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synced 2024-11-24 20:54:10 +08:00
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>
This commit is contained in:
Miklos Szeredi
parent
263b4a0fee
commit
dd662667e6
@ -35,7 +35,8 @@ struct ovl_config {
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/* private information held for overlayfs's superblock */
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struct ovl_fs {
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struct vfsmount *upper_mnt;
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struct vfsmount *lower_mnt;
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unsigned numlower;
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struct vfsmount **lower_mnt;
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struct dentry *workdir;
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long lower_namelen;
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/* pathnames of lower and upper dirs, for show_options */
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@ -47,7 +48,6 @@ struct ovl_dir_cache;
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/* private information held for every overlayfs dentry */
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struct ovl_entry {
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struct dentry *__upperdentry;
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struct dentry *lowerdentry;
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struct ovl_dir_cache *cache;
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union {
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struct {
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@ -56,10 +56,16 @@ struct ovl_entry {
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};
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struct rcu_head rcu;
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};
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unsigned numlower;
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struct path lowerstack[];
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};
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const char *ovl_opaque_xattr = "trusted.overlay.opaque";
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static struct dentry *__ovl_dentry_lower(struct ovl_entry *oe)
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{
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return oe->numlower ? oe->lowerstack[0].dentry : NULL;
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}
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enum ovl_path_type ovl_path_type(struct dentry *dentry)
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{
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@ -69,7 +75,7 @@ enum ovl_path_type ovl_path_type(struct dentry *dentry)
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if (oe->__upperdentry) {
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type = __OVL_PATH_UPPER;
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if (oe->lowerdentry) {
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if (oe->numlower) {
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if (S_ISDIR(dentry->d_inode->i_mode))
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type |= __OVL_PATH_MERGE;
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} else if (!oe->opaque) {
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@ -117,7 +123,7 @@ struct dentry *ovl_dentry_lower(struct dentry *dentry)
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{
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struct ovl_entry *oe = dentry->d_fsdata;
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return oe->lowerdentry;
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return __ovl_dentry_lower(oe);
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}
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struct dentry *ovl_dentry_real(struct dentry *dentry)
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@ -127,7 +133,7 @@ struct dentry *ovl_dentry_real(struct dentry *dentry)
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realdentry = ovl_upperdentry_dereference(oe);
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if (!realdentry)
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realdentry = oe->lowerdentry;
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realdentry = __ovl_dentry_lower(oe);
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return realdentry;
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}
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@ -140,7 +146,7 @@ struct dentry *ovl_entry_real(struct ovl_entry *oe, bool *is_upper)
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if (realdentry) {
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*is_upper = true;
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} else {
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realdentry = oe->lowerdentry;
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realdentry = __ovl_dentry_lower(oe);
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*is_upper = false;
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}
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return realdentry;
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@ -162,11 +168,9 @@ void ovl_set_dir_cache(struct dentry *dentry, struct ovl_dir_cache *cache)
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void ovl_path_lower(struct dentry *dentry, struct path *path)
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{
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struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
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struct ovl_entry *oe = dentry->d_fsdata;
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path->mnt = ofs->lower_mnt;
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path->dentry = oe->lowerdentry;
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*path = oe->numlower ? oe->lowerstack[0] : (struct path) { NULL, NULL };
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}
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int ovl_want_write(struct dentry *dentry)
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@ -258,8 +262,11 @@ static void ovl_dentry_release(struct dentry *dentry)
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struct ovl_entry *oe = dentry->d_fsdata;
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if (oe) {
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unsigned int i;
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dput(oe->__upperdentry);
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dput(oe->lowerdentry);
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for (i = 0; i < oe->numlower; i++)
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dput(oe->lowerstack[i].dentry);
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kfree_rcu(oe, rcu);
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}
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}
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@ -268,9 +275,15 @@ static const struct dentry_operations ovl_dentry_operations = {
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.d_release = ovl_dentry_release,
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};
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static struct ovl_entry *ovl_alloc_entry(void)
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static struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
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{
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return kzalloc(sizeof(struct ovl_entry), GFP_KERNEL);
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size_t size = offsetof(struct ovl_entry, lowerstack[numlower]);
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struct ovl_entry *oe = kzalloc(size, GFP_KERNEL);
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if (oe)
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oe->numlower = numlower;
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return oe;
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}
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static inline struct dentry *ovl_lookup_real(struct dentry *dir,
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@ -297,19 +310,19 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
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{
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struct ovl_entry *oe;
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struct dentry *upperdir;
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struct dentry *lowerdir;
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struct path lowerdir;
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struct dentry *upperdentry = NULL;
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struct dentry *lowerdentry = NULL;
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struct inode *inode = NULL;
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int err;
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err = -ENOMEM;
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oe = ovl_alloc_entry();
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oe = ovl_alloc_entry(1);
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if (!oe)
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goto out;
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upperdir = ovl_dentry_upper(dentry->d_parent);
