eea2fb4851
When mounting overlayfs it needs a clean "work" directory under the supplied workdir. Previously the mount code removed this directory if it already existed and created a new one. If the removal failed (e.g. directory was not empty) then it fell back to a read-only mount not using the workdir. While this has never been reported, it is possible to get a non-empty "work" dir from a previous mount of overlayfs in case of crash in the middle of an operation using the work directory. In this case the left over state should be discarded and the overlay filesystem will be consistent, guaranteed by the atomicity of operations on moving to/from the workdir to the upper layer. This patch implements cleaning out any files left in workdir. It is implemented using real recursion for simplicity, but the depth is limited to 2, because the worst case is that of a directory containing whiteouts under "work". Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Cc: <stable@vger.kernel.org>
670 lines
14 KiB
C
670 lines
14 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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struct dentry *dentry;
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bool is_lowest;
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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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bool d_type_supported;
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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_lowest(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_lowest)
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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_lowest(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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old_cred = ovl_override_creds(rdd->dentry->d_sb);
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err = down_write_killable(&dir->d_inode->i_rwsem);
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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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inode_unlock(dir->d_inode);
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}
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revert_creds(old_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 && rdd->dentry)
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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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.dentry = dentry,
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.list = list,
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.root = RB_ROOT,
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.is_lowest = 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_lowest = 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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inode_lock(file_inode(file));
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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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inode_unlock(file_inode(file));
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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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inode_lock(inode);
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if (!od->upperfile) {
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if (IS_ERR(realfile)) {
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inode_unlock(inode);
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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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inode_unlock(inode);
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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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inode_lock(inode);
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ovl_cache_put(od, file->f_path.dentry);
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inode_unlock(inode);
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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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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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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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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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|
|
|
err = ovl_dir_read_merged(dentry, list);
|
|
if (err)
|
|
return err;
|
|
|
|
err = 0;
|
|
|
|
list_for_each_entry(p, list, l_node) {
|
|
if (p->is_whiteout)
|
|
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;
|
|
|
|
inode_lock_nested(upper->d_inode, 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;
|
|
}
|
|
if (dentry->d_inode)
|
|
ovl_cleanup(upper->d_inode, dentry);
|
|
dput(dentry);
|
|
}
|
|
inode_unlock(upper->d_inode);
|
|
}
|
|
|
|
static int ovl_check_d_type(struct dir_context *ctx, const char *name,
|
|
int namelen, loff_t offset, u64 ino,
|
|
unsigned int d_type)
|
|
{
|
|
struct ovl_readdir_data *rdd =
|
|
container_of(ctx, struct ovl_readdir_data, ctx);
|
|
|
|
/* Even if d_type is not supported, DT_DIR is returned for . and .. */
|
|
if (!strncmp(name, ".", namelen) || !strncmp(name, "..", namelen))
|
|
return 0;
|
|
|
|
if (d_type != DT_UNKNOWN)
|
|
rdd->d_type_supported = true;
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Returns 1 if d_type is supported, 0 not supported/unknown. Negative values
|
|
* if error is encountered.
|
|
*/
|
|
int ovl_check_d_type_supported(struct path *realpath)
|
|
{
|
|
int err;
|
|
struct ovl_readdir_data rdd = {
|
|
.ctx.actor = ovl_check_d_type,
|
|
.d_type_supported = false,
|
|
};
|
|
|
|
err = ovl_dir_read(realpath, &rdd);
|
|
if (err)
|
|
return err;
|
|
|
|
return rdd.d_type_supported;
|
|
}
|
|
|
|
static void ovl_workdir_cleanup_recurse(struct path *path, int level)
|
|
{
|
|
int err;
|
|
struct inode *dir = path->dentry->d_inode;
|
|
LIST_HEAD(list);
|
|
struct ovl_cache_entry *p;
|
|
struct ovl_readdir_data rdd = {
|
|
.ctx.actor = ovl_fill_merge,
|
|
.dentry = NULL,
|
|
.list = &list,
|
|
.root = RB_ROOT,
|
|
.is_lowest = false,
|
|
};
|
|
|
|
err = ovl_dir_read(path, &rdd);
|
|
if (err)
|
|
goto out;
|
|
|
|
inode_lock_nested(dir, I_MUTEX_PARENT);
|
|
list_for_each_entry(p, &list, l_node) {
|
|
struct dentry *dentry;
|
|
|
|
if (p->name[0] == '.') {
|
|
if (p->len == 1)
|
|
continue;
|
|
if (p->len == 2 && p->name[1] == '.')
|
|
continue;
|
|
}
|
|
dentry = lookup_one_len(p->name, path->dentry, p->len);
|
|
if (IS_ERR(dentry))
|
|
continue;
|
|
if (dentry->d_inode)
|
|
ovl_workdir_cleanup(dir, path->mnt, dentry, level);
|
|
dput(dentry);
|
|
}
|
|
inode_unlock(dir);
|
|
out:
|
|
ovl_cache_free(&list);
|
|
}
|
|
|
|
void ovl_workdir_cleanup(struct inode *dir, struct vfsmount *mnt,
|
|
struct dentry *dentry, int level)
|
|
{
|
|
int err;
|
|
|
|
if (!d_is_dir(dentry) || level > 1) {
|
|
ovl_cleanup(dir, dentry);
|
|
return;
|
|
}
|
|
|
|
err = ovl_do_rmdir(dir, dentry);
|
|
if (err) {
|
|
struct path path = { .mnt = mnt, .dentry = dentry };
|
|
|
|
inode_unlock(dir);
|
|
ovl_workdir_cleanup_recurse(&path, level + 1);
|
|
inode_lock_nested(dir, I_MUTEX_PARENT);
|
|
ovl_cleanup(dir, dentry);
|
|
}
|
|
}
|