revalidated (otherwise, the serverfailed flag can't be cleared by
+	 * a remount)
+	 */
+	if (NFS_SERVER(inode)->flags & NFS_MOUNT_SERVERFAILED)
+		return false;
 	if (NFS_I(inode)->cache_validity &
 			(NFS_INO_INVALID_ATTR|NFS_INO_INVALID_LABEL))
 		return true;
fs/nfs/super.c +25 -5
index 777a0cc22704..bca38e1cdd85 100644
@@ -90,6 +90,7 @@ enum {
 	Opt_resvport, Opt_noresvport,
 	Opt_fscache, Opt_nofscache,
 	Opt_migration, Opt_nomigration,
+	Opt_serverfailed, Opt_noserverfailed,
 
 	/* Mount options that take integer arguments */
 	Opt_port,

@@ -151,6 +152,8 @@ static const match_table_t nfs_mount_option_tokens = {
 	{ Opt_nofscache, "nofsc" },
 	{ Opt_migration, "migration" },
 	{ Opt_nomigration, "nomigration" },
+	{ Opt_serverfailed, "serverfailed" },
+	{ Opt_noserverfailed, "noserverfailed" },
 
 	{ Opt_port, "port=%s" },
 	{ Opt_rsize, "rsize=%s" },

@@ -637,6 +640,7 @@ static void nfs_show_mount_options(struct seq_file *m, struct nfs_server *nfss,
 		{ NFS_MOUNT_NORDIRPLUS, ",nordirplus", "" },
 		{ NFS_MOUNT_UNSHARED, ",nosharecache", "" },
 		{ NFS_MOUNT_NORESVPORT, ",noresvport", "" },
+		{ NFS_MOUNT_SERVERFAILED, ",serverfailed", "" },
 		{ 0, NULL, NULL }
 	};
 	const struct proc_nfs_info *nfs_infop;

@@ -1330,6 +1334,11 @@ static int nfs_parse_mount_options(char *raw,
 		case Opt_nomigration:
 			mnt->options &= ~NFS_OPTION_MIGRATION;
 			break;
+		case Opt_serverfailed:
+		case Opt_noserverfailed:
+			set_flag(mnt, NFS_MOUNT_SERVERFAILED,
+				 token == Opt_serverfailed);
+			break;
 
 		/*
 		 * options that take numeric values

@@ -2192,6 +2201,8 @@ static int nfs_validate_text_mount_data(void *options,
 	return -EINVAL;
 }
 
+#define NFS_REMOUNT_CHANGE_FLAGS (NFS_MOUNT_SERVERFAILED)
+
 #define NFS_REMOUNT_CMP_FLAGMASK ~(NFS_MOUNT_INTR \
 		| NFS_MOUNT_SECURE \
 		| NFS_MOUNT_TCP \

@@ -2200,7 +2211,8 @@ static int nfs_validate_text_mount_data(void *options,
 		| NFS_MOUNT_NONLM \
 		| NFS_MOUNT_BROKEN_SUID \
 		| NFS_MOUNT_STRICTLOCK \
-		| NFS_MOUNT_LEGACY_INTERFACE)
+		| NFS_MOUNT_LEGACY_INTERFACE \
+		| NFS_REMOUNT_CHANGE_FLAGS)
 
 #define NFS_MOUNT_CMP_FLAGMASK (NFS_REMOUNT_CMP_FLAGMASK & \
 		~(NFS_MOUNT_UNSHARED | NFS_MOUNT_NORESVPORT))

@@ -2209,12 +2221,15 @@ static int
 nfs_compare_and_set_remount_data(struct nfs_server *nfss,
 				 struct nfs_parsed_mount_data *data)
 {
+	int changed_flags_mask = data->flags_mask & NFS_REMOUNT_CHANGE_FLAGS;
+	struct rpc_clnt *cl = nfss->client;
+
 	if ((data->flags ^ nfss->flags) & NFS_REMOUNT_CMP_FLAGMASK ||
 	    data->rsize != nfss->rsize ||
 	    data->wsize != nfss->wsize ||
 	    data->version != nfss->nfs_client->rpc_ops->version ||
 	    data->minorversion != nfss->nfs_client->cl_minorversion ||
-	    !nfs_auth_info_match(&data->auth_info, nfss->client->cl_auth->au_flavor) ||
+	    !nfs_auth_info_match(&data->auth_info, cl->cl_auth->au_flavor) ||
 	    data->acregmin != nfss->acregmin / HZ ||
 	    data->acregmax != nfss->acregmax / HZ ||
 	    data->acdirmin != nfss->acdirmin / HZ ||

@@ -2225,13 +2240,16 @@ nfs_compare_and_set_remount_data(struct nfs_server *nfss,
 			  (struct sockaddr *)&nfss->nfs_client->cl_addr))
 		return -EINVAL;
 
-	if (data->retrans != nfss->client->cl_timeout->to_retries ||
-	    data->timeo != (10U * nfss->client->cl_timeout->to_initval / HZ)) {
+	/* Update flags */
+	nfss->flags = (nfss->flags & ~changed_flags_mask) |
+		(data->flags & changed_flags_mask);
+
+	if (data->retrans != cl->cl_timeout->to_retries ||
+	    data->timeo != (10U * cl->cl_timeout->to_initval / HZ)) {
 		/* Note that this will affect all mounts from the same server,
 		 * that use the same protocol.  The timeouts are always forced
 		 * to be the same.
 		 */
-		struct rpc_clnt *cl = nfss->client;
 		if (cl->cl_timeout != &cl->cl_timeout_default)
 			memcpy(&cl->cl_timeout_default, cl->cl_timeout,
 			       sizeof(struct rpc_timeout));

