mirror of https://gitee.com/openkylin/linux.git
1115 lines
24 KiB
C
1115 lines
24 KiB
C
/*
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*
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* Copyright (C) 2011 Novell Inc.
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 as published by
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* the Free Software Foundation.
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*/
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#include <linux/fs.h>
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#include <linux/namei.h>
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#include <linux/xattr.h>
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#include <linux/security.h>
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#include <linux/mount.h>
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#include <linux/slab.h>
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#include <linux/parser.h>
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#include <linux/module.h>
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#include <linux/sched.h>
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#include <linux/statfs.h>
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#include <linux/seq_file.h>
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#include "overlayfs.h"
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MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
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MODULE_DESCRIPTION("Overlay filesystem");
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MODULE_LICENSE("GPL");
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#define OVERLAYFS_SUPER_MAGIC 0x794c7630
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struct ovl_config {
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char *lowerdir;
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char *upperdir;
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char *workdir;
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};
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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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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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struct ovl_config config;
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};
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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 ovl_dir_cache *cache;
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union {
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struct {
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u64 version;
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bool opaque;
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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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#define OVL_MAX_STACK 500
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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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struct ovl_entry *oe = dentry->d_fsdata;
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enum ovl_path_type type = 0;
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if (oe->__upperdentry) {
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type = __OVL_PATH_UPPER;
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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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type |= __OVL_PATH_PURE;
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}
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} else {
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if (oe->numlower > 1)
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type |= __OVL_PATH_MERGE;
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}
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return type;
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}
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static struct dentry *ovl_upperdentry_dereference(struct ovl_entry *oe)
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{
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return lockless_dereference(oe->__upperdentry);
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}
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void ovl_path_upper(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->upper_mnt;
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path->dentry = ovl_upperdentry_dereference(oe);
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}
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enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path)
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{
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enum ovl_path_type type = ovl_path_type(dentry);
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if (!OVL_TYPE_UPPER(type))
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ovl_path_lower(dentry, path);
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else
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ovl_path_upper(dentry, path);
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return type;
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}
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struct dentry *ovl_dentry_upper(struct dentry *dentry)
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{
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struct ovl_entry *oe = dentry->d_fsdata;
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return ovl_upperdentry_dereference(oe);
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}
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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 __ovl_dentry_lower(oe);
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}
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struct dentry *ovl_dentry_real(struct dentry *dentry)
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{
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struct ovl_entry *oe = dentry->d_fsdata;
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struct dentry *realdentry;
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realdentry = ovl_upperdentry_dereference(oe);
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if (!realdentry)
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realdentry = __ovl_dentry_lower(oe);
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return realdentry;
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}
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struct dentry *ovl_entry_real(struct ovl_entry *oe, bool *is_upper)
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{
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struct dentry *realdentry;
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realdentry = ovl_upperdentry_dereference(oe);
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if (realdentry) {
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*is_upper = true;
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} else {
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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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}
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struct ovl_dir_cache *ovl_dir_cache(struct dentry *dentry)
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{
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struct ovl_entry *oe = dentry->d_fsdata;
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return oe->cache;
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}
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void ovl_set_dir_cache(struct dentry *dentry, struct ovl_dir_cache *cache)
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{
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struct ovl_entry *oe = dentry->d_fsdata;
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oe->cache = cache;
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}
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void ovl_path_lower(struct dentry *dentry, struct path *path)
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{
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struct ovl_entry *oe = dentry->d_fsdata;
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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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{
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struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
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return mnt_want_write(ofs->upper_mnt);
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}
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void ovl_drop_write(struct dentry *dentry)
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{
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struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
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mnt_drop_write(ofs->upper_mnt);
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}
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struct dentry *ovl_workdir(struct dentry *dentry)
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{
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struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
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return ofs->workdir;
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}
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bool ovl_dentry_is_opaque(struct dentry *dentry)
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{
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struct ovl_entry *oe = dentry->d_fsdata;
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return oe->opaque;
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}
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void ovl_dentry_set_opaque(struct dentry *dentry, bool opaque)
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{
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struct ovl_entry *oe = dentry->d_fsdata;
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oe->opaque = opaque;
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}
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void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry)
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{
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struct ovl_entry *oe = dentry->d_fsdata;
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WARN_ON(!mutex_is_locked(&upperdentry->d_parent->d_inode->i_mutex));
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WARN_ON(oe->__upperdentry);
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BUG_ON(!upperdentry->d_inode);
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/*
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* Make sure upperdentry is consistent before making it visible to
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* ovl_upperdentry_dereference().
