ovl: redirect on rename-dir

[karo-tx-linux.git] / fs / overlayfs / dir.c

diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index f24b6b9679014597b5198ca4c199b92b6edc056c..c1de84c1c5ec924df2c13d96b892552b39fd188d 100644 (file)
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -15,6 +15,7 @@
 #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)
@@ -757,6 +758,104 @@ static bool ovl_type_merge_or_lower(struct dentry *dentry)
        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)
@@ -773,6 +872,7 @@ static int ovl_rename(struct inode *olddir, struct dentry *old,
        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;
 
@@ -784,9 +884,9 @@ static int ovl_rename(struct inode *olddir, struct dentry *old,
 
        /* 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);
@@ -837,7 +937,6 @@ static int ovl_rename(struct inode *olddir, struct dentry *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);
@@ -880,18 +979,29 @@ static int ovl_rename(struct inode *olddir, struct dentry *old,
        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,