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path: root/fs/overlayfs/readdir.c
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-rw-r--r--fs/overlayfs/readdir.c593
1 files changed, 593 insertions, 0 deletions
diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
new file mode 100644
index 000000000000..4e9d7c1fea52
--- /dev/null
+++ b/fs/overlayfs/readdir.c
@@ -0,0 +1,593 @@
+/*
+ *
+ * Copyright (C) 2011 Novell Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ */
+
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/namei.h>
+#include <linux/file.h>
+#include <linux/xattr.h>
+#include <linux/rbtree.h>
+#include <linux/security.h>
+#include <linux/cred.h>
+#include "overlayfs.h"
+
+struct ovl_cache_entry {
+ unsigned int len;
+ unsigned int type;
+ u64 ino;
+ struct list_head l_node;
+ struct rb_node node;
+ bool is_whiteout;
+ bool is_cursor;
+ char name[];
+};
+
+struct ovl_dir_cache {
+ long refcount;
+ u64 version;
+ struct list_head entries;
+};
+
+struct ovl_readdir_data {
+ struct dir_context ctx;
+ bool is_merge;
+ struct rb_root root;
+ struct list_head *list;
+ struct list_head middle;
+ int count;
+ int err;
+};
+
+struct ovl_dir_file {
+ bool is_real;
+ bool is_upper;
+ struct ovl_dir_cache *cache;
+ struct ovl_cache_entry cursor;
+ struct file *realfile;
+ struct file *upperfile;
+};
+
+static struct ovl_cache_entry *ovl_cache_entry_from_node(struct rb_node *n)
+{
+ return container_of(n, struct ovl_cache_entry, node);
+}
+
+static struct ovl_cache_entry *ovl_cache_entry_find(struct rb_root *root,
+ const char *name, int len)
+{
+ struct rb_node *node = root->rb_node;
+ int cmp;
+
+ while (node) {
+ struct ovl_cache_entry *p = ovl_cache_entry_from_node(node);
+
+ cmp = strncmp(name, p->name, len);
+ if (cmp > 0)
+ node = p->node.rb_right;
+ else if (cmp < 0 || len < p->len)
+ node = p->node.rb_left;
+ else
+ return p;
+ }
+
+ return NULL;
+}
+
+static struct ovl_cache_entry *ovl_cache_entry_new(const char *name, int len,
+ u64 ino, unsigned int d_type)
+{
+ struct ovl_cache_entry *p;
+ size_t size = offsetof(struct ovl_cache_entry, name[len + 1]);
+
+ p = kmalloc(size, GFP_KERNEL);
+ if (p) {
+ memcpy(p->name, name, len);
+ p->name[len] = '\0';
+ p->len = len;
+ p->type = d_type;
+ p->ino = ino;
+ p->is_whiteout = false;
+ p->is_cursor = false;
+ }
+
+ return p;
+}
+
+static int ovl_cache_entry_add_rb(struct ovl_readdir_data *rdd,
+ const char *name, int len, u64 ino,
+ unsigned int d_type)
+{
+ struct rb_node **newp = &rdd->root.rb_node;
+ struct rb_node *parent = NULL;
+ struct ovl_cache_entry *p;
+
+ while (*newp) {
+ int cmp;
+ struct ovl_cache_entry *tmp;
+
+ parent = *newp;
+ tmp = ovl_cache_entry_from_node(*newp);
+ cmp = strncmp(name, tmp->name, len);
+ if (cmp > 0)
+ newp = &tmp->node.rb_right;
+ else if (cmp < 0 || len < tmp->len)
+ newp = &tmp->node.rb_left;
+ else
+ return 0;
+ }
+
+ p = ovl_cache_entry_new(name, len, ino, d_type);
+ if (p == NULL)
+ return -ENOMEM;
+
+ list_add_tail(&p->l_node, rdd->list);
+ rb_link_node(&p->node, parent, newp);
+ rb_insert_color(&p->node, &rdd->root);
+
+ return 0;
+}
+
+static int ovl_fill_lower(struct ovl_readdir_data *rdd,
+ const char *name, int namelen,
+ loff_t offset, u64 ino, unsigned int d_type)
+{
+ struct ovl_cache_entry *p;
+
+ p = ovl_cache_entry_find(&rdd->root, name, namelen);
+ if (p) {
+ list_move_tail(&p->l_node, &rdd->middle);
+ } else {
+ p = ovl_cache_entry_new(name, namelen, ino, d_type);
+ if (p == NULL)
+ rdd->err = -ENOMEM;
+ else
+ list_add_tail(&p->l_node, &rdd->middle);
+ }
+
+ return rdd->err;
+}
+
+void ovl_cache_free(struct list_head *list)
+{
+ struct ovl_cache_entry *p;
+ struct ovl_cache_entry *n;
+
+ list_for_each_entry_safe(p, n, list, l_node)
+ kfree(p);
+
+ INIT_LIST_HEAD(list);
+}
+
+static void ovl_cache_put(struct ovl_dir_file *od, struct dentry *dentry)
+{
+ struct ovl_dir_cache *cache = od->cache;
+
+ list_del(&od->cursor.l_node);
+ WARN_ON(cache->refcount <= 0);
+ cache->refcount--;
+ if (!cache->refcount) {
+ if (ovl_dir_cache(dentry) == cache)
+ ovl_set_dir_cache(dentry, NULL);
+
+ ovl_cache_free(&cache->entries);
+ kfree(cache);
+ }
+}
+
+static int ovl_fill_merge(void *buf, const char *name, int namelen,