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*/
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smp_wmb();
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oe->__upperdentry = upperdentry;
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}
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void ovl_dentry_version_inc(struct dentry *dentry)
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{
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struct ovl_entry *oe = dentry->d_fsdata;
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WARN_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
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oe->version++;
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}
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u64 ovl_dentry_version_get(struct dentry *dentry)
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{
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struct ovl_entry *oe = dentry->d_fsdata;
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WARN_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
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return oe->version;
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}
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bool ovl_is_whiteout(struct dentry *dentry)
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{
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struct inode *inode = dentry->d_inode;
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return inode && IS_WHITEOUT(inode);
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}
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static bool ovl_is_opaquedir(struct dentry *dentry)
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{
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int res;
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char val;
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struct inode *inode = dentry->d_inode;
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if (!S_ISDIR(inode->i_mode) || !inode->i_op->getxattr)
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return false;
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res = inode->i_op->getxattr(dentry, OVL_XATTR_OPAQUE, &val, 1);
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if (res == 1 && val == 'y')
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return true;
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return false;
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}
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static void ovl_dentry_release(struct dentry *dentry)
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{
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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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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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static int ovl_dentry_revalidate(struct dentry *dentry, unsigned int flags)
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{
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struct ovl_entry *oe = dentry->d_fsdata;
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unsigned int i;
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int ret = 1;
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for (i = 0; i < oe->numlower; i++) {
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struct dentry *d = oe->lowerstack[i].dentry;
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if (d->d_flags & DCACHE_OP_REVALIDATE) {
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ret = d->d_op->d_revalidate(d, flags);
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if (ret < 0)
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return ret;
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if (!ret) {
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if (!(flags & LOOKUP_RCU))
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d_invalidate(d);
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return -ESTALE;
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}
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}
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}
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return 1;
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}
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static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags)
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{
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struct ovl_entry *oe = dentry->d_fsdata;
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unsigned int i;
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int ret = 1;
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for (i = 0; i < oe->numlower; i++) {
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struct dentry *d = oe->lowerstack[i].dentry;
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if (d->d_flags & DCACHE_OP_WEAK_REVALIDATE) {
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ret = d->d_op->d_weak_revalidate(d, flags);
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if (ret <= 0)
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break;
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}
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}
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return ret;
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}
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static const struct dentry_operations ovl_dentry_operations = {
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.d_release = ovl_dentry_release,
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.d_select_inode = ovl_d_select_inode,
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};
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static const struct dentry_operations ovl_reval_dentry_operations = {
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.d_release = ovl_dentry_release,
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.d_revalidate = ovl_dentry_revalidate,
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.d_weak_revalidate = ovl_dentry_weak_revalidate,
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};
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static struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
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{
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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 bool ovl_dentry_remote(struct dentry *dentry)
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{
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return dentry->d_flags &
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(DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE);
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}
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static bool ovl_dentry_weird(struct dentry *dentry)
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{
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return dentry->d_flags & (DCACHE_NEED_AUTOMOUNT |
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DCACHE_MANAGE_TRANSIT |
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DCACHE_OP_HASH |
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DCACHE_OP_COMPARE);
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}
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static inline struct dentry *ovl_lookup_real(struct dentry *dir,
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struct qstr *name)
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{
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struct dentry *dentry;
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mutex_lock(&dir->d_inode->i_mutex);
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dentry = lookup_one_len(name->name, dir, name->len);
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mutex_unlock(&dir->d_inode->i_mutex);
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if (IS_ERR(dentry)) {
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if (PTR_ERR(dentry) == -ENOENT)
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dentry = NULL;
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} else if (!dentry->d_inode) {
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dput(dentry);
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dentry = NULL;
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} else if (ovl_dentry_weird(dentry)) {
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dput(dentry);
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/* Don't support traversing automounts and other weirdness */
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dentry = ERR_PTR(-EREMOTE);
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}
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return dentry;
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}
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/*
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* Returns next layer in stack starting from top.
