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Date: Mon, 10 Jun 2024 12:42:54 -0400
From: Mike Snitzer <snitzer@kernel.org>
To: Jeff Layton <jlayton@kernel.org>
Cc: linux-nfs@vger.kernel.org, Chuck Lever <chuck.lever@oracle.com>,
	Trond Myklebust <trondmy@hammerspace.com>, snitzer@hammerspace.com
Subject: Re: [for-6.11 PATCH 10/29] nfs/nfsd: add "local io" support
Message-ID: <ZmctDkCCg331JS4M@kernel.org>
References: <20240607142646.20924-1-snitzer@kernel.org>
 <20240607142646.20924-11-snitzer@kernel.org>
 <3ed173a9370c6d386f4c48cc133eb61511e291d0.camel@kernel.org>
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In-Reply-To: <3ed173a9370c6d386f4c48cc133eb61511e291d0.camel@kernel.org>

On Mon, Jun 10, 2024 at 08:43:34AM -0400, Jeff Layton wrote:
> On Fri, 2024-06-07 at 10:26 -0400, Mike Snitzer wrote:
> > From: Weston Andros Adamson <dros@primarydata.com>
> > 
> > Add client support for bypassing NFS for localhost reads, writes, and commits.
> > 
> > This is only useful when the client and the server are running on the same
> > host and in the same container.
> > 
> > This has dynamic binding with the nfsd module. Local i/o will only work if
> > nfsd is already loaded.
> > 
> > [snitm: rebase accounted for commit d8b26071e65e8 ("NFSD: simplify struct nfsfh")
> > ?and commit 7c98f7cb8fda ("remove call_{read,write}_iter() functions")]
> > 
> > Signed-off-by: Weston Andros Adamson <dros@primarydata.com>
> > Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
> > Signed-off-by: Peng Tao <tao.peng@primarydata.com>
> > Signed-off-by: Lance Shelton <lance.shelton@hammerspace.com>
> > Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
> > Signed-off-by: Mike Snitzer <snitzer@kernel.org>
> > ---
> > ?fs/nfs/Makefile??????????????????????? |?? 2 +-
> > ?fs/nfs/client.c??????????????????????? |? 12 +
> > ?fs/nfs/filelayout/filelayout.c???????? |?? 6 +-
> > ?fs/nfs/flexfilelayout/flexfilelayout.c |?? 6 +-
> > ?fs/nfs/inode.c???????????????????????? |?? 5 +
> > ?fs/nfs/internal.h????????????????????? |? 32 +-
> > ?fs/nfs/localio.c?????????????????????? | 933 +++++++++++++++++++++++++
> > ?fs/nfs/nfstrace.h????????????????????? |? 29 +
> > ?fs/nfs/pagelist.c????????????????????? |? 12 +-
> > ?fs/nfs/pnfs_nfs.c????????????????????? |?? 2 +-
> > ?fs/nfs/write.c???????????????????????? |? 14 +-
> > ?fs/nfsd/Makefile?????????????????????? |?? 2 +-
> > ?fs/nfsd/filecache.c??????????????????? |?? 2 +-
> > ?fs/nfsd/localio.c????????????????????? | 179 +++++
> > ?fs/nfsd/trace.h??????????????????????? |?? 3 +-
> > ?fs/nfsd/vfs.h????????????????????????? |?? 8 +
> > ?include/linux/nfs.h??????????????????? |?? 6 +
> > ?include/linux/nfs_fs.h???????????????? |?? 2 +
> > ?include/linux/nfs_fs_sb.h????????????? |?? 2 +
> > ?include/linux/nfs_xdr.h??????????????? |?? 1 +
> > ?20 files changed, 1240 insertions(+), 18 deletions(-)
> > ?create mode 100644 fs/nfs/localio.c
> > ?create mode 100644 fs/nfsd/localio.c
> > 
> > diff --git a/fs/nfs/Makefile b/fs/nfs/Makefile
> > index 5f6db37f461e..af64cf5ea420 100644
> > --- a/fs/nfs/Makefile
> > +++ b/fs/nfs/Makefile
> > @@ -9,7 +9,7 @@ CFLAGS_nfstrace.o += -I$(src)
> > ?nfs-y?			:= client.o dir.o file.o getroot.o inode.o super.o \
> > ?			?? io.o direct.o pagelist.o read.o symlink.o unlink.o \
> > ?			?? write.o namespace.o mount_clnt.o nfstrace.o \
> > -			?? export.o sysfs.o fs_context.o
> > +			?? export.o sysfs.o fs_context.o localio.o
> > ?nfs-$(CONFIG_ROOT_NFS)	+= nfsroot.o
> > ?nfs-$(CONFIG_SYSCTL)	+= sysctl.o
> > ?nfs-$(CONFIG_NFS_FSCACHE) += fscache.o
> > diff --git a/fs/nfs/client.c b/fs/nfs/client.c
> > index dd3278dcfca8..288de750fd3b 100644
> > --- a/fs/nfs/client.c
> > +++ b/fs/nfs/client.c
> > @@ -170,6 +170,7 @@ struct nfs_client *nfs_alloc_client(const struct nfs_client_initdata *cl_init)
> > ?	}
> > ?
> > ?	INIT_LIST_HEAD(&clp->cl_superblocks);
> > +	INIT_LIST_HEAD(&clp->cl_local_addrs);
> > ?	clp->cl_rpcclient = ERR_PTR(-EINVAL);
> > ?
> > ?	clp->cl_flags = cl_init->init_flags;
> > @@ -183,6 +184,7 @@ struct nfs_client *nfs_alloc_client(const struct nfs_client_initdata *cl_init)
> > ?
> > ?	clp->cl_principal = "*";
> > ?	clp->cl_xprtsec = cl_init->xprtsec;
> > +	nfs_probe_local_addr(clp);
> > ?	return clp;
> > ?
> > ?error_cleanup:
> > @@ -236,10 +238,19 @@ static void pnfs_init_server(struct nfs_server *server)
> > ? */
> > ?void nfs_free_client(struct nfs_client *clp)
> > ?{
> > +	struct nfs_local_addr *addr, *tmp;
> > +
> > +	nfs_local_disable(clp);
> > +
> > ?	/* -EIO all pending I/O */
> > ?	if (!IS_ERR(clp->cl_rpcclient))
> > ?		rpc_shutdown_client(clp->cl_rpcclient);
> > ?
> > +	list_for_each_entry_safe(addr, tmp, &clp->cl_local_addrs, cl_addrs) {
> > +		list_del(&addr->cl_addrs);
> > +		kfree(addr);
> > +	}
> > +
> > ?	put_net(clp->cl_net);
> > ?	put_nfs_version(clp->cl_nfs_mod);
> > ?	kfree(clp->cl_hostname);
> > @@ -427,6 +438,7 @@ struct nfs_client *nfs_get_client(const struct nfs_client_initdata *cl_init)
> > ?			list_add_tail(&new->cl_share_link,
> > ?					&nn->nfs_client_list);
> > ?			spin_unlock(&nn->nfs_client_lock);
> > +			nfs_local_probe(new);
> > ?			return rpc_ops->init_client(new, cl_init);
> > ?		}
> > ?
> > diff --git a/fs/nfs/filelayout/filelayout.c b/fs/nfs/filelayout/filelayout.c
> > index d66f2efbd92f..bd8c717c31d2 100644
> > --- a/fs/nfs/filelayout/filelayout.c
> > +++ b/fs/nfs/filelayout/filelayout.c
> > @@ -489,7 +489,7 @@ filelayout_read_pagelist(struct nfs_pageio_descriptor *desc,
> > ?	/* Perform an asynchronous read to ds */
> > ?	nfs_initiate_pgio(desc, ds->ds_clp, ds_clnt, hdr, hdr->cred,
> > ?			? NFS_PROTO(hdr->inode), &filelayout_read_call_ops,
> > -			? 0, RPC_TASK_SOFTCONN);
> > +			? 0, RPC_TASK_SOFTCONN, NULL);
> > ?	return PNFS_ATTEMPTED;
> > ?}
> > ?
> > @@ -532,7 +532,7 @@ filelayout_write_pagelist(struct nfs_pageio_descriptor *desc,
> > ?	/* Perform an asynchronous write */
> > ?	nfs_initiate_pgio(desc, ds->ds_clp, ds_clnt, hdr, hdr->cred,
> > ?			? NFS_PROTO(hdr->inode), &filelayout_write_call_ops,
> > -			? sync, RPC_TASK_SOFTCONN);
> > +			? sync, RPC_TASK_SOFTCONN, NULL);
> > ?	return PNFS_ATTEMPTED;
> > ?}
> > ?
> > @@ -1014,7 +1014,7 @@ static int filelayout_initiate_commit(struct nfs_commit_data *data, int how)
> > ?	return nfs_initiate_commit(ds->ds_clp, ds_clnt, data,
> > ?				?? NFS_PROTO(data->inode),
> > ?				?? &filelayout_commit_call_ops, how,
> > -				?? RPC_TASK_SOFTCONN);
> > +				?? RPC_TASK_SOFTCONN, NULL);
> > ?out_err:
> > ?	pnfs_generic_prepare_to_resend_writes(data);
> > ?	pnfs_generic_commit_release(data);
> > diff --git a/fs/nfs/flexfilelayout/flexfilelayout.c b/fs/nfs/flexfilelayout/flexfilelayout.c
> > index d7e9e5ef4085..ce6cb5d82427 100644
> > --- a/fs/nfs/flexfilelayout/flexfilelayout.c
> > +++ b/fs/nfs/flexfilelayout/flexfilelayout.c
> > @@ -1808,7 +1808,7 @@ ff_layout_read_pagelist(struct nfs_pageio_descriptor *desc,
> > ?			? ds->ds_clp->rpc_ops,
> > ?			? vers == 3 ? &ff_layout_read_call_ops_v3 :
> > ?				????? &ff_layout_read_call_ops_v4,
> > -			? 0, RPC_TASK_SOFTCONN);
> > +			? 0, RPC_TASK_SOFTCONN, NULL);
> > ?	put_cred(ds_cred);
> > ?	return PNFS_ATTEMPTED;
> > ?
> > @@ -1878,7 +1878,7 @@ ff_layout_write_pagelist(struct nfs_pageio_descriptor *desc,
> > ?			? ds->ds_clp->rpc_ops,
> > ?			? vers == 3 ? &ff_layout_write_call_ops_v3 :
> > ?				????? &ff_layout_write_call_ops_v4,
> > -			? sync, RPC_TASK_SOFTCONN);
> > +			? sync, RPC_TASK_SOFTCONN, NULL);
> > ?	put_cred(ds_cred);
> > ?	return PNFS_ATTEMPTED;
> > ?
> > @@ -1953,7 +1953,7 @@ static int ff_layout_initiate_commit(struct nfs_commit_data *data, int how)
> > ?	ret = nfs_initiate_commit(ds->ds_clp, ds_clnt, data, ds->ds_clp->rpc_ops,
> > ?				?? vers == 3 ? &ff_layout_commit_call_ops_v3 :
> > ?					?????? &ff_layout_commit_call_ops_v4,
> > -				?? how, RPC_TASK_SOFTCONN);
> > +				?? how, RPC_TASK_SOFTCONN, NULL);
> > ?	put_cred(ds_cred);
> > ?	return ret;
> > ?out_err:
> > diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
> > index acef52ecb1bb..4f88b860494f 100644
> > --- a/fs/nfs/inode.c
> > +++ b/fs/nfs/inode.c
> > @@ -39,6 +39,7 @@
> > ?#include <linux/slab.h>
> > ?#include <linux/compat.h>
> > ?#include <linux/freezer.h>
> > +#include <linux/file.h>
> > ?#include <linux/uaccess.h>
> > ?#include <linux/iversion.h>
> > ?
> > @@ -1053,6 +1054,7 @@ struct nfs_open_context *alloc_nfs_open_context(struct dentry *dentry,
> > ?	ctx->lock_context.open_context = ctx;
> > ?	INIT_LIST_HEAD(&ctx->list);
> > ?	ctx->mdsthreshold = NULL;
> > +	ctx->local_filp = NULL;
> > ?	return ctx;
> > ?}
> > ?EXPORT_SYMBOL_GPL(alloc_nfs_open_context);
> > @@ -1084,6 +1086,8 @@ static void __put_nfs_open_context(struct nfs_open_context *ctx, int is_sync)
> > ?	nfs_sb_deactive(sb);
> > ?	put_rpccred(rcu_dereference_protected(ctx->ll_cred, 1));
> > ?	kfree(ctx->mdsthreshold);
> > +	if (!IS_ERR_OR_NULL(ctx->local_filp))
> > +		fput(ctx->local_filp);
> > ?	kfree_rcu(ctx, rcu_head);
> > ?}
> > ?
> > @@ -2495,6 +2499,7 @@ static int __init init_nfs_fs(void)
> > ?	if (err)
> > ?		goto out1;
> > ?
> > +	nfs_local_init();
> > ?	err = register_nfs_fs();
> > ?	if (err)
> > ?		goto out0;
> > diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
> > index 873c2339b78a..67b348447a40 100644
> > --- a/fs/nfs/internal.h
> > +++ b/fs/nfs/internal.h
> > @@ -204,6 +204,12 @@ struct nfs_mount_request {
> > ?	struct net		*net;
> > ?};
> > ?
> > +struct nfs_local_addr {
> > +	struct list_head	cl_addrs;
> > +	struct sockaddr_storage	address;
> > +	size_t			addrlen;
> > +};
> > +
> > ?extern int nfs_mount(struct nfs_mount_request *info, int timeo, int retrans);
> > ?extern void nfs_umount(const struct nfs_mount_request *info);
> > ?
> > @@ -309,7 +315,8 @@ int nfs_generic_pgio(struct nfs_pageio_descriptor *, struct nfs_pgio_header *);
> > ?int nfs_initiate_pgio(struct nfs_pageio_descriptor *, struct nfs_client *clp,
> > ?		????? struct rpc_clnt *rpc_clnt, struct nfs_pgio_header *hdr,
> > ?		????? const struct cred *cred, const struct nfs_rpc_ops *rpc_ops,
> > -		????? const struct rpc_call_ops *call_ops, int how, int flags);
> > +		????? const struct rpc_call_ops *call_ops, int how, int flags,
> > +		????? struct file *localio);
> > ?void nfs_free_request(struct nfs_page *req);
> > ?struct nfs_pgio_mirror *
> > ?nfs_pgio_current_mirror(struct nfs_pageio_descriptor *desc);
> > @@ -450,6 +457,26 @@ extern void nfs_set_cache_invalid(struct inode *inode, unsigned long flags);
> > ?extern bool nfs_check_cache_invalid(struct inode *, unsigned long);
> > ?extern int nfs_wait_bit_killable(struct wait_bit_key *key, int mode);
> > ?
> > +/* localio.c */
> > +extern void nfs_local_init(void);
> > +extern void nfs_local_enable(struct nfs_client *);
> > +extern void nfs_local_disable(struct nfs_client *);
> > +extern void nfs_local_probe(struct nfs_client *);
> > +extern struct file *nfs_local_open_fh(struct nfs_client *, const struct cred *,
> > +				????? struct nfs_fh *, const fmode_t);
> > +extern struct file *nfs_local_file_open(struct nfs_client *clp,
> > +					const struct cred *cred,
> > +					struct nfs_fh *fh,
> > +					struct nfs_open_context *ctx);
> > +extern int nfs_local_doio(struct nfs_client *, struct file *,
> > +			? struct nfs_pgio_header *,
> > +			? const struct rpc_call_ops *);
> > +extern int nfs_local_commit(struct nfs_client *, struct file *,
> > +			??? struct nfs_commit_data *,
> > +			??? const struct rpc_call_ops *, int);
> > +extern void nfs_probe_local_addr(struct nfs_client *clnt);
> > +extern bool nfs_server_is_local(const struct nfs_client *clp);
> > +
> > ?/* super.c */
> > ?extern const struct super_operations nfs_sops;
> > ?bool nfs_auth_info_match(const struct nfs_auth_info *, rpc_authflavor_t);
> > @@ -530,7 +557,8 @@ extern int nfs_initiate_commit(struct nfs_client *clp,
> > ?			?????? struct nfs_commit_data *data,
> > ?			?????? const struct nfs_rpc_ops *nfs_ops,
> > ?			?????? const struct rpc_call_ops *call_ops,
> > -			?????? int how, int flags);
> > +			?????? int how, int flags,
> > +			?????? struct file *localio);
> > ?extern void nfs_init_commit(struct nfs_commit_data *data,
> > ?			??? struct list_head *head,
> > ?			??? struct pnfs_layout_segment *lseg,
> > diff --git a/fs/nfs/localio.c b/fs/nfs/localio.c
> > new file mode 100644
> > index 000000000000..5c69eb0fe7b6
> > --- /dev/null
> > +++ b/fs/nfs/localio.c
> > @@ -0,0 +1,933 @@
> > +/*
> > + *? linux/fs/nfs/localio.c
> > + *
> > + *? Copyright (C) 2014? Weston Andros Adamson <dros@primarydata.com>
> > + *
> > + */
> > +
> > +#include <linux/module.h>
> > +#include <linux/errno.h>
> > +#include <linux/vfs.h>
> > +#include <linux/file.h>
> > +#include <linux/inet.h>
> > +#include <linux/sunrpc/addr.h>
> > +#include <linux/inetdevice.h>
> > +#include <net/addrconf.h>
> > +#include <linux/module.h>
> > +#include <linux/bvec.h>
> > +
> > +#include <linux/nfs.h>
> > +#include <linux/nfs_fs.h>
> > +#include <linux/nfs_xdr.h>
> > +
> > +#include <uapi/linux/if_arp.h>
> > +
> > +#include "internal.h"
> > +#include "pnfs.h"
> > +#include "nfstrace.h"
> > +
> > +#define NFSDBG_FACILITY		NFSDBG_VFS
> > +
> > +extern int nfsd_open_local_fh(struct rpc_clnt *rpc_clnt,
> > +			????? const struct cred *cred,
> > +			????? const struct nfs_fh *nfs_fh, const fmode_t fmode,
> > +			????? struct file **pfilp);
> > +/*
> > + * The localio code needs to call into nfsd to do the filehandle -> struct path
> > + * mapping, but cannot be statically linked, because that will make the nfs
> > + * module depend on the nfsd module.