@@ -2239,6 +2257,8 @@ nfs_compare_and_set_remount_data(struct nfs_server *nfss,
 		cl->cl_timeout_default.to_initval = data->timeo * HZ / 10U;
 	}
 
+	cl->cl_kill_new_tasks = !!(nfss->flags & NFS_MOUNT_SERVERFAILED);
+
 	return 0;
 }
include/uapi/linux/nfs_mount.h +1 -0
index e44e00616ab5..8ad931cdca20 100644
@@ -74,5 +74,6 @@ struct nfs_mount_data {
 
 #define NFS_MOUNT_LOCAL_FLOCK	0x100000
 #define NFS_MOUNT_LOCAL_FCNTL	0x200000
+#define NFS_MOUNT_SERVERFAILED	0x400000
 
 #endif
Signature · 1 line
2.13.6
#6 lore raw

Re: [RFC v2 5/7] NFS: Add serverfailed mount option

Quoted 10 lines · Joshua Watt

Specifying the serverfailed mount option causes all subsequent RPC tasks that are queued to fail with -EIO instead of timing out. For example, if a server has disappeared, the sequence:

mount -o remount,serverfailed
umount -f

Quoted 7 lines

will ensure that all pending I/O requests are cancelled, and any new requests will also fail. In the event that the server returns, the flag can be removed with a remount:

mount -o remount,noserverfailed

Although bringing the server back may result in a loss of data

Hi Joshua, interesting work!

A couple of things I'm wondering:

1. Does this also change the serverfailed setting on submounts (ie mounts that the kernel did when traversing an NFSv4 referral or when going from the server's pseudofs into a real fs). These need to be unmounted first before the parent mount can be unmounted, and in the latter case they would all be backed by the same stuck NFS server.

2. If there is a hanging sync(2), does the umount -f unstick it? That seems relevant for Neil's "make shutdown reliable" use case. I would like a stuck NFS mount not to result in local file system corruption, if possible, during a hard shutdown.

Quoted 148 lines
Signed-off-by Joshua Watt <[email protected]>

---

fs/nfs/inode.c                 |  6 ++++++
fs/nfs/super.c                 | 30 +++++++++++++++++++++++++-----
include/uapi/linux/nfs_mount.h |  1 +
3 files changed, 32 insertions(+), 5 deletions(-)
fs/nfs/inode.c +6 -0
index 134d9f560240..55b7cd40508d 100644
@@ -723,6 +723,12 @@ static void nfs_readdirplus_parent_cache_hit(struct dentry *dentry)
 
 static bool nfs_need_revalidate_inode(struct inode *inode)
 {
+	/* If the server has failed, it is not going to respond, so don't try
+	 * and revalidated (otherwise, the serverfailed flag can't be cleared by
+	 * a remount)
+	 */
+	if (NFS_SERVER(inode)->flags & NFS_MOUNT_SERVERFAILED)
+		return false;
 	if (NFS_I(inode)->cache_validity &
 			(NFS_INO_INVALID_ATTR|NFS_INO_INVALID_LABEL))
 		return true;
fs/nfs/super.c +25 -5
index 777a0cc22704..bca38e1cdd85 100644
@@ -90,6 +90,7 @@ enum {
 	Opt_resvport, Opt_noresvport,
 	Opt_fscache, Opt_nofscache,
 	Opt_migration, Opt_nomigration,
+	Opt_serverfailed, Opt_noserverfailed,
 
 	/* Mount options that take integer arguments */
 	Opt_port,

@@ -151,6 +152,8 @@ static const match_table_t nfs_mount_option_tokens = {
 	{ Opt_nofscache, "nofsc" },
 	{ Opt_migration, "migration" },
 	{ Opt_nomigration, "nomigration" },
+	{ Opt_serverfailed, "serverfailed" },
+	{ Opt_noserverfailed, "noserverfailed" },
 
 	{ Opt_port, "port=%s" },
 	{ Opt_rsize, "rsize=%s" },

@@ -637,6 +640,7 @@ static void nfs_show_mount_options(struct seq_file *m, struct nfs_server *nfss,
 		{ NFS_MOUNT_NORDIRPLUS, ",nordirplus", "" },
 		{ NFS_MOUNT_UNSHARED, ",nosharecache", "" },
 		{ NFS_MOUNT_NORESVPORT, ",noresvport", "" },
+		{ NFS_MOUNT_SERVERFAILED, ",serverfailed", "" },
 		{ 0, NULL, NULL }
 	};
 	const struct proc_nfs_info *nfs_infop;

@@ -1330,6 +1334,11 @@ static int nfs_parse_mount_options(char *raw,
 		case Opt_nomigration:
 			mnt->options &= ~NFS_OPTION_MIGRATION;
 			break;
+		case Opt_serverfailed:
+		case Opt_noserverfailed:
+			set_flag(mnt, NFS_MOUNT_SERVERFAILED,
+				 token == Opt_serverfailed);
+			break;
 
 		/*
 		 * options that take numeric values

@@ -2192,6 +2201,8 @@ static int nfs_validate_text_mount_data(void *options,
 	return -EINVAL;
 }
 
