[PATCH 22/42] Unionfs: unlink/rmdir operations

[Erez Zadok <ezk@cs.sunysb.edu>]

Signed-off-by: Erez Zadok <ezk@cs.sunysb.edu>
---
 fs/unionfs/unlink.c |  236 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 236 insertions(+), 0 deletions(-)
 create mode 100644 fs/unionfs/unlink.c

diff --git a/fs/unionfs/unlink.c b/fs/unionfs/unlink.c
new file mode 100644
index 0000000..423ff36
--- /dev/null
+++ b/fs/unionfs/unlink.c
@@ -0,0 +1,236 @@
+/*
+ * Copyright (c) 2003-2007 Erez Zadok
+ * Copyright (c) 2003-2006 Charles P. Wright
+ * Copyright (c) 2005-2007 Josef 'Jeff' Sipek
+ * Copyright (c) 2005-2006 Junjiro Okajima
+ * Copyright (c) 2005      Arun M. Krishnakumar
+ * Copyright (c) 2004-2006 David P. Quigley
+ * Copyright (c) 2003-2004 Mohammad Nayyer Zubair
+ * Copyright (c) 2003      Puja Gupta
+ * Copyright (c) 2003      Harikesavan Krishnan
+ * Copyright (c) 2003-2007 Stony Brook University
+ * Copyright (c) 2003-2007 The Research Foundation of SUNY
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include "union.h"
+
+/* unlink a file by creating a whiteout */
+static int unionfs_unlink_whiteout(struct inode *dir, struct dentry *dentry)
+{
+	struct dentry *lower_dentry;
+	struct dentry *lower_dir_dentry;
+	int bindex;
+	int err = 0;
+
+	err = unionfs_partial_lookup(dentry);
+	if (err)
+		goto out;
+
+	bindex = dbstart(dentry);
+
+	lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
+	if (!lower_dentry)
+		goto out;
+
+	lower_dir_dentry = lock_parent(lower_dentry);
+
+	/* avoid destroying the lower inode if the file is in use */
+	dget(lower_dentry);
+	err = is_robranch_super(dentry->d_sb, bindex);
+	if (!err)
+		err = vfs_unlink(lower_dir_dentry->d_inode, lower_dentry);
+	/* if vfs_unlink succeeded, update our inode's times */
+	if (!err)
+		unionfs_copy_attr_times(dentry->d_inode);
+	dput(lower_dentry);
+	fsstack_copy_attr_times(dir, lower_dir_dentry->d_inode);
+	unlock_dir(lower_dir_dentry);
+
+	if (err && !IS_COPYUP_ERR(err))
+		goto out;
+
+	/*
+	 * We create whiteouts if (1) there was an error unlinking the main
+	 * file; (2) there is a lower priority file with the same name
+	 * (dbopaque); (3) the branch in which the file is not the last
+	 * (rightmost0 branch.  The last rule is an optimization to avoid
+	 * creating all those whiteouts if there's no chance they'd be
+	 * masking any lower-priority branch, as well as unionfs is used
+	 * with only one branch (using only one branch, while odd, is still
+	 * possible).
+	 */
+	if (err) {
+		if (dbstart(dentry) == 0)
+			goto out;
+		err = create_whiteout(dentry, dbstart(dentry) - 1);
+	} else if (dbopaque(dentry) != -1) {
+		err = create_whiteout(dentry, dbopaque(dentry));
+	} else if (dbstart(dentry) < sbend(dentry->d_sb)) {
+		err = create_whiteout(dentry, dbstart(dentry));
+	}
+
+out:
+	if (!err)
+		dentry->d_inode->i_nlink--;
+
+	/* We don't want to leave negative leftover dentries for revalidate. */
+	if (!err && (dbopaque(dentry) != -1))
+		update_bstart(dentry);
+
+	return err;
+}
+
+int unionfs_unlink(struct inode *dir, struct dentry *dentry)
+{
+	int err = 0;
+
+	unionfs_read_lock(dentry->d_sb);
+	unionfs_lock_dentry(dentry);
+
+	if (unlikely(!__unionfs_d_revalidate_chain(dentry, NULL, false))) {
+		err = -ESTALE;
+		goto out;
+	}
+	unionfs_check_dentry(dentry);
+
+	err = unionfs_unlink_whiteout(dir, dentry);
+	/* call d_drop so the system "forgets" about us */
+	if (!err) {
+		if (!S_ISDIR(dentry->d_inode->i_mode))
+			unionfs_postcopyup_release(dentry);