> > + *
> > + * Instead, do dynamic linking to the nfsd module. This way the nfs module
> > + * will only hold a reference on nfsd when it's actually in use. This also
> > + * allows some sanity checking, like giving up on localio if nfsd isn't loaded.
> > + */
> > +
> > +struct nfs_local_open_ctx {
> > +	spinlock_t lock;
> > +	nfs_to_nfsd_open_t open_f;
> > +	atomic_t refcount;
> > +};
> > +
> > +struct nfs_local_kiocb {
> > +	struct kiocb		kiocb;
> > +	struct bio_vec		*bvec;
> > +	struct nfs_pgio_header	*hdr;
> > +	struct work_struct	work;
> > +};
> > +
> > +struct nfs_local_fsync_ctx {
> > +	struct file		*filp;
> > +	struct nfs_commit_data	*data;
> > +	struct work_struct	work;
> > +	struct kref		kref;
> > +};
> > +static void nfs_local_fsync_work(struct work_struct *work);
> > +
> > +/*
> > + * We need to translate between nfs status return values and
> > + * the local errno values which may not be the same.
> > + */
> > +static struct {
> > +	__u32 stat;
> > +	int errno;
> > +} nfs_errtbl[] = {
> > +	{ NFS4_OK,		0		},
> > +	{ NFS4ERR_PERM,		-EPERM		},
> > +	{ NFS4ERR_NOENT,	-ENOENT		},
> > +	{ NFS4ERR_IO,		-EIO		},
> > +	{ NFS4ERR_NXIO,		-ENXIO		},
> > +	{ NFS4ERR_FBIG,		-E2BIG		},
> > +	{ NFS4ERR_STALE,	-EBADF		},
> > +	{ NFS4ERR_ACCESS,	-EACCES		},
> > +	{ NFS4ERR_EXIST,	-EEXIST		},
> > +	{ NFS4ERR_XDEV,		-EXDEV		},
> > +	{ NFS4ERR_MLINK,	-EMLINK		},
> > +	{ NFS4ERR_NOTDIR,	-ENOTDIR	},
> > +	{ NFS4ERR_ISDIR,	-EISDIR		},
> > +	{ NFS4ERR_INVAL,	-EINVAL		},
> > +	{ NFS4ERR_FBIG,		-EFBIG		},
> > +	{ NFS4ERR_NOSPC,	-ENOSPC		},
> > +	{ NFS4ERR_ROFS,		-EROFS		},
> > +	{ NFS4ERR_NAMETOOLONG,	-ENAMETOOLONG	},
> > +	{ NFS4ERR_NOTEMPTY,	-ENOTEMPTY	},
> > +	{ NFS4ERR_DQUOT,	-EDQUOT		},
> > +	{ NFS4ERR_STALE,	-ESTALE		},
> > +	{ NFS4ERR_STALE,	-EOPENSTALE	},
> > +	{ NFS4ERR_DELAY,	-ETIMEDOUT	},
> > +	{ NFS4ERR_DELAY,	-ERESTARTSYS	},
> > +	{ NFS4ERR_DELAY,	-EAGAIN		},
> > +	{ NFS4ERR_DELAY,	-ENOMEM		},
> > +	{ NFS4ERR_IO,		-ETXTBSY	},
> > +	{ NFS4ERR_IO,		-EBUSY		},
> > +	{ NFS4ERR_BADHANDLE,	-EBADHANDLE	},
> > +	{ NFS4ERR_BAD_COOKIE,	-EBADCOOKIE	},
> > +	{ NFS4ERR_NOTSUPP,	-EOPNOTSUPP	},
> > +	{ NFS4ERR_TOOSMALL,	-ETOOSMALL	},
> > +	{ NFS4ERR_SERVERFAULT,	-ESERVERFAULT	},
> > +	{ NFS4ERR_SERVERFAULT,	-ENFILE		},
> > +	{ NFS4ERR_IO,		-EREMOTEIO	},
> > +	{ NFS4ERR_IO,		-EUCLEAN	},
> > +	{ NFS4ERR_PERM,		-ENOKEY		},
> > +	{ NFS4ERR_BADTYPE,	-EBADTYPE	},
> > +	{ NFS4ERR_SYMLINK,	-ELOOP		},
> > +	{ NFS4ERR_DEADLOCK,	-EDEADLK	},
> > +};
> > +
> > +/*
> > + * Convert an NFS error code to a local one.
> > + * This one is used jointly by NFSv2 and NFSv3.
> > + */
> > +static __u32
> > +nfs4errno(int errno)
> > +{
> > +	unsigned int i;
> > +	for (i = 0; i < ARRAY_SIZE(nfs_errtbl); i++) {
> > +		if (nfs_errtbl[i].errno == errno)
> > +			return nfs_errtbl[i].stat;
> > +	}
> > +	/* If we cannot translate the error, the recovery routines should
> > +	 * handle it.
> > +	 * Note: remaining NFSv4 error codes have values > 10000, so should
> > +	 * not conflict with native Linux error codes.
