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Subject[PATCH 29/42] Unionfs: miscellaneous helper routines
Date
Mostly related to whiteouts.

Signed-off-by: Erez Zadok <ezk@cs.sunysb.edu>
---
fs/unionfs/subr.c | 242 +++++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 242 insertions(+), 0 deletions(-)
create mode 100644 fs/unionfs/subr.c

diff --git a/fs/unionfs/subr.c b/fs/unionfs/subr.c
new file mode 100644
index 0000000..1a26c57
--- /dev/null
+++ b/fs/unionfs/subr.c
@@ -0,0 +1,242 @@
+/*
+ * 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"
+
+/*
+ * Pass an unionfs dentry and an index. It will try to create a whiteout
+ * for the filename in dentry, and will try in branch 'index'. On error,
+ * it will proceed to a branch to the left.
+ */
+int create_whiteout(struct dentry *dentry, int start)
+{
+ int bstart, bend, bindex;
+ struct dentry *lower_dir_dentry;
+ struct dentry *lower_dentry;
+ struct dentry *lower_wh_dentry;
+ struct nameidata nd;
+ char *name = NULL;
+ int err = -EINVAL;
+
+ verify_locked(dentry);
+
+ bstart = dbstart(dentry);
+ bend = dbend(dentry);
+
+ /* create dentry's whiteout equivalent */
+ name = alloc_whname(dentry->d_name.name, dentry->d_name.len);
+ if (unlikely(IS_ERR(name))) {
+ err = PTR_ERR(name);
+ goto out;
+ }
+
+ for (bindex = start; bindex >= 0; bindex--) {
+ lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
+
+ if (!lower_dentry) {
+ /*
+ * if lower dentry is not present, create the
+ * entire lower dentry directory structure and go
+ * ahead. Since we want to just create whiteout, we
+ * only want the parent dentry, and hence get rid of
+ * this dentry.
+ */
+ lower_dentry = create_parents(dentry->d_inode,
+ dentry,
+ dentry->d_name.name,
+ bindex);
+ if (!lower_dentry || IS_ERR(lower_dentry)) {
+ int ret = PTR_ERR(lower_dentry);
+ if (!IS_COPYUP_ERR(ret))
+ printk(KERN_ERR
+ "unionfs: create_parents for "
+ "whiteout failed: bindex=%d "
+ "err=%d\n", bindex, ret);
+ continue;
+ }
+ }
+
+ lower_wh_dentry =
+ lookup_one_len(name, lower_dentry->d_parent,
+ dentry->d_name.len + UNIONFS_WHLEN);
+ if (IS_ERR(lower_wh_dentry))
+ continue;
+
+ /*
+ * The whiteout already exists. This used to be impossible,
+ * but now is possible because of opaqueness.
+ */
+ if (lower_wh_dentry->d_inode) {
+ dput(lower_wh_dentry);
+ err = 0;
+ goto out;
+ }
+
+ err = init_lower_nd(&nd, LOOKUP_CREATE);
+ if (unlikely(err < 0))
+ goto out;
+ lower_dir_dentry = lock_parent(lower_wh_dentry);
+ err = is_robranch_super(dentry->d_sb, bindex);
+ if (!err)
+ err = vfs_create(lower_dir_dentry->d_inode,
+ lower_wh_dentry,
+ ~current->fs->umask & S_IRWXUGO,
+ &nd);
+ unlock_dir(lower_dir_dentry);
+ dput(lower_wh_dentry);
+ release_lower_nd(&nd, err);
+
+ if (!err || !IS_COPYUP_ERR(err))
+ break;
+ }
+
+ /* set dbopaque so that lookup will not proceed after this branch */
+ if (!err)
+ set_dbopaque(dentry, bindex);
+
+out:
+ kfree(name);
+ return err;
+}
+
+/*
+ * This is a helper function for rename, which ends up with hosed over
+ * dentries when it needs to revert.
+ */
+int unionfs_refresh_lower_dentry(struct dentry *dentry, int bindex)
+{
+ struct dentry *lower_dentry;
+ struct dentry *lower_parent;
