[RFC PATCH 3/6] NFSD: Avoid using rqstp->rq_vers in nfsd_set_fh_dentry()

[cel@kernel.org]

From: Chuck Lever <chuck.lever@oracle.com>

Currently, fh_verify() makes some daring assumptions about which
version of file handle the caller wants, based on the things it can
find in the passed-in rqstp. The about-to-be-introduced LOCALIO use
case sometimes has no svc_rqst context, so this logic won't work in
that case.

Instead, examine the passed-in file handle. It's .max_size field
should carry information to allow nfsd_set_fh_dentry() to initialize
the file handle appropriately.

lockd appears to be the only kernel consumer that does not set the
file handle .max_size when during initialization.

write_filehandle() is the other question mark, as it looks possible
to specify a maxsize between NFS_FHSIZE and NFS3_FHSIZE here.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 fs/nfsd/lockd.c |  6 ++++--
 fs/nfsd/nfsfh.c | 11 +++++++----
 2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/fs/nfsd/lockd.c b/fs/nfsd/lockd.c
index 46a7f9b813e5..e636d2a1e664 100644
--- a/fs/nfsd/lockd.c
+++ b/fs/nfsd/lockd.c
@@ -32,8 +32,10 @@ nlm_fopen(struct svc_rqst *rqstp, struct nfs_fh *f, struct file **filp,
 	int		access;
 	struct svc_fh	fh;
 
-	/* must initialize before using! but maxsize doesn't matter */
-	fh_init(&fh,0);
+	if (rqstp->rq_vers == 4)
+		fh_init(&fh, NFS3_FHSIZE);
+	else
+		fh_init(&fh, NFS_FHSIZE);
 	fh.fh_handle.fh_size = f->size;
 	memcpy(&fh.fh_handle.fh_raw, f->data, f->size);
 	fh.fh_export = NULL;
diff --git a/fs/nfsd/nfsfh.c b/fs/nfsd/nfsfh.c
index 4b964a71a504..77acc26e8b02 100644
--- a/fs/nfsd/nfsfh.c
+++ b/fs/nfsd/nfsfh.c
@@ -267,25 +267,28 @@ static __be32 nfsd_set_fh_dentry(struct svc_rqst *rqstp, struct svc_fh *fhp)
 	fhp->fh_dentry = dentry;
 	fhp->fh_export = exp;
 
-	switch (rqstp->rq_vers) {
-	case 4:
+	switch (fhp->fh_maxsize) {
+	case NFS4_FHSIZE:
 		if (dentry->d_sb->s_export_op->flags & EXPORT_OP_NOATOMIC_ATTR)
 			fhp->fh_no_atomic_attr = true;
 		fhp->fh_64bit_cookies = true;
 		break;
-	case 3:
+	case NFS3_FHSIZE:
 		if (dentry->d_sb->s_export_op->flags & EXPORT_OP_NOWCC)
 			fhp->fh_no_wcc = true;
 		fhp->fh_64bit_cookies = true;
 		if (exp->ex_flags & NFSEXP_V4ROOT)
 			goto out;
 		break;
-	case 2:
+	case NFS_FHSIZE:
 		fhp->fh_no_wcc = true;
 		if (EX_WGATHER(exp))
 			fhp->fh_use_wgather = true;
 		if (exp->ex_flags & NFSEXP_V4ROOT)
 			goto out;
+		break;
+	case 0:
+		WARN_ONCE(1, "Uninitialized file handle");
 	}
 
 	return 0;
-- 
2.45.2