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    SubjectRe: [RFC PATCH] nfs: Add NFS3PROC_UMOUNT procedure.
    Date
    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@netapp.com
    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@netapp.com
    > www.netapp.com
    >
    > On Jun 23, 2012, at 6:46 AM, Namjae Jeon wrote:
    >
    >> From: Namjae Jeon <namjae.jeon@samsung.com>
    >>
    >> 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@samsung.com>
    >> Signed-off-by: Vivek Trivedi <t.vivek@samsung.com>
    >> Signed-off-by: Amit Sahrawat <a.sahrawat@samsung.com>
    >> ---
    >> 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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