Re: [RFC PATCH] nfs: Add NFS3PROC_UMOUNT procedure.

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The other objection is that NFSv3 already has a way to do this via the MOUNT protocol. We already call MOUNTPROC3_UMNT/MOUNTPROC_UMNT on unmount of a filesystem.

The problem with this approach is that if the NFS client crashes before it can call this function, then the server never gets notified. That is a problem that your patch has too...


--
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@xxxxxxxxxx
www.netapp.com

On Jun 23, 2012, at 11:07 AM, Myklebust, Trond wrote:

> BIG NACK... We don't do embrace and extend in Linux...
> 
> 
> The whole point of the NFS protocol is to be a standard. We can't just go adding new functionality to one implementation of that standard without breaking interoperability with other implementations...
> 
> Trond
> 
> --
> Trond Myklebust
> Linux NFS client maintainer
> 
> NetApp
> Trond.Myklebust@xxxxxxxxxx
> www.netapp.com
> 
> On Jun 23, 2012, at 6:46 AM, Namjae Jeon wrote:
> 
>> From: Namjae Jeon <namjae.jeon@xxxxxxxxxxx>
>> 
>> Without this patch:
>> 
>> On NFS Client:
>> $ mount -t nfs <NFS_SERVER>:/mnt /mnt
>> $ umount /mnt
>> 
>> On NFS Server:
>> $ umount /mnt
>> umount: can't umount /mnt: Device or resource busy
>> 
>> If user has to remove storage device user needs to unplug the
>> device.
>> This may result in file system corruption on attached media.
>> 
>> This patch tries to add a NFS UMOUNT procedure for NFSv3 for safe
>> removal of attached media at NFS Server.
>> 
>> With this patch:
>> 
>> On NFS Client:
>> $ mount -t nfs <NFS_SERVER>:/mnt /mnt
>> $ umount /mnt
>> 
>> On NFS Server:
>> $ umount /mnt --> umount successful
>> 
>> Signed-off-by: Namjae Jeon <namjae.jeon@xxxxxxxxxxx>
>> Signed-off-by: Vivek Trivedi <t.vivek@xxxxxxxxxxx>
>> Signed-off-by: Amit Sahrawat <a.sahrawat@xxxxxxxxxxx>
>> ---
>> fs/nfs/nfs3proc.c       |   29 +++++++++++++++++++++++++++++
>> fs/nfs/nfs3xdr.c        |   39 +++++++++++++++++++++++++++++++++++++++
>> fs/nfs/super.c          |   10 ++++++++++
>> fs/nfsd/nfs3proc.c      |   28 +++++++++++++++++++++++++++-
>> fs/nfsd/nfs3xdr.c       |   19 +++++++++++++++++++
>> fs/nfsd/nfsctl.c        |   22 ++++++++++++++++++++++
>> fs/nfsd/nfsd.h          |    3 +++
>> fs/nfsd/nfssvc.c        |    3 +++
>> fs/nfsd/xdr3.h          |   14 +++++++++++++-
>> include/linux/nfs3.h    |    1 +
>> include/linux/nfs_xdr.h |    9 +++++++++
>> 11 files changed, 175 insertions(+), 2 deletions(-)
>> 
>> diff --git a/fs/nfs/nfs3proc.c b/fs/nfs/nfs3proc.c
>> index 2292a0f..726227f 100644
>> --- a/fs/nfs/nfs3proc.c
>> +++ b/fs/nfs/nfs3proc.c
>> @@ -877,6 +877,34 @@ nfs3_proc_lock(struct file *filp, int cmd, struct file_lock *fl)
>> 	return nlmclnt_proc(NFS_SERVER(inode)->nlm_host, cmd, fl);
>> }
>> 
>> +static int nfs3_proc_umount(struct nfs_server *server)
>> +{
>> +	/*
>> +	 * dummy argument and response are assigned to UMOUNT request
