diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 8a283ec21e34dca78026475f4e784d99f3ecacb1..cfccd91c51e319e5cfe76d5a6bb7a04583d8e546 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -83,14 +83,15 @@ static int ovl_map_dev_ino(struct dentry *dentry, struct kstat *stat,
*/
stat->dev = dentry->d_sb->s_dev;
stat->ino = dentry->d_inode->i_ino;
- } else if (lower_layer) {
+ } else if (lower_layer && lower_layer->fsid) {
/*
* For non-samefs setup, if we cannot map all layers st_ino
* to a unified address space, we need to make sure that st_dev
- * is unique per layer. Upper layer uses real st_dev and lower
- * layers use the unique anonymous bdev.
+ * is unique per lower fs. Upper layer uses real st_dev and
+ * lower layers use the unique anonymous bdev assigned to the
+ * lower fs.
*/
- stat->dev = lower_layer->pseudo_dev;
+ stat->dev = lower_layer->fs->pseudo_dev;
}
return 0;
diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
index bfef6edcc1112853e750a3a5468334aa39991465..e1c838c27a742bda334285e1b3e2887383b15328 100644
--- a/fs/overlayfs/ovl_entry.h
+++ b/fs/overlayfs/ovl_entry.h
@@ -20,11 +20,18 @@ struct ovl_config {
bool nfs_export;
};
+struct ovl_sb {
+ struct super_block *sb;
+ dev_t pseudo_dev;
+};
+
struct ovl_layer {
struct vfsmount *mnt;
- dev_t pseudo_dev;
- /* Index of this layer in fs root (upper == 0) */
+ struct ovl_sb *fs;
+ /* Index of this layer in fs root (upper idx == 0) */
int idx;
+ /* One fsid per unique underlying sb (upper fsid == 0) */
+ int fsid;
};
struct ovl_path {
@@ -35,8 +42,11 @@ struct ovl_path {
/* private information held for overlayfs's superblock */
struct ovl_fs {
struct vfsmount *upper_mnt;
- unsigned numlower;
+ unsigned int numlower;
+ /* Number of unique lower sb that differ from upper sb */
+ unsigned int numlowerfs;
struct ovl_layer *lower_layers;
+ struct ovl_sb *lower_fs;
/* workbasedir is the path at workdir= mount option */
struct dentry *workbasedir;
/* workdir is the 'work' directory under workbasedir */
@@ -50,8 +60,6 @@ struct ovl_fs {
const struct cred *creator_cred;
bool tmpfile;
bool noxattr;
- /* sb common to all layers */
- struct super_block *same_sb;
/* Did we take the inuse lock? */
bool upperdir_locked;
bool workdir_locked;
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 7c24619ae7fc5229a5d3af6c9298b51064498325..7d97d30cad397eed320ee01e5a4dd3b5c921828d 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -236,11 +236,12 @@ static void ovl_free_fs(struct ovl_fs *ofs)
if (ofs->upperdir_locked)
ovl_inuse_unlock(ofs->upper_mnt->mnt_root);
mntput(ofs->upper_mnt);
- for (i = 0; i < ofs->numlower; i++) {
+ for (i = 0; i < ofs->numlower; i++)
mntput(ofs->lower_layers[i].mnt);
- free_anon_bdev(ofs->lower_layers[i].pseudo_dev);
- }
+ for (i = 0; i < ofs->numlowerfs; i++)
+ free_anon_bdev(ofs->lower_fs[i].pseudo_dev);
kfree(ofs->lower_layers);
+ kfree(ofs->lower_fs);
kfree(ofs->config.lowerdir);
kfree(ofs->config.upperdir);
@@ -1108,6 +1109,35 @@ static int ovl_get_indexdir(struct ovl_fs *ofs, struct ovl_entry *oe,
return err;
}
+/* Get a unique fsid for the layer */
