The logic that manages negotiating NFS version and protocol settings
is getting more complex over time, so let's split this out of
nfs_try_mount().
This should make Bruce a little happier, as it eliminates the silent
switch case fall through in nfs_try_mount(). And it should help Neil
fix some bugs he's found in this logic.
We can reduce indenting and use a more clear switch over the errno's
as well. Adding more comments can only help.
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
utils/mount/stropts.c | 59 +++++++++++++++++++++++++++++++++++++------------
1 files changed, 45 insertions(+), 14 deletions(-)
diff --git a/utils/mount/stropts.c b/utils/mount/stropts.c
index 0241400..94e75be 100644
--- a/utils/mount/stropts.c
+++ b/utils/mount/stropts.c
@@ -747,6 +747,49 @@ static int nfs_try_mount_v4(struct nfsmount_info *mi)
}
/*
+ * Handle NFS version and transport protocol autonegotiation.
+ *
+ * When no version or protocol is specified on the command line,
+ * mount.nfs negotiates with the server to determine appropriate
+ * settings.
+ *
+ * Employ a set of wonky heuristics to work around missing server
+ * features and work in the face of not-yet-ready servers.
+ */
+static int nfs_autonegotiate(struct nfsmount_info *mi)
+{
+ int result;
+
+ /*
+ * Before 2.6.31, the kernel NFS client didn't support
+ * "-t nfs vers=4" mounts, so we can't include NFSv4
+ * when autonegotiating.
+ */
+ if (linux_version_code() <= MAKE_VERSION(2, 6, 31))
+ goto fall_back;
+
+ errno = 0;
+ result = nfs_try_mount_v4(mi);
+ switch (errno) {
+ case EPROTONOSUPPORT:
+ goto fall_back;
+ case ENOENT:
+ /* Legacy Linux servers don't export an NFSv4
+ * pseudoroot. */
+ goto fall_back;
+ case EPERM:
+ /* Linux servers prior to 2.6.25 may return
+ * EPERM when NFSv4 is not supported. */
+ goto fall_back;
+ default:
+ return result;
+ }
+
+fall_back:
+ return nfs_try_mount_v3v2(mi);
+}
+
+/*
* This is a single pass through the fg/bg loop.
*
* Returns TRUE if successful, otherwise FALSE.
@@ -758,20 +801,8 @@ static int nfs_try_mount(struct nfsmount_info *mi)
switch (mi->version) {
case 0:
- if (linux_version_code() > MAKE_VERSION(2, 6, 31)) {
- errno = 0;
- result = nfs_try_mount_v4(mi);
- if (errno != EPROTONOSUPPORT) {
- /*
- * To deal with legacy Linux servers that don't
- * automatically export a pseudo root, retry
- * ENOENT errors using version 3. And for
- * Linux servers prior to 2.6.25, retry EPERM
- */
- if (errno != ENOENT && errno != EPERM)
- break;
- }
- }
+ result = nfs_autonegotiate(mi);
+ break;
case 2:
case 3:
result = nfs_try_mount_v3v2(mi);
--
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