>> +	 * to avoid BUG_ON(proc->p_arglen == 0); in net/sunrpc/clnt.c
>> +	 */
>> +	struct nfs3_umountargs  arg = {
>> +		.dummy          = 0,
>> +	};
>> +	struct nfs3_umountres   res;
>> +
>> +	struct rpc_message msg = {
>> +		.rpc_proc       = &nfs3_procedures[NFS3PROC_UMOUNT],
>> +		.rpc_argp       = &arg,
>> +		.rpc_resp       = &res,
>> +
>> +	};
>> +	int err;
>> +
>> +	msg.rpc_cred = authnull_ops.lookup_cred(NULL, NULL, 0);
>> +	dprintk("NFS call  umount\n");
>> +	err = rpc_call_sync(server->client, &msg,
>> +			RPC_TASK_SOFT | RPC_TASK_SOFTCONN);
>> +	put_rpccred(msg.rpc_cred);
>> +	dprintk("NFS reply umount: %d\n", err);
>> +	return err;
>> +}
>> +
>> const struct nfs_rpc_ops nfs_v3_clientops = {
>> 	.version	= 3,			/* protocol version */
>> 	.dentry_ops	= &nfs_dentry_operations,
>> @@ -922,4 +950,5 @@ const struct nfs_rpc_ops nfs_v3_clientops = {
>> 	.clear_acl_cache = nfs3_forget_cached_acls,
>> 	.close_context	= nfs_close_context,
>> 	.init_client	= nfs_init_client,
>> +	.umount			= nfs3_proc_umount,
>> };
>> diff --git a/fs/nfs/nfs3xdr.c b/fs/nfs/nfs3xdr.c
>> index 6cbe894..874b8b2 100644
>> --- a/fs/nfs/nfs3xdr.c
>> +++ b/fs/nfs/nfs3xdr.c
>> @@ -61,6 +61,7 @@
>> #define NFS3_readdirargs_sz	(NFS3_fh_sz+NFS3_cookieverf_sz+3)
>> #define NFS3_readdirplusargs_sz	(NFS3_fh_sz+NFS3_cookieverf_sz+4)
>> #define NFS3_commitargs_sz	(NFS3_fh_sz+3)
>> +#define NFS3_umountargs_sz	(1)
>> 
>> #define NFS3_getattrres_sz	(1+NFS3_fattr_sz)
>> #define NFS3_setattrres_sz	(1+NFS3_wcc_data_sz)
>> @@ -78,6 +79,7 @@
>> #define NFS3_fsinfores_sz	(1+NFS3_post_op_attr_sz+12)
>> #define NFS3_pathconfres_sz	(1+NFS3_post_op_attr_sz+6)
>> #define NFS3_commitres_sz	(1+NFS3_wcc_data_sz+2)
>> +#define NFS3_umountres_sz	(1 + 1)
>> 
>> #define ACL3_getaclargs_sz	(NFS3_fh_sz+1)
>> #define ACL3_setaclargs_sz	(NFS3_fh_sz+1+ \
>> @@ -1306,6 +1308,22 @@ static void nfs3_xdr_enc_commit3args(struct rpc_rqst *req,
>> 	encode_commit3args(xdr, args);
>> }
>> 
>> +/*
>> + *   UMOUNT3args
>> + */
>> +static void encode_umount3args(struct xdr_stream *xdr,
>> +		const struct nfs3_umountargs *args)
>> +{
>> +	encode_uint32(xdr, args->dummy);
>> +}
>> +
>> +static void nfs3_xdr_enc_umount3args(struct rpc_rqst *req,
>> +		struct xdr_stream *xdr,
>> +		const struct nfs3_umountargs *args)
>> +{
>> +	encode_umount3args(xdr, args);
>> +}
>> +
>> #ifdef CONFIG_NFS_V3_ACL
>> 
>> static void nfs3_xdr_enc_getacl3args(struct rpc_rqst *req,
>> @@ -1429,6 +1447,26 @@ out_status:
>> }
>> 
>> /*
>> + *   UMOUNT3res
>> + */
>> +static int nfs3_xdr_dec_umount3res(struct rpc_rqst *req,
>> +		struct xdr_stream *xdr,
>> +		struct nfs3_umountres *result)
>> +{
>> +	enum nfs_stat status;
>> +	int error;
>> +
>> +	error = decode_nfsstat3(xdr, &status);
>> +	if (unlikely(error))
>> +		goto out;
>> +	if (status != NFS3_OK)
>> +		return nfs3_stat_to_errno(status);
>> +	error = decode_uint32(xdr, &result->dummy);
>> +out:
>> +	return error;
>> +}
>> +
>> +/*
>> * 3.3.3  LOOKUP3res
>> *
>> *	struct LOOKUP3resok {
>> @@ -2508,6 +2546,7 @@ struct rpc_procinfo	nfs3_procedures[] = {
>> 	PROC(FSINFO,		getattr,	fsinfo,		0),
>> 	PROC(PATHCONF,		getattr,	pathconf,	0),
>> 	PROC(COMMIT,		commit,		commit,		5),
>> +	PROC(UMOUNT,		umount,		umount,		0),
>> };
>> 
>> const struct rpc_version nfs_version3 = {
>> diff --git a/fs/nfs/super.c b/fs/nfs/super.c
>> index 906f09c..9fa295b 100644
>> --- a/fs/nfs/super.c
>> +++ b/fs/nfs/super.c
>> @@ -2525,6 +2525,16 @@ static void nfs_kill_super(struct super_block *s)
>> {
>> 	struct nfs_server *server = NFS_SB(s);
>> 
>> +	int err;
>> +
>> +	if (server->nfs_client->rpc_ops->umount) {
>> +		err = server->nfs_client->rpc_ops->umount(server);
>> +		if (err < 0) {
>> +			printk(KERN_ERR "%s: nfs_proc3_umount() failed err = %d\n",
>> +					__func__, err);
>> +		}
>> +	}
>> +
>> 	kill_anon_super(s);
>> 	nfs_fscache_release_super_cookie(s);
>> 	nfs_free_server(server);
>> diff --git a/fs/nfsd/nfs3proc.c b/fs/nfsd/nfs3proc.c
>> index 9095f3c..12ca821 100644
>> --- a/fs/nfsd/nfs3proc.c
>> +++ b/fs/nfsd/nfs3proc.c
>> @@ -8,6 +8,7 @@
>> #include <linux/ext2_fs.h>
>> #include <linux/magic.h>
>> 
>> +#include "nfsd.h"
>> #include "cache.h"
>> #include "xdr3.h"
>> #include "vfs.h"
>> @@ -63,6 +64,21 @@ nfsd3_proc_getattr(struct svc_rqst *rqstp, struct nfsd_fhandle  *argp,
>> }
>> 
>> /*
>> + * UMOUNT call.
>> + */
>> +static __be32
>> +nfsd3_proc_umount(struct svc_rqst *rqstp, struct nfsd3_umountargs *argp,
>> +		struct nfsd3_umountres *resp)
>> +{
>> +	dprintk("nfsd: UMOUNT(3)\n");
>> +
>> +	if (nfs_umountd_workqueue)
>> +		queue_work(nfs_umountd_workqueue, &nfs_umount_work);
>> +
>> +	return nfs_ok;
>> +}
>> +
>> +/*
>> * Set a file's attributes
>> */
>> static __be32
>> @@ -671,7 +687,7 @@ struct nfsd3_voidargs { int dummy; };
>> #define pAT (1+AT)	/* post attributes - conditional */
>> #define WC (7+pAT)	/* WCC attributes */
>> 
>> -static struct svc_procedure		nfsd_procedures3[22] = {
>> +static struct svc_procedure		nfsd_procedures3[23] = {
>> 	[NFS3PROC_NULL] = {
>> 		.pc_func = (svc_procfunc) nfsd3_proc_null,
>> 		.pc_encode = (kxdrproc_t) nfs3svc_encode_voidres,
>> @@ -885,11 +901,21 @@ static struct svc_procedure		nfsd_procedures3[22] = {
>> 		.pc_cachetype = RC_NOCACHE,
>> 		.pc_xdrressize = ST+WC+2,
>> 	},
>> +	[NFS3PROC_UMOUNT] = {
>> +		.pc_func = (svc_procfunc) nfsd3_proc_umount,
>> +		.pc_decode = (kxdrproc_t) nfs3svc_decode_umountargs,
>> +		.pc_encode = (kxdrproc_t) nfs3svc_encode_umountres,
>> +		.pc_argsize = sizeof(struct nfsd3_umountargs),
>> +		.pc_ressize = sizeof(struct nfsd3_umountres),
>> +		.pc_cachetype = RC_NOCACHE,
>> +		.pc_xdrressize = ST+1,
>> +	},
>> };
>> 
>> struct svc_version	nfsd_version3 = {
>> 		.vs_vers	= 3,
>> 		.vs_nproc	= 22,
>> +		.vs_nproc	= 23,
>> 		.vs_proc	= nfsd_procedures3,
>> 		.vs_dispatch	= nfsd_dispatch,
>> 		.vs_xdrsize	= NFS3_SVC_XDRSIZE,
>> diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
>> index 43f46cd..8610282 100644
