[PATCH v10 04/19] nfsd: add "localio" support

[Mike Snitzer <snitzer@kernel.org>]

From: Weston Andros Adamson <dros@primarydata.com>

Add server support for bypassing NFS for localhost reads, writes, and
commits. This is only useful when both the client and server are
running on the same host.

If nfsd_open_local_fh() fails (e.g. due to allocation failure in
nfsd_local_fakerqst_create) then the NFS client will both retry and
fallback to normal network-based read, write and commit operations if
localio is no longer supported.

To ensure the server's network namespace is used for localio (to allow
for access to the proper 'struct nfsd_net') the NFS client code will
pass the server's 'struct net' (stored as cl_nfssvc_net in 'struct
nfs_client') as first argument to nfsd_open_local_fh().

It is expected that both the client and server are using the same
mount namespace.

Signed-off-by: Weston Andros Adamson <dros@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/nfsd/Makefile    |   1 +
 fs/nfsd/filecache.c |   2 +-
 fs/nfsd/localio.c   | 248 ++++++++++++++++++++++++++++++++++++++++++++
 fs/nfsd/nfssvc.c    |   1 +
 fs/nfsd/trace.h     |   3 +-
 fs/nfsd/vfs.h       |   9 ++
 6 files changed, 262 insertions(+), 2 deletions(-)
 create mode 100644 fs/nfsd/localio.c

