ovl: check on mount time if upper fs supports setting xattr

xattr are needed by overlayfs for setting opaque dir, redirect dir
and copy up origin.

Check at mount time by trying to set the overlay.opaque xattr on the
workdir and if that fails issue a warning message.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index caa36cb..ce7c3ab 100644 (file)
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -279,3 +279,6 @@ int ovl_copy_up(struct dentry *dentry);
 int ovl_copy_up_flags(struct dentry *dentry, int flags);
 int ovl_copy_xattr(struct dentry *old, struct dentry *new);
 int ovl_set_attr(struct dentry *upper, struct kstat *stat);
+int ovl_check_setxattr(struct dentry *dentry, struct dentry *upperdentry,
+                      const char *name, const void *value, size_t size,
+                      int xerr);

diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
index b2023dd..ad86c0a 100644 (file)
--- a/fs/overlayfs/ovl_entry.h
+++ b/fs/overlayfs/ovl_entry.h
@@ -28,6 +28,7 @@ struct ovl_fs {
        /* creds of process who forced instantiation of super block */
        const struct cred *creator_cred;
        bool tmpfile;
+       bool noxattr;
        wait_queue_head_t copyup_wq;
        /* sb common to all layers */
        struct super_block *same_sb;

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 9828b7d..f164762 100644 (file)
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -891,6 +891,19 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
                                dput(temp);
                        else
                                pr_warn("overlayfs: upper fs does not support tmpfile.\n");
+
+                       /*
+                        * Check if upper/work fs supports trusted.overlay.*
+                        * xattr
+                        */
+                       err = ovl_do_setxattr(ufs->workdir, OVL_XATTR_OPAQUE,
+                                             "0", 1, 0);
+                       if (err) {
+                               ufs->noxattr = true;
+                               pr_warn("overlayfs: upper fs does not support xattr.\n");
+                       } else {
+                               vfs_removexattr(ufs->workdir, OVL_XATTR_OPAQUE);
+                       }
                }
        }
 

diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index cfdea47..b5a0dc3 100644 (file)
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -303,3 +303,24 @@ void ovl_copy_up_end(struct dentry *dentry)
        wake_up_locked(&ofs->copyup_wq);
        spin_unlock(&ofs->copyup_wq.lock);
 }
+
+int ovl_check_setxattr(struct dentry *dentry, struct dentry *upperdentry,
+                      const char *name, const void *value, size_t size,
+                      int xerr)
+{
+       int err;
+       struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+
+       if (ofs->noxattr)
+               return xerr;
+
+       err = ovl_do_setxattr(upperdentry, name, value, size, 0);
+
+       if (err == -EOPNOTSUPP) {
+               pr_warn("overlayfs: cannot set %s xattr on upper\n", name);
+               ofs->noxattr = true;
+               return xerr;
+       }
+
+       return err;
+}