ovl_statfs() reports the f_fsid filled by underlying upper fs.
This fsid is not unique among overlayfs instances on the same upper fs.
Generate a non-persistent uuid per overlayfs instance and use it as the
seed for f_fsid, similar to tmpfs instance uuid/fsid.
The old behavior can be restored with mount option uuid=nogen.
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
---
Documentation/filesystems/overlayfs.rst | 10 +++---
fs/overlayfs/overlayfs.h | 6 ++++
fs/overlayfs/ovl_entry.h | 2 +-
fs/overlayfs/super.c | 46 +++++++++++++++++++++----
4 files changed, 52 insertions(+), 12 deletions(-)
diff --git a/Documentation/filesystems/overlayfs.rst b/Documentation/filesystems/overlayfs.rst
index 4c76fda07645..ad48ae9d3c43 100644
--- a/Documentation/filesystems/overlayfs.rst
+++ b/Documentation/filesystems/overlayfs.rst
@@ -571,10 +571,12 @@ Note: the mount options index=off,nfs_export=on are conflicting for a
read-write mount and will result in an error.
Note: the mount option uuid=off can be used to replace UUID of the underlying
-filesystem in file handles with null, and effectively disable UUID checks. This
-can be useful in case the underlying disk is copied and the UUID of this copy
-is changed. This is only applicable if all lower/upper/work directories are on
-the same filesystem, otherwise it will fallback to normal behaviour.
+filesystem in file handles with null, and effectively disable UUID checks.
+This can be useful in case the underlying disk is copied and the UUID of this
+copy is changed. This is only applicable if all lower/upper/work directories
+are on the same filesystem, otherwise it will fallback to normal behaviour.
+The mount option uuid=nogen can be used to disable UUID generation for the
+overlay filesystem itself. The two mount options are mutually exclusive.
Volatile mount
--------------
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 87d44b889129..dcdb02d0ddf8 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -63,6 +63,12 @@ enum {
OVL_XINO_ON,
};
+enum {
+ OVL_UUID_OFF,
+ OVL_UUID_NOGEN,
+ OVL_UUID_ON,
+};
+
/*
* The tuple (fh,uuid) is a universal unique identifier for a copy up origin,
* where:
diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
index 5cc0b6e65488..4f396b1ce2fb 100644
--- a/fs/overlayfs/ovl_entry.h
+++ b/fs/overlayfs/ovl_entry.h
@@ -14,7 +14,7 @@ struct ovl_config {
bool redirect_follow;
const char *redirect_mode;
bool index;
- bool uuid;
+ int uuid;
bool nfs_export;
int xino;
bool metacopy;
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 5ed8c2650293..ad2250f98b38 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -317,6 +317,7 @@ static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
{
struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
struct dentry *root_dentry = dentry->d_sb->s_root;
+ uuid_t *uuid = &dentry->d_sb->s_uuid;
struct path path;
int err;
@@ -326,6 +327,8 @@ static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
if (!err) {
buf->f_namelen = ofs->namelen;
buf->f_type = OVERLAYFS_SUPER_MAGIC;
+ if (!uuid_is_null(uuid))
+ buf->f_fsid = uuid_to_fsid(uuid->b);
}
return err;
@@ -353,6 +356,25 @@ static inline int ovl_xino_def(void)
return ovl_xino_auto_def ? OVL_XINO_AUTO : OVL_XINO_OFF;
}
+static const char * const ovl_uuid_str[] = {
+ "off",
+ "nogen",
+ "on",
+};
+
+/* XXX: do we need a config for this? */
+static const bool ovl_uuid_gen_def = true;
+
+static inline int ovl_uuid_def(void)
+{
+ return ovl_uuid_gen_def ? OVL_UUID_ON : OVL_UUID_NOGEN;
+}
+
+static inline int ovl_want_uuid_gen(struct ovl_fs *ofs)
+{
+ return ofs->config.uuid != OVL_UUID_NOGEN;
+}
+
/**
* ovl_show_options
* @m: the seq_file handle
@@ -377,8 +399,8 @@ static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
seq_printf(m, ",redirect_dir=%s", ofs->config.redirect_mode);
if (ofs->config.index != ovl_index_def)
seq_printf(m, ",index=%s", ofs->config.index ? "on" : "off");
- if (!ofs->config.uuid)
- seq_puts(m, ",uuid=off");
+ if (ofs->config.uuid != ovl_uuid_def())
+ seq_printf(m, ",uuid=%s", ovl_uuid_str[ofs->config.uuid]);
if (ofs->config.nfs_export != ovl_nfs_export_def)
seq_printf(m, ",nfs_export=%s", ofs->config.nfs_export ?
"on" : "off");
@@ -437,6 +459,7 @@ enum {
OPT_INDEX_OFF,
OPT_UUID_ON,
OPT_UUID_OFF,
+ OPT_UUID_NOGEN,
OPT_NFS_EXPORT_ON,
OPT_USERXATTR,
OPT_NFS_EXPORT_OFF,
@@ -460,6 +483,7 @@ static const match_table_t ovl_tokens = {
{OPT_USERXATTR, "userxattr"},
{OPT_UUID_ON, "uuid=on"},
{OPT_UUID_OFF, "uuid=off"},
+ {OPT_UUID_NOGEN, "uuid=nogen"},
{OPT_NFS_EXPORT_ON, "nfs_export=on"},
{OPT_NFS_EXPORT_OFF, "nfs_export=off"},
{OPT_XINO_ON, "xino=on"},
@@ -581,11 +605,15 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
break;
case OPT_UUID_ON:
- config->uuid = true;
+ config->uuid = OVL_UUID_ON;
break;
case OPT_UUID_OFF:
- config->uuid = false;
+ config->uuid = OVL_UUID_OFF;
+ break;
+
+ case OPT_UUID_NOGEN:
+ config->uuid = OVL_UUID_NOGEN;
break;
case OPT_NFS_EXPORT_ON:
@@ -1924,7 +1952,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
ofs->share_whiteout = true;
ofs->config.index = ovl_index_def;
- ofs->config.uuid = true;
+ ofs->config.uuid = ovl_uuid_def();
ofs->config.nfs_export = ovl_nfs_export_def;
ofs->config.xino = ovl_xino_def();
ofs->config.metacopy = ovl_metacopy_def;
@@ -2019,10 +2047,14 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
sb->s_flags |= SB_RDONLY;
if (!ofs->config.uuid && ofs->numfs > 1) {
- pr_warn("The uuid=off requires a single fs for lower and upper, falling back to uuid=on.\n");
- ofs->config.uuid = true;
+ ofs->config.uuid = ovl_uuid_def();
+ pr_warn("The uuid=off requires a single fs for lower and upper, falling back to uuid=%s.\n",
+ ovl_uuid_str[ofs->config.uuid]);
}
+ if (ovl_want_uuid_gen(ofs))
+ uuid_gen(&sb->s_uuid);
+
if (!ovl_force_readonly(ofs) && ofs->config.index) {
err = ovl_get_indexdir(sb, ofs, oe, &upperpath);
if (err)
--
2.34.1