+#define NFS_REMOUNT_CHANGE_FLAGS (NFS_MOUNT_SERVERFAILED)
+
 #define NFS_REMOUNT_CMP_FLAGMASK ~(NFS_MOUNT_INTR \
 		| NFS_MOUNT_SECURE \
 		| NFS_MOUNT_TCP \

@@ -2200,7 +2211,8 @@ static int nfs_validate_text_mount_data(void *options,
 		| NFS_MOUNT_NONLM \
 		| NFS_MOUNT_BROKEN_SUID \
 		| NFS_MOUNT_STRICTLOCK \
-		| NFS_MOUNT_LEGACY_INTERFACE)
+		| NFS_MOUNT_LEGACY_INTERFACE \
+		| NFS_REMOUNT_CHANGE_FLAGS)
 
 #define NFS_MOUNT_CMP_FLAGMASK (NFS_REMOUNT_CMP_FLAGMASK & \
 		~(NFS_MOUNT_UNSHARED | NFS_MOUNT_NORESVPORT))

@@ -2209,12 +2221,15 @@ static int
 nfs_compare_and_set_remount_data(struct nfs_server *nfss,
 				 struct nfs_parsed_mount_data *data)
 {
+	int changed_flags_mask = data->flags_mask & NFS_REMOUNT_CHANGE_FLAGS;
+	struct rpc_clnt *cl = nfss->client;
+
 	if ((data->flags ^ nfss->flags) & NFS_REMOUNT_CMP_FLAGMASK ||
 	    data->rsize != nfss->rsize ||
 	    data->wsize != nfss->wsize ||
 	    data->version != nfss->nfs_client->rpc_ops->version ||
 	    data->minorversion != nfss->nfs_client->cl_minorversion ||
-	    !nfs_auth_info_match(&data->auth_info, nfss->client->cl_auth->au_flavor) ||
+	    !nfs_auth_info_match(&data->auth_info, cl->cl_auth->au_flavor) ||
 	    data->acregmin != nfss->acregmin / HZ ||
 	    data->acregmax != nfss->acregmax / HZ ||
 	    data->acdirmin != nfss->acdirmin / HZ ||

@@ -2225,13 +2240,16 @@ nfs_compare_and_set_remount_data(struct nfs_server *nfss,
 			  (struct sockaddr *)&nfss->nfs_client->cl_addr))
 		return -EINVAL;
 
-	if (data->retrans != nfss->client->cl_timeout->to_retries ||
-	    data->timeo != (10U * nfss->client->cl_timeout->to_initval / HZ)) {
+	/* Update flags */
+	nfss->flags = (nfss->flags & ~changed_flags_mask) |
+		(data->flags & changed_flags_mask);
+
+	if (data->retrans != cl->cl_timeout->to_retries ||
+	    data->timeo != (10U * cl->cl_timeout->to_initval / HZ)) {
 		/* Note that this will affect all mounts from the same server,
 		 * that use the same protocol.  The timeouts are always forced
 		 * to be the same.
 		 */
-		struct rpc_clnt *cl = nfss->client;
 		if (cl->cl_timeout != &cl->cl_timeout_default)
 			memcpy(&cl->cl_timeout_default, cl->cl_timeout,
 			       sizeof(struct rpc_timeout));

@@ -2239,6 +2257,8 @@ nfs_compare_and_set_remount_data(struct nfs_server *nfss,
 		cl->cl_timeout_default.to_initval = data->timeo * HZ / 10U;
 	}
 
+	cl->cl_kill_new_tasks = !!(nfss->flags & NFS_MOUNT_SERVERFAILED);
+
 	return 0;
 }
include/uapi/linux/nfs_mount.h +1 -0
index e44e00616ab5..8ad931cdca20 100644
@@ -74,5 +74,6 @@ struct nfs_mount_data {
 
 #define NFS_MOUNT_LOCAL_FLOCK	0x100000
 #define NFS_MOUNT_LOCAL_FCNTL	0x200000
+#define NFS_MOUNT_SERVERFAILED	0x400000
 
 #endif
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Chuck Lever

author
#7 lore raw

Re: [RFC v2 5/7] NFS: Add serverfailed mount option

Quoted 24 lines · Chuck Lever
Quoted 18 lines

On Nov 10, 2017, at 5:37 PM, Joshua Watt <[email protected]> wrote:

Specifying the serverfailed mount option causes all subsequent RPC tasks
that are queued to fail with -EIO instead of timing out. For example, if
a server has disappeared, the sequence:

mount -o remount,serverfailed
umount -f

will ensure that all pending I/O requests are cancelled, and any new
requests will also fail. In the event that the server returns, the flag
can be removed with a remount:

Quoted 3 lines

mount -o remount,noserverfailed

Although bringing the server back may result in a loss of data

Hi Joshua, interesting work!

Quoted 8 lines

A couple of things I'm wondering:

1. Does this also change the serverfailed setting on submounts (ie mounts that the kernel did when traversing an NFSv4 referral or when going from the server's pseudofs into a real fs). These need to be unmounted first before the parent mount can be unmounted, and in the latter case they would all be backed by the same stuck NFS server.

I don't honestly know, but I will find out. Our use case doens't deal with either of those cases much.

Quoted 6 lines

2. If there is a hanging sync(2), does the umount -f unstick it? That seems relevant for Neil's "make shutdown reliable" use case. I would like a stuck NFS mount not to result in local file system corruption, if possible, during a hard shutdown.

