Introduce a new config option OVERLAY_FS_INDEX_INCOMPAT.
If this config option is enabled then inodes index is declared
an incompatible feature and kernel will refuse to mount an overlay
with inodes index off when a non-empty index directory exists.
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
---
fs/overlayfs/Kconfig | 8 ++++++++
fs/overlayfs/dir.c | 30 ++++++++++++++++++++++++++++++
fs/overlayfs/overlayfs.h | 3 ++-
fs/overlayfs/super.c | 24 +++++++++++++++++++++++-
4 files changed, 63 insertions(+), 2 deletions(-)
diff --git a/fs/overlayfs/Kconfig b/fs/overlayfs/Kconfig
index cbfc196e5dc5..e5e6dec7d177 100644
--- a/fs/overlayfs/Kconfig
+++ b/fs/overlayfs/Kconfig
@@ -43,3 +43,11 @@ config OVERLAY_FS_INDEX
outcomes. However, mounting the same overlay with an old kernel
read-write and then mounting it again with a new kernel, will have
unexpected results.
+
+config OVERLAY_FS_INDEX_INCOMPAT
+ bool "Overlayfs: support incompatible index feature"
+ depends on OVERLAY_FS_INDEX
+ help
+ If this config option is enabled then inodes index is declared an
+ incompatible feature and kernel will refuse to mount an overlay with
+ inodes index off when a non-empty index directory exists.
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index cc961a3bd3bd..7e2f748d5a7c 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -8,6 +8,7 @@
*/
#include <linux/fs.h>
+#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/xattr.h>
#include <linux/security.h>
@@ -43,6 +44,35 @@ int ovl_cleanup(struct inode *wdir, struct dentry *wdentry)
return err;
}
+int ovl_cleanup_path(struct path *path, const char *name)
+{
+ struct inode *dir = path->dentry->d_inode;
+ struct dentry *dentry;
+ int err;
+
+ err = mnt_want_write(path->mnt);
+ if (err)
+ return err;
+
+ inode_lock_nested(dir, I_MUTEX_PARENT);
+
+ dentry = lookup_one_len(name, path->dentry, strlen(name));
+ if (IS_ERR(dentry)) {
+ err = PTR_ERR(dentry);
+ dentry = NULL;
+ } else if (!dentry->d_inode) {
+ err = -ENOENT;
+ } else {
+ err = ovl_cleanup(dir, dentry);
+ }
+
+ dput(dentry);
+ inode_unlock(dir);
+ mnt_drop_write(path->mnt);
+
+ return err;
+}
+
struct dentry *ovl_lookup_temp(struct dentry *workdir)
{
struct dentry *temp;
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index d9a0edd4e57e..3f9a7625bded 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -300,6 +300,8 @@ static inline void ovl_copyattr(struct inode *from, struct inode *to)
/* dir.c */
extern const struct inode_operations ovl_dir_inode_operations;
+int ovl_cleanup(struct inode *dir, struct dentry *dentry);
+int ovl_cleanup_path(struct path *path, const char *name);
struct dentry *ovl_lookup_temp(struct dentry *workdir);
struct cattr {
dev_t rdev;
@@ -309,7 +311,6 @@ struct cattr {
int ovl_create_real(struct inode *dir, struct dentry *newdentry,
struct cattr *attr,
struct dentry *hardlink, bool debug);
-int ovl_cleanup(struct inode *dir, struct dentry *dentry);
/* copy_up.c */
int ovl_copy_up(struct dentry *dentry);
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index f5738e96a052..0dc6d61f828a 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -39,6 +39,9 @@ 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 const bool ovl_incompat_index =
+ IS_ENABLED(CONFIG_OVERLAY_FS_INDEX_INCOMPAT);
+
static void ovl_dentry_release(struct dentry *dentry)
{
struct ovl_entry *oe = dentry->d_fsdata;
@@ -1060,7 +1063,15 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
else if (ufs->upper_mnt->mnt_sb != ufs->same_sb)
ufs->same_sb = NULL;
- if (!(ovl_force_readonly(ufs)) && ufs->config.index) {
+ if (ovl_force_readonly(ufs)) {
+ /*
+ * Cannot enable index without upperdir/workdir and cannot
+ * test for incompat index dir, but cannot corrupt incompat
+ * index dir either.
+ */
+ ufs->config.index = false;
+ pr_warn("overlayfs: no upperdir/workdir, falling back to index=off.\n");
+ } else if (ufs->config.index) {
/* Verify lower root is upper root origin */
err = ovl_verify_origin(upperpath.dentry, ufs->lower_mnt[0],
stack[0].dentry, false, true);
@@ -1088,6 +1099,17 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
pr_warn("overlayfs: try deleting index dir or mounting with '-o index=off' to disable inodes index.\n");
if (err)
goto out_put_indexdir;
+
+ } else if (ovl_incompat_index) {
+ /*
+ * Try to remove empty index dir if it exists -
+ * failure means we need to abort the mount.
+ */
+ err = ovl_cleanup_path(&workpath, OVL_INDEXDIR_NAME);
+ if (err && err != -ENOENT) {
+ pr_err("overlayfs: incompatible index dir exists, try deleting index dir to disable inodes index.\n");
+ goto out_put_lower_mnt;
+ }
}
/* Show index=off/on in /proc/mounts for any of the reasons above */
--
2.7.4
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