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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