[CIFS] use sensible file nlink values if unprovided

Certain servers may not set the NumberOfLinks field in query file/path
info responses. In such a case, cifs_inode_needs_reval() assumes that
all regular files are hardlinks and triggers revalidation, leading to
excessive and unnecessary network traffic.

This change hardcodes cf_nlink (and subsequently i_nlink) when not
returned by the server, similar to what already occurs in cifs_mkdir().

Cc: <stable@vger.kernel.org>
Signed-off-by: David Disseldorp <ddiss@suse.de>
Signed-off-by: Steve French <smfrench@gmail.com>

fs/cifs/inode.c

@@ -558,6 +558,11 @@ cifs_all_info_to_fattr(struct cifs_fattr *fattr, FILE_ALL_INFO *info,
 			fattr->cf_mode &= ~(S_IWUGO);
 
 		fattr->cf_nlink = le32_to_cpu(info->NumberOfLinks);
+		if (fattr->cf_nlink < 1) {
+			cifs_dbg(1, "replacing bogus file nlink value %u\n",
+				fattr->cf_nlink);
+			fattr->cf_nlink = 1;
+		}
 	}
 
 	fattr->cf_uid = cifs_sb->mnt_uid;