579 lines
12 KiB
C
579 lines
12 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/slab.h>
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#include <linux/namei.h>
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#include <linux/file.h>
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#include <linux/xattr.h>
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#include <linux/rbtree.h>
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#include <linux/security.h>
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#include <linux/cred.h>
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#include "overlayfs.h"
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struct ovl_cache_entry {
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unsigned int len;
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unsigned int type;
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u64 ino;
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struct list_head l_node;
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struct rb_node node;
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struct ovl_cache_entry *next_maybe_whiteout;
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bool is_whiteout;
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char name[];
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};
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struct ovl_dir_cache {
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long refcount;
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u64 version;
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struct list_head entries;
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};
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struct ovl_readdir_data {
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struct dir_context ctx;
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bool is_merge;
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struct rb_root root;
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struct list_head *list;
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struct list_head middle;
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struct ovl_cache_entry *first_maybe_whiteout;
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int count;
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int err;
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};
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struct ovl_dir_file {
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bool is_real;
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bool is_upper;
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struct ovl_dir_cache *cache;
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struct list_head *cursor;
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struct file *realfile;
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struct file *upperfile;
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};
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static struct ovl_cache_entry *ovl_cache_entry_from_node(struct rb_node *n)
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{
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return container_of(n, struct ovl_cache_entry, node);
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}
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static struct ovl_cache_entry *ovl_cache_entry_find(struct rb_root *root,
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const char *name, int len)
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{
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struct rb_node *node = root->rb_node;
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int cmp;
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while (node) {
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struct ovl_cache_entry *p = ovl_cache_entry_from_node(node);
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cmp = strncmp(name, p->name, len);
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if (cmp > 0)
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node = p->node.rb_right;
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else if (cmp < 0 || len < p->len)
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node = p->node.rb_left;
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else
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return p;
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}
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return NULL;
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}
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static struct ovl_cache_entry *ovl_cache_entry_new(struct ovl_readdir_data *rdd,
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const char *name, int len,
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u64 ino, unsigned int d_type)
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{
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struct ovl_cache_entry *p;
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size_t size = offsetof(struct ovl_cache_entry, name[len + 1]);
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p = kmalloc(size, GFP_KERNEL);
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if (!p)
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return NULL;
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memcpy(p->name, name, len);
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p->name[len] = '\0';
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p->len = len;
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p->type = d_type;
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p->ino = ino;
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p->is_whiteout = false;
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if (d_type == DT_CHR) {
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p->next_maybe_whiteout = rdd->first_maybe_whiteout;
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rdd->first_maybe_whiteout = p;
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}
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return p;
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}
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static int ovl_cache_entry_add_rb(struct ovl_readdir_data *rdd,
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const char *name, int len, u64 ino,
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unsigned int d_type)
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{
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struct rb_node **newp = &rdd->root.rb_node;
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struct rb_node *parent = NULL;
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struct ovl_cache_entry *p;
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while (*newp) {
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int cmp;
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struct ovl_cache_entry *tmp;
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parent = *newp;
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tmp = ovl_cache_entry_from_node(*newp);
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cmp = strncmp(name, tmp->name, len);
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if (cmp > 0)
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newp = &tmp->node.rb_right;
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else if (cmp < 0 || len < tmp->len)
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newp = &tmp->node.rb_left;
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else
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return 0;
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}
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p = ovl_cache_entry_new(rdd, name, len, ino, d_type);
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if (p == NULL)
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return -ENOMEM;
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list_add_tail(&p->l_node, rdd->list);
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rb_link_node(&p->node, parent, newp);
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rb_insert_color(&p->node, &rdd->root);
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return 0;
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}
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static int ovl_fill_lower(struct ovl_readdir_data *rdd,
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const char *name, int namelen,
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loff_t offset, u64 ino, unsigned int d_type)
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{
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struct ovl_cache_entry *p;
