Over NFS, an open() call could result in multiple over-the-wire

GETATTRs being generated - one from lookup()/namei() and the other
from nfs_open() (for cto consistency). This change eliminates the
GETATTR in nfs_open() if an otw GETATTR was done from the namei()
path. Instead of extending the vop interface, we timestamp each attr
load, and use this to detect whether a GETATTR was done from namei()
for this syscall. Introduces a thread-local variable that counts the
syscalls made by the thread and uses <pid, tid, thread syscalls> as
the attrload timestamp. Thanks to jhb@ and peter@ for a discussion on
thread state that could be used as the timestamp with minimal overhead.

1 files changed, 11 insertions, 0 deletions

diff --git a/sys/nfsclient/nfsnode.h b/sys/nfsclient/nfsnode.h
index 2287235..f6d898a 100644
--- a/sys/nfsclient/nfsnode.h
+++ b/sys/nfsclient/nfsnode.h
@@ -74,6 +74,16 @@ struct nfsdmap {
 #define ndm_cookies	ndm_un1.ndmu3_cookies
 #define ndm4_cookies	ndm_un1.ndmu4_cookies
 
+#define n_ac_ts_tid		n_ac_ts.nfs_ac_ts_tid
+#define n_ac_ts_pid		n_ac_ts.nfs_ac_ts_pid
+#define n_ac_ts_syscalls	n_ac_ts.nfs_ac_ts_syscalls
+
+struct nfs_attrcache_timestamp {
+	lwpid_t		nfs_ac_ts_tid;
+	pid_t		nfs_ac_ts_pid;
+	unsigned long	nfs_ac_ts_syscalls;	
+};
+
 /*
  * The nfsnode is the nfs equivalent to ufs's inode. Any similarity
  * is purely coincidental.
@@ -127,6 +137,7 @@ struct nfsnode {
 	uint32_t		n_namelen;
 	int			n_directio_opens;
 	int                     n_directio_asyncwr;
+	struct nfs_attrcache_timestamp n_ac_ts;
 };
 
 #define n_atim		n_un1.nf_atim