diff --git a/fs/nfsd/Makefile b/fs/nfsd/Makefile
index b8736a82e57c..78b421778a79 100644
--- a/fs/nfsd/Makefile
+++ b/fs/nfsd/Makefile
@@ -23,3 +23,4 @@ nfsd-$(CONFIG_NFSD_PNFS) += nfs4layouts.o
 nfsd-$(CONFIG_NFSD_BLOCKLAYOUT) += blocklayout.o blocklayoutxdr.o
 nfsd-$(CONFIG_NFSD_SCSILAYOUT) += blocklayout.o blocklayoutxdr.o
 nfsd-$(CONFIG_NFSD_FLEXFILELAYOUT) += flexfilelayout.o flexfilelayoutxdr.o
+nfsd-$(CONFIG_NFSD_LOCALIO) += localio.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..2eedeaeab533
--- /dev/null
+++ b/fs/nfsd/localio.c
@@ -0,0 +1,248 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * NFS server support for local clients to bypass network stack
+ *
+ * Copyright (C) 2014 Weston Andros Adamson <dros@primarydata.com>
+ * Copyright (C) 2019 Trond Myklebust <trond.myklebust@hammerspace.com>
+ * Copyright (C) 2024 Mike Snitzer <snitzer@hammerspace.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"
+
+/*
+ * We need to translate between nfs status return values and
+ * the local errno values which may not be the same.
+ * - duplicated from fs/nfs/nfs2xdr.c to avoid needless bloat of
+ *   all compiled nfs objects if it were in include/linux/nfs.h
+ */
+static const struct {
+	int stat;
+	int errno;
+} nfs_common_errtbl[] = {
+	{ NFS_OK,		0		},
+	{ NFSERR_PERM,		-EPERM		},
+	{ NFSERR_NOENT,		-ENOENT		},
+	{ NFSERR_IO,		-EIO		},
+	{ NFSERR_NXIO,		-ENXIO		},
+/*	{ NFSERR_EAGAIN,	-EAGAIN		}, */
+	{ NFSERR_ACCES,		-EACCES		},
+	{ NFSERR_EXIST,		-EEXIST		},
+	{ NFSERR_XDEV,		-EXDEV		},
+	{ NFSERR_NODEV,		-ENODEV		},
+	{ NFSERR_NOTDIR,	-ENOTDIR	},
+	{ NFSERR_ISDIR,		-EISDIR		},
+	{ NFSERR_INVAL,		-EINVAL		},
+	{ NFSERR_FBIG,		-EFBIG		},
+	{ NFSERR_NOSPC,		-ENOSPC		},
+	{ NFSERR_ROFS,		-EROFS		},
+	{ NFSERR_MLINK,		-EMLINK		},
+	{ NFSERR_NAMETOOLONG,	-ENAMETOOLONG	},
+	{ NFSERR_NOTEMPTY,	-ENOTEMPTY	},
+	{ NFSERR_DQUOT,		-EDQUOT		},
+	{ NFSERR_STALE,		-ESTALE		},
+	{ NFSERR_REMOTE,	-EREMOTE	},
+#ifdef EWFLUSH
+	{ NFSERR_WFLUSH,	-EWFLUSH	},
+#endif
+	{ NFSERR_BADHANDLE,	-EBADHANDLE	},
+	{ NFSERR_NOT_SYNC,	-ENOTSYNC	},
+	{ NFSERR_BAD_COOKIE,	-EBADCOOKIE	},
+	{ NFSERR_NOTSUPP,	-ENOTSUPP	},
+	{ NFSERR_TOOSMALL,	-ETOOSMALL	},
+	{ NFSERR_SERVERFAULT,	-EREMOTEIO	},
+	{ NFSERR_BADTYPE,	-EBADTYPE	},
+	{ NFSERR_JUKEBOX,	-EJUKEBOX	},
+	{ -1,			-EIO		}
+};
+
+/**
+ * nfs_stat_to_errno - convert an NFS status code to a local errno
+ * @status: NFS status code to convert
+ *
+ * Returns a local errno value, or -EIO if the NFS status code is
+ * not recognized.  nfsd_file_acquire() returns an nfsstat that
+ * needs to be translated to an errno before being returned to a
+ * local client application.
+ */
+static int nfs_stat_to_errno(enum nfs_stat status)
+{
+	int i;
+
+	for (i = 0; nfs_common_errtbl[i].stat != -1; i++) {
+		if (nfs_common_errtbl[i].stat == (int)status)
+			return nfs_common_errtbl[i].errno;
+	}
+	return nfs_common_errtbl[i].errno;
+}
+
+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);
+	/* rpcauth_map_to_svc_cred_local() clears cr_principal */
+	WARN_ON_ONCE(rqstp->rq_cred.cr_principal != NULL);
+	kfree(rqstp->rq_xprt);
+	kfree(rqstp);
+}
+
+static struct svc_rqst *
+nfsd_local_fakerqst_create(struct net *net, struct rpc_clnt *rpc_clnt,
+			const struct cred *cred)
+{
+	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
+	struct svc_rqst *rqstp;
+	int status;
+
+	/* FIXME: not running in nfsd context, must get reference on nfsd_serv */
+	if (unlikely(!READ_ONCE(nn->nfsd_serv)))
+		return ERR_PTR(-ENXIO);
+
+	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_server = nn->nfsd_serv;
+	/*
+	 * These constants aren't actively used in this fake svc_rqst,
+	 * which bypasses SUNRPC, but they must pass negative checks.
+	 */
+	rqstp->rq_proc = 1;
+	rqstp->rq_vers = 3;
+	rqstp->rq_prot = IPPROTO_TCP;
+
+	/* Note: we're connecting to ourself, so source addr == peer addr */
+	rqstp->rq_addrlen = rpc_peeraddr(rpc_clnt,
+			(struct sockaddr *)&rqstp->rq_addr,
+			sizeof(rqstp->rq_addr));
+
+	rpcauth_map_to_svc_cred_local(rpc_clnt->cl_auth, cred, &rqstp->rq_cred);
+
+	/*
+	 * set up enough for svcauth_unix_set_client to be able to wait
+	 * for the cache downcall. Note that we do _not_ want to allow the
+	 * request to be deferred for later revisit since this rqst and xprt
+	 * are not set up to run inside of the normal svc_rqst engine.
+	 */
+	INIT_LIST_HEAD(&rqstp->rq_xprt->xpt_deferred);
+	kref_init(&rqstp->rq_xprt->xpt_ref);
+	spin_lock_init(&rqstp->rq_xprt->xpt_lock);
+	rqstp->rq_chandle.thread_wait = 5 * HZ;
+
+	status = svcauth_unix_set_client(rqstp);
+	switch (status) {
+	case SVC_OK:
+		break;
+	case SVC_DENIED:
+		status = -ENXIO;
+		goto out_err;
+	default:
+		status = -ETIMEDOUT;
+		goto out_err;
+	}
+
+	return rqstp;
+
+out_err:
+	nfsd_local_fakerqst_destroy(rqstp);
+	return ERR_PTR(status);
+}
+
+/**
+ * nfsd_open_local_fh - lookup a local filehandle @nfs_fh and map to @file
+ *
+ * @cl_nfssvc_net: the 'struct net' to use to get the proper nfsd_net
+ * @rpc_clnt: rpc_clnt that the client established, used for sockaddr and cred
+ * @cred: cred that the client established
+ * @nfs_fh: filehandle to lookup
+ * @fmode: fmode_t to use for open
+ * @pfilp: returned file pointer that maps to @nfs_fh
+ *
+ * This function maps a local fh to a path on a local filesystem.
+ * This is useful when the nfs client has the local server mounted - it can
+ * avoid all the NFS overhead with reads, writes and commits.
+ *
+ * On successful return, caller is responsible for calling path_put. Also
+ * note that this is called from nfs.ko via find_symbol() to avoid an explicit
+ * dependency on knfsd. So, there is no forward declaration in a header file
+ * for it that is shared with the client.
+ */
+int nfsd_open_local_fh(struct net *cl_nfssvc_net,
+			 struct rpc_clnt *rpc_clnt,
+			 const struct cred *cred,
+			 const struct nfs_fh *nfs_fh,
+			 const fmode_t fmode,
+			 struct file **pfilp)
+{
+	int mayflags = NFSD_MAY_LOCALIO;
+	int status = 0;
+	const struct cred *save_cred;
+	struct svc_rqst *rqstp;
+	struct svc_fh fh;
+	struct nfsd_file *nf;
+	__be32 beres;
+
+	/* Save creds before calling into nfsd */
+	save_cred = get_current_cred();
+
+	rqstp = nfsd_local_fakerqst_create(cl_nfssvc_net, rpc_clnt, cred);
+	if (IS_ERR(rqstp)) {
+		status = PTR_ERR(rqstp);
+		goto out_revertcred;
+	}
+
+	/* nfs_fh -> svc_fh */
+	if (nfs_fh->size > NFS4_FHSIZE) {
+		status = -EINVAL;
+		goto out;
+	}
+	fh_init(&fh, NFS4_FHSIZE);
+	fh.fh_handle.fh_size = nfs_fh->size;
+	memcpy(fh.fh_handle.fh_raw, nfs_fh->data, nfs_fh->size);
+
+	if (fmode & FMODE_READ)
+		mayflags |= NFSD_MAY_READ;
+	if (fmode & FMODE_WRITE)
+		mayflags |= NFSD_MAY_WRITE;
+
+	beres = nfsd_file_acquire(rqstp, &fh, mayflags, &nf);
+	if (beres) {
+		status = nfs_stat_to_errno(be32_to_cpu(beres));
+		goto out_fh_put;
+	}
+
+	*pfilp = get_file(nf->nf_file);
+
+	nfsd_file_put(nf);
+out_fh_put:
+	fh_put(&fh);
+
+out:
+	nfsd_local_fakerqst_destroy(rqstp);
+out_revertcred:
+	revert_creds(save_cred);
+	return status;
+}
+EXPORT_SYMBOL_GPL(nfsd_open_local_fh);
+
+/* Compile time type checking, not used by anything */
+static nfs_to_nfsd_open_t __maybe_unused nfsd_open_local_fh_typecheck = nfsd_open_local_fh;
diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
index 402d436cbd24..5c99ba9abb03 100644
--- a/fs/nfsd/nfssvc.c
+++ b/fs/nfsd/nfssvc.c
@@ -431,6 +431,7 @@ static int nfsd_startup_net(struct net *net, const struct cred *cred)
 #endif
 #if IS_ENABLED(CONFIG_NFSD_LOCALIO)
 	INIT_LIST_HEAD(&nn->nfsd_uuid.list);
+	nn->nfsd_uuid.net = net;
 	list_add_tail_rcu(&nn->nfsd_uuid.list, &nfsd_uuids);
 #endif
 	nn->nfsd_net_up = true;
diff --git a/fs/nfsd/trace.h b/fs/nfsd/trace.h
index 77bbd23aa150..9c0610fdd11c 100644
--- a/fs/nfsd/trace.h
+++ b/fs/nfsd/trace.h
@@ -86,7 +86,8 @@ DEFINE_NFSD_XDR_ERR_EVENT(cant_encode);
 		{ NFSD_MAY_NOT_BREAK_LEASE,	"NOT_BREAK_LEASE" },	\
 		{ NFSD_MAY_BYPASS_GSS,		"BYPASS_GSS" },		\
 		{ NFSD_MAY_READ_IF_EXEC,	"READ_IF_EXEC" },	\
-		{ NFSD_MAY_64BIT_COOKIE,	"64BIT_COOKIE" })
+		{ NFSD_MAY_64BIT_COOKIE,	"64BIT_COOKIE" },	\
+		{ NFSD_MAY_LOCALIO,		"LOCALIO" })
 
