[PATCH] NFS: Ensure that fstat() always returns the correct mtime

 Even if the file is open for writes.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/file.c

@@ -127,6 +127,21 @@ nfs_file_release(struct inode *inode, struct file *filp)
 	return NFS_PROTO(inode)->file_release(inode, filp);
 }
 
+/**
+ * nfs_revalidate_file - Revalidate the page cache & related metadata
+ * @inode - pointer to inode struct
+ * @file - pointer to file
+ */
+static int nfs_revalidate_file(struct inode *inode, struct file *filp)
+{
+	int retval = 0;
+
+	if ((NFS_FLAGS(inode) & NFS_INO_REVAL_PAGECACHE) || nfs_attribute_timeout(inode))
+		retval = __nfs_revalidate_inode(NFS_SERVER(inode), inode);
+	nfs_revalidate_mapping(inode, filp->f_mapping);
+	return 0;
+}
+
 /**
  * nfs_revalidate_size - Revalidate the file size
  * @inode - pointer to inode struct
@@ -149,7 +164,8 @@ static int nfs_revalidate_file_size(struct inode *inode, struct file *filp)
 		goto force_reval;
 	if (nfsi->npages != 0)
 		return 0;
-	return nfs_revalidate_inode(server, inode);
+	if (!(NFS_FLAGS(inode) & NFS_INO_REVAL_PAGECACHE) && !nfs_attribute_timeout(inode))
+		return 0;
 force_reval:
 	return __nfs_revalidate_inode(server, inode);
 }
@@ -210,7 +226,7 @@ nfs_file_read(struct kiocb *iocb, char __user * buf, size_t count, loff_t pos)
 		dentry->d_parent->d_name.name, dentry->d_name.name,
 		(unsigned long) count, (unsigned long) pos);
 
-	result = nfs_revalidate_inode(NFS_SERVER(inode), inode);
+	result = nfs_revalidate_file(inode, iocb->ki_filp);
 	if (!result)
 		result = generic_file_aio_read(iocb, buf, count, pos);
 	return result;
@@ -228,7 +244,7 @@ nfs_file_sendfile(struct file *filp, loff_t *ppos, size_t count,
 		dentry->d_parent->d_name.name, dentry->d_name.name,
 		(unsigned long) count, (unsigned long long) *ppos);
 
-	res = nfs_revalidate_inode(NFS_SERVER(inode), inode);
+	res = nfs_revalidate_file(inode, filp);
 	if (!res)
 		res = generic_file_sendfile(filp, ppos, count, actor, target);
 	return res;
@@ -244,7 +260,7 @@ nfs_file_mmap(struct file * file, struct vm_area_struct * vma)
 	dfprintk(VFS, "nfs: mmap(%s/%s)\n",
 		dentry->d_parent->d_name.name, dentry->d_name.name);
 
-	status = nfs_revalidate_inode(NFS_SERVER(inode), inode);
+	status = nfs_revalidate_file(inode, file);
 	if (!status)
 		status = generic_file_mmap(file, vma);
 	return status;
@@ -340,7 +356,7 @@ nfs_file_write(struct kiocb *iocb, const char __user *buf, size_t count, loff_t
 		result = nfs_revalidate_file_size(inode, iocb->ki_filp);
 		if (result)
 			goto out;
-	} else
+	}
 	nfs_revalidate_mapping(inode, iocb->ki_filp->f_mapping);
 
 	result = count;

fs/nfs/inode.c

@@ -620,9 +620,9 @@ nfs_zap_caches(struct inode *inode)
 
 	memset(NFS_COOKIEVERF(inode), 0, sizeof(NFS_COOKIEVERF(inode)));
 	if (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode))
-		nfsi->flags |= NFS_INO_INVALID_ATTR|NFS_INO_INVALID_DATA|NFS_INO_INVALID_ACCESS|NFS_INO_INVALID_ACL;
+		nfsi->flags |= NFS_INO_INVALID_ATTR|NFS_INO_INVALID_DATA|NFS_INO_INVALID_ACCESS|NFS_INO_INVALID_ACL|NFS_INO_REVAL_PAGECACHE;
 	else
-		nfsi->flags |= NFS_INO_INVALID_ATTR|NFS_INO_INVALID_ACCESS|NFS_INO_INVALID_ACL;
+		nfsi->flags |= NFS_INO_INVALID_ATTR|NFS_INO_INVALID_ACCESS|NFS_INO_INVALID_ACL|NFS_INO_REVAL_PAGECACHE;
 }
 
 static void nfs_zap_acl_cache(struct inode *inode)
@@ -1055,6 +1055,7 @@ __nfs_revalidate_inode(struct nfs_server *server, struct inode *inode)
 		goto out;
 	}
 	flags = nfsi->flags;
+	nfsi->flags &= ~NFS_INO_REVAL_PAGECACHE;
 	/*
 	 * We may need to keep the attributes marked as invalid if
 	 * we raced with nfs_end_attr_update().
@@ -1187,8 +1188,11 @@ int nfs_refresh_inode(struct inode *inode, struct nfs_fattr *fattr)
 		if ((fattr->valid & NFS_ATTR_PRE_CHANGE) != 0
 				&& nfsi->change_attr == fattr->pre_change_attr)
 			nfsi->change_attr = fattr->change_attr;
-		if (!data_unstable && nfsi->change_attr != fattr->change_attr)
+		if (nfsi->change_attr != fattr->change_attr) {
 			nfsi->flags |= NFS_INO_INVALID_ATTR;
+			if (!data_unstable)
+				nfsi->flags |= NFS_INO_REVAL_PAGECACHE;
+		}
 	}
 
 	if ((fattr->valid & NFS_ATTR_FATTR) == 0)
@@ -1211,12 +1215,16 @@ int nfs_refresh_inode(struct inode *inode, struct nfs_fattr *fattr)
 	}
 
 	/* Verify a few of the more important attributes */
-	if (!data_unstable) {
-		if (!timespec_equal(&inode->i_mtime, &fattr->mtime)
-				|| cur_size != new_isize)
+	if (!timespec_equal(&inode->i_mtime, &fattr->mtime)) {
 		nfsi->flags |= NFS_INO_INVALID_ATTR;
-	} else if (new_isize != cur_size && nfsi->npages == 0)
+		if (!data_unstable)
+			nfsi->flags |= NFS_INO_REVAL_PAGECACHE;
+	}
+	if (cur_size != new_isize) {
 		nfsi->flags |= NFS_INO_INVALID_ATTR;
+		if (nfsi->npages == 0)
+			nfsi->flags |= NFS_INO_REVAL_PAGECACHE;
+	}
 
 	/* Have any file permissions changed? */
 	if ((inode->i_mode & S_IALLUGO) != (fattr->mode & S_IALLUGO)

include/linux/nfs_fs.h

@@ -198,6 +198,7 @@ struct nfs_inode {
 #define NFS_INO_INVALID_ATIME	0x0020		/* cached atime is invalid */
 #define NFS_INO_INVALID_ACCESS	0x0040		/* cached access cred invalid */
 #define NFS_INO_INVALID_ACL	0x0080		/* cached acls are invalid */
+#define NFS_INO_REVAL_PAGECACHE	0x1000		/* must revalidate pagecache */
 
 static inline struct nfs_inode *NFS_I(struct inode *inode)
 {