diff options
Diffstat (limited to 'fs/overlayfs/util.c')
| -rw-r--r-- | fs/overlayfs/util.c | 31 |
1 files changed, 30 insertions, 1 deletions
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c index 23c0224779be..939e4d586ec2 100644 --- a/fs/overlayfs/util.c +++ b/fs/overlayfs/util.c @@ -229,8 +229,14 @@ void ovl_path_lowerdata(struct dentry *dentry, struct path *path) struct dentry *lowerdata_dentry = ovl_lowerdata_dentry(oe); if (lowerdata_dentry) { - path->mnt = lowerdata->layer->mnt; path->dentry = lowerdata_dentry; + /* + * Pairs with smp_wmb() in ovl_dentry_set_lowerdata(). + * Make sure that if lowerdata->dentry is visible, then + * datapath->layer is visible as well. + */ + smp_rmb(); + path->mnt = READ_ONCE(lowerdata->layer)->mnt; } else { *path = (struct path) { }; } @@ -292,6 +298,29 @@ struct dentry *ovl_dentry_lowerdata(struct dentry *dentry) return ovl_lowerdata_dentry(OVL_E(dentry)); } +int ovl_dentry_set_lowerdata(struct dentry *dentry, struct ovl_path *datapath) +{ + struct ovl_entry *oe = OVL_E(dentry); + struct ovl_path *lowerdata = ovl_lowerdata(oe); + struct dentry *datadentry = datapath->dentry; + + if (WARN_ON_ONCE(ovl_numlower(oe) <= 1)) + return -EIO; + + WRITE_ONCE(lowerdata->layer, datapath->layer); + /* + * Pairs with smp_rmb() in ovl_path_lowerdata(). + * Make sure that if lowerdata->dentry is visible, then + * lowerdata->layer is visible as well. + */ + smp_wmb(); + WRITE_ONCE(lowerdata->dentry, dget(datadentry)); + + ovl_dentry_update_reval(dentry, datadentry); + + return 0; +} + struct dentry *ovl_dentry_real(struct dentry *dentry) { return ovl_dentry_upper(dentry) ?: ovl_dentry_lower(dentry); |