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* Returns -1 if this is the last layer.
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*/
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int ovl_path_next(int idx, struct dentry *dentry, struct path *path)
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{
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struct ovl_entry *oe = dentry->d_fsdata;
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BUG_ON(idx < 0);
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if (idx == 0) {
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ovl_path_upper(dentry, path);
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if (path->dentry)
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return oe->numlower ? 1 : -1;
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idx++;
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}
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BUG_ON(idx > oe->numlower);
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*path = oe->lowerstack[idx - 1];
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return (idx < oe->numlower) ? idx + 1 : -1;
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}
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struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
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unsigned int flags)
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{
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struct ovl_entry *oe;
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struct ovl_entry *poe = dentry->d_parent->d_fsdata;
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struct path *stack = NULL;
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struct dentry *upperdir, *upperdentry = NULL;
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unsigned int ctr = 0;
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struct inode *inode = NULL;
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bool upperopaque = false;
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struct dentry *this, *prev = NULL;
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unsigned int i;
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int err;
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upperdir = ovl_upperdentry_dereference(poe);
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if (upperdir) {
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this = ovl_lookup_real(upperdir, &dentry->d_name);
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err = PTR_ERR(this);
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if (IS_ERR(this))
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goto out;
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if (this) {
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if (unlikely(ovl_dentry_remote(this))) {
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dput(this);
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err = -EREMOTE;
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goto out;
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}
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if (ovl_is_whiteout(this)) {
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dput(this);
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this = NULL;
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upperopaque = true;
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} else if (poe->numlower && ovl_is_opaquedir(this)) {
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upperopaque = true;
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}
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}
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upperdentry = prev = this;
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}
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if (!upperopaque && poe->numlower) {
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err = -ENOMEM;
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stack = kcalloc(poe->numlower, sizeof(struct path), GFP_KERNEL);
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if (!stack)
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goto out_put_upper;
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}
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for (i = 0; !upperopaque && i < poe->numlower; i++) {
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bool opaque = false;
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struct path lowerpath = poe->lowerstack[i];
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this = ovl_lookup_real(lowerpath.dentry, &dentry->d_name);
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err = PTR_ERR(this);
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if (IS_ERR(this)) {
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/*
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* If it's positive, then treat ENAMETOOLONG as ENOENT.
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*/
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if (err == -ENAMETOOLONG && (upperdentry || ctr))
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continue;
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goto out_put;
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}
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if (!this)
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continue;
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if (ovl_is_whiteout(this)) {
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dput(this);
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break;
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}
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/*
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* Only makes sense to check opaque dir if this is not the
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* lowermost layer.
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*/
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if (i < poe->numlower - 1 && ovl_is_opaquedir(this))
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opaque = true;
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if (prev && (!S_ISDIR(prev->d_inode->i_mode) ||
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!S_ISDIR(this->d_inode->i_mode))) {
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/*
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* FIXME: check for upper-opaqueness maybe better done
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* in remove code.
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*/
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if (prev == upperdentry)
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upperopaque = true;
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dput(this);
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break;
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}
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/*
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* If this is a non-directory then stop here.
