Readdir on directories that are not merged is simply handled by the
underlying directory (upper or lower).
+renaming directories
+--------------------
+
+When renaming a directory that is on the lower layer or merged (i.e. the
+directory was not created on the upper layer to start with) overlayfs can
+handle it in two different ways:
+
+1) return EXDEV error: this error is returned by rename(2) when trying to
+ move a file or directory across filesystem boundaries. Hence
+ applications are usually prepared to hande this error (mv(1) for example
+ recursively copies the directory tree). This is the default behavior.
+
+2) If the "redirect_dir" feature is enabled, then the directory will be
+ copied up (but not the contents). Then the "trusted.overlay.redirect"
+ extended attribute is set to the path of the original location from the
+ root of the overlay. Finally the directory is moved to the new
+ location.
Non-directories
---------------
"break" the link. Changes will not be propagated to other names
referring to the same inode.
-Directory trees are not copied up. If rename(2) is performed on a directory
-which is on the lower layer or is merged, then -EXDEV will be returned.
+Unless "redirect_dir" feature is enabled, rename(2) on a lower or merged
+directory will fail with EXDEV.
Changes to underlying filesystems
---------------------------------
/*
* Copy up a single dentry
*
- * Directory renames only allowed on "pure upper" (already created on
- * upper filesystem, never copied up). Directories which are on lower or
- * are merged may not be renamed. For these -EXDEV is returned and
- * userspace has to deal with it. This means, when copying up a
- * directory we can rely on it and ancestors being stable.
- *
- * Non-directory renames start with copy up of source if necessary. The
- * actual rename will only proceed once the copy up was successful. Copy
- * up uses upper parent i_mutex for exclusion. Since rename can change
- * d_parent it is possible that the copy up will lock the old parent. At
- * that point the file will have already been copied up anyway.
+ * All renames start with copy up of source if necessary. The actual
+ * rename will only proceed once the copy up was successful. Copy up uses
+ * upper parent i_mutex for exclusion. Since rename can change d_parent it
+ * is possible that the copy up will lock the old parent. At that point
+ * the file will have already been copied up anyway.
*/
int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
struct path *lowerpath, struct kstat *stat)
struct path parentpath;
struct dentry *lowerdentry = lowerpath->dentry;
struct dentry *upperdir;
- struct dentry *upperdentry;
const char *link = NULL;
if (WARN_ON(!workdir))
pr_err("overlayfs: failed to lock workdir+upperdir\n");
goto out_unlock;
}
- upperdentry = ovl_dentry_upper(dentry);
- if (upperdentry) {
+ if (ovl_dentry_upper(dentry)) {
/* Raced with another copy-up? Nothing to do, then... */
err = 0;
goto out_unlock;
#include <linux/posix_acl.h>
#include <linux/posix_acl_xattr.h>
#include <linux/atomic.h>
+#include <linux/ratelimit.h>
#include "overlayfs.h"
void ovl_cleanup(struct inode *wdir, struct dentry *wdentry)
return OVL_TYPE_MERGE(type) || !OVL_TYPE_UPPER(type);
}
+static bool ovl_can_move(struct dentry *dentry)
+{
+ return ovl_redirect_dir(dentry->d_sb) ||
+ !d_is_dir(dentry) || !ovl_type_merge_or_lower(dentry);
+}
+
+#define OVL_REDIRECT_MAX 256
+
+static char *ovl_get_redirect(struct dentry *dentry, bool samedir)
+{
+ char *buf, *ret;
+ struct dentry *d, *tmp;
+ int buflen = OVL_REDIRECT_MAX + 1;
+
+ if (samedir) {
