nfs: Introduce trusted-write and trusted-sync options

Introduces two new options:

1. nfs3.*.trusted-write: Forces UNSTABLE writes to return STABLE to NFS
clients to prevent the clients from sending a COMMIT. STABLE writes
are still handled in a sync manner and so are COMMITs if they're sent
at all.

2. nfs3.*.trusted-sync: Forces all WRITEs and COMMITs to return STABLE
return flags to NFS clients to avoid the overhead of STABLE writes, and
COMMITs that follow UNSTABLE writes. This includes the trusted-write
functionality. In addition to the trusted-write, it also writes
STABLE writes in an UNSTABLE manner.

Both violate the NFS protocol but allow better write perf in most
configurations. Use with caution.

Signed-off-by: Shehjar Tikoo <shehjart@gluster.com>
Signed-off-by: Anand V. Avati <avati@dev.gluster.com>

BUG: 924 (Slow NFS synchronous writes)
URL: http://bugs.gluster.com/cgi-bin/bugzilla3/show_bug.cgi?id=924

1 files changed, 23 insertions, 0 deletions

diff --git a/xlators/nfs/server/src/nfs.c b/xlators/nfs/server/src/nfs.c
index 65ff55c76c1..cb5f19ef992 100644
--- a/xlators/nfs/server/src/nfs.c
+++ b/xlators/nfs/server/src/nfs.c
@@ -601,6 +601,29 @@ struct volume_options options[] = {
           .description = "Type of access desired for this subvolume: "
                          " read-only, read-write(default)"
         },
+        { .key  = {"nfs3.*.trusted-write"},
+          .type = GF_OPTION_TYPE_BOOL,
+          .description = "On an UNSTABLE write from client, return STABLE flag"
+                         " to force client to not send a COMMIT request. In "
+                         "some environments, combined with a replicated "
+                         "GlusterFS setup, this option can improve write "
+                         "performance. This flag allows user to trust Gluster"
+                         " replication logic to sync data to the disks and "
+                         "recover when required. COMMIT requests if received "
+                         "will be handled in a default manner by fsyncing."
+                         " STABLE writes are still handled in a sync manner. "
+                         "Off by default."
+
+        },
+        { .key  = {"nfs3.*.trusted-sync"},
+          .type = GF_OPTION_TYPE_BOOL,
+          .description = "All writes and COMMIT requests are treated as async."
+                         " This implies that no write requests are guaranteed"
+                         " to be on server disks when the write reply is "
+                         "received at the NFS client. Trusted sync includes "
+                         " trusted-write behaviour. Off by default."
+
+        },
         { .key  = {"rpc-auth.auth-unix"},
           .type = GF_OPTION_TYPE_BOOL,
           .description = "Disable or enable the AUTH_UNIX authentication type."