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*/
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if (!S_ISDIR(this->d_inode->i_mode))
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opaque = true;
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stack[ctr].dentry = this;
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stack[ctr].mnt = lowerpath.mnt;
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ctr++;
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prev = this;
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if (opaque)
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break;
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}
|
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oe = ovl_alloc_entry(ctr);
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err = -ENOMEM;
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if (!oe)
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goto out_put;
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|
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if (upperdentry || ctr) {
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struct dentry *realdentry;
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realdentry = upperdentry ? upperdentry : stack[0].dentry;
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err = -ENOMEM;
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inode = ovl_new_inode(dentry->d_sb, realdentry->d_inode->i_mode,
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oe);
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if (!inode)
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goto out_free_oe;
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ovl_copyattr(realdentry->d_inode, inode);
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}
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oe->opaque = upperopaque;
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oe->__upperdentry = upperdentry;
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memcpy(oe->lowerstack, stack, sizeof(struct path) * ctr);
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kfree(stack);
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dentry->d_fsdata = oe;
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d_add(dentry, inode);
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|
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return NULL;
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|
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out_free_oe:
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kfree(oe);
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out_put:
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for (i = 0; i < ctr; i++)
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dput(stack[i].dentry);
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kfree(stack);
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out_put_upper:
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dput(upperdentry);
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out:
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return ERR_PTR(err);
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}
|
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|
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struct file *ovl_path_open(struct path *path, int flags)
