ovl: split super.c

fs/overlayfs/super.c is the biggest of the overlayfs source files and it
contains various utility functions as well as the rather complicated lookup
code.  Split these parts out to separate files.

Before:

 1446 fs/overlayfs/super.c

After:

  919 fs/overlayfs/super.c
  267 fs/overlayfs/namei.c
  235 fs/overlayfs/util.c
   51 fs/overlayfs/ovl_entry.h

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

1 files changed, 267 insertions, 0 deletions

diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
new file mode 100644
index 000000000000..f4057fcb0246
--- /dev/null
+++ b/fs/overlayfs/namei.c
@@ -0,0 +1,267 @@
+/*
+ * Copyright (C) 2011 Novell Inc.
+ * Copyright (C) 2016 Red Hat, Inc.
+ *
+ * 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 <linux/fs.h>
+#include <linux/namei.h>
+#include <linux/xattr.h>
+#include "overlayfs.h"
+#include "ovl_entry.h"
+
+static struct dentry *ovl_lookup_real(struct dentry *dir,
+				      const struct qstr *name)
+{
+	struct dentry *dentry;
+
+	dentry = lookup_one_len_unlocked(name->name, dir, name->len);
+	if (IS_ERR(dentry)) {
+		if (PTR_ERR(dentry) == -ENOENT)
+			dentry = NULL;
+	} else if (!dentry->d_inode) {
+		dput(dentry);
+		dentry = NULL;
+	} else if (ovl_dentry_weird(dentry)) {
+		dput(dentry);
+		/* Don't support traversing automounts and other weirdness */
+		dentry = ERR_PTR(-EREMOTE);
+	}
+	return dentry;
+}
+
+static bool ovl_is_opaquedir(struct dentry *dentry)
+{
+	int res;
+	char val;
+
+	if (!d_is_dir(dentry))
+		return false;
+
+	res = vfs_getxattr(dentry, OVL_XATTR_OPAQUE, &val, 1);
+	if (res == 1 && val == 'y')
+		return true;
+
+	return false;
+}
+
+/*
+ * Returns next layer in stack starting from top.
+ * Returns -1 if this is the last layer.
+ */
+int ovl_path_next(int idx, struct dentry *dentry, struct path *path)
+{
+	struct ovl_entry *oe = dentry->d_fsdata;
+
+	BUG_ON(idx < 0);
+	if (idx == 0) {
+		ovl_path_upper(dentry, path);
+		if (path->dentry)
+			return oe->numlower ? 1 : -1;
+		idx++;
+	}
+	BUG_ON(idx > oe->numlower);
+	*path = oe->lowerstack[idx - 1];
+
+	return (idx < oe->numlower) ? idx + 1 : -1;
+}
+
+struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
+			  unsigned int flags)
+{
+	struct ovl_entry *oe;
+	const struct cred *old_cred;
+	struct ovl_entry *poe = dentry->d_parent->d_fsdata;
+	struct path *stack = NULL;
+	struct dentry *upperdir, *upperdentry = NULL;
+	unsigned int ctr = 0;
+	struct inode *inode = NULL;
+	bool upperopaque = false;
+	bool stop = false;
+	bool isdir = false;
+	struct dentry *this;
+	unsigned int i;
+	int err;
+
+	old_cred = ovl_override_creds(dentry->d_sb);
+	upperdir = ovl_upperdentry_dereference(poe);
+	if (upperdir) {
+		this = ovl_lookup_real(upperdir, &dentry->d_name);
+		err = PTR_ERR(this);
+		if (IS_ERR(this))
+			goto out;
+
+		if (this) {
+			if (unlikely(ovl_dentry_remote(this))) {
+				dput(this);
+				err = -EREMOTE;
+				goto out;
+			}
+			if (ovl_is_whiteout(this)) {
+				dput(this);
+				this = NULL;
+				stop = upperopaque = true;
+			} else if (!d_is_dir(this)) {
+				stop = true;
+			} else {
+				isdir = true;
+				if (poe->numlower && ovl_is_opaquedir(this))
+					stop = upperopaque = true;
+			}
+		}
+		upperdentry = this;
+	}
+
+	if (!stop && poe->numlower) {