Several previous posts have aluded to calling "umount -f" repeatedly to get a "stuck" NFS mount to actually unmount. This patch set is effectively a way of automating that process. More formally, the sequence of commands:

mount PATH -o remount,serverfailed
umount -f PATH

Is closely approximated by:

while(1)

     umount2(PATH, MNT_FORCE);

from userspace.

In retrospect, I think that the "umount -f" shouldn't be required after
remount: If the serverfailed mount option is specified it should also kill all pending RPCs. A umount -f is undesirable, because you may not actually want to (potentially) unmount the file system just to cancel the RPCs.

More directly to your question: I don't honestly know if this can "unstick" a hanging sync(2). If repeatedly calling umount -f will unstick it, then these patches will exhibit the same behavior. I will continue to do some research on this, but if anyone knows the answer they might be able to chime in.

Could you clarify on what you mean by a stuck NFS mount not resulting in local filesystem corruption? I'm not sure I undertsand well enough to follow that comment.

Thanks for the feedback

Quoted 178 lines
Quoted 172 lines
Signed-off-by Joshua Watt <[email protected]>

---

fs/nfs/inode.c                 |  6 ++++++
fs/nfs/super.c                 | 30 +++++++++++++++++++++++++-----
include/uapi/linux/nfs_mount.h |  1 +
3 files changed, 32 insertions(+), 5 deletions(-)
fs/nfs/inode.c +1 -0
index 134d9f560240..55b7cd40508d 100644
@@ -723,6 +723,12 @@ static void
 nfs_readdirplus_parent_cache_hit(struct dentry *dentry)
 
 static bool nfs_need_revalidate_inode(struct inode *inode)
 {
+	/* If the server has failed, it is not going to respond,

so don't try

fs/nfs/inode.c +1 -0
+	 * and revalidated (otherwise, the serverfailed flag can't

be cleared by

fs/nfs/inode.c +4 -0
+	 * a remount)
+	 */
+	if (NFS_SERVER(inode)->flags & NFS_MOUNT_SERVERFAILED)
+		return false;

	if (NFS_I(inode)->cache_validity &
			(NFS_INO_INVALID_ATTR|NFS_INO_INVALID_LABEL))
		return true;
fs/nfs/super.c +3 -0
index 777a0cc22704..bca38e1cdd85 100644
@@ -90,6 +90,7 @@ enum {
 	Opt_resvport, Opt_noresvport,
 	Opt_fscache, Opt_nofscache,
 	Opt_migration, Opt_nomigration,
+	Opt_serverfailed, Opt_noserverfailed,
 
 	/* Mount options that take integer arguments */
 	Opt_port,

@@ -151,6 +152,8 @@ static const match_table_t
 nfs_mount_option_tokens = {
 	{ Opt_nofscache, "nofsc" },
 	{ Opt_migration, "migration" },
 	{ Opt_nomigration, "nomigration" },
+	{ Opt_serverfailed, "serverfailed" },
+	{ Opt_noserverfailed, "noserverfailed" },
 
 	{ Opt_port, "port=%s" },

	{ Opt_rsize, "rsize=%s" },
fs/nfs/super.c +1 -0
@@ -637,6 +640,7 @@ static void nfs_show_mount_options(struct
 seq_file *m, struct nfs_server *nfss,
 		{ NFS_MOUNT_NORDIRPLUS, ",nordirplus", "" },
 		{ NFS_MOUNT_UNSHARED, ",nosharecache", "" },
 		{ NFS_MOUNT_NORESVPORT, ",noresvport", "" },
+		{ NFS_MOUNT_SERVERFAILED, ",serverfailed", "" },
 		{ 0, NULL, NULL }
 	};

	const struct proc_nfs_info *nfs_infop;
fs/nfs/super.c +5 -0
@@ -1330,6 +1334,11 @@ static int nfs_parse_mount_options(char
 *raw,
 		case Opt_nomigration:
 			mnt->options &= ~NFS_OPTION_MIGRATION;
 			break;
+		case Opt_serverfailed:
+		case Opt_noserverfailed:
+			set_flag(mnt, NFS_MOUNT_SERVERFAILED,
+				 token == Opt_serverfailed);
+			break;
 
 		/*

* options that take numeric values

fs/nfs/super.c +2 -0
@@ -2192,6 +2201,8 @@ static int nfs_validate_text_mount_data(void
 *options,
 	return -EINVAL;
 }
 
+#define NFS_REMOUNT_CHANGE_FLAGS (NFS_MOUNT_SERVERFAILED)
+
 #define NFS_REMOUNT_CMP_FLAGMASK ~(NFS_MOUNT_INTR \
 		| NFS_MOUNT_SECURE \

		| NFS_MOUNT_TCP \
fs/nfs/super.c +2 -1
@@ -2200,7 +2211,8 @@ static int nfs_validate_text_mount_data(void
 *options,
 		| NFS_MOUNT_NONLM \
 		| NFS_MOUNT_BROKEN_SUID \
 		| NFS_MOUNT_STRICTLOCK \
-		| NFS_MOUNT_LEGACY_INTERFACE)
+		| NFS_MOUNT_LEGACY_INTERFACE \
+		| NFS_REMOUNT_CHANGE_FLAGS)
 
