[CIFS] Provide sane values for nlink

Since we don't get info about the number of links from the readdir
linfo levels, stat() will return 0 for st_nlink, and in particular,
samba re-exported shares will show directories as files (as samba is
keying off st_nlink before evaluating how to set the dos modebits)
when doing a dir or ls.

Copy nlink to the inode, unless it wasn't provided.  Provide
sane values if we don't have an existing one and none was provided.

Signed-off-by: Jim McDonough <jmcd@samba.org>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: David Disseldorp <ddiss@samba.org>
Signed-off-by: Steve French <smfrench@gmail.com>

fs/cifs/cifsglob.h

@@ -1268,6 +1268,7 @@ struct dfs_info3_param {
 #define CIFS_FATTR_DELETE_PENDING	0x2
 #define CIFS_FATTR_NEED_REVAL		0x4
 #define CIFS_FATTR_INO_COLLISION	0x8
+#define CIFS_FATTR_UNKNOWN_NLINK	0x10
 
 struct cifs_fattr {
 	u32		cf_flags;

fs/cifs/inode.c

@@ -120,6 +120,33 @@ cifs_revalidate_cache(struct inode *inode, struct cifs_fattr *fattr)
 	cifs_i->invalid_mapping = true;
 }
 
+/*
+ * copy nlink to the inode, unless it wasn't provided.  Provide
+ * sane values if we don't have an existing one and none was provided
+ */
+static void
+cifs_nlink_fattr_to_inode(struct inode *inode, struct cifs_fattr *fattr)
+{
+	/*
+	 * if we're in a situation where we can't trust what we
+	 * got from the server (readdir, some non-unix cases)
+	 * fake reasonable values
+	 */
+	if (fattr->cf_flags & CIFS_FATTR_UNKNOWN_NLINK) {
+		/* only provide fake values on a new inode */
+		if (inode->i_state & I_NEW) {
+			if (fattr->cf_cifsattrs & ATTR_DIRECTORY)
+				set_nlink(inode, 2);
+			else
+				set_nlink(inode, 1);
+		}
+		return;
+	}
+
+	/* we trust the server, so update it */
+	set_nlink(inode, fattr->cf_nlink);
+}
+
 /* populate an inode with info from a cifs_fattr struct */
 void
 cifs_fattr_to_inode(struct inode *inode, struct cifs_fattr *fattr)
@@ -134,7 +161,7 @@ cifs_fattr_to_inode(struct inode *inode, struct cifs_fattr *fattr)
 	inode->i_mtime = fattr->cf_mtime;
 	inode->i_ctime = fattr->cf_ctime;
 	inode->i_rdev = fattr->cf_rdev;
-	set_nlink(inode, fattr->cf_nlink);
+	cifs_nlink_fattr_to_inode(inode, fattr);
 	inode->i_uid = fattr->cf_uid;
 	inode->i_gid = fattr->cf_gid;
 
@@ -541,14 +568,16 @@ cifs_all_info_to_fattr(struct cifs_fattr *fattr, FILE_ALL_INFO *info,
 	fattr->cf_bytes = le64_to_cpu(info->AllocationSize);
 	fattr->cf_createtime = le64_to_cpu(info->CreationTime);
 
+	fattr->cf_nlink = le32_to_cpu(info->NumberOfLinks);
 	if (fattr->cf_cifsattrs & ATTR_DIRECTORY) {
 		fattr->cf_mode = S_IFDIR | cifs_sb->mnt_dir_mode;
 		fattr->cf_dtype = DT_DIR;
 		/*
 		 * Server can return wrong NumberOfLinks value for directories
 		 * when Unix extensions are disabled - fake it.
 		 */
-		fattr->cf_nlink = 2;
+		if (!tcon->unix_ext)
+			fattr->cf_flags |= CIFS_FATTR_UNKNOWN_NLINK;
 	} else if (fattr->cf_cifsattrs & ATTR_REPARSE) {
 		fattr->cf_mode = S_IFLNK;
 		fattr->cf_dtype = DT_LNK;
@@ -561,11 +590,15 @@ cifs_all_info_to_fattr(struct cifs_fattr *fattr, FILE_ALL_INFO *info,
 		if (fattr->cf_cifsattrs & ATTR_READONLY)
 			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",
+		/*
+		 * Don't accept zero nlink from non-unix servers unless
+		 * delete is pending.  Instead mark it as unknown.
+		 */
+		if ((fattr->cf_nlink < 1) && !tcon->unix_ext &&
+		    !info->DeletePending) {
+			cifs_dbg(1, "bogus file nlink value %u\n",
 				fattr->cf_nlink);
-			fattr->cf_nlink = 1;
+			fattr->cf_flags |= CIFS_FATTR_UNKNOWN_NLINK;
 		}
 	}
 

fs/cifs/readdir.c

@@ -180,6 +180,9 @@ cifs_fill_common_info(struct cifs_fattr *fattr, struct cifs_sb_info *cifs_sb)
 		fattr->cf_dtype = DT_REG;
 	}
 
+	/* non-unix readdir doesn't provide nlink */
+	fattr->cf_flags |= CIFS_FATTR_UNKNOWN_NLINK;
+
 	if (fattr->cf_cifsattrs & ATTR_READONLY)
 		fattr->cf_mode &= ~S_IWUGO;