+		err = -ENOMEM;
+		stack = kcalloc(poe->numlower, sizeof(struct path), GFP_KERNEL);
+		if (!stack)
+			goto out_put_upper;
+	}
+
+	for (i = 0; !stop && i < poe->numlower; i++) {
+		struct path lowerpath = poe->lowerstack[i];
+
+		this = ovl_lookup_real(lowerpath.dentry, &dentry->d_name);
+		err = PTR_ERR(this);
+		if (IS_ERR(this)) {
+			/*
+			 * If it's positive, then treat ENAMETOOLONG as ENOENT.
+			 */
+			if (err == -ENAMETOOLONG && (upperdentry || ctr))
+				continue;
+			goto out_put;
+		}
+		if (!this)
+			continue;
+		if (ovl_is_whiteout(this)) {
+			dput(this);
+			break;
+		}
+		/*
+		 * If this is a non-directory then stop here.
+		 */
+		if (!d_is_dir(this)) {
+			if (isdir) {
+				dput(this);
+				break;
+			}
+			stop = true;
+		} else {
+			/*
+			 * Only makes sense to check opaque dir if this is not
+			 * the lowermost layer.
+			 */
+			if (i < poe->numlower - 1 && ovl_is_opaquedir(this))
+				stop = true;
+		}
+
+		stack[ctr].dentry = this;
+		stack[ctr].mnt = lowerpath.mnt;
+		ctr++;
+	}
+
+	oe = ovl_alloc_entry(ctr);
+	err = -ENOMEM;
+	if (!oe)
+		goto out_put;
+
+	if (upperdentry || ctr) {
+		struct dentry *realdentry;
+		struct inode *realinode;
+
+		realdentry = upperdentry ? upperdentry : stack[0].dentry;
+		realinode = d_inode(realdentry);
+
+		err = -ENOMEM;
+		if (upperdentry && !d_is_dir(upperdentry)) {
+			inode = ovl_get_inode(dentry->d_sb, realinode);
+		} else {
+			inode = ovl_new_inode(dentry->d_sb, realinode->i_mode,
+					      realinode->i_rdev);
+			if (inode)
+				ovl_inode_init(inode, realinode, !!upperdentry);
+		}
+		if (!inode)
+			goto out_free_oe;
+		ovl_copyattr(realdentry->d_inode, inode);
+	}
+
+	revert_creds(old_cred);
+	oe->opaque = upperopaque;
+	oe->__upperdentry = upperdentry;
+	memcpy(oe->lowerstack, stack, sizeof(struct path) * ctr);
+	kfree(stack);
+	dentry->d_fsdata = oe;
+	d_add(dentry, inode);
+
+	return NULL;
+
+out_free_oe:
+	kfree(oe);
+out_put:
+	for (i = 0; i < ctr; i++)
+		dput(stack[i].dentry);
+	kfree(stack);
+out_put_upper:
+	dput(upperdentry);
+out:
+	revert_creds(old_cred);
+	return ERR_PTR(err);
+}
+
+bool ovl_lower_positive(struct dentry *dentry)
+{
+	struct ovl_entry *oe = dentry->d_fsdata;
+	struct ovl_entry *poe = dentry->d_parent->d_fsdata;
+	const struct qstr *name = &dentry->d_name;
+	unsigned int i;
+	bool positive = false;
+	bool done = false;
+
+	/*
+	 * If dentry is negative, then lower is positive iff this is a
+	 * whiteout.
+	 */
+	if (!dentry->d_inode)
+		return oe->opaque;
+
+	/* Negative upper -> positive lower */
+	if (!oe->__upperdentry)
+		return true;
+
+	/* Positive upper -> have to look up lower to see whether it exists */
+	for (i = 0; !done && !positive && i < poe->numlower; i++) {
+		struct dentry *this;
+		struct dentry *lowerdir = poe->lowerstack[i].dentry;
+
+		this = lookup_one_len_unlocked(name->name, lowerdir,
+					       name->len);
+		if (IS_ERR(this)) {
+			switch (PTR_ERR(this)) {
+			case -ENOENT:
+			case -ENAMETOOLONG:
+				break;
+
+			default:
+				/*
+				 * Assume something is there, we just couldn't
+				 * access it.
+				 */
+				positive = true;
+				break;
+			}
+		} else {
+			if (this->d_inode) {
+				positive = !ovl_is_whiteout(this);
+				done = true;
+			}
+			dput(this);
+		}
+	}
+
+	return positive;
+}