 #define NFS_MOUNT_CMP_FLAGMASK (NFS_REMOUNT_CMP_FLAGMASK & \

~(NFS_MOUNT_UNSHARED | NFS_MOUNT_NORESVPORT))

fs/nfs/super.c +3 -1
@@ -2209,12 +2221,15 @@ static int
 nfs_compare_and_set_remount_data(struct nfs_server *nfss,
 				 struct nfs_parsed_mount_data *data)
 {
+	int changed_flags_mask = data->flags_mask &
 NFS_REMOUNT_CHANGE_FLAGS;
+	struct rpc_clnt *cl = nfss->client;
+
 	if ((data->flags ^ nfss->flags) & NFS_REMOUNT_CMP_FLAGMASK ||
 	    data->rsize != nfss->rsize ||
 	    data->wsize != nfss->wsize ||
 	    data->version != nfss->nfs_client->rpc_ops->version ||
 	    data->minorversion != nfss->nfs_client->cl_minorversion ||
-	    !nfs_auth_info_match(&data->auth_info, nfss->client-
Quoted 1 line

cl_auth->au_flavor) ||

fs/nfs/super.c +1 -0
+	    !nfs_auth_info_match(&data->auth_info, cl->cl_auth-
Quoted 1 line

au_flavor) ||

	    data->acregmin != nfss->acregmin / HZ ||
	    data->acregmax != nfss->acregmax / HZ ||
	    data->acdirmin != nfss->acdirmin / HZ ||
fs/nfs/super.c +0 -1
@@ -2225,13 +2240,16 @@ nfs_compare_and_set_remount_data(struct
 nfs_server *nfss,
 			  (struct sockaddr *)&nfss->nfs_client-
 >cl_addr))
 		return -EINVAL;
 
-	if (data->retrans != nfss->client->cl_timeout->to_retries

||

fs/nfs/super.c +0 -1
-	    data->timeo != (10U * nfss->client->cl_timeout-
Quoted 1 line

to_initval / HZ)) {

fs/nfs/super.c +6 -0
+	/* Update flags */
+	nfss->flags = (nfss->flags & ~changed_flags_mask) |
+		(data->flags & changed_flags_mask);
+
+	if (data->retrans != cl->cl_timeout->to_retries ||
+	    data->timeo != (10U * cl->cl_timeout->to_initval /

HZ)) {
		/* Note that this will affect all mounts from the same
server,
		 * that use the same protocol.  The timeouts are always
forced
		 * to be the same.
		 */
fs/nfs/super.c +0 -1
-		struct rpc_clnt *cl = nfss->client;

		if (cl->cl_timeout != &cl->cl_timeout_default)
			memcpy(&cl->cl_timeout_default, cl->cl_timeout,
			       sizeof(struct rpc_timeout));
fs/nfs/super.c +2 -0
@@ -2239,6 +2257,8 @@ nfs_compare_and_set_remount_data(struct
 nfs_server *nfss,
 		cl->cl_timeout_default.to_initval = data->timeo * HZ /
 10U;
 	}
 
+	cl->cl_kill_new_tasks = !!(nfss->flags &
 NFS_MOUNT_SERVERFAILED);
+

	return 0;
}
include/uapi/linux/nfs_mount.h +1 -0
index e44e00616ab5..8ad931cdca20 100644
@@ -74,5 +74,6 @@ struct nfs_mount_data {
 
 #define NFS_MOUNT_LOCAL_FLOCK	0x100000
 #define NFS_MOUNT_LOCAL_FCNTL	0x200000
+#define NFS_MOUNT_SERVERFAILED	0x400000
 
 #endif
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#8 lore raw

Re: [RFC v2 5/7] NFS: Add serverfailed mount option

Quoted 74 lines · Joshua Watt
Quoted 24 lines · Chuck Lever
Quoted 18 lines

On Nov 10, 2017, at 5:37 PM, Joshua Watt <[email protected]> wrote:

Specifying the serverfailed mount option causes all subsequent RPC tasks
that are queued to fail with -EIO instead of timing out. For example, if
a server has disappeared, the sequence:

mount -o remount,serverfailed
umount -f

will ensure that all pending I/O requests are cancelled, and any new
requests will also fail. In the event that the server returns, the flag
can be removed with a remount:

Quoted 3 lines

mount -o remount,noserverfailed

Although bringing the server back may result in a loss of data

Hi Joshua, interesting work!

Quoted 8 lines

A couple of things I'm wondering:

1. Does this also change the serverfailed setting on submounts (ie mounts that the kernel did when traversing an NFSv4 referral or when going from the server's pseudofs into a real fs). These need to be unmounted first before the parent mount can be unmounted, and in the latter case they would all be backed by the same stuck NFS server.

I don't honestly know, but I will find out. Our use case doens't deal with either of those cases much.

Quoted 6 lines

2. If there is a hanging sync(2), does the umount -f unstick it? That seems relevant for Neil's "make shutdown reliable" use case. I would like a stuck NFS mount not to result in local file system corruption, if possible, during a hard shutdown.

Several previous posts have aluded to calling "umount -f" repeatedly to get a "stuck" NFS mount to actually unmount. This patch set is effectively a way of automating that process. More formally, the sequence of commands:

mount PATH -o remount,serverfailed
umount -f PATH

Is closely approximated by:

while(1)

    umount2(PATH, MNT_FORCE);

from userspace.

In retrospect, I think that the "umount -f" shouldn't be required after
remount: If the serverfailed mount option is specified it should also kill all pending RPCs. A umount -f is undesirable, because you may not actually want to (potentially) unmount the file system just to cancel the RPCs.

More directly to your question: I don't honestly know if this can "unstick" a hanging sync(2). If repeatedly calling umount -f will unstick it, then these patches will exhibit the same behavior. I will continue to do some research on this, but if anyone knows the answer they might be able to chime in.