>> --- a/fs/nfsd/nfs3xdr.c
>> +++ b/fs/nfsd/nfs3xdr.c
>> @@ -611,6 +611,15 @@ nfs3svc_decode_commitargs(struct svc_rqst *rqstp, __be32 *p,
>> 	return xdr_argsize_check(rqstp, p);
>> }
>> 
>> +int
>> +nfs3svc_decode_umountargs(struct svc_rqst *rqstp, __be32 *p,
>> +		struct nfsd3_umountargs *args)
>> +{
>> +	args->dummy = ntohl(*p++);
>> +
>> +	return xdr_argsize_check(rqstp, p);
>> +}
>> +
>> /*
>> * XDR encode functions
>> */
>> @@ -1091,6 +1100,16 @@ nfs3svc_encode_commitres(struct svc_rqst *rqstp, __be32 *p,
>> 	return xdr_ressize_check(rqstp, p);
>> }
>> 
>> +/* UMOUNT */
>> +int
>> +nfs3svc_encode_umountres(struct svc_rqst *rqstp, __be32 *p,
>> +		struct nfsd3_umountres *resp)
>> +{
>> +	if (resp->status == 0)
>> +		*p++ = htonl(resp->dummy);
>> +	return xdr_ressize_check(rqstp, p);
>> +}
>> +
>> /*
>> * XDR release functions
>> */
>> diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
>> index c55298e..53748ac 100644
>> --- a/fs/nfsd/nfsctl.c
>> +++ b/fs/nfsd/nfsctl.c
>> @@ -50,6 +50,9 @@ enum {
>> #endif
>> };
>> 
>> +struct workqueue_struct *nfs_umountd_workqueue;
>> +struct work_struct nfs_umount_work;
>> +
>> /*
>> * write() for these nodes.
>> */
>> @@ -1175,6 +1178,17 @@ static struct pernet_operations nfsd_net_ops = {
>> 	.size = sizeof(struct nfsd_net),
>> };
>> 
>> +static void nfs_umountd_fn(struct work_struct *unused)
>> +{
>> +	nfsd_export_flush(&init_net);
>> +}
>> +
>> +static void nfsd_umount_destroy(void)
>> +{
>> +	if (nfs_umountd_workqueue)
>> +		destroy_workqueue(nfs_umountd_workqueue);
>> +}
>> +
>> static int __init init_nfsd(void)
>> {
>> 	int retval;
>> @@ -1204,6 +1218,13 @@ static int __init init_nfsd(void)
>> 	retval = register_filesystem(&nfsd_fs_type);
>> 	if (retval)
>> 		goto out_free_all;
>> +
>> +	nfs_umountd_workqueue = create_singlethread_workqueue("nfs.umountd");
>> +	if (!nfs_umountd_workqueue)
>> +		printk(KERN_ERR "nfsd: Failed to create nfs.umountd workqueue\n");
>> +	else
>> +		INIT_WORK(&nfs_umount_work, nfs_umountd_fn);
>> +
>> 	return 0;
>> out_free_all:
>> 	remove_proc_entry("fs/nfs/exports", NULL);
>> @@ -1225,6 +1246,7 @@ out_unregister_notifier:
>> 
>> static void __exit exit_nfsd(void)
>> {
>> +	nfsd_umount_destroy();
>> 	nfsd_reply_cache_shutdown();
>> 	remove_proc_entry("fs/nfs/exports", NULL);
>> 	remove_proc_entry("fs/nfs", NULL);
>> diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h
>> index 1671429..691450a 100644
>> --- a/fs/nfsd/nfsd.h
>> +++ b/fs/nfsd/nfsd.h
>> @@ -20,6 +20,7 @@
>> #include <linux/nfsd/debug.h>
>> #include <linux/nfsd/export.h>
>> #include <linux/nfsd/stats.h>
>> +#include <linux/workqueue.h>
>> 
>> /*
>> * nfsd version
>> @@ -61,6 +62,8 @@ extern unsigned int		nfsd_drc_max_mem;
>> extern unsigned int		nfsd_drc_mem_used;
>> 
>> extern const struct seq_operations nfs_exports_op;
>> +extern struct workqueue_struct *nfs_umountd_workqueue;
>> +extern struct work_struct nfs_umount_work;
>> 
>> /*
>> * Function prototypes.
>> diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
>> index ee709fc..1fb3598 100644
>> --- a/fs/nfsd/nfssvc.c
>> +++ b/fs/nfsd/nfssvc.c
>> @@ -256,6 +256,9 @@ static void nfsd_last_thread(struct svc_serv *serv, struct net *net)
>> {
>> 	/* When last nfsd thread exits we need to do some clean-up */
>> 	nfsd_serv = NULL;
>> +	if (nfs_umountd_workqueue)
>> +		flush_workqueue(nfs_umountd_workqueue);
>> +
>> 	nfsd_shutdown();
>> 
>> 	svc_rpcb_cleanup(serv, net);
>> diff --git a/fs/nfsd/xdr3.h b/fs/nfsd/xdr3.h
>> index 7df980e..b542c92 100644
>> --- a/fs/nfsd/xdr3.h
>> +++ b/fs/nfsd/xdr3.h
>> @@ -106,6 +106,10 @@ struct nfsd3_commitargs {
>> 	__u32			count;
>> };
>> 
>> +struct nfsd3_umountargs {
>> +	__u32	dummy;
>> +};
>> +
>> struct nfsd3_getaclargs {
>> 	struct svc_fh		fh;
>> 	int			mask;
>> @@ -219,6 +223,11 @@ struct nfsd3_commitres {
>> 	struct svc_fh		fh;
>> };
>> 
>> +struct nfsd3_umountres {
>> +	__be32	status;
>> +	__u32	dummy;
>> +};
>> +
>> struct nfsd3_getaclres {
>> 	__be32			status;
>> 	struct svc_fh		fh;
>> @@ -295,6 +304,8 @@ int nfs3svc_decode_readdirplusargs(struct svc_rqst *, __be32 *,
>> 				struct nfsd3_readdirargs *);
>> int nfs3svc_decode_commitargs(struct svc_rqst *, __be32 *,
>> 				struct nfsd3_commitargs *);
>> +int nfs3svc_decode_umountargs(struct svc_rqst *, __be32 *,
>> +				struct nfsd3_umountargs *);
>> int nfs3svc_encode_voidres(struct svc_rqst *, __be32 *, void *);
>> int nfs3svc_encode_attrstat(struct svc_rqst *, __be32 *,
>> 				struct nfsd3_attrstat *);
>> @@ -324,7 +335,8 @@ int nfs3svc_encode_pathconfres(struct svc_rqst *, __be32 *,
>> 				struct nfsd3_pathconfres *);
>> int nfs3svc_encode_commitres(struct svc_rqst *, __be32 *,
>> 				struct nfsd3_commitres *);
>> -
>> +int nfs3svc_encode_umountres(struct svc_rqst *, __be32 *,
>> +				struct nfsd3_umountres *);
>> int nfs3svc_release_fhandle(struct svc_rqst *, __be32 *,
>> 				struct nfsd3_attrstat *);
>> int nfs3svc_release_fhandle2(struct svc_rqst *, __be32 *,
>> diff --git a/include/linux/nfs3.h b/include/linux/nfs3.h
>> index 6ccfe3b..968e2e0 100644
>> --- a/include/linux/nfs3.h
>> +++ b/include/linux/nfs3.h
>> @@ -90,6 +90,7 @@ struct nfs3_fh {
>> #define NFS3PROC_FSINFO		19
>> #define NFS3PROC_PATHCONF	20
>> #define NFS3PROC_COMMIT		21
>> +#define NFS3PROC_UMOUNT		22
>> 
>> #define NFS_MNT3_VERSION	3
>> 
>> diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
>> index 5c0014d..da53bd8 100644
>> --- a/include/linux/nfs_xdr.h
>> +++ b/include/linux/nfs_xdr.h
>> @@ -786,6 +786,14 @@ struct nfs3_readdirargs {
>> 	struct page **		pages;
>> };
>> 
>> +struct nfs3_umountargs {
>> +	__u32			dummy;
>> +};
>> +
>> +struct nfs3_umountres {
>> +	__u32			dummy;
>> +};
>> +
>> struct nfs3_diropres {
>> 	struct nfs_fattr *	dir_attr;
>> 	struct nfs_fh *		fh;
>> @@ -1425,6 +1433,7 @@ struct nfs_rpc_ops {
>> 	struct nfs_client *
>> 		(*init_client) (struct nfs_client *, const struct rpc_timeout *,
>> 				const char *, rpc_authflavor_t);
>> +	int	(*umount)(struct nfs_server *);
>> };
>> 
>> /*
>> -- 
>> 1.7.9.5
>> 
> 

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