NFS: Fix a few further cache consistency regressions

Steve Dickson writes:
Doing the following:
1. On server:
$ mkdir ~/t
$ echo Hello > ~/t/tmp

2. On client, wait for a string to appear in this file:
$ until grep -q foo t/tmp ; do echo -n . ; sleep 1 ; done

3. On server, create a *new* file with the same name containing that
string:
$ mv ~/t/tmp ~/t/tmp.old; echo foo > ~/t/tmp

will show how the client will never (and I mean never ;-) ) see
the updated file.

The problem is that we do not update nfsi->cache_change_attribute when the
file changes on the server (we only update it when our client makes the
changes). This again means that functions like nfs_check_verifier() will
fail to register when the parent directory has changed and should trigger
a dentry lookup revalidation.

Signed-off-by: Trond Myklebust <[e-mail]>

fs/nfs/inode.c

···
 #define NFS_MAX_READAHEAD	(RPC_DEF_SLOT_TABLE - 1)
 
 static void nfs_invalidate_inode(struct inode *);
-static int nfs_update_inode(struct inode *, struct nfs_fattr *, unsigned long);
+static int nfs_update_inode(struct inode *, struct nfs_fattr *);
 
 static struct inode *nfs_alloc_inode(struct super_block *sb);
 static void nfs_destroy_inode(struct inode *);
···
 	int		 status = -ESTALE;
 	struct nfs_fattr fattr;
 	struct nfs_inode *nfsi = NFS_I(inode);
-	unsigned long verifier;
-	unsigned long cache_validity;
 
 	dfprintk(PAGECACHE, "NFS: revalidating (%s/%Ld)\n",
 		inode->i_sb->s_id, (long long)NFS_FILEID(inode));
···
 		}
 	}
 
-	/* Protect against RPC races by saving the change attribute */
-	verifier = nfs_save_change_attribute(inode);
 	status = NFS_PROTO(inode)->getattr(server, NFS_FH(inode), &fattr);
 	if (status != 0) {
 		dfprintk(PAGECACHE, "nfs_revalidate_inode: (%s/%Ld) getattr failed, error=%d\n",
···
 	}
 
 	spin_lock(&inode->i_lock);
-	status = nfs_update_inode(inode, &fattr, verifier);
+	status = nfs_update_inode(inode, &fattr);
 	if (status) {
 		spin_unlock(&inode->i_lock);
 		dfprintk(PAGECACHE, "nfs_revalidate_inode: (%s/%Ld) refresh failed, error=%d\n",
···
 			 (long long)NFS_FILEID(inode), status);
 		goto out;
 	}
-	cache_validity = nfsi->cache_validity;
-	nfsi->cache_validity &= ~NFS_INO_REVAL_PAGECACHE;
-
-	/*
-	 * We may need to keep the attributes marked as invalid if
-	 * we raced with nfs_end_attr_update().
-	 */
-	if (time_after_eq(verifier, nfsi->cache_change_attribute))
-		nfsi->cache_validity &= ~(NFS_INO_INVALID_ATTR|NFS_INO_INVALID_ATIME);
 	spin_unlock(&inode->i_lock);
 
 	nfs_revalidate_mapping(inode, inode->i_mapping);
 
-	if (cache_validity & NFS_INO_INVALID_ACL)
+	if (nfsi->cache_validity & NFS_INO_INVALID_ACL)
 		nfs_zap_acl_cache(inode);
 
 	dfprintk(PAGECACHE, "NFS: (%s/%Ld) revalidation complete\n",
···
 		return 0;
 	spin_lock(&inode->i_lock);
 	nfsi->cache_validity &= ~NFS_INO_REVAL_PAGECACHE;
-	if (nfs_verify_change_attribute(inode, fattr->time_start))
-		nfsi->cache_validity &= ~(NFS_INO_INVALID_ATTR|NFS_INO_INVALID_ATIME);
 	if (time_after(fattr->time_start, nfsi->last_updated))
-		status = nfs_update_inode(inode, fattr, fattr->time_start);
+		status = nfs_update_inode(inode, fattr);
 	else
 		status = nfs_check_inode_attributes(inode, fattr);
 
