ovl: add mutli-layer infrastructure
Add multiple lower layers to 'struct ovl_fs' and 'struct ovl_entry'.
ovl_entry will have an array of paths, instead of just the dentry. This
allows a compact array containing just the layers which exist at current
point in the tree (which is expected to be a small number for the majority
of dentries).
The number of layers is not limited by this infrastructure.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 821719c..460d866 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -35,7 +35,8 @@
/* private information held for overlayfs's superblock */
struct ovl_fs {
struct vfsmount *upper_mnt;
- struct vfsmount *lower_mnt;
+ unsigned numlower;
+ struct vfsmount **lower_mnt;
struct dentry *workdir;
long lower_namelen;
/* pathnames of lower and upper dirs, for show_options */
@@ -47,7 +48,6 @@
/* private information held for every overlayfs dentry */
struct ovl_entry {
struct dentry *__upperdentry;
- struct dentry *lowerdentry;
struct ovl_dir_cache *cache;
union {
struct {
@@ -56,10 +56,16 @@
};
struct rcu_head rcu;
};
+ unsigned numlower;
+ struct path lowerstack[];
};
const char *ovl_opaque_xattr = "trusted.overlay.opaque";
+static struct dentry *__ovl_dentry_lower(struct ovl_entry *oe)
+{
+ return oe->numlower ? oe->lowerstack[0].dentry : NULL;
+}
enum ovl_path_type ovl_path_type(struct dentry *dentry)
{
@@ -69,7 +75,7 @@
if (oe->__upperdentry) {
type = __OVL_PATH_UPPER;
- if (oe->lowerdentry) {
+ if (oe->numlower) {
if (S_ISDIR(dentry->d_inode->i_mode))
type |= __OVL_PATH_MERGE;
} else if (!oe->opaque) {
@@ -117,7 +123,7 @@
{
struct ovl_entry *oe = dentry->d_fsdata;
- return oe->lowerdentry;
+ return __ovl_dentry_lower(oe);
}
struct dentry *ovl_dentry_real(struct dentry *dentry)
@@ -127,7 +133,7 @@
realdentry = ovl_upperdentry_dereference(oe);
if (!realdentry)
- realdentry = oe->lowerdentry;
+ realdentry = __ovl_dentry_lower(oe);
return realdentry;
}
@@ -140,7 +146,7 @@
if (realdentry) {
*is_upper = true;
} else {
- realdentry = oe->lowerdentry;
+ realdentry = __ovl_dentry_lower(oe);
*is_upper = false;
}
return realdentry;
@@ -162,11 +168,9 @@
void ovl_path_lower(struct dentry *dentry, struct path *path)
{
- struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
struct ovl_entry *oe = dentry->d_fsdata;
- path->mnt = ofs->lower_mnt;
- path->dentry = oe->lowerdentry;
+ *path = oe->numlower ? oe->lowerstack[0] : (struct path) { NULL, NULL };
}
int ovl_want_write(struct dentry *dentry)
@@ -258,8 +262,11 @@
struct ovl_entry *oe = dentry->d_fsdata;
if (oe) {
+ unsigned int i;
+
dput(oe->__upperdentry);
- dput(oe->lowerdentry);
+ for (i = 0; i < oe->numlower; i++)
+ dput(oe->lowerstack[i].dentry);
kfree_rcu(oe, rcu);
}
}
@@ -268,9 +275,15 @@
.d_release = ovl_dentry_release,
};
-static struct ovl_entry *ovl_alloc_entry(void)
+static struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
{
- return kzalloc(sizeof(struct ovl_entry), GFP_KERNEL);
+ size_t size = offsetof(struct ovl_entry, lowerstack[numlower]);
+ struct ovl_entry *oe = kzalloc(size, GFP_KERNEL);
+
+ if (oe)
+ oe->numlower = numlower;
+
+ return oe;
}
static inline struct dentry *ovl_lookup_real(struct dentry *dir,
@@ -297,19 +310,19 @@
{
struct ovl_entry *oe;
struct dentry *upperdir;
- struct dentry *lowerdir;
+ struct path lowerdir;
struct dentry *upperdentry = NULL;
struct dentry *lowerdentry = NULL;