+		d_drop(dentry);
+		/*
+		 * if unlink/whiteout succeeded, parent dir mtime has
+		 * changed
+		 */
+		unionfs_copy_attr_times(dir);
+	}
+
+out:
+	if (!err) {
+		unionfs_check_dentry(dentry);
+		unionfs_check_inode(dir);
+	}
+	unionfs_unlock_dentry(dentry);
+	unionfs_read_unlock(dentry->d_sb);
+	return err;
+}
+
+static int unionfs_rmdir_first(struct inode *dir, struct dentry *dentry,
+			       struct unionfs_dir_state *namelist)
+{
+	int err;
+	struct dentry *lower_dentry;
+	struct dentry *lower_dir_dentry = NULL;
+
+	/* Here we need to remove whiteout entries. */
+	err = delete_whiteouts(dentry, dbstart(dentry), namelist);
+	if (err)
+		goto out;
+
+	lower_dentry = unionfs_lower_dentry(dentry);
+
+	lower_dir_dentry = lock_parent(lower_dentry);
+
+	/* avoid destroying the lower inode if the file is in use */
+	dget(lower_dentry);
+	err = is_robranch(dentry);
+	if (!err)
+		err = vfs_rmdir(lower_dir_dentry->d_inode, lower_dentry);
+	dput(lower_dentry);
+
+	fsstack_copy_attr_times(dir, lower_dir_dentry->d_inode);
+	/* propagate number of hard-links */
+	dentry->d_inode->i_nlink = unionfs_get_nlinks(dentry->d_inode);
+
+out:
+	if (lower_dir_dentry)
+		unlock_dir(lower_dir_dentry);
+	return err;
+}
+
+int unionfs_rmdir(struct inode *dir, struct dentry *dentry)
+{
+	int err = 0;
+	struct unionfs_dir_state *namelist = NULL;
+	int dstart, dend;
+
+	unionfs_read_lock(dentry->d_sb);
+	unionfs_lock_dentry(dentry);
+
+	if (unlikely(!__unionfs_d_revalidate_chain(dentry, NULL, false))) {
+		err = -ESTALE;
+		goto out;
+	}
+	unionfs_check_dentry(dentry);
+
+	/* check if this unionfs directory is empty or not */
+	err = check_empty(dentry, &namelist);
+	if (err)
+		goto out;
+
+	err = unionfs_rmdir_first(dir, dentry, namelist);
+	dstart = dbstart(dentry);
+	dend = dbend(dentry);
+	/*
+	 * We create a whiteout for the directory if there was an error to
+	 * rmdir the first directory entry in the union.  Otherwise, we
+	 * create a whiteout only if there is no chance that a lower
+	 * priority branch might also have the same named directory.  IOW,
+	 * if there is not another same-named directory at a lower priority
+	 * branch, then we don't need to create a whiteout for it.
+	 */
+	if (!err) {
+		if (dstart < dend)
+			err = create_whiteout(dentry, dstart);
+	} else {
+		int new_err;
+
+		if (dstart == 0)
+			goto out;
+
+		/* exit if the error returned was NOT -EROFS */
+		if (!IS_COPYUP_ERR(err))
+			goto out;
+
+		new_err = create_whiteout(dentry, dstart - 1);
+		if (new_err != -EEXIST)
+			err = new_err;
+	}
+
+out:
+	/*
+	 * Drop references to lower dentry/inode so storage space for them
+	 * can be reclaimed.  Then, call d_drop so the system "forgets"
+	 * about us.
+	 */
+	if (!err) {
+		struct inode *inode = dentry->d_inode;
+		BUG_ON(!inode);
+		iput(unionfs_lower_inode_idx(inode, dstart));
+		unionfs_set_lower_inode_idx(inode, dstart, NULL);
+		dput(unionfs_lower_dentry_idx(dentry, dstart));
+		unionfs_set_lower_dentry_idx(dentry, dstart, NULL);
+		/*
+		 * If the last directory is unlinked, then mark istart/end
+		 * as -1, (to maintain the invariant that if there are no
+		 * lower objects, then branch index start and end are set to
+		 * -1).
+		 */
+		if (!unionfs_lower_inode_idx(inode, dstart) &&
+		    !unionfs_lower_inode_idx(inode, dend))
+			ibstart(inode) = ibend(inode) = -1;
+		d_drop(dentry);
+	}
+
+	if (namelist)
+		free_rdstate(namelist);
+
+	unionfs_unlock_dentry(dentry);
+	unionfs_read_unlock(dentry->d_sb);
+	return err;
+}
-- 
1.5.2.2