On Tue, Jul 31, 2018 at 12:37 PM, zhangyi (F) <yi.zhang@xxxxxxxxxx> wrote:
> overlayfs will want to add the upper layer's feature bitset if some
> overlay file system features were set. For example: redirect dir feature
> will be set when user rename a lower/merge dir if redirect dir feature
> is enabled. So add helper functions to set feature sets to the upper
> layer for future use.
>
> This patch introduce helper functions only, does not set any feature
> bits.
>
> Signed-off-by: zhangyi (F) <yi.zhang@xxxxxxxxxx>
> ---
> fs/overlayfs/feature.c | 85 ++++++++++++++++++++++++++++++++++++++++++++++++
> fs/overlayfs/overlayfs.h | 46 ++++++++++++++++++++++++++
> fs/overlayfs/ovl_entry.h | 2 ++
> fs/overlayfs/super.c | 1 +
> 4 files changed, 134 insertions(+)
>
> diff --git a/fs/overlayfs/feature.c b/fs/overlayfs/feature.c
> index fac4d7544475..7c66e71bdd98 100644
> --- a/fs/overlayfs/feature.c
> +++ b/fs/overlayfs/feature.c
> @@ -10,6 +10,8 @@
>
> #include <linux/fs.h>
> #include <linux/xattr.h>
> +#include <linux/mount.h>
> +#include <linux/ratelimit.h>
> #include "overlayfs.h"
>
> /*
> @@ -63,6 +65,89 @@ static struct ovl_d_feature *ovl_get_feature(struct dentry *realroot)
> }
>
> /*
> + * Set overlay features to the upper root dir.
> + *
> + * @upper_layer: overlay upper layer information,
> + * @upper: upper root dentry.
> + *
> + * Return 0 if success, error number otherwise.
> + */
> +static int ovl_set_feature(struct ovl_layer *upper_layer,
> + struct dentry *upper)
> +{
> + struct vfsmount *upper_mnt = upper_layer->mnt;
> + struct ovl_d_feature odf = {};
> + int err;
> +
> + odf.magic = OVL_FEATURE_MAGIC;
> + odf.compat = cpu_to_be64(upper_layer->compat);
> + odf.ro_compat = cpu_to_be64(upper_layer->ro_compat);
> + odf.incompat = cpu_to_be64(upper_layer->incompat);
> +
> + err = mnt_want_write(upper_mnt);
> + if (err)
> + return err;
> +
> + err = ovl_do_setxattr(upper, OVL_XATTR_FEATURE,
> + &odf, sizeof(odf), 0);
> + if (err)
> + pr_err_ratelimited("overlayfs: failed to set features (%i)\n", err);
> +
> + mnt_drop_write(upper_mnt);
> + return err;
> +}
> +
> +/*
> + * Add feature bit mask to the upper root dir.
> + *
> + * @ofs: overlay filesystem information
> + * @type: feature set type, compat, ro compat or incompat
> + * @mask: new features mask want to add
> + *
> + * Return 0 if success, error number otherwise.
> + */
> +int ovl_set_upper_feature(struct ovl_fs *ofs,
> + enum ovl_feature_type type,
> + u64 mask)
> +{
> + struct ovl_layer *upper_layer = ofs->upper_layer;
> + u64 *features;
> + int err;
> +
> + if (!upper_layer)
> + return -EINVAL;
> +
> + switch (type) {
> + case OVL_FEATURE_COMPAT:
> + features = &upper_layer->compat;
> + break;
> + case OVL_FEATURE_RO_COMPAT:
> + features = &upper_layer->ro_compat;
> + break;
> + case OVL_FEATURE_INCOMPAT:
> + features = &upper_layer->incompat;
> + break;
> + default:
> + return -EINVAL;
> + }
> +
> + spin_lock(&upper_layer->lock);
> + if ((*features) & mask) {
> + spin_unlock(&upper_layer->lock);
> + return 0;
> + }
> +
> + (*features) |= mask;
> + spin_unlock(&upper_layer->lock);
> +
Seems like you can move the above test and set into
ovl_set_feature() and you can also use upperdir->d_lock
and don't need to introduce a new spinlock for this.
Thanks,
Amir.
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