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p = ovl_cache_entry_find(&rdd->root, name, namelen);
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if (p) {
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list_move_tail(&p->l_node, &rdd->middle);
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} else {
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p = ovl_cache_entry_new(rdd, name, namelen, ino, d_type);
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if (p == NULL)
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rdd->err = -ENOMEM;
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else
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list_add_tail(&p->l_node, &rdd->middle);
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}
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return rdd->err;
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}
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void ovl_cache_free(struct list_head *list)
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{
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struct ovl_cache_entry *p;
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struct ovl_cache_entry *n;
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list_for_each_entry_safe(p, n, list, l_node)
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kfree(p);
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INIT_LIST_HEAD(list);
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}
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static void ovl_cache_put(struct ovl_dir_file *od, struct dentry *dentry)
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{
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struct ovl_dir_cache *cache = od->cache;
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WARN_ON(cache->refcount <= 0);
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cache->refcount--;
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if (!cache->refcount) {
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if (ovl_dir_cache(dentry) == cache)
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ovl_set_dir_cache(dentry, NULL);
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ovl_cache_free(&cache->entries);
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kfree(cache);
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}
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}
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static int ovl_fill_merge(struct dir_context *ctx, const char *name,
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int namelen, loff_t offset, u64 ino,
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unsigned int d_type)
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{
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struct ovl_readdir_data *rdd =
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container_of(ctx, struct ovl_readdir_data, ctx);
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rdd->count++;
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if (!rdd->is_merge)
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return ovl_cache_entry_add_rb(rdd, name, namelen, ino, d_type);
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else
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return ovl_fill_lower(rdd, name, namelen, offset, ino, d_type);
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}
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static int ovl_check_whiteouts(struct dentry *dir, struct ovl_readdir_data *rdd)
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{
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int err;
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struct ovl_cache_entry *p;
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struct dentry *dentry;
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const struct cred *old_cred;
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struct cred *override_cred;
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override_cred = prepare_creds();
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if (!override_cred)
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return -ENOMEM;
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/*
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* CAP_DAC_OVERRIDE for lookup
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*/
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cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
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old_cred = override_creds(override_cred);
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err = mutex_lock_killable(&dir->d_inode->i_mutex);
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if (!err) {
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while (rdd->first_maybe_whiteout) {
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p = rdd->first_maybe_whiteout;
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rdd->first_maybe_whiteout = p->next_maybe_whiteout;
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dentry = lookup_one_len(p->name, dir, p->len);
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if (!IS_ERR(dentry)) {
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p->is_whiteout = ovl_is_whiteout(dentry);
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dput(dentry);
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}
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}
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mutex_unlock(&dir->d_inode->i_mutex);
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}
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revert_creds(old_cred);
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put_cred(override_cred);
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return err;
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}
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static inline int ovl_dir_read(struct path *realpath,
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struct ovl_readdir_data *rdd)
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{
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struct file *realfile;
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int err;
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realfile = ovl_path_open(realpath, O_RDONLY | O_DIRECTORY);
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if (IS_ERR(realfile))
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return PTR_ERR(realfile);
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rdd->first_maybe_whiteout = NULL;
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rdd->ctx.pos = 0;
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do {
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rdd->count = 0;
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rdd->err = 0;
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err = iterate_dir(realfile, &rdd->ctx);
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if (err >= 0)
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err = rdd->err;
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} while (!err && rdd->count);
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if (!err && rdd->first_maybe_whiteout)
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err = ovl_check_whiteouts(realpath->dentry, rdd);
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fput(realfile);
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return err;
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}
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static void ovl_dir_reset(struct file *file)
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{
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struct ovl_dir_file *od = file->private_data;
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struct ovl_dir_cache *cache = od->cache;
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struct dentry *dentry = file->f_path.dentry;
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enum ovl_path_type type = ovl_path_type(dentry);
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if (cache && ovl_dentry_version_get(dentry) != cache->version) {
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ovl_cache_put(od, dentry);
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od->cache = NULL;
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od->cursor = NULL;
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}
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WARN_ON(!od->is_real && !OVL_TYPE_MERGE(type));
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if (od->is_real && OVL_TYPE_MERGE(type))
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od->is_real = false;