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{
|
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return dentry_open(path, flags, current_cred());
|
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}
|
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|
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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);
|
|
for (i = 0; i < ufs->numlower; i++)
|
|
mntput(ufs->lower_mnt[i]);
|
|
|
|
kfree(ufs->config.lowerdir);
|
|
kfree(ufs->config.upperdir);
|
|
kfree(ufs->config.workdir);
|
|
kfree(ufs);
|
|
}
|
|
|
|
/**
|
|
* ovl_statfs
|
|
* @sb: The overlayfs super block
|
|
* @buf: The struct kstatfs to fill in with stats
|
|
*
|
|
* Get the filesystem statistics. As writes always target the upper layer
|
|
* filesystem pass the statfs to the upper filesystem (if it exists)
|
|
*/
|
|
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;
|
|
struct path path;
|
|
int err;
|
|
|
|
ovl_path_real(root_dentry, &path);
|
|
|
|
err = vfs_statfs(&path, buf);
|
|
if (!err) {
|
|
buf->f_namelen = max(buf->f_namelen, ofs->lower_namelen);
|
|
buf->f_type = OVERLAYFS_SUPER_MAGIC;
|
|
}
|
|
|
|
return err;
|
|
}
|
|
|
|
/**
|
|
* ovl_show_options
|
|
*
|
|
* Prints the mount options for a given superblock.
|
|
* Returns zero; does not fail.
|
|
*/
|
|
static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
|
|
{
|
|
struct super_block *sb = dentry->d_sb;
|
|
struct ovl_fs *ufs = sb->s_fs_info;
|
|
|
|
seq_printf(m, ",lowerdir=%s", ufs->config.lowerdir);
|
|
if (ufs->config.upperdir) {
|
|
seq_printf(m, ",upperdir=%s", ufs->config.upperdir);
|
|
seq_printf(m, ",workdir=%s", ufs->config.workdir);
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
static int ovl_remount(struct super_block *sb, int *flags, char *data)
|
|
{
|
|
struct ovl_fs *ufs = sb->s_fs_info;
|
|
|
|
if (!(*flags & MS_RDONLY) && (!ufs->upper_mnt || !ufs->workdir))
|
|
return -EROFS;
|
|
|
|
return 0;
|
|
}
|
|
|
|
static const struct super_operations ovl_super_operations = {
|
|
.put_super = ovl_put_super,
|
|
.statfs = ovl_statfs,
|
|
.show_options = ovl_show_options,
|
|
.remount_fs = ovl_remount,
|
|
};
|
|
|
|
enum {
|
|
OPT_LOWERDIR,
|
|
OPT_UPPERDIR,
|
|
OPT_WORKDIR,
|
|
OPT_ERR,
|
|
};
|
|
|
|
static const match_table_t ovl_tokens = {
|
|
{OPT_LOWERDIR, "lowerdir=%s"},
|
|
{OPT_UPPERDIR, "upperdir=%s"},
|
|
{OPT_WORKDIR, "workdir=%s"},
|
|
{OPT_ERR, NULL}
|
|
};
|
|
|
|
static char *ovl_next_opt(char **s)
|
|
{
|
|
char *sbegin = *s;
|
|
char *p;
|
|
|
|
if (sbegin == NULL)
|
|
return NULL;
|
|
|
|
for (p = sbegin; *p; p++) {
|
|
if (*p == '\\') {
|
|
p++;
|
|
if (!*p)
|
|
break;
|
|
} else if (*p == ',') {
|
|
*p = '\0';
|
|
*s = p + 1;
|
|
return sbegin;
|
|
}
|
|
}
|
|
*s = NULL;
|
|
return sbegin;
|
|
}
|
|
|
|
static int ovl_parse_opt(char *opt, struct ovl_config *config)
|
|
{
|
|
char *p;
|
|
|
|
while ((p = ovl_next_opt(&opt)) != NULL) {
|
|
int token;
|
|
substring_t args[MAX_OPT_ARGS];
|
|
|
|
if (!*p)
|
|
continue;
|
|
|
|
token = match_token(p, ovl_tokens, args);
|
|
switch (token) {
|
|
case OPT_UPPERDIR:
|
|
kfree(config->upperdir);
|
|
config->upperdir = match_strdup(&args[0]);
|
|
if (!config->upperdir)
|
|
return -ENOMEM;
|
|
break;
|
|
|
|
case OPT_LOWERDIR:
|
|
kfree(config->lowerdir);
|
|
config->lowerdir = match_strdup(&args[0]);
|
|
if (!config->lowerdir)
|
|
return -ENOMEM;
|
|
break;
|
|
|
|
case OPT_WORKDIR:
|
|
