[PATCH v2 1/2] nfsd: Allow enabling NFSv4.x without also requiring NFSv4.0

[Trond Myklebust <trond.myklebust@primarydata.com>]

For some setups, we may want to allow clients to fall back to NFSv3, or
even to fail, if a specific minor version of NFSv4 is not enabled.
For instance, an application that relies on NFSv4.2 CLONE functionality
is simply not going to work when it falls back to NFSv4.1 or NFSv4.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
---
 fs/nfsd/nfsctl.c | 16 ++++++++--------
 fs/nfsd/nfssvc.c | 14 ++++++++++++++
 2 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index d54fb0e3f30e..4bbba88416dc 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -561,6 +561,7 @@ static ssize_t __write_versions(struct file *file, char *buf, size_t size)
 		len = qword_get(&mesg, vers, size);
 		if (len <= 0) return -EINVAL;
 		do {
+			enum vers_op cmd;
 			sign = *vers;
 			if (sign == '+' || sign == '-')
 				num = simple_strtol((vers+1), &minorp, 0);
@@ -571,21 +572,20 @@ static ssize_t __write_versions(struct file *file, char *buf, size_t size)
 					return -EINVAL;
 				if (kstrtouint(minorp+1, 0, &minor) < 0)
 					return -EINVAL;
-				if (nfsd_minorversion(minor, sign == '-' ?
-						     NFSD_CLEAR : NFSD_SET) < 0)
-					return -EINVAL;
-				goto next;
-			}
+			} else
+				minor = 0;
+			cmd = sign == '-' ? NFSD_CLEAR : NFSD_SET;
 			switch(num) {
 			case 2:
 			case 3:
-			case 4:
-				nfsd_vers(num, sign == '-' ? NFSD_CLEAR : NFSD_SET);
+				nfsd_vers(num, cmd);
 				break;
+			case 4:
+				if (nfsd_minorversion(minor, cmd) >= 0)
+					break;
 			default:
 				return -EINVAL;
 			}
-		next:
 			vers += len + 1;
 		} while ((len = qword_get(&mesg, vers, size)) > 0);
 		/* If all get turned off, turn them back on, as
diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
index e6bfd96734c0..07bf3bd9687b 100644
--- a/fs/nfsd/nfssvc.c
+++ b/fs/nfsd/nfssvc.c
@@ -153,6 +153,18 @@ int nfsd_vers(int vers, enum vers_op change)
 	return 0;
 }
 
+static void
+nfsd_adjust_nfsd_versions4(void)
+{
+	unsigned i;
+
+	for (i = 0; i <= NFSD_SUPPORTED_MINOR_VERSION; i++) {
+		if (nfsd_supported_minorversions[i])
+			return;
+	}
+	nfsd_vers(4, NFSD_CLEAR);
+}
+
 int nfsd_minorversion(u32 minorversion, enum vers_op change)
 {
 	if (minorversion > NFSD_SUPPORTED_MINOR_VERSION)
@@ -160,9 +172,11 @@ int nfsd_minorversion(u32 minorversion, enum vers_op change)
 	switch(change) {
 	case NFSD_SET:
 		nfsd_supported_minorversions[minorversion] = true;
+		nfsd_vers(4, NFSD_SET);
 		break;
 	case NFSD_CLEAR:
 		nfsd_supported_minorversions[minorversion] = false;
+		nfsd_adjust_nfsd_versions4();
 		break;
 	case NFSD_TEST:
 		return nfsd_supported_minorversions[minorversion];
-- 
2.9.3