> > +	 */
> > +	return NFS4ERR_SERVERFAULT;
> > +}
> > +
> > +static struct nfs_local_open_ctx __local_open_ctx __read_mostly;
> > +
> > +static bool localio_enabled __read_mostly = true;
> > +module_param(localio_enabled, bool, 0644);
> > +
> > +bool nfs_server_is_local(const struct nfs_client *clp)
> > +{
> > +	return test_bit(NFS_CS_LOCAL_IO, &clp->cl_flags) != 0 &&
> > +		localio_enabled;
> > +}
> > +EXPORT_SYMBOL_GPL(nfs_server_is_local);
> > +
> > +void
> > +nfs_local_init(void)
> > +{
> > +	struct nfs_local_open_ctx *ctx = &__local_open_ctx;
> > +
> > +	ctx->open_f = NULL;
> > +	spin_lock_init(&ctx->lock);
> > +	atomic_set(&ctx->refcount, 0);
> > +}
> > +
> > +static bool
> > +nfs_local_get_lookup_ctx(void)
> > +{
> > +	struct nfs_local_open_ctx *ctx = &__local_open_ctx;
> > +	nfs_to_nfsd_open_t fn = NULL;
> > +
> > +	spin_lock(&ctx->lock);
> > +	if (ctx->open_f == NULL) {
> > +		spin_unlock(&ctx->lock);
> > +
> > +		fn = symbol_request(nfsd_open_local_fh);
> > +		if (!fn)
> > +			return false;
> > +
> > +		spin_lock(&ctx->lock);
> > +		/* catch race */
> > +		if (ctx->open_f == NULL) {
> > +			ctx->open_f = fn;
> > +			fn = NULL;
> > +		}
> > +	}
> > +	atomic_inc(&ctx->refcount);
> > +	spin_unlock(&ctx->lock);
> > +	if (fn)
> > +		symbol_put(nfsd_open_local_fh);
> > +	return true;
> > +}
> > +
> > +static void
> > +nfs_local_put_lookup_ctx(void)
> > +{
> > +	struct nfs_local_open_ctx *ctx = &__local_open_ctx;
> > +	nfs_to_nfsd_open_t fn;
> > +
> > +	if (atomic_dec_and_lock(&ctx->refcount, &ctx->lock)) {
> > +		fn = ctx->open_f;
> > +		ctx->open_f = NULL;
> > +		spin_unlock(&ctx->lock);
> > +		if (fn)
> > +			symbol_put(nfsd_open_local_fh);
> > +		dprintk("destroy lookup context\n");
> > +	}
> > +}
> > +
> > +/*
> > + * nfs_local_enable - attempt to enable local i/o for an nfs_client
> > + */
> > +void
> > +nfs_local_enable(struct nfs_client *clp)
> > +{
> > +	if (nfs_local_get_lookup_ctx()) {
> > +		dprintk("enabled local i/o\n");
> > +		set_bit(NFS_CS_LOCAL_IO, &clp->cl_flags);
> > +	}
> > +}
> > +EXPORT_SYMBOL_GPL(nfs_local_enable);
> > +
> > +/*
> > + * nfs_local_disable - disable local i/o for an nfs_client
> > + */
> > +void
> > +nfs_local_disable(struct nfs_client *clp)
> > +{
> > +	if (test_and_clear_bit(NFS_CS_LOCAL_IO, &clp->cl_flags)) {
> > +		dprintk("disabled local i/o\n");
> > +		nfs_local_put_lookup_ctx();
> > +	}
> > +}
> > +
> > +/*
> > + * nfs_local_probe - probe local i/o support for an nfs_client
> > + */
> > +void
> > +nfs_local_probe(struct nfs_client *clp)
> > +{
> > +	struct sockaddr_in *sin;
> > +	struct sockaddr_in6 *sin6;
> > +	struct nfs_local_addr *addr;
> > +	struct sockaddr *sap;
> > +	bool enable = false;
> > +
> > +	switch (clp->cl_addr.ss_family) {
> > +	case AF_INET:
> > +		sin = (struct sockaddr_in *)&clp->cl_addr;
> > +		if (ipv4_is_loopback(sin->sin_addr.s_addr)) {
> > +			dprintk("%s: detected IPv4 loopback address\n",
> > +				__func__);
> > +			enable = true;
> > +		}
> > +		break;
> > +	case AF_INET6:
> > +		sin6 = (struct sockaddr_in6 *)&clp->cl_addr;
> > +		if (memcmp(&sin6->sin6_addr, &in6addr_loopback,
> > +		??? sizeof(struct in6_addr)) == 0) {
> > +			dprintk("%s: detected IPv6 loopback address\n",
> > +				__func__);
> > +			enable = true;
> > +		}
> > +		break;
> > +	default:
> > +		break;
> > +	}
> > +
> > +	if (enable)
> > +		goto out;
> > +
> > +	list_for_each_entry(addr, &clp->cl_local_addrs, cl_addrs) {
> > +		sap = (struct sockaddr *)&addr->address;
> > +		if (rpc_cmp_addr((struct sockaddr *)&clp->cl_addr, sap)) {
> > +			dprintk("%s: detected local server.\n", __func__);
> > +			enable = true;
> > +			break;
> > +		}
> > +	}
> > +
> > +out:
> > +	if (enable)
> > +		nfs_local_enable(clp);
> > +}
> > +
> > +/*
> > + * nfs_local_open_fh - open a local filehandle
> > + *
> > + * Returns a pointer to a struct file or an ERR_PTR
> > + */
> > +struct file *
> > +nfs_local_open_fh(struct nfs_client *clp, const struct cred *cred,
> > +		? struct nfs_fh *fh, const fmode_t mode)
> > +{
> > +	struct nfs_local_open_ctx *ctx = &__local_open_ctx;
> > +	struct file *filp;
> > +	int status;
> > +
> > +	if (mode & ~(FMODE_READ | FMODE_WRITE))
> > +		return ERR_PTR(-EINVAL);
> > +
> > +	status = ctx->open_f(clp->cl_rpcclient, cred, fh, mode, &filp);
> > +	if (status < 0) {
> > +		dprintk("%s: open local file failed error=%d\n",
> > +				__func__, status);
> > +		trace_nfs_local_open_fh(fh, mode, status);
> > +		switch (status) {
> > +		case -ENXIO:
> > +			nfs_local_disable(clp);
> > +			fallthrough;
> > +		case -ETIMEDOUT:
> > +			status = -EAGAIN;
> > +		}
> > +		filp = ERR_PTR(status);
> > +	}
> > +	return filp;
> > +}
> > +EXPORT_SYMBOL_GPL(nfs_local_open_fh);
> > +
> > +static struct bio_vec *
> > +nfs_bvec_alloc_and_import_pagevec(struct page **pagevec,
> > +		unsigned int npages, gfp_t flags)
> > +{
> > +	struct bio_vec *bvec, *p;
> > +
> > +	bvec = kmalloc_array(npages, sizeof(*bvec), flags);
> > +	if (bvec != NULL) {
> > +		for (p = bvec; npages > 0; p++, pagevec++, npages--) {
> > +			p->bv_page = *pagevec;
> > +			p->bv_len = PAGE_SIZE;
> > +			p->bv_offset = 0;
> > +		}
> > +	}
> > +	return bvec;
> > +}
> > +
> > +static void
> > +nfs_local_iocb_free(struct nfs_local_kiocb *iocb)
> > +{
> > +	kfree(iocb->bvec);
> > +	kfree(iocb);
> > +}
> > +
> > +static struct nfs_local_kiocb *
> > +nfs_local_iocb_alloc(struct nfs_pgio_header *hdr, struct file *filp,
> > +		gfp_t flags)
> > +{
> > +	struct nfs_local_kiocb *iocb;
> > +
> > +	iocb = kmalloc(sizeof(*iocb), flags);
> > +	if (iocb == NULL)
> > +		return NULL;
> > +	iocb->bvec = nfs_bvec_alloc_and_import_pagevec(hdr->page_array.pagevec,
> > +			hdr->page_array.npages, flags);
> > +	if (iocb->bvec == NULL) {
> > +		kfree(iocb);
> > +		return NULL;
> > +	}
> > +	init_sync_kiocb(&iocb->kiocb, filp);
> > +	iocb->kiocb.ki_pos = hdr->args.offset;
> > +	iocb->hdr = hdr;
> > +	/* FIXME: NFS_IOHDR_ODIRECT isn't ever set */
> > +	if (test_bit(NFS_IOHDR_ODIRECT, &hdr->flags))
> > +		iocb->kiocb.ki_flags |= IOCB_DIRECT|IOCB_DSYNC;
> > +	iocb->kiocb.ki_flags &= ~IOCB_APPEND;
> > +	return iocb;
> > +}
> > +
> > +static void
> > +nfs_local_iter_init(struct iov_iter *i, struct nfs_local_kiocb *iocb, int dir)
> > +{
> > +	struct nfs_pgio_header *hdr = iocb->hdr;
> > +
> > +	if (hdr->args.pgbase != 0) {
> > +		iov_iter_bvec(i, dir, iocb->bvec,
> > +				hdr->page_array.npages,
> > +				hdr->args.count + hdr->args.pgbase);
> > +		iov_iter_advance(i, hdr->args.pgbase);
> > +	} else
> > +		iov_iter_bvec(i, dir, iocb->bvec,
> > +				hdr->page_array.npages, hdr->args.count);
> > +}
> > +
> > +static void
> > +nfs_local_hdr_release(struct nfs_pgio_header *hdr,
> > +		const struct rpc_call_ops *call_ops)
> > +{
> > +	call_ops->rpc_call_done(&hdr->task, hdr);
> > +	call_ops->rpc_release(hdr);
> > +}
> > +
> > +static void
> > +nfs_local_pgio_init(struct nfs_pgio_header *hdr,
> > +		const struct rpc_call_ops *call_ops)
> > +{
> > +	hdr->task.tk_ops = call_ops;
> > +	if (!hdr->task.tk_start)
> > +		hdr->task.tk_start = ktime_get();
> > +}
> > +
> > +static void
> > +nfs_local_pgio_done(struct nfs_pgio_header *hdr, long status)
> > +{
> > +	if (status >= 0) {
> > +		hdr->res.count = status;
> > +		hdr->res.op_status = NFS4_OK;
> > +		hdr->task.tk_status = 0;
> > +	} else {
> > +		hdr->res.op_status = nfs4errno(status);