kfree(config->workdir);
|
|
config->workdir = match_strdup(&args[0]);
|
|
if (!config->workdir)
|
|
return -ENOMEM;
|
|
break;
|
|
|
|
default:
|
|
pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p);
|
|
return -EINVAL;
|
|
}
|
|
}
|
|
|
|
/* Workdir is useless in non-upper mount */
|
|
if (!config->upperdir && config->workdir) {
|
|
pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
|
|
config->workdir);
|
|
kfree(config->workdir);
|
|
config->workdir = NULL;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
#define OVL_WORKDIR_NAME "work"
|
|
|
|
static struct dentry *ovl_workdir_create(struct vfsmount *mnt,
|
|
struct dentry *dentry)
|
|
{
|
|
struct inode *dir = dentry->d_inode;
|
|
struct dentry *work;
|
|
int err;
|
|
bool retried = false;
|
|
|
|
err = mnt_want_write(mnt);
|
|
if (err)
|
|
return ERR_PTR(err);
|
|
|
|
mutex_lock_nested(&dir->i_mutex, I_MUTEX_PARENT);
|
|
retry:
|
|
work = lookup_one_len(OVL_WORKDIR_NAME, dentry,
|
|
strlen(OVL_WORKDIR_NAME));
|
|
|
|
if (!IS_ERR(work)) {
|
|
struct kstat stat = {
|
|
.mode = S_IFDIR | 0,
|
|
};
|
|
|
|
if (work->d_inode) {
|
|
err = -EEXIST;
|
|
if (retried)
|
|
goto out_dput;
|
|
|
|
retried = true;
|
|
ovl_cleanup(dir, work);
|
|
dput(work);
|
|
goto retry;
|
|
}
|
|
|
|
err = ovl_create_real(dir, work, &stat, NULL, NULL, true);
|
|
if (err)
|
|
goto out_dput;
|
|
}
|
|
out_unlock:
|
|
mutex_unlock(&dir->i_mutex);
|
|
mnt_drop_write(mnt);
|
|
|
|
return work;
|
|
|
|
out_dput:
|
|
dput(work);
|
|
work = ERR_PTR(err);
|
|
goto out_unlock;
|
|
}
|
|
|
|
static void ovl_unescape(char *s)
|
|
{
|
|
char *d = s;
|
|
|
|
for (;; s++, d++) {
|
|
if (*s == '\\')
|
|
s++;
|
|
*d = *s;
|
|
if (!*s)
|
|
break;
|
|
}
|
|
}
|
|
|
|
static int ovl_mount_dir_noesc(const char *name, struct path *path)
|
|
{
|
|
int err = -EINVAL;
|
|
|
|
if (!*name) {
|
|
pr_err("overlayfs: empty lowerdir\n");
|
|
goto out;
|
|
}
|
|
err = kern_path(name, LOOKUP_FOLLOW, path);
|
|
if (err) {
|
|
pr_err("overlayfs: failed to resolve '%s': %i\n", name, err);
|
|
goto out;
|
|
}
|
|
err = -EINVAL;
|
|
if (ovl_dentry_weird(path->dentry)) {
|
|
pr_err("overlayfs: filesystem on '%s' not supported\n", name);
|
|
goto out_put;
|
|
}
|
|
if (!S_ISDIR(path->dentry->d_inode->i_mode)) {
|
|
pr_err("overlayfs: '%s' not a directory\n", name);
|
|
goto out_put;
|
|
}
|
|
return 0;
|
|
|
|
out_put:
|
|
path_put(path);
|
|
out:
|
|
return err;
|
|
}
|
|
|
|
static int ovl_mount_dir(const char *name, struct path *path)
|
|
{
|
|
int err = -ENOMEM;
|
|
char *tmp = kstrdup(name, GFP_KERNEL);
|
|
|
|
if (tmp) {
|
|
ovl_unescape(tmp);
|
|
err = ovl_mount_dir_noesc(tmp, path);
|
|
|
|
if (!err)
|
|
if (ovl_dentry_remote(path->dentry)) {
|
|
pr_err("overlayfs: filesystem on '%s' not supported as upperdir\n",
|
|
tmp);
|
|
path_put(path);
|
|
err = -EINVAL;
|
|
}
|
|
kfree(tmp);
|
|
}
|
|
return err;
|
|
}
|
|
|
|
static int ovl_lower_dir(const char *name, struct path *path, long *namelen,
|
|
int *stack_depth, bool *remote)
|
|
{
|
|
int err;
|
|
struct kstatfs statfs;
|
|
|
|
err = ovl_mount_dir_noesc(name, path);
|
|
if (err)
|
|
goto out;
|
|
|
|
err = vfs_statfs(path, &statfs);
|
|
if (err) {
|
|
pr_err("overlayfs: statfs failed on '%s'\n", name);
|
|
goto out_put;
|
|
}
|
|
*namelen = max(*namelen, statfs.f_namelen);
|
|
*stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);
|
|
|
|
if (ovl_dentry_remote(path->dentry))
|
|