+static int ovl_get_fsid(struct ovl_fs *ofs, struct super_block *sb)
+{
+ unsigned int i;
+ dev_t dev;
+ int err;
+
+ /* fsid 0 is reserved for upper fs even with non upper overlay */
+ if (ofs->upper_mnt && ofs->upper_mnt->mnt_sb == sb)
+ return 0;
+
+ for (i = 0; i < ofs->numlowerfs; i++) {
+ if (ofs->lower_fs[i].sb == sb)
+ return i + 1;
+ }
+
+ err = get_anon_bdev(&dev);
+ if (err) {
+ pr_err("overlayfs: failed to get anonymous bdev for lowerpath\n");
+ return err;
+ }
+
+ ofs->lower_fs[ofs->numlowerfs].sb = sb;
+ ofs->lower_fs[ofs->numlowerfs].pseudo_dev = dev;
+ ofs->numlowerfs++;
+
+ return ofs->numlowerfs;
+}
+
static int ovl_get_lower_layers(struct ovl_fs *ofs, struct path *stack,
unsigned int numlower)
{
@@ -1119,23 +1149,27 @@ static int ovl_get_lower_layers(struct ovl_fs *ofs, struct path *stack,
GFP_KERNEL);
if (ofs->lower_layers == NULL)
goto out;
+
+ ofs->lower_fs = kcalloc(numlower, sizeof(struct ovl_sb),
+ GFP_KERNEL);
+ if (ofs->lower_fs == NULL)
+ goto out;
+
for (i = 0; i < numlower; i++) {
struct vfsmount *mnt;
- dev_t dev;
+ int fsid;
- err = get_anon_bdev(&dev);
- if (err) {
- pr_err("overlayfs: failed to get anonymous bdev for lowerpath\n");
+ err = fsid = ovl_get_fsid(ofs, stack[i].mnt->mnt_sb);
+ if (err < 0)
goto out;
- }
mnt = clone_private_mount(&stack[i]);
err = PTR_ERR(mnt);
if (IS_ERR(mnt)) {
pr_err("overlayfs: failed to clone lowerpath\n");
- free_anon_bdev(dev);
goto out;
}
+
/*
* Make lower layers R/O. That way fchmod/fchown on lower file
* will fail instead of modifying lower fs.
@@ -1143,15 +1177,13 @@ static int ovl_get_lower_layers(struct ovl_fs *ofs, struct path *stack,
mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
ofs->lower_layers[ofs->numlower].mnt = mnt;
- ofs->lower_layers[ofs->numlower].pseudo_dev = dev;
ofs->lower_layers[ofs->numlower].idx = i + 1;
+ ofs->lower_layers[ofs->numlower].fsid = fsid;
+ if (fsid) {
+ ofs->lower_layers[ofs->numlower].fs =
+ &ofs->lower_fs[fsid - 1];
+ }
ofs->numlower++;
-
- /* Check if all lower layers are on same sb */
- if (i == 0)
- ofs->same_sb = mnt->mnt_sb;
- else if (ofs->same_sb != mnt->mnt_sb)
- ofs->same_sb = NULL;
}
err = 0;
out:
@@ -1305,8 +1337,6 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
/* If the upper fs is nonexistent, we mark overlayfs r/o too */
if (!ofs->upper_mnt)
sb->s_flags |= SB_RDONLY;
- else if (ofs->upper_mnt->mnt_sb != ofs->same_sb)
- ofs->same_sb = NULL;
if (!(ovl_force_readonly(ofs)) && ofs->config.index) {
err = ovl_get_indexdir(ofs, oe, &upperpath);
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index 5042293d2078902dbba3f96a55f6d73f126dba4e..9dfec74ec77d466aac575438aecc1328f5907f81 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -47,7 +47,12 @@ struct super_block *ovl_same_sb(struct super_block *sb)
{
struct ovl_fs *ofs = sb->s_fs_info;
- return ofs->same_sb;
+ if (!ofs->numlowerfs)
+ return ofs->upper_mnt->mnt_sb;
+ else if (ofs->numlowerfs == 1 && !ofs->upper_mnt)
+ return ofs->lower_fs[0].sb;
+ else
+ return NULL;
}
bool ovl_can_decode_fh(struct super_block *sb)