> > +		hdr->task.tk_status = status;
> > +	}
> > +}
> > +
> > +static void
> > +nfs_local_pgio_release(struct nfs_local_kiocb *iocb)
> > +{
> > +	struct nfs_pgio_header *hdr = iocb->hdr;
> > +
> > +	fput(iocb->kiocb.ki_filp);
> > +	nfs_local_iocb_free(iocb);
> > +	nfs_local_hdr_release(hdr, hdr->task.tk_ops);
> > +}
> > +
> > +static void
> > +nfs_local_read_aio_complete_work(struct work_struct *work)
> > +{
> > +	struct nfs_local_kiocb *iocb = container_of(work,
> > +			struct nfs_local_kiocb, work);
> > +
> > +	nfs_local_pgio_release(iocb);
> > +}
> > +
> > +/*
> > + * Complete the I/O from iocb->kiocb.ki_complete()
> > + *
> > + * Note that this function can be called from a bottom half context,
> > + * hence we need to queue the fput() etc to a workqueue
> > + */
> > +static void
> > +nfs_local_pgio_complete(struct nfs_local_kiocb *iocb)
> > +{
> > +	queue_work(nfsiod_workqueue, &iocb->work);
> > +}
> > +
> > +static void
> > +nfs_local_read_done(struct nfs_local_kiocb *iocb, long status)
> > +{
> > +	struct nfs_pgio_header *hdr = iocb->hdr;
> > +	struct file *filp = iocb->kiocb.ki_filp;
> > +
> > +	nfs_local_pgio_done(hdr, status);
> > +
> > +	if (hdr->res.count != hdr->args.count ||
> > +	??? hdr->args.offset + hdr->res.count >= i_size_read(file_inode(filp)))
> > +		hdr->res.eof = true;
> > +
> > +	dprintk("%s: read %ld bytes eof %d.\n", __func__,
> > +			status > 0 ? status : 0, hdr->res.eof);
> > +}
> > +
> > +static void
> > +nfs_local_read_aio_complete(struct kiocb *kiocb, long ret)
> > +{
> > +	struct nfs_local_kiocb *iocb = container_of(kiocb,
> > +			struct nfs_local_kiocb, kiocb);
> > +
> > +	nfs_local_read_done(iocb, ret);
> > +	nfs_local_pgio_complete(iocb);
> > +}
> > +
> > +static int
> > +nfs_do_local_read(struct nfs_pgio_header *hdr, struct file *filp,
> > +		const struct rpc_call_ops *call_ops)
> > +{
> > +	struct nfs_local_kiocb *iocb;
> > +	struct iov_iter iter;
> > +	ssize_t status;
> > +
> > +	dprintk("%s: vfs_read count=%u pos=%llu\n",
> > +		__func__, hdr->args.count, hdr->args.offset);
> > +
> > +	iocb = nfs_local_iocb_alloc(hdr, filp, GFP_KERNEL);
> > +	if (iocb == NULL)
> > +		return -ENOMEM;
> > +	nfs_local_iter_init(&iter, iocb, READ);
> > +
> > +	nfs_local_pgio_init(hdr, call_ops);
> > +	hdr->res.eof = false;
> > +
> > +	if (iocb->kiocb.ki_flags & IOCB_DIRECT) {
> > +		INIT_WORK(&iocb->work, nfs_local_read_aio_complete_work);
> > +		iocb->kiocb.ki_complete = nfs_local_read_aio_complete;
> > +	}
> > +
> > +	status = filp->f_op->read_iter(&iocb->kiocb, &iter);
> > +	if (status != -EIOCBQUEUED) {
> > +		nfs_local_read_done(iocb, status);
> > +		nfs_local_pgio_release(iocb);
> > +	}
> > +	return 0;
> > +}
> > +
> > +static void
> > +nfs_copy_boot_verifier(struct nfs_write_verifier *verifier, struct inode *inode)
> > +{
> > +	struct nfs_client *clp = NFS_SERVER(inode)->nfs_client;
> > +	u32 *verf = (u32 *)verifier->data;
> > +	int seq = 0;
> > +
> > +	do {
> > +		read_seqbegin_or_lock(&clp->cl_boot_lock, &seq);
> > +		verf[0] = (u32)clp->cl_nfssvc_boot.tv_sec;
> > +		verf[1] = (u32)clp->cl_nfssvc_boot.tv_nsec;
> > +	} while (need_seqretry(&clp->cl_boot_lock, seq));
> > +	done_seqretry(&clp->cl_boot_lock, seq);
> > +}
> > +
> > +static void
> > +nfs_reset_boot_verifier(struct inode *inode)
> > +{
> > +	struct nfs_client *clp = NFS_SERVER(inode)->nfs_client;
> > +
> > +	write_seqlock(&clp->cl_boot_lock);
> > +	ktime_get_real_ts64(&clp->cl_nfssvc_boot);
> > +	write_sequnlock(&clp->cl_boot_lock);
> > +}
> > +
> > +static void
> > +nfs_set_local_verifier(struct inode *inode,
> > +		struct nfs_writeverf *verf,
> > +		enum nfs3_stable_how how)
> > +{
> > +
> > +	nfs_copy_boot_verifier(&verf->verifier, inode);
> > +	verf->committed = how;
> > +}
> > +
> > +static void
> > +nfs_get_vfs_attr(struct file *filp, struct nfs_fattr *fattr)
> > +{
> > +	struct kstat stat;
> > +
> > +	if (fattr != NULL && vfs_getattr(&filp->f_path, &stat,
> > +					 STATX_INO |
> > +					 STATX_ATIME |
> > +					 STATX_MTIME |
> > +					 STATX_CTIME |
> > +					 STATX_SIZE |
> > +					 STATX_BLOCKS,
> > +					 AT_STATX_SYNC_AS_STAT) == 0) {
> > +		fattr->valid = NFS_ATTR_FATTR_FILEID |
> > +			NFS_ATTR_FATTR_CHANGE |
> > +			NFS_ATTR_FATTR_SIZE |
> > +			NFS_ATTR_FATTR_ATIME |
> > +			NFS_ATTR_FATTR_MTIME |
> > +			NFS_ATTR_FATTR_CTIME |
> > +			NFS_ATTR_FATTR_SPACE_USED;
> > +		fattr->fileid = stat.ino;
> > +		fattr->size = stat.size;
> > +		fattr->atime = stat.atime;
> > +		fattr->mtime = stat.mtime;
> > +		fattr->ctime = stat.ctime;
> > +		fattr->change_attr = nfs_timespec_to_change_attr(&fattr->ctime);
> > +		fattr->du.nfs3.used = stat.blocks << 9;
> > +	}
> > +}
> > +
> > +static void
> > +nfs_local_write_done(struct nfs_local_kiocb *iocb, long status)
> > +{
> > +	struct nfs_pgio_header *hdr = iocb->hdr;
> > +
> > +	dprintk("%s: wrote %ld bytes.\n", __func__, status > 0 ? status : 0);
> > +
> > +	/* Handle short writes as if they are ENOSPC */
> > +	if (status > 0 && status < hdr->args.count) {
> > +		hdr->mds_offset += status;
> > +		hdr->args.offset += status;
> > +		hdr->args.pgbase += status;
> > +		hdr->args.count -= status;
> > +		nfs_set_pgio_error(hdr, -ENOSPC, hdr->args.offset);
> > +		status = -ENOSPC;
> > +	}
> > +	if (status < 0)
> > +		nfs_reset_boot_verifier(hdr->inode);
> > +	nfs_local_pgio_done(hdr, status);
> > +}
> > +
> > +static void
> > +nfs_local_write_aio_complete_work(struct work_struct *work)
> > +{
> > +	struct nfs_local_kiocb *iocb = container_of(work,
> > +			struct nfs_local_kiocb, work);
> > +
> > +	nfs_get_vfs_attr(iocb->kiocb.ki_filp, iocb->hdr->res.fattr);
> > +	nfs_local_pgio_release(iocb);
> > +}
> > +
> > +static void
> > +nfs_local_write_aio_complete(struct kiocb *kiocb, long ret)
> > +{
> > +	struct nfs_local_kiocb *iocb = container_of(kiocb,
> > +			struct nfs_local_kiocb, kiocb);
> > +
> > +	nfs_local_write_done(iocb, ret);
> > +	nfs_local_pgio_complete(iocb);
> > +}
> > +
> > +static int
> > +nfs_do_local_write(struct nfs_pgio_header *hdr, struct file *filp,
> > +		const struct rpc_call_ops *call_ops)
> > +{
> > +	struct nfs_local_kiocb *iocb;
> > +	struct iov_iter iter;
> > +	ssize_t status;
> > +
> > +	dprintk("%s: vfs_write count=%u pos=%llu %s\n",
> > +		__func__, hdr->args.count, hdr->args.offset,
> > +		(hdr->args.stable == NFS_UNSTABLE) ?? "unstable" : "stable");
> > +
> > +	iocb = nfs_local_iocb_alloc(hdr, filp, GFP_NOIO);
> > +	if (iocb == NULL)
> > +		return -ENOMEM;
> > +	nfs_local_iter_init(&iter, iocb, WRITE);
> > +
> > +	switch (hdr->args.stable) {
> > +	default:
> > +		break;
> > +	case NFS_DATA_SYNC:
> > +		iocb->kiocb.ki_flags |= IOCB_DSYNC;
> > +		break;
> > +	case NFS_FILE_SYNC:
> > +		iocb->kiocb.ki_flags |= IOCB_DSYNC|IOCB_SYNC;
> > +	}
> > +	nfs_local_pgio_init(hdr, call_ops);
> > +
> > +	if (iocb->kiocb.ki_flags & IOCB_DIRECT) {
> > +		INIT_WORK(&iocb->work, nfs_local_write_aio_complete_work);
> > +		iocb->kiocb.ki_complete = nfs_local_write_aio_complete;
> > +	}
> > +
> > +	nfs_set_local_verifier(hdr->inode, hdr->res.verf, hdr->args.stable);
> > +
> > +	file_start_write(filp);
> > +	status = filp->f_op->write_iter(&iocb->kiocb, &iter);
> > +	file_end_write(filp);
> > +	if (status != -EIOCBQUEUED) {
> > +		nfs_local_write_done(iocb, status);
> > +		nfs_get_vfs_attr(filp, hdr->res.fattr);
> > +		nfs_local_pgio_release(iocb);
> > +	}
> > +	return 0;