*remote = true;
|
|
|
|
return 0;
|
|
|
|
out_put:
|
|
path_put(path);
|
|
out:
|
|
return err;
|
|
}
|
|
|
|
/* Workdir should not be subdir of upperdir and vice versa */
|
|
static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
|
|
{
|
|
bool ok = false;
|
|
|
|
if (workdir != upperdir) {
|
|
ok = (lock_rename(workdir, upperdir) == NULL);
|
|
unlock_rename(workdir, upperdir);
|
|
}
|
|
return ok;
|
|
}
|
|
|
|
static unsigned int ovl_split_lowerdirs(char *str)
|
|
{
|
|
unsigned int ctr = 1;
|
|
char *s, *d;
|
|
|
|
for (s = d = str;; s++, d++) {
|
|
if (*s == '\\') {
|
|
s++;
|
|
} else if (*s == ':') {
|
|
*d = '\0';
|
|
ctr++;
|
|
continue;
|
|
}
|
|
*d = *s;
|
|
if (!*s)
|
|
break;
|
|
}
|
|
return ctr;
|
|
}
|
|
|
|
static int ovl_fill_super(struct super_block *sb, void *data, int silent)
|
|
{
|
|
struct path upperpath = { NULL, NULL };
|
|
struct path workpath = { NULL, NULL };
|
|
struct dentry *root_dentry;
|
|
struct ovl_entry *oe;
|
|
struct ovl_fs *ufs;
|
|
struct path *stack = NULL;
|
|
char *lowertmp;
|
|
char *lower;
|
|
unsigned int numlower;
|
|
unsigned int stacklen = 0;
|
|
unsigned int i;
|
|
bool remote = false;
|
|
int err;
|
|
|
|
err = -ENOMEM;
|
|
ufs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
|
|
if (!ufs)
|
|
goto out;
|
|
|
|
err = ovl_parse_opt((char *) data, &ufs->config);
|
|
if (err)
|
|
goto out_free_config;
|
|
|
|
err = -EINVAL;
|
|
if (!ufs->config.lowerdir) {
|
|
pr_err("overlayfs: missing 'lowerdir'\n");
|
|
goto out_free_config;
|
|
}
|
|
|
|
sb->s_stack_depth = 0;
|
|
if (ufs->config.upperdir) {
|
|
if (!ufs->config.workdir) {
|
|
pr_err("overlayfs: missing 'workdir'\n");
|
|
goto out_free_config;
|
|
}
|
|
|
|
err = ovl_mount_dir(ufs->config.upperdir, &upperpath);
|
|
if (err)
|
|
goto out_free_config;
|
|
|
|
/* Upper fs should not be r/o */
|
|
if (upperpath.mnt->mnt_sb->s_flags & MS_RDONLY) {
|
|
pr_err("overlayfs: upper fs is r/o, try multi-lower layers mount\n");
|
|
err = -EINVAL;
|
|
goto out_put_upperpath;
|
|
}
|
|
|
|
err = ovl_mount_dir(ufs->config.workdir, &workpath);
|
|
if (err)
|
|
goto out_put_upperpath;
|
|
|
|
err = -EINVAL;
|
|
if (upperpath.mnt != workpath.mnt) {
|
|
pr_err("overlayfs: workdir and upperdir must reside under the same mount\n");
|
|
goto out_put_workpath;
|
|
}
|
|
if (!ovl_workdir_ok(workpath.dentry, upperpath.dentry)) {
|
|
pr_err("overlayfs: workdir and upperdir must be separate subtrees\n");
|
|
goto out_put_workpath;
|
|
}
|
|
sb->s_stack_depth = upperpath.mnt->mnt_sb->s_stack_depth;
|
|
}
|
|
err = -ENOMEM;
|
|
lowertmp = kstrdup(ufs->config.lowerdir, GFP_KERNEL);
|
|
if (!lowertmp)
|
|
goto out_put_workpath;
|
|
|
|
err = -EINVAL;
|
|
stacklen = ovl_split_lowerdirs(lowertmp);
|
|
if (stacklen > OVL_MAX_STACK) {
|
|
pr_err("overlayfs: too many lower directries, limit is %d\n",
|
|
OVL_MAX_STACK);
|
|
goto out_free_lowertmp;
|
|
} else if (!ufs->config.upperdir && stacklen == 1) {
|
|
pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n");
|
|
goto out_free_lowertmp;
|
|
}
|
|
|
|
stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL);
|
|
if (!stack)
|
|
goto out_free_lowertmp;
|
|
|
|
lower = lowertmp;
|
|
for (numlower = 0; numlower < stacklen; numlower++) {
|
|
err = ovl_lower_dir(lower, &stack[numlower],
|
|
&ufs->lower_namelen, &sb->s_stack_depth,
|
|
&remote);
|
|
if (err)
|
|
goto out_put_lowerpath;
|
|
|
|
lower = strchr(lower, '\0') + 1;
|
|
}
|
|
