NFS: Fix the resolution problem with nfs_inode_attrs_need_update()

It appears that 'jiffies' timestamps do not have high enough resolution for
nfs_inode_attrs_need_update(). One problem is that a GETATTR can be
launched within < 1 jiffy of the last operation that updated the attribute.
Another problem is that RPC calls can take < 1 jiffy to execute.

We can fix this by switching the variables to use a simple global counter
that gets incremented every time we start another GETATTR call.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

2 files changed, 4 insertions, 7 deletions

diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index ca563ee13e32..ac8d0233b05c 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -137,7 +137,7 @@ struct nfs_inode {
         unsigned long           attrtimeo_timestamp;
         __u64                   change_attr;            /* v4 only */
 
-        unsigned long           last_updated;
+        unsigned long           attr_gencount;
         /* "Generation counter" for the attribute cache. This is
          * bumped whenever we update the metadata on the
          * server.
@@ -344,15 +344,11 @@ extern struct nfs_open_context *get_nfs_open_context(struct nfs_open_context *ct
 extern void put_nfs_open_context(struct nfs_open_context *ctx);
 extern struct nfs_open_context *nfs_find_open_context(struct inode *inode, struct rpc_cred *cred, int mode);
 extern u64 nfs_compat_user_ino64(u64 fileid);
+extern void nfs_fattr_init(struct nfs_fattr *fattr);
 
 /* linux/net/ipv4/ipconfig.c: trims ip addr off front of name, too. */
 extern __be32 root_nfs_parse_addr(char *name); /*__init*/
-
-static inline void nfs_fattr_init(struct nfs_fattr *fattr)
-{
-        fattr->valid = 0;
-        fattr->time_start = jiffies;
-}
+extern unsigned long nfs_inc_attr_generation_counter(void);
 
 /*
  * linux/fs/nfs/file.c
diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
index 6ee6ae3f095c..c1c31acb8a2b 100644
--- a/include/linux/nfs_xdr.h
+++ b/include/linux/nfs_xdr.h
@@ -56,6 +56,7 @@ struct nfs_fattr {
         __u64                   change_attr;    /* NFSv4 change attribute */
         __u64                   pre_change_attr;/* pre-op NFSv4 change attribute */
         unsigned long           time_start;
+        unsigned long           gencount;
 };
 
 #define NFS_ATTR_WCC            0x0001          /* pre-op WCC data    */