> > +}
> > +
> > +static struct file *
> > +nfs_local_file_open_cached(struct nfs_client *clp, const struct cred *cred,
> > +			?? struct nfs_fh *fh, struct nfs_open_context *ctx)
> > +{
> > +	struct file *filp = ctx->local_filp;
> > +
> > +	if (!filp) {
> > +		struct file *new = nfs_local_open_fh(clp, cred, fh, ctx->mode);
> > +		if (IS_ERR_OR_NULL(new))
> > +			return NULL;
> > +		/* try to put this one in the slot */
> > +		filp = cmpxchg(&ctx->local_filp, NULL, new);
> > +		if (filp != NULL)
> > +			fput(new);
> > +		else
> > +			filp = new;
> > +	}
> > +	return get_file(filp);
> > +}
> > +
> > +struct file *
> > +nfs_local_file_open(struct nfs_client *clp, const struct cred *cred,
> > +		??? struct nfs_fh *fh, struct nfs_open_context *ctx)
> > +{
> > +	if (!nfs_server_is_local(clp))
> > +		return NULL;
> > +	return nfs_local_file_open_cached(clp, cred, fh, ctx);
> > +}
> > +
> > +int
> > +nfs_local_doio(struct nfs_client *clp, struct file *filp,
> > +	?????? struct nfs_pgio_header *hdr,
> > +	?????? const struct rpc_call_ops *call_ops)
> > +{
> > +	int status = 0;
> > +
> > +	if (!hdr->args.count)
> > +		goto out_fput;
> > +	/* Don't support filesystems without read_iter/write_iter */
> > +	if (!filp->f_op->read_iter || !filp->f_op->write_iter) {
> > +		nfs_local_disable(clp);
> > +		status = -EAGAIN;
> > +		goto out_fput;
> > +	}
> > +
> > +	switch (hdr->rw_mode) {
> > +	case FMODE_READ:
> > +		status = nfs_do_local_read(hdr, filp, call_ops);
> > +		break;
> > +	case FMODE_WRITE:
> > +		status = nfs_do_local_write(hdr, filp, call_ops);
> > +		break;
> > +	default:
> > +		dprintk("%s: invalid mode: %d\n", __func__,
> > +			hdr->rw_mode);
> > +		status = -EINVAL;
> > +	}
> > +out_fput:
> > +	if (status != 0) {
> > +		fput(filp);
> > +		hdr->task.tk_status = status;
> > +		nfs_local_hdr_release(hdr, call_ops);
> > +	}
> > +	return status;
> > +}
> > +
> > +static void
> > +nfs_local_init_commit(struct nfs_commit_data *data,
> > +		const struct rpc_call_ops *call_ops)
> > +{
> > +	data->task.tk_ops = call_ops;
> > +}
> > +
> > +static int
> > +nfs_local_run_commit(struct file *filp, struct nfs_commit_data *data)
> > +{
> > +	loff_t start = data->args.offset;
> > +	loff_t end = LLONG_MAX;
> > +
> > +	if (data->args.count > 0) {
> > +		end = start + data->args.count - 1;
> > +		if (end < start)
> > +			end = LLONG_MAX;
> > +	}
> > +
> > +	dprintk("%s: commit %llu - %llu\n", __func__, start, end);
> > +	return vfs_fsync_range(filp, start, end, 0);
> > +}
> > +
> > +static void
> > +nfs_local_commit_done(struct nfs_commit_data *data, int status)
> > +{
> > +	if (status >= 0) {
> > +		nfs_set_local_verifier(data->inode,
> > +				data->res.verf,
> > +				NFS_FILE_SYNC);
> > +		data->res.op_status = NFS4_OK;
> > +		data->task.tk_status = 0;
> > +	} else {
> > +		nfs_reset_boot_verifier(data->inode);
> > +		data->res.op_status = nfs4errno(status);
> > +		data->task.tk_status = status;
> > +	}
> > +}
> > +
> > +static void
> > +nfs_local_release_commit_data(struct file *filp,
> > +		struct nfs_commit_data *data,
> > +		const struct rpc_call_ops *call_ops)
> > +{
> > +	fput(filp);
> > +	call_ops->rpc_call_done(&data->task, data);
> > +	call_ops->rpc_release(data);
> > +}
> > +
> > +static struct nfs_local_fsync_ctx *
> > +nfs_local_fsync_ctx_alloc(struct nfs_commit_data *data, struct file *filp,
> > +		gfp_t flags)
> > +{
> > +	struct nfs_local_fsync_ctx *ctx = kmalloc(sizeof(*ctx), flags);
> > +
> > +	if (ctx != NULL) {
> > +		ctx->filp = filp;
> > +		ctx->data = data;
> > +		INIT_WORK(&ctx->work, nfs_local_fsync_work);
> > +		kref_init(&ctx->kref);
> > +	}
> > +	return ctx;
> > +}
> > +
> > +static void
> > +nfs_local_fsync_ctx_kref_free(struct kref *kref)
> > +{
> > +	kfree(container_of(kref, struct nfs_local_fsync_ctx, kref));
> > +}
> > +
> > +static void
> > +nfs_local_fsync_ctx_put(struct nfs_local_fsync_ctx *ctx)
> > +{
> > +	kref_put(&ctx->kref, nfs_local_fsync_ctx_kref_free);
> > +}
> > +
> > +static void
> > +nfs_local_fsync_ctx_free(struct nfs_local_fsync_ctx *ctx)
> > +{
> > +	nfs_local_release_commit_data(ctx->filp, ctx->data,
> > +			ctx->data->task.tk_ops);
> > +	nfs_local_fsync_ctx_put(ctx);
> > +}
> > +
> > +static void
> > +nfs_local_fsync_work(struct work_struct *work)
> > +{
> > +	struct nfs_local_fsync_ctx *ctx;
> > +	int status;
> > +
> > +	ctx = container_of(work, struct nfs_local_fsync_ctx, work);
> > +
> > +	status = nfs_local_run_commit(ctx->filp, ctx->data);
> > +	nfs_local_commit_done(ctx->data, status);
> > +	nfs_local_fsync_ctx_free(ctx);
> > +}
> > +
> > +int
> > +nfs_local_commit(struct nfs_client *clp, struct file *filp,
> > +		 struct nfs_commit_data *data,
> > +		 const struct rpc_call_ops *call_ops, int how)
> > +{
> > +	struct nfs_local_fsync_ctx *ctx;
> > +
> > +	ctx = nfs_local_fsync_ctx_alloc(data, filp, GFP_KERNEL);
> > +	if (!ctx) {
> > +		nfs_local_commit_done(data, -ENOMEM);
> > +		nfs_local_release_commit_data(filp, data, call_ops);
> > +		return -ENOMEM;
> > +	}
> > +
> > +	nfs_local_init_commit(data, call_ops);
> > +	kref_get(&ctx->kref);
> > +	queue_work(nfsiod_workqueue, &ctx->work);
> > +	if (how & FLUSH_SYNC)
> > +		flush_work(&ctx->work);
> > +	nfs_local_fsync_ctx_put(ctx);
> > +	return 0;
> > +}
> > +
> > +static int
> > +nfs_client_add_addr(struct nfs_client *clnt, char *buf, gfp_t flags)
> > +{
> > +	struct nfs_local_addr *addr;
> > +	struct sockaddr *sap;
> > +
> > +	dprintk("%s: adding new local IP %s\n", __func__, buf);
> > +	addr = kmalloc(sizeof(*addr), flags);
> > +	if (!addr) {
> > +		printk(KERN_WARNING "NFS: cannot alloc new addr\n");
> > +		return -ENOMEM;
> > +	}
> > +	sap = (struct sockaddr *)&addr->address;
> > +	addr->addrlen = rpc_pton(clnt->cl_net, buf, strlen(buf),
> > +				sap, sizeof(addr->address));
> > +	if (!addr->addrlen) {
> > +		printk(KERN_WARNING "NFS: cannot parse new addr %s\n",
> > +				buf);
> > +		kfree(addr);
> > +		return -EINVAL;
> > +	}
> > +	list_add(&addr->cl_addrs, &clnt->cl_local_addrs);
> > +
> > +	return 0;
> > +}
> > +
> > +static int
> > +nfs_client_add_v4_addr(struct nfs_client *clnt, struct in_device *indev,
> > +		?????? char *buf, size_t buflen)
> > +{
> > +	struct in_ifaddr *ifa;
> > +	int ret;
> > +
> > +	in_dev_for_each_ifa_rtnl(ifa, indev) {
> > +		snprintf(buf, buflen, "%pI4", &ifa->ifa_local);
> > +		ret = nfs_client_add_addr(clnt, buf, GFP_KERNEL);
> > +		if (ret < 0)
> > +			return ret;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +#if IS_ENABLED(CONFIG_IPV6)
> > +static int
> > +nfs_client_add_v6_addr(struct nfs_client *clnt, struct inet6_dev *in6dev,
> > +		?????? char *buf, size_t buflen)
> > +{
> > +	struct inet6_ifaddr *ifp;
> > +	int ret = 0;
> > +
> > +	read_lock_bh(&in6dev->lock);
> > +	list_for_each_entry(ifp, &in6dev->addr_list, if_list) {
> > +		rpc_ntop6_addr_noscopeid(&ifp->addr, buf, buflen);
> > +		ret = nfs_client_add_addr(clnt, buf, GFP_ATOMIC);
> > +		if (ret < 0)
> > +			goto out;
> > +	}
> > +out:
> > +	read_unlock_bh(&in6dev->lock);
> > +	return ret;
> > +}
> > +#else /* CONFIG_IPV6 */
> > +static int
> > +nfs_client_add_v6_addr(struct nfs_client *clnt, struct inet6_dev *in6dev,
> > +		?????? char *buf, size_t buflen)
> > +{
> > +	return 0;
> > +}
> > +#endif
> > +
> > +/* Find out all local IP addresses. Ignore errors
> > + * because local IO can be optional.