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}
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static int ovl_dir_read_merged(struct dentry *dentry, struct list_head *list)
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{
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int err;
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struct path realpath;
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struct ovl_readdir_data rdd = {
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.ctx.actor = ovl_fill_merge,
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.list = list,
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.root = RB_ROOT,
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.is_merge = false,
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};
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int idx, next;
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for (idx = 0; idx != -1; idx = next) {
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next = ovl_path_next(idx, dentry, &realpath);
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if (next != -1) {
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err = ovl_dir_read(&realpath, &rdd);
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if (err)
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break;
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} else {
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/*
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* Insert lowest layer entries before upper ones, this
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* allows offsets to be reasonably constant
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*/
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list_add(&rdd.middle, rdd.list);
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rdd.is_merge = true;
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err = ovl_dir_read(&realpath, &rdd);
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list_del(&rdd.middle);
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}
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}
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return err;
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}
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static void ovl_seek_cursor(struct ovl_dir_file *od, loff_t pos)
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{
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struct list_head *p;
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loff_t off = 0;
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list_for_each(p, &od->cache->entries) {
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if (off >= pos)
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break;
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off++;
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}
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/* Cursor is safe since the cache is stable */
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od->cursor = p;
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}
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static struct ovl_dir_cache *ovl_cache_get(struct dentry *dentry)
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{
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int res;
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struct ovl_dir_cache *cache;
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cache = ovl_dir_cache(dentry);
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if (cache && ovl_dentry_version_get(dentry) == cache->version) {
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cache->refcount++;
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return cache;
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}
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ovl_set_dir_cache(dentry, NULL);
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cache = kzalloc(sizeof(struct ovl_dir_cache), GFP_KERNEL);
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if (!cache)
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return ERR_PTR(-ENOMEM);
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cache->refcount = 1;
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INIT_LIST_HEAD(&cache->entries);
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res = ovl_dir_read_merged(dentry, &cache->entries);
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if (res) {
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ovl_cache_free(&cache->entries);
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kfree(cache);
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return ERR_PTR(res);
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}
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cache->version = ovl_dentry_version_get(dentry);
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ovl_set_dir_cache(dentry, cache);
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return cache;
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}
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static int ovl_iterate(struct file *file, struct dir_context *ctx)
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{
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struct ovl_dir_file *od = file->private_data;
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struct dentry *dentry = file->f_path.dentry;
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struct ovl_cache_entry *p;
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if (!ctx->pos)
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ovl_dir_reset(file);
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if (od->is_real)
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return iterate_dir(od->realfile, ctx);
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if (!od->cache) {
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struct ovl_dir_cache *cache;
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cache = ovl_cache_get(dentry);
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if (IS_ERR(cache))
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return PTR_ERR(cache);
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od->cache = cache;
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ovl_seek_cursor(od, ctx->pos);
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}
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while (od->cursor != &od->cache->entries) {
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p = list_entry(od->cursor, struct ovl_cache_entry, l_node);
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if (!p->is_whiteout)
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if (!dir_emit(ctx, p->name, p->len, p->ino, p->type))
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break;
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od->cursor = p->l_node.next;
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ctx->pos++;
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}
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return 0;
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}
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static loff_t ovl_dir_llseek(struct file *file, loff_t offset, int origin)
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{
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loff_t res;
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struct ovl_dir_file *od = file->private_data;
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mutex_lock(&file_inode(file)->i_mutex);
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if (!file->f_pos)
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ovl_dir_reset(file);
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if (od->is_real) {
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res = vfs_llseek(od->realfile, offset, origin);
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file->f_pos = od->realfile->f_pos;
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} else {
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res = -EINVAL;
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switch (origin) {
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case SEEK_CUR:
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offset += file->f_pos;
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break;
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case SEEK_SET:
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break;
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default:
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goto out_unlock;
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}
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if (offset < 0)