 TRACE_EVENT(nfsd_compound,
 	TP_PROTO(
diff --git a/fs/nfsd/vfs.h b/fs/nfsd/vfs.h
index 57cd70062048..5146f0c81752 100644
--- a/fs/nfsd/vfs.h
+++ b/fs/nfsd/vfs.h
@@ -33,6 +33,8 @@
 
 #define NFSD_MAY_64BIT_COOKIE		0x1000 /* 64 bit readdir cookies for >= NFSv3 */
 
+#define NFSD_MAY_LOCALIO		0x2000
+
 #define NFSD_MAY_CREATE		(NFSD_MAY_EXEC|NFSD_MAY_WRITE)
 #define NFSD_MAY_REMOVE		(NFSD_MAY_EXEC|NFSD_MAY_WRITE|NFSD_MAY_TRUNC)
 
@@ -158,6 +160,13 @@ __be32		nfsd_permission(struct svc_rqst *, struct svc_export *,
 
 void		nfsd_filp_close(struct file *fp);
 
+int		nfsd_open_local_fh(struct net *net,
+				   struct rpc_clnt *rpc_clnt,
+				   const struct cred *cred,
+				   const struct nfs_fh *nfs_fh,
+				   const fmode_t fmode,
+				   struct file **pfilp);
+
 static inline int fh_want_write(struct svc_fh *fh)
 {
 	int ret;
-- 
2.44.0