···
 		nfsi->cache_validity |= NFS_INO_INVALID_ATTR | NFS_INO_INVALID_ACCESS;
 		goto out;
 	}
-	status = nfs_update_inode(inode, fattr, fattr->time_start);
-	if (time_after_eq(fattr->time_start, nfsi->cache_change_attribute))
-		nfsi->cache_validity &= ~(NFS_INO_INVALID_ATTR|NFS_INO_INVALID_ATIME|NFS_INO_REVAL_PAGECACHE);
-	nfsi->cache_change_attribute = jiffies;
+	status = nfs_update_inode(inode, fattr);
 out:
 	spin_unlock(&inode->i_lock);
 	return status;
···
  *
  * A very similar scenario holds for the dir cache.
  */
-static int nfs_update_inode(struct inode *inode, struct nfs_fattr *fattr, unsigned long verifier)
+static int nfs_update_inode(struct inode *inode, struct nfs_fattr *fattr)
 {
 	struct nfs_inode *nfsi = NFS_I(inode);
 	loff_t cur_isize, new_isize;
 	unsigned int	invalid = 0;
-	int data_unstable;
+	int data_stable;
 
 	dfprintk(VFS, "NFS: %s(%s/%ld ct=%d info=0x%x)\n",
 			__FUNCTION__, inode->i_sb->s_id, inode->i_ino,
···
 	nfsi->last_updated = jiffies;
 
 	/* Are we racing with known updates of the metadata on the server? */
-	data_unstable = ! (nfs_verify_change_attribute(inode, verifier) ||
-		(nfsi->cache_validity & NFS_INO_REVAL_PAGECACHE));
+	data_stable = nfs_verify_change_attribute(inode, fattr->time_start);
+	if (data_stable)
+		nfsi->cache_validity &= ~(NFS_INO_INVALID_ATTR|NFS_INO_INVALID_ATIME);
 
 	/* Check if our cached file size is stale */
  	new_isize = nfs_size_to_loff_t(fattr->size);
···
 		/* Do we perhaps have any outstanding writes? */
 		if (nfsi->npages == 0) {
 			/* No, but did we race with nfs_end_data_update()? */
-			if (time_after_eq(verifier,  nfsi->cache_change_attribute)) {
+			if (data_stable) {
 				inode->i_size = new_isize;
 				invalid |= NFS_INO_INVALID_DATA;
 			}
···
 			inode->i_size = new_isize;
 			invalid |= NFS_INO_INVALID_ATTR|NFS_INO_INVALID_DATA;
 		}
+		nfsi->cache_change_attribute = jiffies;
 		dprintk("NFS: isize change on server for file %s/%ld\n",
 				inode->i_sb->s_id, inode->i_ino);
 	}
···
 		memcpy(&inode->i_mtime, &fattr->mtime, sizeof(inode->i_mtime));
 		dprintk("NFS: mtime change on server for file %s/%ld\n",
 				inode->i_sb->s_id, inode->i_ino);
-		if (!data_unstable)
-			invalid |= NFS_INO_INVALID_ATTR|NFS_INO_INVALID_DATA;
+		invalid |= NFS_INO_INVALID_ATTR|NFS_INO_INVALID_DATA;
+		nfsi->cache_change_attribute = jiffies;
 	}
 
 	if ((fattr->valid & NFS_ATTR_FATTR_V4)
···
 		dprintk("NFS: change_attr change on server for file %s/%ld\n",
 		       inode->i_sb->s_id, inode->i_ino);
 		nfsi->change_attr = fattr->change_attr;
-		if (!data_unstable)
-			invalid |= NFS_INO_INVALID_ATTR|NFS_INO_INVALID_DATA|NFS_INO_INVALID_ACCESS|NFS_INO_INVALID_ACL;
+		invalid |= NFS_INO_INVALID_ATTR|NFS_INO_INVALID_DATA|NFS_INO_INVALID_ACCESS|NFS_INO_INVALID_ACL;
+		nfsi->cache_change_attribute = jiffies;
 	}
 
 	/* If ctime has changed we should definitely clear access+acl caches */
 	if (!timespec_equal(&inode->i_ctime, &fattr->ctime)) {
-		if (!data_unstable)
-			invalid |= NFS_INO_INVALID_ACCESS|NFS_INO_INVALID_ACL;
+		invalid |= NFS_INO_INVALID_ACCESS|NFS_INO_INVALID_ACL;
 		memcpy(&inode->i_ctime, &fattr->ctime, sizeof(inode->i_ctime));
+		nfsi->cache_change_attribute = jiffies;
 	}
 	memcpy(&inode->i_atime, &fattr->atime, sizeof(inode->i_atime));
 
···
 	if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode)
 				|| S_ISLNK(inode->i_mode)))
 		invalid &= ~NFS_INO_INVALID_DATA;
+	if (data_stable)
+		invalid &= ~(NFS_INO_INVALID_ATTR|NFS_INO_INVALID_ATIME|NFS_INO_REVAL_PAGECACHE);
 	if (!nfs_have_delegation(inode, FMODE_READ))
 		nfsi->cache_validity |= invalid;