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>

1 files changed, 10 insertions, 4 deletions

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 49d565412827..4807074ada8c 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -156,6 +156,7 @@ typedef struct {
         decode_dirent_t decode;
         int             plus;
         unsigned long   timestamp;
+        unsigned long   gencount;
         int             timestamp_valid;
 } nfs_readdir_descriptor_t;
 
@@ -177,7 +178,7 @@ int nfs_readdir_filler(nfs_readdir_descriptor_t *desc, struct page *page)
         struct file     *file = desc->file;
         struct inode    *inode = file->f_path.dentry->d_inode;
         struct rpc_cred *cred = nfs_file_cred(file);
-        unsigned long   timestamp;
+        unsigned long   timestamp, gencount;
         int             error;
 
         dfprintk(DIRCACHE, "NFS: %s: reading cookie %Lu into page %lu\n",
@@ -186,6 +187,7 @@ int nfs_readdir_filler(nfs_readdir_descriptor_t *desc, struct page *page)
 
  again:
         timestamp = jiffies;
+        gencount = nfs_inc_attr_generation_counter();
         error = NFS_PROTO(inode)->readdir(file->f_path.dentry, cred, desc->entry->cookie, page,
                                           NFS_SERVER(inode)->dtsize, desc->plus);
         if (error < 0) {
@@ -199,6 +201,7 @@ int nfs_readdir_filler(nfs_readdir_descriptor_t *desc, struct page *page)
                 goto error;
         }
         desc->timestamp = timestamp;
+        desc->gencount = gencount;
         desc->timestamp_valid = 1;
         SetPageUptodate(page);
         /* Ensure consistent page alignment of the data.
@@ -224,9 +227,10 @@ int dir_decode(nfs_readdir_descriptor_t *desc)
         if (IS_ERR(p))
                 return PTR_ERR(p);
         desc->ptr = p;
-        if (desc->timestamp_valid)
+        if (desc->timestamp_valid) {
                 desc->entry->fattr->time_start = desc->timestamp;
-        else
+                desc->entry->fattr->gencount = desc->gencount;
+        } else
                 desc->entry->fattr->valid &= ~NFS_ATTR_FATTR;
         return 0;
 }
@@ -471,7 +475,7 @@ int uncached_readdir(nfs_readdir_descriptor_t *desc, void *dirent,
         struct rpc_cred *cred = nfs_file_cred(file);
         struct page     *page = NULL;
         int             status;
-        unsigned long   timestamp;
+        unsigned long   timestamp, gencount;
 
         dfprintk(DIRCACHE, "NFS: uncached_readdir() searching for cookie %Lu\n",
                         (unsigned long long)*desc->dir_cookie);
@@ -482,6 +486,7 @@ int uncached_readdir(nfs_readdir_descriptor_t *desc, void *dirent,
                 goto out;
         }
         timestamp = jiffies;
+        gencount = nfs_inc_attr_generation_counter();
         status = NFS_PROTO(inode)->readdir(file->f_path.dentry, cred,
                                                 *desc->dir_cookie, page,
                                                 NFS_SERVER(inode)->dtsize,
@@ -490,6 +495,7 @@ int uncached_readdir(nfs_readdir_descriptor_t *desc, void *dirent,
         desc->ptr = kmap(page);         /* matching kunmap in nfs_do_filldir */
         if (status >= 0) {
                 desc->timestamp = timestamp;
+                desc->gencount = gencount;
                 desc->timestamp_valid = 1;
                 if ((status = dir_decode(desc)) == 0)
                         desc->entry->prev_cookie = *desc->dir_cookie;