Re: [RFC PATCH] nfs: Add NFS3PROC_UMOUNT procedure.
From: Fields James
Date: Sat Jun 23 2012 - 11:57:11 EST
On Sat, Jun 23, 2012 at 03:52:20PM +0000, Myklebust, Trond wrote:
> 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...
Yes. Could you instead work on describing *exactly* what the original
problem was that prompted this?
--b.
>
>
> --
> 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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