> > + */
> > +void
> > +nfs_probe_local_addr(struct nfs_client *clnt)
> > +{
> > +	struct net_device *dev;
> > +	struct in_device *indev;
> > +	struct inet6_dev *in6dev;
> > +	char buf[INET6_ADDRSTRLEN + IPV6_SCOPE_ID_LEN];
> > +	size_t buflen = sizeof(buf);
> > +
> > +	rtnl_lock();
> > +
> > +	for_each_netdev(clnt->cl_net, dev) {
> > +		if (dev->type == ARPHRD_LOOPBACK ||
> > +		??? !(dev->flags & IFF_UP))
> > +			continue;
> > +		indev = __in_dev_get_rtnl(dev);
> > +		if (indev &&
> > +		??? nfs_client_add_v4_addr(clnt, indev, buf, buflen) < 0)
> > +			break;
> > +		in6dev = __in6_dev_get(dev);
> > +		if (in6dev &&
> > +		??? nfs_client_add_v6_addr(clnt, in6dev, buf, buflen) < 0)
> > +			break;
> > +	}
> > +
> > +	rtnl_unlock();
> > +}
> > diff --git a/fs/nfs/nfstrace.h b/fs/nfs/nfstrace.h
> > index 1e710654af11..45d4086cdeb1 100644
> > --- a/fs/nfs/nfstrace.h
> > +++ b/fs/nfs/nfstrace.h
> > @@ -1681,6 +1681,35 @@ TRACE_EVENT(nfs_mount_path,
> > ?	TP_printk("path='%s'", __get_str(path))
> > ?);
> > ?
> > +TRACE_EVENT(nfs_local_open_fh,
> > +		TP_PROTO(
> > +			const struct nfs_fh *fh,
> > +			fmode_t fmode,
> > +			int error
> > +		),
> > +
> > +		TP_ARGS(fh, fmode, error),
> > +
> > +		TP_STRUCT__entry(
> > +			__field(int, error)
> > +			__field(u32, fhandle)
> > +			__field(unsigned int, fmode)
> > +		),
> > +
> > +		TP_fast_assign(
> > +			__entry->error = error;
> > +			__entry->fhandle = nfs_fhandle_hash(fh);
> > +			__entry->fmode = (__force unsigned int)fmode;
> > +		),
> > +
> > +		TP_printk(
> > +			"error=%d fhandle=0x%08x mode=%s",
> > +			__entry->error,
> > +			__entry->fhandle,
> > +			show_fs_fmode_flags(__entry->fmode)
> > +		)
> > +);
> > +
> > ?DECLARE_EVENT_CLASS(nfs_xdr_event,
> > ?		TP_PROTO(
> > ?			const struct xdr_stream *xdr,
> > diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
> > index 3786d767e2ff..9210a1821ec9 100644
> > --- a/fs/nfs/pagelist.c
> > +++ b/fs/nfs/pagelist.c
> > @@ -848,7 +848,8 @@ int nfs_initiate_pgio(struct nfs_pageio_descriptor *desc,
> > ?		????? struct nfs_client *clp, struct rpc_clnt *rpc_clnt,
> > ?		????? struct nfs_pgio_header *hdr, const struct cred *cred,
> > ?		????? const struct nfs_rpc_ops *rpc_ops,
> > -		????? const struct rpc_call_ops *call_ops, int how, int flags)
> > +		????? const struct rpc_call_ops *call_ops, int how, int flags,
> > +		????? struct file *localio)
> > ?{
> > ?	struct rpc_task *task;
> > ?	struct rpc_message msg = {
> > @@ -878,10 +879,16 @@ int nfs_initiate_pgio(struct nfs_pageio_descriptor *desc,
> > ?		hdr->args.count,
> > ?		(unsigned long long)hdr->args.offset);
> > ?
> > +	if (localio) {
> > +		nfs_local_doio(clp, localio, hdr, call_ops);
> > +		goto out;
> > +	}
> > +
> > ?	task = rpc_run_task(&task_setup_data);
> > ?	if (IS_ERR(task))
> > ?		return PTR_ERR(task);
> > ?	rpc_put_task(task);
> > +out:
> > ?	return 0;
> > ?}
> > ?EXPORT_SYMBOL_GPL(nfs_initiate_pgio);
> > @@ -1080,7 +1087,8 @@ static int nfs_generic_pg_pgios(struct nfs_pageio_descriptor *desc)
> > ?					NFS_PROTO(hdr->inode),
> > ?					desc->pg_rpc_callops,
> > ?					desc->pg_ioflags,
> > -					RPC_TASK_CRED_NOREF | task_flags);
> > +					RPC_TASK_CRED_NOREF | task_flags,
> > +					NULL);
> > ?	}
> > ?	return ret;
> > ?}
> > diff --git a/fs/nfs/pnfs_nfs.c b/fs/nfs/pnfs_nfs.c
> > index b29b50c2c933..ac3c5e6d4c5e 100644
> > --- a/fs/nfs/pnfs_nfs.c
> > +++ b/fs/nfs/pnfs_nfs.c
> > @@ -538,7 +538,7 @@ pnfs_generic_commit_pagelist(struct inode *inode, struct list_head *mds_pages,
> > ?					??? NFS_CLIENT(inode), data,
> > ?					??? NFS_PROTO(data->inode),
> > ?					??? data->mds_ops, how,
> > -					??? RPC_TASK_CRED_NOREF);
> > +					??? RPC_TASK_CRED_NOREF, NULL);
> > ?		} else {
> > ?			nfs_init_commit(data, NULL, data->lseg, cinfo);
> > ?			initiate_commit(data, how);
> > diff --git a/fs/nfs/write.c b/fs/nfs/write.c
> > index c9cfa1308264..ba0b36b15bc1 100644
> > --- a/fs/nfs/write.c
> > +++ b/fs/nfs/write.c
> > @@ -1672,7 +1672,8 @@ int nfs_initiate_commit(struct nfs_client *clp,
> > ?			struct nfs_commit_data *data,
> > ?			const struct nfs_rpc_ops *nfs_ops,
> > ?			const struct rpc_call_ops *call_ops,
> > -			int how, int flags)
> > +			int how, int flags,
> > +			struct file *localio)
> > ?{
> > ?	struct rpc_task *task;
> > ?	int priority = flush_task_priority(how);
> > @@ -1691,6 +1692,7 @@ int nfs_initiate_commit(struct nfs_client *clp,
> > ?		.flags = RPC_TASK_ASYNC | flags,
> > ?		.priority = priority,
> > ?	};
> > +	int status = 0;
> > ?