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lowerdir = ovl_dentry_lower(dentry->d_parent);
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ovl_path_lower(dentry->d_parent, &lowerdir);
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if (upperdir) {
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upperdentry = ovl_lookup_real(upperdir, &dentry->d_name);
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@ -317,7 +330,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
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if (IS_ERR(upperdentry))
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goto out_put_dir;
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if (lowerdir && upperdentry) {
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if (lowerdir.dentry && upperdentry) {
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if (ovl_is_whiteout(upperdentry)) {
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dput(upperdentry);
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upperdentry = NULL;
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@ -327,8 +340,8 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
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}
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}
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}
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if (lowerdir && !oe->opaque) {
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lowerdentry = ovl_lookup_real(lowerdir, &dentry->d_name);
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if (lowerdir.dentry && !oe->opaque) {
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lowerdentry = ovl_lookup_real(lowerdir.dentry, &dentry->d_name);
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err = PTR_ERR(lowerdentry);
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if (IS_ERR(lowerdentry))
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goto out_dput_upper;
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@ -355,8 +368,12 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
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}
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oe->__upperdentry = upperdentry;
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oe->lowerdentry = lowerdentry;
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if (lowerdentry) {
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oe->lowerstack[0].dentry = lowerdentry;
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oe->lowerstack[0].mnt = lowerdir.mnt;
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} else {
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oe->numlower = 0;
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}
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dentry->d_fsdata = oe;
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d_add(dentry, inode);
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@ -380,10 +397,12 @@ struct file *ovl_path_open(struct path *path, int flags)
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static void ovl_put_super(struct super_block *sb)
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{
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struct ovl_fs *ufs = sb->s_fs_info;
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unsigned i;
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dput(ufs->workdir);
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mntput(ufs->upper_mnt);
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mntput(ufs->lower_mnt);
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for (i = 0; i < ufs->numlower; i++)
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mntput(ufs->lower_mnt[i]);
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kfree(ufs->config.lowerdir);
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kfree(ufs->config.upperdir);
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@ -641,6 +660,8 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
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struct ovl_entry *oe;
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struct ovl_fs *ufs;
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struct kstatfs statfs;
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struct vfsmount *mnt;
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unsigned int i;
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int err;
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err = -ENOMEM;
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@ -661,7 +682,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
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}
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err = -ENOMEM;
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oe = ovl_alloc_entry();
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oe = ovl_alloc_entry(1);
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if (oe == NULL)
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goto out_free_config;
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@ -727,12 +748,24 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
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goto out_put_workpath;
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}
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ufs->lower_mnt = clone_private_mount(&lowerpath);
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err = PTR_ERR(ufs->lower_mnt);
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if (IS_ERR(ufs->lower_mnt)) {
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pr_err("overlayfs: failed to clone lowerpath\n");
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ufs->lower_mnt = kcalloc(1, sizeof(struct vfsmount *), GFP_KERNEL);
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if (ufs->lower_mnt == NULL)
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goto out_put_upper_mnt;
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mnt = clone_private_mount(&lowerpath);
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err = PTR_ERR(mnt);
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if (IS_ERR(mnt)) {
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pr_err("overlayfs: failed to clone lowerpath\n");
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goto out_put_lower_mnt;
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}
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/*
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* Make lower_mnt R/O. That way fchmod/fchown on lower file
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* will fail instead of modifying lower fs.
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*/
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mnt->mnt_flags |= MNT_READONLY;
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ufs->lower_mnt[0] = mnt;
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ufs->numlower = 1;
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ufs->workdir = ovl_workdir_create(ufs->upper_mnt, workpath.dentry);
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err = PTR_ERR(ufs->workdir);
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@ -742,12 +775,6 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
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goto out_put_lower_mnt;
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}
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/*
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* Make lower_mnt R/O. That way fchmod/fchown on lower file
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* will fail instead of modifying lower fs.
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*/
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ufs->lower_mnt->mnt_flags |= MNT_READONLY;
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/* If the upper fs is r/o, we mark overlayfs r/o too */
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if (ufs->upper_mnt->mnt_sb->s_flags & MS_RDONLY)
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sb->s_flags |= MS_RDONLY;
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@ -768,7 +795,8 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
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path_put(&workpath);
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oe->__upperdentry = upperpath.dentry;
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oe->lowerdentry = lowerpath.dentry;
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oe->lowerstack[0].dentry = lowerpath.dentry;
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oe->lowerstack[0].mnt = ufs->lower_mnt[0];
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root_dentry->d_fsdata = oe;
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@ -782,7 +810,9 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
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out_put_workdir:
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dput(ufs->workdir);
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out_put_lower_mnt:
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mntput(ufs->lower_mnt);
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for (i = 0; i < ufs->numlower; i++)
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mntput(ufs->lower_mnt[i]);
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kfree(ufs->lower_mnt);
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out_put_upper_mnt:
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mntput(ufs->upper_mnt);
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out_put_workpath:
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