struct inode *inode = NULL;
int err;
err = -ENOMEM;
- oe = ovl_alloc_entry();
+ oe = ovl_alloc_entry(1);
if (!oe)
goto out;
upperdir = ovl_dentry_upper(dentry->d_parent);
- lowerdir = ovl_dentry_lower(dentry->d_parent);
+ ovl_path_lower(dentry->d_parent, &lowerdir);
if (upperdir) {
upperdentry = ovl_lookup_real(upperdir, &dentry->d_name);
@@ -317,7 +330,7 @@
if (IS_ERR(upperdentry))
goto out_put_dir;
- if (lowerdir && upperdentry) {
+ if (lowerdir.dentry && upperdentry) {
if (ovl_is_whiteout(upperdentry)) {
dput(upperdentry);
upperdentry = NULL;
@@ -327,8 +340,8 @@
}
}
}
- if (lowerdir && !oe->opaque) {
- lowerdentry = ovl_lookup_real(lowerdir, &dentry->d_name);
+ if (lowerdir.dentry && !oe->opaque) {
+ lowerdentry = ovl_lookup_real(lowerdir.dentry, &dentry->d_name);
err = PTR_ERR(lowerdentry);
if (IS_ERR(lowerdentry))
goto out_dput_upper;
@@ -355,8 +368,12 @@
}
oe->__upperdentry = upperdentry;
- oe->lowerdentry = lowerdentry;
-
+ if (lowerdentry) {
+ oe->lowerstack[0].dentry = lowerdentry;
+ oe->lowerstack[0].mnt = lowerdir.mnt;
+ } else {
+ oe->numlower = 0;
+ }
dentry->d_fsdata = oe;
d_add(dentry, inode);
@@ -380,10 +397,12 @@
static void ovl_put_super(struct super_block *sb)
{
struct ovl_fs *ufs = sb->s_fs_info;
+ unsigned i;
dput(ufs->workdir);
mntput(ufs->upper_mnt);
- mntput(ufs->lower_mnt);
+ for (i = 0; i < ufs->numlower; i++)
+ mntput(ufs->lower_mnt[i]);
kfree(ufs->config.lowerdir);
kfree(ufs->config.upperdir);
@@ -641,6 +660,8 @@
struct ovl_entry *oe;
struct ovl_fs *ufs;
struct kstatfs statfs;
+ struct vfsmount *mnt;
+ unsigned int i;
int err;
err = -ENOMEM;
@@ -661,7 +682,7 @@
}
err = -ENOMEM;
- oe = ovl_alloc_entry();
+ oe = ovl_alloc_entry(1);
if (oe == NULL)
goto out_free_config;
@@ -727,12 +748,24 @@
goto out_put_workpath;
}
- ufs->lower_mnt = clone_private_mount(&lowerpath);
- err = PTR_ERR(ufs->lower_mnt);
- if (IS_ERR(ufs->lower_mnt)) {
- pr_err("overlayfs: failed to clone lowerpath\n");
+ ufs->lower_mnt = kcalloc(1, sizeof(struct vfsmount *), GFP_KERNEL);
+ if (ufs->lower_mnt == NULL)
goto out_put_upper_mnt;
+
+ mnt = clone_private_mount(&lowerpath);
+ err = PTR_ERR(mnt);
+ if (IS_ERR(mnt)) {
+ pr_err("overlayfs: failed to clone lowerpath\n");
+ goto out_put_lower_mnt;
}
+ /*
+ * Make lower_mnt R/O. That way fchmod/fchown on lower file
+ * will fail instead of modifying lower fs.
+ */
+ mnt->mnt_flags |= MNT_READONLY;
+
+ ufs->lower_mnt[0] = mnt;
+ ufs->numlower = 1;
ufs->workdir = ovl_workdir_create(ufs->upper_mnt, workpath.dentry);
err = PTR_ERR(ufs->workdir);
@@ -742,12 +775,6 @@
goto out_put_lower_mnt;
}
- /*
- * Make lower_mnt R/O. That way fchmod/fchown on lower file
- * will fail instead of modifying lower fs.
- */
- ufs->lower_mnt->mnt_flags |= MNT_READONLY;
-
/* If the upper fs is r/o, we mark overlayfs r/o too */
if (ufs->upper_mnt->mnt_sb->s_flags & MS_RDONLY)
sb->s_flags |= MS_RDONLY;
@@ -768,7 +795,8 @@
path_put(&workpath);
oe->__upperdentry = upperpath.dentry;
- oe->lowerdentry = lowerpath.dentry;
+ oe->lowerstack[0].dentry = lowerpath.dentry;
+ oe->lowerstack[0].mnt = ufs->lower_mnt[0];
root_dentry->d_fsdata = oe;
@@ -782,7 +810,9 @@
out_put_workdir:
dput(ufs->workdir);
out_put_lower_mnt:
- mntput(ufs->lower_mnt);
+ for (i = 0; i < ufs->numlower; i++)
+ mntput(ufs->lower_mnt[i]);
+ kfree(ufs->lower_mnt);
out_put_upper_mnt:
mntput(ufs->upper_mnt);
out_put_workpath: