cifs: invalidate cache when we truncate a file

RHBZ: 1566345

When truncating a file we always do this synchronously to the server.
Thus we need to make sure that the cached inode metadata is
marked as stale so that on next getattr we will refresh the metadata.
In this particular bug we want to ensure that both ctime and mtime
are updated and become visible to the application after a truncate.
Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Reported-by: Xiaoli Feng <xifeng@redhat.com>

fs/cifs/inode.c

@@ -746,7 +746,8 @@ cifs_get_inode_info(struct inode **inode, const char *full_path,
 	cifs_dbg(FYI, "Getting info on %s\n", full_path);
 
 	if ((data == NULL) && (*inode != NULL)) {
-		if (CIFS_CACHE_READ(CIFS_I(*inode))) {
+		if (CIFS_CACHE_READ(CIFS_I(*inode)) &&
+		    CIFS_I(*inode)->time != 0) {
 			cifs_dbg(FYI, "No need to revalidate cached inode sizes\n");
 			goto cgii_exit;
 		}
@@ -1857,15 +1858,15 @@ cifs_inode_needs_reval(struct inode *inode)
 	struct cifsInodeInfo *cifs_i = CIFS_I(inode);
 	struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
 
+	if (cifs_i->time == 0)
+		return true;
+
 	if (CIFS_CACHE_READ(cifs_i))
 		return false;
 
 	if (!lookupCacheEnabled)
 		return true;
 
-	if (cifs_i->time == 0)
-		return true;
-
 	if (!cifs_sb->actimeo)
 		return true;
 
@@ -2104,10 +2105,14 @@ static int cifs_truncate_page(struct address_space *mapping, loff_t from)
 
 static void cifs_setsize(struct inode *inode, loff_t offset)
 {
+	struct cifsInodeInfo *cifs_i = CIFS_I(inode);
+
 	spin_lock(&inode->i_lock);
 	i_size_write(inode, offset);
 	spin_unlock(&inode->i_lock);
 
+	/* Cached inode must be refreshed on truncate */
+	cifs_i->time = 0;
 	truncate_pagecache(inode, offset);
 }