|
|
err = -EINVAL;
|
|
sb->s_stack_depth++;
|
|
if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
|
|
pr_err("overlayfs: maximum fs stacking depth exceeded\n");
|
|
goto out_put_lowerpath;
|
|
}
|
|
|
|
if (ufs->config.upperdir) {
|
|
ufs->upper_mnt = clone_private_mount(&upperpath);
|
|
err = PTR_ERR(ufs->upper_mnt);
|
|
if (IS_ERR(ufs->upper_mnt)) {
|
|
pr_err("overlayfs: failed to clone upperpath\n");
|
|
goto out_put_lowerpath;
|
|
}
|
|
|
|
ufs->workdir = ovl_workdir_create(ufs->upper_mnt, workpath.dentry);
|
|
err = PTR_ERR(ufs->workdir);
|
|
if (IS_ERR(ufs->workdir)) {
|
|
pr_warn("overlayfs: failed to create directory %s/%s (errno: %i); mounting read-only\n",
|
|
ufs->config.workdir, OVL_WORKDIR_NAME, -err);
|
|
sb->s_flags |= MS_RDONLY;
|
|
ufs->workdir = NULL;
|
|
}
|
|
}
|
|
|
|
err = -ENOMEM;
|
|
ufs->lower_mnt = kcalloc(numlower, sizeof(struct vfsmount *), GFP_KERNEL);
|
|
if (ufs->lower_mnt == NULL)
|
|
goto out_put_workdir;
|
|
for (i = 0; i < numlower; i++) {
|
|
struct vfsmount *mnt = clone_private_mount(&stack[i]);
|
|
|
|
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[ufs->numlower] = mnt;
|
|
ufs->numlower++;
|
|
}
|
|
|
|
/* If the upper fs is nonexistent, we mark overlayfs r/o too */
|
|
if (!ufs->upper_mnt)
|
|
sb->s_flags |= MS_RDONLY;
|
|
|
|
if (remote)
|
|
sb->s_d_op = &ovl_reval_dentry_operations;
|
|
else
|
|
sb->s_d_op = &ovl_dentry_operations;
|
|
|
|
err = -ENOMEM;
|
|
oe = ovl_alloc_entry(numlower);
|
|
if (!oe)
|
|
goto out_put_lower_mnt;
|
|
|
|
root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, oe));
|
|
if (!root_dentry)
|
|
goto out_free_oe;
|
|
|
|
mntput(upperpath.mnt);
|
|
for (i = 0; i < numlower; i++)
|
|
mntput(stack[i].mnt);
|
|
path_put(&workpath);
|
|
kfree(lowertmp);
|
|
|
|
oe->__upperdentry = upperpath.dentry;
|
|
for (i = 0; i < numlower; i++) {
|
|
oe->lowerstack[i].dentry = stack[i].dentry;
|
|
oe->lowerstack[i].mnt = ufs->lower_mnt[i];
|
|
}
|
|
|
|
root_dentry->d_fsdata = oe;
|
|
|
|
sb->s_magic = OVERLAYFS_SUPER_MAGIC;
|
|
sb->s_op = &ovl_super_operations;
|
|
sb->s_root = root_dentry;
|
|
sb->s_fs_info = ufs;
|
|
|
|
return 0;
|
|
|
|
out_free_oe:
|
|
kfree(oe);
|
|
out_put_lower_mnt:
|
|
for (i = 0; i < ufs->numlower; i++)
|
|
mntput(ufs->lower_mnt[i]);
|
|
kfree(ufs->lower_mnt);
|
|
out_put_workdir:
|
|
dput(ufs->workdir);
|
|
mntput(ufs->upper_mnt);
|
|
out_put_lowerpath:
|
|
for (i = 0; i < numlower; i++)
|
|
path_put(&stack[i]);
|
|
kfree(stack);
|
|
out_free_lowertmp:
|
|
kfree(lowertmp);
|
|
out_put_workpath:
|
|
path_put(&workpath);
|
|
out_put_upperpath:
|
|
path_put(&upperpath);
|
|
out_free_config:
|
|
kfree(ufs->config.lowerdir);
|
|
kfree(ufs->config.upperdir);
|
|
kfree(ufs->config.workdir);
|
|
kfree(ufs);
|
|
out:
|
|
return err;
|
|
}
|
|
|
|
static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
|
|
const char *dev_name, void *raw_data)
|
|
{
|
|
return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
|
|
}
|
|
|
|
static struct file_system_type ovl_fs_type = {
|
|
.owner = THIS_MODULE,
|
|
.name = "overlay",
|
|
.mount = ovl_mount,
|
|
.kill_sb = kill_anon_super,
|
|
};
|
|
MODULE_ALIAS_FS("overlay");
|
|
|
|
static int __init ovl_init(void)
|
|
{
|
|
return register_filesystem(&ovl_fs_type);
|
|
}
|
|
|
|
static void __exit ovl_exit(void)
|
|
{
|
|
unregister_filesystem(&ovl_fs_type);
|
|
}
|
|
|
|
module_init(ovl_init);
|
|
module_exit(ovl_exit);
|