> > ?	if (nfs_server_capable(data->inode, NFS_CAP_MOVEABLE))
> > ?		task_setup_data.flags |= RPC_TASK_MOVEABLE;
> > @@ -1701,13 +1703,19 @@ int nfs_initiate_commit(struct nfs_client *clp,
> > ?
> > ?	dprintk("NFS: initiated commit call\n");
> > ?
> > +	if (localio) {
> > +		nfs_local_commit(clp, localio, data, call_ops, how);
> > +		goto out;
> > +	}
> > +
> > ?	task = rpc_run_task(&task_setup_data);
> > ?	if (IS_ERR(task))
> > ?		return PTR_ERR(task);
> > ?	if (how & FLUSH_SYNC)
> > ?		rpc_wait_for_completion_task(task);
> > ?	rpc_put_task(task);
> > -	return 0;
> > +out:
> > +	return status;
> > ?}
> > ?EXPORT_SYMBOL_GPL(nfs_initiate_commit);
> > ?
> > @@ -1819,7 +1827,7 @@ nfs_commit_list(struct inode *inode, struct list_head *head, int how,
> > ?	return nfs_initiate_commit(NFS_SERVER(inode)->nfs_client,
> > ?				?? NFS_CLIENT(inode), data, NFS_PROTO(inode),
> > ?				?? data->mds_ops, how,
> > -				?? RPC_TASK_CRED_NOREF | task_flags);
> > +				?? RPC_TASK_CRED_NOREF | task_flags, NULL);
> > ?}
> > ?
> > ?/*
> > diff --git a/fs/nfsd/Makefile b/fs/nfsd/Makefile
> > index b8736a82e57c..702f277394f1 100644
> > --- a/fs/nfsd/Makefile
> > +++ b/fs/nfsd/Makefile
> > @@ -13,7 +13,7 @@ nfsd-y			+= trace.o
> > ?nfsd-y?			+= nfssvc.o nfsctl.o nfsfh.o vfs.o \
> > ?			?? export.o auth.o lockd.o nfscache.o \
> > ?			?? stats.o filecache.o nfs3proc.o nfs3xdr.o \
> > -			?? netlink.o
> > +			?? netlink.o localio.o
> 
> Isn't there a Kconfig option this should be behind?

I backfill Kconfig knobs in patch 21 and later.  I left this patch as
was developed/delivered back in 2014.

> > ?nfsd-$(CONFIG_NFSD_V2) += nfsproc.o nfsxdr.o
> > ?nfsd-$(CONFIG_NFSD_V2_ACL) += nfs2acl.o
> > ?nfsd-$(CONFIG_NFSD_V3_ACL) += nfs3acl.o
> > diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
> > index ad9083ca144b..99631fa56662 100644
> > --- a/fs/nfsd/filecache.c
> > +++ b/fs/nfsd/filecache.c
> > @@ -52,7 +52,7 @@
> > ?#define NFSD_FILE_CACHE_UP		???? (0)
> > ?
> > ?/* We only care about NFSD_MAY_READ/WRITE for this cache */
> > -#define NFSD_FILE_MAY_MASK	(NFSD_MAY_READ|NFSD_MAY_WRITE)
> > +#define NFSD_FILE_MAY_MASK	(NFSD_MAY_READ|NFSD_MAY_WRITE|NFSD_MAY_LOCALIO)
> > ?
> > ?static DEFINE_PER_CPU(unsigned long, nfsd_file_cache_hits);
> > ?static DEFINE_PER_CPU(unsigned long, nfsd_file_acquisitions);
> > diff --git a/fs/nfsd/localio.c b/fs/nfsd/localio.c
> > new file mode 100644
> > index 000000000000..ff68454a4017
> > --- /dev/null
> > +++ b/fs/nfsd/localio.c
> > @@ -0,0 +1,179 @@
> > +/*
> > + * NFS server support for local clients to bypass network stack
> > + *
> > + * Copyright (C) 2014 Weston Andros Adamson <dros@primarydata.com>
> > + */
> > +
> > +#include <linux/exportfs.h>
> > +#include <linux/sunrpc/svcauth_gss.h>
> > +#include <linux/sunrpc/clnt.h>
> > +#include <linux/nfs.h>
> > +#include <linux/string.h>
> > +
> > +#include "nfsd.h"
> > +#include "vfs.h"
> > +#include "netns.h"
> > +#include "filecache.h"
> > +
> > +#define NFSDDBG_FACILITY		NFSDDBG_FH
> > +
> > +static void
> > +nfsd_local_fakerqst_destroy(struct svc_rqst *rqstp)
> > +{
> > +	if (rqstp->rq_client)
> > +		auth_domain_put(rqstp->rq_client);
> > +	if (rqstp->rq_cred.cr_group_info)
> > +		put_group_info(rqstp->rq_cred.cr_group_info);
> > +	kfree(rqstp->rq_cred.cr_principal);
> > +	kfree(rqstp->rq_xprt);
> > +	kfree(rqstp);
> > +}
> > +
> > +static struct svc_rqst *
> > +nfsd_local_fakerqst_create(struct rpc_clnt *rpc_clnt, const struct cred *cred)
> > +{
> > +	struct svc_rqst *rqstp;
> > +	struct net *net = rpc_net_ns(rpc_clnt);
> > +	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
> > +	int status;
> > +
> > +	if (!nn->nfsd_serv) {
> > +		dprintk("%s: localio denied. Server not running\n", __func__);
> > +		return ERR_PTR(-ENXIO);
> > +	}
> > +
> 
> Note that the above check is racy. The nfsd_serv can go away at any
> time since you're not holding the (global) nfsd_mutex (I assume?).

Yes, worst case we should fallback to going over the network.

> > +	rqstp = kzalloc(sizeof(*rqstp), GFP_KERNEL);
> > +	if (!rqstp)
> > +		return ERR_PTR(-ENOMEM);
> > +
> > +	rqstp->rq_xprt = kzalloc(sizeof(*rqstp->rq_xprt), GFP_KERNEL);
> > +	if (!rqstp->rq_xprt) {
> > +		status = -ENOMEM;
> > +		goto out_err;
> > +	}
> > +
> > +	rqstp->rq_xprt->xpt_net = net;
> > +	__set_bit(RQ_SECURE, &rqstp->rq_flags);
> > +	rqstp->rq_proc = 1;
> > +	rqstp->rq_vers = 3;
> > +	rqstp->rq_prot = IPPROTO_TCP;
> > +	rqstp->rq_server = nn->nfsd_serv;
> > +
> 
> I suspect you need to carry a reference of some sort so that the
> nfsd_serv doesn't go away out from under you while this is running,
> since this is not operating in nfsd thread context.
> 
> Typically, every nfsd thread holds a reference to the serv (in serv-
> >sv_nrthreads), so that when you shut down all of the threads, it goes
> away. The catch is that that refcount is currently under the protection
> of the global nfsd_mutex and I doubt you want to take that in this
> codepath.

OK, I can look closer at the inplications.

> > diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h
> > index 82a6f66fe1d0..6b603b0247f1 100644
> > --- a/include/linux/nfs_fs_sb.h
> > +++ b/include/linux/nfs_fs_sb.h
> > @@ -49,12 +49,14 @@ struct nfs_client {
> > ?#define NFS_CS_DS		7		/* - Server is a DS */
> > ?#define NFS_CS_REUSEPORT	8		/* - reuse src port on reconnect */
> > ?#define NFS_CS_PNFS		9		/* - Server used for pnfs */
> > +#define NFS_CS_LOCAL_IO		10		/* - client is local */
> > ?	struct sockaddr_storage	cl_addr;	/* server identifier */
> > ?	size_t			cl_addrlen;
> > ?	char *			cl_hostname;	/* hostname of server */
> > ?	char *			cl_acceptor;	/* GSSAPI acceptor name */
> > ?	struct list_head	cl_share_link;	/* link in global client list */
> > ?	struct list_head	cl_superblocks;	/* List of nfs_server structs */
> > +	struct list_head	cl_local_addrs;	/* List of local addresses */
> > ?
> 
> Is the above needed? I thought you weren't tracking addresses now and
> were using the new RPC protocol to determine locality?
> 
> OIC, this goes away in patch #20...

Right.  Like I said above, just left the baseline has untouched as
possible.  I can go a different way and forcibly rip out the network
interface (sockaddr) matching so as to limit churn if you prefer?

Thanks,
Mike