On Wed, Oct 18, 2017 at 12:05 AM, Vivek Goyal <vgoyal@xxxxxxxxxx> wrote:
> During lookup, check for presence of OVL_XATTR_METACOPY and if present,
> set OVL_METACOPY bit in flags.
>
> Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
> ---
> fs/overlayfs/namei.c | 40 ++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 40 insertions(+)
>
> diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
> index 88ff1daeb3d7..d32da041f4bf 100644
> --- a/fs/overlayfs/namei.c
> +++ b/fs/overlayfs/namei.c
> @@ -26,6 +26,24 @@ struct ovl_lookup_data {
> char *redirect;
> };
>
> +/* err < 0, 0 if no metacopy xattr, 1 if metacopy xattr found */
> +static int ovl_check_metacopy(struct dentry *dentry)
> +{
> + int res;
> +
> + res = vfs_getxattr(dentry, OVL_XATTR_METACOPY, NULL, 0);
> + if (res < 0) {
> + if (res == -ENODATA || res == -EOPNOTSUPP)
> + return 0;
> + goto out;
> + }
> +
> + return 1;
> +out:
> + pr_warn_ratelimited("overlayfs: failed to get metacopy (%i)\n", res);
> + return res;
> +}
> +
> static int ovl_check_redirect(struct dentry *dentry, struct ovl_lookup_data *d,
> size_t prelen, const char *post)
> {
> @@ -594,6 +612,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
> struct dentry *this;
> unsigned int i;
> int err;
> + bool metacopy = false;
> struct ovl_lookup_data d = {
> .name = dentry->d_name,
> .is_dir = false,
> @@ -634,6 +653,12 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
> roe->numlower, &stack, &ctr);
> if (err)
> goto out;
> +
> + err = ovl_check_metacopy(upperdentry);
> + if (err < 0)
> + goto out;
> + if (err == 1)
> + metacopy = true;
Miklos seems to prefer
metacopy = err;
if (err < 0)
goto out;
Not sure if it is just coding style or for better branch prediction code.
> }
>
> if (d.redirect) {
> @@ -719,6 +744,19 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
> OVL_I(inode)->redirect = upperredirect;
> if (index)
> ovl_set_flag(OVL_INDEX, inode);
> +
> + if (metacopy) {
> + /*
> + * Found an upper with metacopy set but at the same
> + * time there is no lower dentry. Something is not
> + * right.
> + */
> + if (!ctr) {
Please move this test up right after ovl_check_metacopy()
There is no reason to wait as ctr is not going to grow for non-dir after
that point.
> + err = -ESTALE;
> + goto out_put_inode;
> + }
> + ovl_set_flag(OVL_METACOPY, inode);
> + }
> }
>
> revert_creds(old_cred);
> @@ -729,6 +767,8 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
>
> return NULL;
>
> +out_put_inode:
> + iput(inode);
And than new goto label becomes obsolete
> out_free_oe:
> dentry->d_fsdata = NULL;
> kfree(oe);
> --
> 2.13.5
>
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