Quoted 3 lines

Could you clarify on what you mean by a stuck NFS mount not resulting in local filesystem corruption? I'm not sure I undertsand well enough to follow that comment.

During my own development work, I often cause NFS mount failures that leave an NFS mount deadlocked or otherwise stuck. It behaves as if the server is not responding.

If I'm sloppy, I will sometimes be looking at kernel source code trying to debug the problem and may modify one or more local files before then rebooting the client to unstick the NFS mount.

In these cases I use "echo b > /proc/sysrq-trigger". Sometimes I type "sync" first, and that will often hang, then I have to pop the "reset" button. In some rare instances, after the client restarts, there can be file system corruption on the client's local file systems (say, empty files that used to have content), or for example missing entries in /var/log/messages.

I could be wrong, but I attribute this to the sync(2) hanging on the stuck NFS mount before it can flush dirty data in the local file systems on the client.

I suspect this is not uncommon during typical NFS usage scenarios, and it could be one cause of a stuck shutdown when an NFS mount is stuck.

So what I'm wondering is if you remount "soft,timeo=1" and let the NFS mount unstick itself, is that enough to allow an already running sync(2) to complete? It probably is.

Quoted 177 lines

Thanks for the feedback

Quoted 175 lines
Quoted 172 lines
Signed-off-by Joshua Watt <[email protected]>

---

fs/nfs/inode.c                 |  6 ++++++
fs/nfs/super.c                 | 30 +++++++++++++++++++++++++-----
include/uapi/linux/nfs_mount.h |  1 +
3 files changed, 32 insertions(+), 5 deletions(-)
fs/nfs/inode.c +1 -0
index 134d9f560240..55b7cd40508d 100644
@@ -723,6 +723,12 @@ static void
 nfs_readdirplus_parent_cache_hit(struct dentry *dentry)
 
 static bool nfs_need_revalidate_inode(struct inode *inode)
 {
+	/* If the server has failed, it is not going to respond,

so don't try

fs/nfs/inode.c +1 -0
+	 * and revalidated (otherwise, the serverfailed flag can't

be cleared by

fs/nfs/inode.c +4 -0
+	 * a remount)
+	 */
+	if (NFS_SERVER(inode)->flags & NFS_MOUNT_SERVERFAILED)
+		return false;

	if (NFS_I(inode)->cache_validity &
			(NFS_INO_INVALID_ATTR|NFS_INO_INVALID_LABEL))
		return true;
fs/nfs/super.c +3 -0
index 777a0cc22704..bca38e1cdd85 100644
@@ -90,6 +90,7 @@ enum {
 	Opt_resvport, Opt_noresvport,
 	Opt_fscache, Opt_nofscache,
 	Opt_migration, Opt_nomigration,
+	Opt_serverfailed, Opt_noserverfailed,
 
 	/* Mount options that take integer arguments */
 	Opt_port,

@@ -151,6 +152,8 @@ static const match_table_t
 nfs_mount_option_tokens = {
 	{ Opt_nofscache, "nofsc" },
 	{ Opt_migration, "migration" },
 	{ Opt_nomigration, "nomigration" },
+	{ Opt_serverfailed, "serverfailed" },
+	{ Opt_noserverfailed, "noserverfailed" },
 
 	{ Opt_port, "port=%s" },

	{ Opt_rsize, "rsize=%s" },
fs/nfs/super.c +1 -0
@@ -637,6 +640,7 @@ static void nfs_show_mount_options(struct
 seq_file *m, struct nfs_server *nfss,
 		{ NFS_MOUNT_NORDIRPLUS, ",nordirplus", "" },
 		{ NFS_MOUNT_UNSHARED, ",nosharecache", "" },
 		{ NFS_MOUNT_NORESVPORT, ",noresvport", "" },
+		{ NFS_MOUNT_SERVERFAILED, ",serverfailed", "" },
 		{ 0, NULL, NULL }
 	};

	const struct proc_nfs_info *nfs_infop;
fs/nfs/super.c +5 -0
@@ -1330,6 +1334,11 @@ static int nfs_parse_mount_options(char
 *raw,
 		case Opt_nomigration:
 			mnt->options &= ~NFS_OPTION_MIGRATION;
 			break;
+		case Opt_serverfailed:
+		case Opt_noserverfailed:
+			set_flag(mnt, NFS_MOUNT_SERVERFAILED,
+				 token == Opt_serverfailed);
+			break;
 
 		/*

* options that take numeric values

fs/nfs/super.c +2 -0
@@ -2192,6 +2201,8 @@ static int nfs_validate_text_mount_data(void
 *options,
 	return -EINVAL;
 }
 
+#define NFS_REMOUNT_CHANGE_FLAGS (NFS_MOUNT_SERVERFAILED)
+
 #define NFS_REMOUNT_CMP_FLAGMASK ~(NFS_MOUNT_INTR \
 		| NFS_MOUNT_SECURE \

		| NFS_MOUNT_TCP \
fs/nfs/super.c +2 -1
@@ -2200,7 +2211,8 @@ static int nfs_validate_text_mount_data(void
 *options,
 		| NFS_MOUNT_NONLM \
 		| NFS_MOUNT_BROKEN_SUID \
 		| NFS_MOUNT_STRICTLOCK \
-		| NFS_MOUNT_LEGACY_INTERFACE)
+		| NFS_MOUNT_LEGACY_INTERFACE \
+		| NFS_REMOUNT_CHANGE_FLAGS)
 