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goto out_unlock;
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if (offset != file->f_pos) {
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file->f_pos = offset;
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if (od->cache)
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ovl_seek_cursor(od, offset);
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}
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res = offset;
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}
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out_unlock:
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mutex_unlock(&file_inode(file)->i_mutex);
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return res;
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}
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static int ovl_dir_fsync(struct file *file, loff_t start, loff_t end,
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int datasync)
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{
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struct ovl_dir_file *od = file->private_data;
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struct dentry *dentry = file->f_path.dentry;
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struct file *realfile = od->realfile;
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/*
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* Need to check if we started out being a lower dir, but got copied up
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*/
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if (!od->is_upper && OVL_TYPE_UPPER(ovl_path_type(dentry))) {
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struct inode *inode = file_inode(file);
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realfile = lockless_dereference(od->upperfile);
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if (!realfile) {
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struct path upperpath;
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ovl_path_upper(dentry, &upperpath);
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realfile = ovl_path_open(&upperpath, O_RDONLY);
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smp_mb__before_spinlock();
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mutex_lock(&inode->i_mutex);
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if (!od->upperfile) {
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if (IS_ERR(realfile)) {
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mutex_unlock(&inode->i_mutex);
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return PTR_ERR(realfile);
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}
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od->upperfile = realfile;
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} else {
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/* somebody has beaten us to it */
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if (!IS_ERR(realfile))
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fput(realfile);
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realfile = od->upperfile;
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}
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mutex_unlock(&inode->i_mutex);
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}
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}
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return vfs_fsync_range(realfile, start, end, datasync);
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}
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static int ovl_dir_release(struct inode *inode, struct file *file)
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{
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struct ovl_dir_file *od = file->private_data;
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if (od->cache) {
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mutex_lock(&inode->i_mutex);
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ovl_cache_put(od, file->f_path.dentry);
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mutex_unlock(&inode->i_mutex);
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}
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fput(od->realfile);
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if (od->upperfile)
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fput(od->upperfile);
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kfree(od);
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return 0;
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}
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|
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static int ovl_dir_open(struct inode *inode, struct file *file)
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{
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struct path realpath;
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struct file *realfile;
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struct ovl_dir_file *od;
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enum ovl_path_type type;
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od = kzalloc(sizeof(struct ovl_dir_file), GFP_KERNEL);
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if (!od)
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return -ENOMEM;
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type = ovl_path_real(file->f_path.dentry, &realpath);
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realfile = ovl_path_open(&realpath, file->f_flags);
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if (IS_ERR(realfile)) {
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kfree(od);
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return PTR_ERR(realfile);
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}
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od->realfile = realfile;
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od->is_real = !OVL_TYPE_MERGE(type);
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od->is_upper = OVL_TYPE_UPPER(type);
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file->private_data = od;
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return 0;
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}
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|
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const struct file_operations ovl_dir_operations = {
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.read = generic_read_dir,
|
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.open = ovl_dir_open,
|
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.iterate = ovl_iterate,
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.llseek = ovl_dir_llseek,
|
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.fsync = ovl_dir_fsync,
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.release = ovl_dir_release,
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};
|
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|
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int ovl_check_empty_dir(struct dentry *dentry, struct list_head *list)
|
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{
|
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int err;
|
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struct ovl_cache_entry *p;
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|
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err = ovl_dir_read_merged(dentry, list);
|
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if (err)
|
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return err;
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|
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err = 0;
|
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|
|
list_for_each_entry(p, list, l_node) {
|
|
if (p->is_whiteout)
|
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continue;
|
|
|
|
if (p->name[0] == '.') {
|
|
if (p->len == 1)
|
|
continue;
|
|
if (p->len == 2 && p->name[1] == '.')
|
|
continue;
|
|
}
|
|
err = -ENOTEMPTY;
|
|
break;
|
|
}
|
|
|
|
return err;
|
|
}
|
|
|
|
void ovl_cleanup_whiteouts(struct dentry *upper, struct list_head *list)
|
|
{
|
|
struct ovl_cache_entry *p;
|
|
|
|
mutex_lock_nested(&upper->d_inode->i_mutex, I_MUTEX_CHILD);
|
|
list_for_each_entry(p, list, l_node) {
|
|
struct dentry *dentry;
|
|
|
|
if (!p->is_whiteout)
|
|
continue;
|
|
|
|
dentry = lookup_one_len(p->name, upper, p->len);
|
|
if (IS_ERR(dentry)) {
|
|
pr_err("overlayfs: lookup '%s/%.*s' failed (%i)\n",
|
|
upper->d_name.name, p->len, p->name,
|
|
(int) PTR_ERR(dentry));
|
|
continue;
|
|
}
|
|
ovl_cleanup(upper->d_inode, dentry);
|
|
dput(dentry);
|
|
}
|
|
mutex_unlock(&upper->d_inode->i_mutex);
|
|
}
|