ovl: introduce the inodes index dir feature
Create the index dir on mount. The index dir will contain hardlinks to
upper inodes, named after the hex representation of their origin lower
inodes.
The index dir is going to be used to prevent breaking lower hardlinks
on copy up and to implement overlayfs NFS export.
Because the feature is not fully backward compat, enabling the feature
is opt-in by config/module/mount option.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index fea7bd4..fa83b32 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -34,6 +34,11 @@
MODULE_PARM_DESC(ovl_redirect_dir_def,
"Default to on or off for the redirect_dir feature");
+static bool ovl_index_def = IS_ENABLED(CONFIG_OVERLAY_FS_INDEX);
+module_param_named(index, ovl_index_def, bool, 0644);
+MODULE_PARM_DESC(ovl_index_def,
+ "Default to on or off for the inodes index feature");
+
static void ovl_dentry_release(struct dentry *dentry)
{
struct ovl_entry *oe = dentry->d_fsdata;
@@ -203,6 +208,7 @@
struct ovl_fs *ufs = sb->s_fs_info;
unsigned i;
+ dput(ufs->indexdir);
dput(ufs->workdir);
ovl_inuse_unlock(ufs->workbasedir);
dput(ufs->workbasedir);
@@ -265,6 +271,12 @@
return err;
}
+/* Will this overlay be forced to mount/remount ro? */
+static bool ovl_force_readonly(struct ovl_fs *ufs)
+{
+ return (!ufs->upper_mnt || !ufs->workdir);
+}
+
/**
* ovl_show_options
*
@@ -286,6 +298,9 @@
if (ufs->config.redirect_dir != ovl_redirect_dir_def)
seq_printf(m, ",redirect_dir=%s",
ufs->config.redirect_dir ? "on" : "off");
+ if (ufs->config.index != ovl_index_def)
+ seq_printf(m, ",index=%s",
+ ufs->config.index ? "on" : "off");
return 0;
}
@@ -293,7 +308,7 @@
{
struct ovl_fs *ufs = sb->s_fs_info;
- if (!(*flags & MS_RDONLY) && (!ufs->upper_mnt || !ufs->workdir))
+ if (!(*flags & MS_RDONLY) && ovl_force_readonly(ufs))
return -EROFS;
return 0;
@@ -317,6 +332,8 @@
OPT_DEFAULT_PERMISSIONS,
OPT_REDIRECT_DIR_ON,
OPT_REDIRECT_DIR_OFF,
+ OPT_INDEX_ON,
+ OPT_INDEX_OFF,
OPT_ERR,
};
@@ -327,6 +344,8 @@
{OPT_DEFAULT_PERMISSIONS, "default_permissions"},
{OPT_REDIRECT_DIR_ON, "redirect_dir=on"},
{OPT_REDIRECT_DIR_OFF, "redirect_dir=off"},
+ {OPT_INDEX_ON, "index=on"},
+ {OPT_INDEX_OFF, "index=off"},
{OPT_ERR, NULL}
};
@@ -399,6 +418,14 @@
config->redirect_dir = false;
break;
+ case OPT_INDEX_ON:
+ config->index = true;
+ break;
+
+ case OPT_INDEX_OFF:
+ config->index = false;
+ break;
+
default:
pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p);
return -EINVAL;
@@ -417,6 +444,7 @@
}
#define OVL_WORKDIR_NAME "work"
+#define OVL_INDEXDIR_NAME "index"
static struct dentry *ovl_workdir_create(struct super_block *sb,
struct ovl_fs *ufs,
@@ -610,6 +638,15 @@
if (ovl_dentry_remote(path->dentry))
*remote = true;
+ /*
+ * The inodes index feature needs to encode and decode file
+ * handles, so it requires that all layers support them.
+ */
+ if (ofs->config.index && !ovl_can_decode_fh(path->dentry->d_sb)) {
+ ofs->config.index = false;
+ pr_warn("overlayfs: fs on '%s' does not support file handles, falling back to index=off.\n", name);
+ }
+
return 0;
out_put:
@@ -807,6 +844,7 @@
goto out;
ufs->config.redirect_dir = ovl_redirect_dir_def;
+ ufs->config.index = ovl_index_def;
err = ovl_parse_opt((char *) data, &ufs->config);
if (err)
goto out_free_config;
@@ -965,6 +1003,13 @@
} else {
vfs_removexattr(ufs->workdir, OVL_XATTR_OPAQUE);
}
+
+ /* Check if upper/work fs supports file handles */
+ if (ufs->config.index &&
+ !ovl_can_decode_fh(ufs->workdir->d_sb)) {
+ ufs->config.index = false;
+ pr_warn("overlayfs: upper fs does not support file handles, falling back to index=off.\n");
+ }
}
}
@@ -1002,6 +1047,21 @@
else if (ufs->upper_mnt->mnt_sb != ufs->same_sb)
ufs->same_sb = NULL;
+ if (!(ovl_force_readonly(ufs)) && ufs->config.index) {
+ ufs->indexdir = ovl_workdir_create(sb, ufs, workpath.dentry,
+ OVL_INDEXDIR_NAME, true);
+ err = PTR_ERR(ufs->indexdir);
+ if (IS_ERR(ufs->indexdir))
+ goto out_put_lower_mnt;
+
+ if (!ufs->indexdir)
+ pr_warn("overlayfs: try deleting index dir or mounting with '-o index=off' to disable inodes index.\n");
+ }
+
+ /* Show index=off/on in /proc/mounts for any of the reasons above */
+ if (!ufs->indexdir)
+ ufs->config.index = false;
+
if (remote)
sb->s_d_op = &ovl_reval_dentry_operations;
else
@@ -1009,7 +1069,7 @@
ufs->creator_cred = cred = prepare_creds();
if (!cred)
- goto out_put_lower_mnt;
+ goto out_put_indexdir;
/* Never override disk quota limits or use reserved space */
cap_lower(cred->cap_effective, CAP_SYS_RESOURCE);
@@ -1058,6 +1118,8 @@
kfree(oe);
out_put_cred:
put_cred(ufs->creator_cred);
+out_put_indexdir:
+ dput(ufs->indexdir);
out_put_lower_mnt:
for (i = 0; i < ufs->numlower; i++)
mntput(ufs->lower_mnt[i]);