 #define NFS_MOUNT_CMP_FLAGMASK (NFS_REMOUNT_CMP_FLAGMASK & \

~(NFS_MOUNT_UNSHARED | NFS_MOUNT_NORESVPORT))

fs/nfs/super.c +3 -1
@@ -2209,12 +2221,15 @@ static int
 nfs_compare_and_set_remount_data(struct nfs_server *nfss,
 				 struct nfs_parsed_mount_data *data)
 {
+	int changed_flags_mask = data->flags_mask &
 NFS_REMOUNT_CHANGE_FLAGS;
+	struct rpc_clnt *cl = nfss->client;
+
 	if ((data->flags ^ nfss->flags) & NFS_REMOUNT_CMP_FLAGMASK ||
 	    data->rsize != nfss->rsize ||
 	    data->wsize != nfss->wsize ||
 	    data->version != nfss->nfs_client->rpc_ops->version ||
 	    data->minorversion != nfss->nfs_client->cl_minorversion ||
-	    !nfs_auth_info_match(&data->auth_info, nfss->client-
Quoted 1 line

cl_auth->au_flavor) ||

fs/nfs/super.c +1 -0
+	    !nfs_auth_info_match(&data->auth_info, cl->cl_auth-
Quoted 1 line

au_flavor) ||

	    data->acregmin != nfss->acregmin / HZ ||
	    data->acregmax != nfss->acregmax / HZ ||
	    data->acdirmin != nfss->acdirmin / HZ ||
fs/nfs/super.c +0 -1
@@ -2225,13 +2240,16 @@ nfs_compare_and_set_remount_data(struct
 nfs_server *nfss,
 			  (struct sockaddr *)&nfss->nfs_client-
 > cl_addr))
 		return -EINVAL;
 
-	if (data->retrans != nfss->client->cl_timeout->to_retries

||

fs/nfs/super.c +0 -1
-	    data->timeo != (10U * nfss->client->cl_timeout-
Quoted 1 line

to_initval / HZ)) {

fs/nfs/super.c +6 -0
+	/* Update flags */
+	nfss->flags = (nfss->flags & ~changed_flags_mask) |
+		(data->flags & changed_flags_mask);
+
+	if (data->retrans != cl->cl_timeout->to_retries ||
+	    data->timeo != (10U * cl->cl_timeout->to_initval /

HZ)) {
		/* Note that this will affect all mounts from the same
server,
		 * that use the same protocol.  The timeouts are always
forced
		 * to be the same.
		 */
fs/nfs/super.c +0 -1
-		struct rpc_clnt *cl = nfss->client;

		if (cl->cl_timeout != &cl->cl_timeout_default)
			memcpy(&cl->cl_timeout_default, cl->cl_timeout,
			       sizeof(struct rpc_timeout));
fs/nfs/super.c +2 -0
@@ -2239,6 +2257,8 @@ nfs_compare_and_set_remount_data(struct
 nfs_server *nfss,
 		cl->cl_timeout_default.to_initval = data->timeo * HZ /
 10U;
 	}
 
+	cl->cl_kill_new_tasks = !!(nfss->flags &
 NFS_MOUNT_SERVERFAILED);
+

	return 0;
}
include/uapi/linux/nfs_mount.h +1 -0
index e44e00616ab5..8ad931cdca20 100644
@@ -74,5 +74,6 @@ struct nfs_mount_data {
 
 #define NFS_MOUNT_LOCAL_FLOCK	0x100000
 #define NFS_MOUNT_LOCAL_FCNTL	0x200000
+#define NFS_MOUNT_SERVERFAILED	0x400000
 
 #endif
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author
#9 lore raw

RFC v2 6/7 NFS: Propagate NFS_MOUNT_UNSHARED to clients

In reply to Joshua Watt

Propagating the flag allows operations to be performed on the client without affecting other mounts to the same client, much like operations on the superblock will not affect other superblocks.

Signed-off-by Joshua Watt <[email protected]>
---
 fs/nfs/client.c           | 9 +++++++--
 fs/nfs/nfs3client.c       | 2 ++
 fs/nfs/nfs4client.c       | 4 ++++
 include/linux/nfs_fs_sb.h | 1 +
 4 files changed, 14 insertions(+), 2 deletions(-)
fs/nfs/client.c +7 -2
index 22880ef6d8dd..c5872286f322 100644
@@ -297,6 +297,10 @@ static struct nfs_client *nfs_match_client(const struct nfs_client_initdata *dat
 		if (clp->cl_cons_state < 0)
 			continue;
 
+		/* Don't match clients that don't want to be shared */
+		if (test_bit(NFS_CS_UNSHARED, &clp->cl_flags))
+			continue;
+
 		/* Different NFS versions cannot share the same nfs_client */
 		if (clp->rpc_ops != data->nfs_mod->rpc_ops)
 			continue;

@@ -386,7 +390,7 @@ nfs_found_client(const struct nfs_client_initdata *cl_init,
  */
 struct nfs_client *nfs_get_client(const struct nfs_client_initdata *cl_init)
 {
-	struct nfs_client *clp, *new = NULL;
+	struct nfs_client *clp = NULL, *new = NULL;
 	struct nfs_net *nn = net_generic(cl_init->net, nfs_net_id);
 	const struct nfs_rpc_ops *rpc_ops = cl_init->nfs_mod->rpc_ops;
 