+ int err = 0;
+
+ verify_locked(dentry);
+
+ unionfs_lock_dentry(dentry->d_parent);
+ lower_parent = unionfs_lower_dentry_idx(dentry->d_parent, bindex);
+ unionfs_unlock_dentry(dentry->d_parent);
+
+ BUG_ON(!S_ISDIR(lower_parent->d_inode->i_mode));
+
+ lower_dentry = lookup_one_len(dentry->d_name.name, lower_parent,
+ dentry->d_name.len);
+ if (IS_ERR(lower_dentry)) {
+ err = PTR_ERR(lower_dentry);
+ goto out;
+ }
+
+ dput(unionfs_lower_dentry_idx(dentry, bindex));
+ iput(unionfs_lower_inode_idx(dentry->d_inode, bindex));
+ unionfs_set_lower_inode_idx(dentry->d_inode, bindex, NULL);
+
+ if (!lower_dentry->d_inode) {
+ dput(lower_dentry);
+ unionfs_set_lower_dentry_idx(dentry, bindex, NULL);
+ } else {
+ unionfs_set_lower_dentry_idx(dentry, bindex, lower_dentry);
+ unionfs_set_lower_inode_idx(dentry->d_inode, bindex,
+ igrab(lower_dentry->d_inode));
+ }
+
+out:
+ return err;
+}
+
+int make_dir_opaque(struct dentry *dentry, int bindex)
+{
+ int err = 0;
+ struct dentry *lower_dentry, *diropq;
+ struct inode *lower_dir;
+ struct nameidata nd;
+ kernel_cap_t orig_cap;
+
+ /*
+ * Opaque directory whiteout markers are special files (like regular
+ * whiteouts), and should appear to the users as if they don't
+ * exist. They should be created/deleted regardless of directory
+ * search/create permissions, but only for the duration of this
+ * creation of the .wh.__dir_opaque: file. Note, this does not
+ * circumvent normal ->permission).
+ */
+ orig_cap = current->cap_effective;
+ cap_raise(current->cap_effective, CAP_DAC_READ_SEARCH);
+ cap_raise(current->cap_effective, CAP_DAC_OVERRIDE);
+
+ lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
+ lower_dir = lower_dentry->d_inode;
+ BUG_ON(!S_ISDIR(dentry->d_inode->i_mode) ||
+ !S_ISDIR(lower_dir->i_mode));
+
+ mutex_lock(&lower_dir->i_mutex);
+ diropq = lookup_one_len(UNIONFS_DIR_OPAQUE, lower_dentry,
+ sizeof(UNIONFS_DIR_OPAQUE) - 1);
+ if (IS_ERR(diropq)) {
+ err = PTR_ERR(diropq);
+ goto out;
+ }
+
+ err = init_lower_nd(&nd, LOOKUP_CREATE);
+ if (unlikely(err < 0))
+ goto out;
+ if (!diropq->d_inode)
+ err = vfs_create(lower_dir, diropq, S_IRUGO, &nd);
+ if (!err)
+ set_dbopaque(dentry, bindex);
+ release_lower_nd(&nd, err);
+
+ dput(diropq);
+
+out:
+ mutex_unlock(&lower_dir->i_mutex);
+ current->cap_effective = orig_cap;
+ return err;
+}
+
+/*
+ * returns the right n_link value based on the inode type
+ */
+int unionfs_get_nlinks(const struct inode *inode)
+{
+ /* don't bother to do all the work since we're unlinked */
+ if (inode->i_nlink == 0)
+ return 0;
+
+ if (!S_ISDIR(inode->i_mode))
+ return unionfs_lower_inode(inode)->i_nlink;
+
+ /*
+ * For directories, we return 1. The only place that could cares
+ * about links is readdir, and there's d_type there so even that
+ * doesn't matter.
+ */
+ return 1;
+}
+
+/* construct whiteout filename */
+char *alloc_whname(const char *name, int len)
+{
+ char *buf;
+
+ buf = kmalloc(len + UNIONFS_WHLEN + 1, GFP_KERNEL);
+ if (unlikely(!buf))
+ return ERR_PTR(-ENOMEM);
+
+ strcpy(buf, UNIONFS_WHPFX);
+ strlcat(buf, name, len + UNIONFS_WHLEN + 1);
+
+ return buf;
+}
--
1.5.2.2


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