+ ret = kstrndup(dentry->d_name.name, dentry->d_name.len,
+ GFP_KERNEL);
+ goto out;
+ }
+
+ buf = ret = kmalloc(buflen, GFP_TEMPORARY);
+ if (!buf)
+ goto out;
+
+ buflen--;
+ buf[buflen] = '\0';
+ for (d = dget(dentry); !IS_ROOT(d);) {
+ const char *name;
+ int thislen;
+
+ spin_lock(&d->d_lock);
+ name = ovl_dentry_get_redirect(d);
+ if (name) {
+ thislen = strlen(name);
+ } else {
+ name = d->d_name.name;
+ thislen = d->d_name.len;
+ }
+
+ /* If path is too long, fall back to userspace move */
+ if (thislen + (name[0] != '/') > buflen) {
+ ret = ERR_PTR(-EXDEV);
+ spin_unlock(&d->d_lock);
+ goto out_put;
+ }
+
+ buflen -= thislen;
+ memcpy(&buf[buflen], name, thislen);
+ tmp = dget_dlock(d->d_parent);
+ spin_unlock(&d->d_lock);
+
+ dput(d);
+ d = tmp;
+
+ /* Absolute redirect: finished */
+ if (buf[buflen] == '/')
+ break;
+ buflen--;
+ buf[buflen] = '/';
+ }
+ ret = kstrdup(&buf[buflen], GFP_KERNEL);
+out_put:
+ dput(d);
+ kfree(buf);
+out:
+ return ret ? ret : ERR_PTR(-ENOMEM);
+}
+
+static int ovl_set_redirect(struct dentry *dentry, bool samedir)
+{
+ int err;
+ const char *redirect = ovl_dentry_get_redirect(dentry);
+
+ if (redirect && (samedir || redirect[0] == '/'))
+ return 0;
+
+ redirect = ovl_get_redirect(dentry, samedir);
+ if (IS_ERR(redirect))
+ return PTR_ERR(redirect);
+
+ err = ovl_do_setxattr(ovl_dentry_upper(dentry), OVL_XATTR_REDIRECT,
+ redirect, strlen(redirect), 0);
+ if (!err) {
+ spin_lock(&dentry->d_lock);
+ ovl_dentry_set_redirect(dentry, redirect);
+ spin_unlock(&dentry->d_lock);
+ } else {
+ kfree(redirect);
+ if (err == -EOPNOTSUPP)
+ ovl_clear_redirect_dir(dentry->d_sb);
+ else
+ pr_warn_ratelimited("overlay: failed to set redirect (%i)\n", err);
+ /* Fall back to userspace copy-up */
+ err = -EXDEV;
+ }
+ return err;
+}
+
static int ovl_rename(struct inode *olddir, struct dentry *old,
struct inode *newdir, struct dentry *new,
unsigned int flags)
bool overwrite = !(flags & RENAME_EXCHANGE);
bool is_dir = d_is_dir(old);
bool new_is_dir = d_is_dir(new);
+ bool samedir = olddir == newdir;
struct dentry *opaquedir = NULL;
const struct cred *old_cred = NULL;
/* Don't copy up directory trees */
err = -EXDEV;
- if (is_dir && ovl_type_merge_or_lower(old))
+ if (!ovl_can_move(old))
goto out;
- if (!overwrite && new_is_dir && ovl_type_merge_or_lower(new))
+ if (!overwrite && !ovl_can_move(new))
goto out;
err = ovl_want_write(old);
trap = lock_rename(new_upperdir, old_upperdir);
-
olddentry = lookup_one_len(old->d_name.name, old_upperdir,
old->d_name.len);
err = PTR_ERR(olddentry);
if (WARN_ON(olddentry->d_inode == newdentry->d_inode))
goto out_dput;
- if (is_dir && !old_opaque && ovl_lower_positive(new)) {
- err = ovl_set_opaque(olddentry);
- if (err)
- goto out_dput;
- ovl_dentry_set_opaque(old, true);
+ if (is_dir) {
+ if (ovl_type_merge_or_lower(old)) {
+ err = ovl_set_redirect(old, samedir);
+ if (err)
+ goto out_dput;
+ } else if (!old_opaque && ovl_lower_positive(new)) {
+ err = ovl_set_opaque(olddentry);
+ if (err)
+ goto out_dput;
+ ovl_dentry_set_opaque(old, true);
+ }
}
- if (!overwrite &&
- new_is_dir && !new_opaque && ovl_lower_positive(old)) {
- err = ovl_set_opaque(newdentry);
- if (err)
- goto out_dput;
- ovl_dentry_set_opaque(new, true);
+ if (!overwrite && new_is_dir) {
+ if (ovl_type_merge_or_lower(new)) {
+ err = ovl_set_redirect(new, samedir);
+ if (err)
+ goto out_dput;
+ } else if (!new_opaque && ovl_lower_positive(old)) {
+ err = ovl_set_opaque(newdentry);
+ if (err)
+ goto out_dput;
+ ovl_dentry_set_opaque(new, true);
+ }
}
err = ovl_do_rename(old_upperdir->d_inode, olddentry,
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