@@ -399,7 +403,8 @@ struct nfs_client *nfs_get_client(const struct nfs_client_initdata *cl_init)
 	do {
 		spin_lock(&nn->nfs_client_lock);
 
-		clp = nfs_match_client(cl_init);
+		if (!test_bit(NFS_CS_UNSHARED, &cl_init->init_flags))
+			clp = nfs_match_client(cl_init);
 		if (clp) {
 			spin_unlock(&nn->nfs_client_lock);
 			if (new)
fs/nfs/nfs3client.c +2 -0
index 7879f2a0fcfd..b62bed41053f 100644
@@ -102,6 +102,8 @@ struct nfs_client *nfs3_set_ds_client(struct nfs_server *mds_srv,
 
 	if (mds_srv->flags & NFS_MOUNT_NORESVPORT)
 		set_bit(NFS_CS_NORESVPORT, &cl_init.init_flags);
+	if (mds_srv->flags & NFS_MOUNT_UNSHARED)
+		__set_bit(NFS_CS_UNSHARED, &cl_init.init_flags);
 
 	/* Use the MDS nfs_client cl_ipaddr. */
 	nfs_init_timeout_values(&ds_timeout, ds_proto, ds_timeo, ds_retrans);
fs/nfs/nfs4client.c +4 -0
index e9bea90dc017..e51467f5b3bc 100644
@@ -852,6 +852,8 @@ static int nfs4_set_client(struct nfs_server *server,
 		set_bit(NFS_CS_MIGRATION, &cl_init.init_flags);
 	if (test_bit(NFS_MIG_TSM_POSSIBLE, &server->mig_status))
 		set_bit(NFS_CS_TSM_POSSIBLE, &cl_init.init_flags);
+	if (server->flags & NFS_MOUNT_UNSHARED)
+		__set_bit(NFS_CS_UNSHARED, &cl_init.init_flags);
 
 	/* Allocate or find a client reference we can use */
 	clp = nfs_get_client(&cl_init);

@@ -910,6 +912,8 @@ struct nfs_client *nfs4_set_ds_client(struct nfs_server *mds_srv,
 
 	if (mds_srv->flags & NFS_MOUNT_NORESVPORT)
 		__set_bit(NFS_CS_NORESVPORT, &cl_init.init_flags);
+	if (mds_srv->flags & NFS_MOUNT_UNSHARED)
+		__set_bit(NFS_CS_UNSHARED, &cl_init.init_flags);
 
 	/*
 	 * Set an authflavor equual to the MDS value. Use the MDS nfs_client
include/linux/nfs_fs_sb.h +1 -0
index 286b71c418b4..8761f729921a 100644
@@ -44,6 +44,7 @@ struct nfs_client {
 #define NFS_CS_INFINITE_SLOTS	3		/* - don't limit TCP slots */
 #define NFS_CS_NO_RETRANS_TIMEOUT	4	/* - Disable retransmit timeouts */
 #define NFS_CS_TSM_POSSIBLE	5		/* - Maybe state migration */
+#define NFS_CS_UNSHARED		6		/* - Client state is not shared */
 	struct sockaddr_storage	cl_addr;	/* server identifier */
 	size_t			cl_addrlen;
 	char *			cl_hostname;	/* hostname of server */
Signature · 1 line
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author
#10 lore raw

RFC v2 7/7 NFS: Propagate operations to unshared clients

In reply to Joshua Watt

If a struct nfs_server's client is not shared with other superblocks, propagate the umount_begin and serverfailed behavior to it.

Signed-off-by Joshua Watt <[email protected]>
---
 fs/nfs/super.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)
fs/nfs/super.c +11 -1
index bca38e1cdd85..0348fd43ffe4 100644
@@ -911,6 +911,11 @@ void nfs_umount_begin(struct super_block *sb)
 	rpc = server->client;
 	if (!IS_ERR(rpc))
 		rpc_killall_tasks(rpc);
+
+	rpc = server->nfs_client->cl_rpcclient;
+	if (test_bit(NFS_CS_UNSHARED, &server->nfs_client->cl_flags) &&
+	    !IS_ERR(rpc))
+		rpc_killall_tasks(rpc);
 }
 EXPORT_SYMBOL_GPL(nfs_umount_begin);
 

@@ -2223,6 +2228,7 @@ nfs_compare_and_set_remount_data(struct nfs_server *nfss,
 {
 	int changed_flags_mask = data->flags_mask & NFS_REMOUNT_CHANGE_FLAGS;
 	struct rpc_clnt *cl = nfss->client;
+	bool serverfailed;
 
 	if ((data->flags ^ nfss->flags) & NFS_REMOUNT_CMP_FLAGMASK ||
 	    data->rsize != nfss->rsize ||

@@ -2257,7 +2263,11 @@ nfs_compare_and_set_remount_data(struct nfs_server *nfss,
 		cl->cl_timeout_default.to_initval = data->timeo * HZ / 10U;
 	}
 
-	cl->cl_kill_new_tasks = !!(nfss->flags & NFS_MOUNT_SERVERFAILED);
+	serverfailed = !!(nfss->flags & NFS_MOUNT_SERVERFAILED);
+	cl->cl_kill_new_tasks = serverfailed;
+	if (test_bit(NFS_CS_UNSHARED, &nfss->nfs_client->cl_flags))
+		nfss->nfs_client->cl_rpcclient->cl_kill_new_tasks =
+			serverfailed;
 
 	return 0;
 }
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