+ loff_t offset, u64 ino, unsigned int d_type)
+{
+ struct ovl_readdir_data *rdd = buf;
+
+ rdd->count++;
+ if (!rdd->is_merge)
+ return ovl_cache_entry_add_rb(rdd, name, namelen, ino, d_type);
+ else
+ return ovl_fill_lower(rdd, name, namelen, offset, ino, d_type);
+}
+
+static inline int ovl_dir_read(struct path *realpath,
+ struct ovl_readdir_data *rdd)
+{
+ struct file *realfile;
+ int err;
+
+ realfile = ovl_path_open(realpath, O_RDONLY | O_DIRECTORY);
+ if (IS_ERR(realfile))
+ return PTR_ERR(realfile);
+
+ rdd->ctx.pos = 0;
+ do {
+ rdd->count = 0;
+ rdd->err = 0;
+ err = iterate_dir(realfile, &rdd->ctx);
+ if (err >= 0)
+ err = rdd->err;
+ } while (!err && rdd->count);
+ fput(realfile);
+
+ return err;
+}
+
+static void ovl_dir_reset(struct file *file)
+{
+ struct ovl_dir_file *od = file->private_data;
+ struct ovl_dir_cache *cache = od->cache;
+ struct dentry *dentry = file->f_path.dentry;
+ enum ovl_path_type type = ovl_path_type(dentry);
+
+ if (cache && ovl_dentry_version_get(dentry) != cache->version) {
+ ovl_cache_put(od, dentry);
+ od->cache = NULL;
+ }
+ WARN_ON(!od->is_real && type != OVL_PATH_MERGE);
+ if (od->is_real && type == OVL_PATH_MERGE)
+ od->is_real = false;
+}
+
+static int ovl_dir_mark_whiteouts(struct dentry *dir,
+ struct ovl_readdir_data *rdd)
+{
+ struct ovl_cache_entry *p;
+ struct dentry *dentry;
+ const struct cred *old_cred;
+ struct cred *override_cred;
+
+ override_cred = prepare_creds();
+ if (!override_cred) {
+ ovl_cache_free(rdd->list);
+ return -ENOMEM;
+ }
+
+ /*
+ * CAP_DAC_OVERRIDE for lookup
+ */
+ cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
+ old_cred = override_creds(override_cred);
+
+ mutex_lock(&dir->d_inode->i_mutex);
+ list_for_each_entry(p, rdd->list, l_node) {
+ if (p->is_cursor)
+ continue;
+
+ if (p->type != DT_CHR)
+ continue;
+
+ dentry = lookup_one_len(p->name, dir, p->len);
+ if (IS_ERR(dentry))
+ continue;
+
+ p->is_whiteout = ovl_is_whiteout(dentry);
+ dput(dentry);
+ }
+ mutex_unlock(&dir->d_inode->i_mutex);
+
+ revert_creds(old_cred);
+ put_cred(override_cred);
+
+ return 0;
+}
+
+static inline int ovl_dir_read_merged(struct path *upperpath,
+ struct path *lowerpath,
+ struct list_head *list)
+{
+ int err;
+ struct ovl_readdir_data rdd = {
+ .ctx.actor = ovl_fill_merge,
+ .list = list,
+ .root = RB_ROOT,
+ .is_merge = false,
+ };
+
+ if (upperpath->dentry) {
+ err = ovl_dir_read(upperpath, &rdd);
+ if (err)
+ goto out;
+
+ if (lowerpath->dentry) {
+ err = ovl_dir_mark_whiteouts(upperpath->dentry, &rdd);
+ if (err)
+ goto out;
+ }
+ }
+ if (lowerpath->dentry) {
+ /*
+ * Insert lowerpath entries before upperpath ones, this allows
+ * offsets to be reasonably constant
+ */
+ list_add(&rdd.middle, rdd.list);
+ rdd.is_merge = true;
+ err = ovl_dir_read(lowerpath, &rdd);
+ list_del(&rdd.middle);
+ }
+out:
+ return err;
+}
+
+static void ovl_seek_cursor(struct ovl_dir_file *od, loff_t pos)
+{
+ struct ovl_cache_entry *p;
+ loff_t off = 0;
+
+ list_for_each_entry(p, &od->cache->entries, l_node) {
+ if (p->is_cursor)
+ continue;
+ if (off >= pos)
+ break;
+ off++;
+ }
+ list_move_tail(&od->cursor.l_node, &p->l_node);
+}
+
+static struct ovl_dir_cache *ovl_cache_get(struct dentry *dentry)
+{
+ int res;
+ struct path lowerpath;
+ struct path upperpath;
+ struct ovl_dir_cache *cache;
+
+ cache = ovl_dir_cache(dentry);
+ if (cache && ovl_dentry_version_get(dentry) == cache->version) {
+ cache->refcount++;
+ return cache;
+ }
+ ovl_set_dir_cache(dentry, NULL);
+
+ cache = kzalloc(sizeof(struct ovl_dir_cache), GFP_KERNEL);
+ if (!cache)
+ return ERR_PTR(-ENOMEM);
+
+ cache->refcount = 1;
+ INIT_LIST_HEAD(&cache->entries);
+
+ ovl_path_lower(dentry, &lowerpath);
+ ovl_path_upper(dentry, &upperpath);
+
+ res = ovl_dir_read_merged(&upperpath, &lowerpath, &cache->entries);
+ if (res) {
+ ovl_cache_free(&cache->entries);
+ kfree(cache);
+ return ERR_PTR(res);
+ }
+
+ cache->version = ovl_dentry_version_get(dentry);
+ ovl_set_dir_cache(dentry, cache);
+
+ return cache;
+}
+
+static int ovl_iterate(struct file *file, struct dir_context *ctx)
+{
+ struct ovl_dir_file *od = file->private_data;
+ struct dentry *dentry = file->f_path.dentry;
+
+ if (!ctx->pos)
+ ovl_dir_reset(file);
+
+ if (od->is_real)
+ return iterate_dir(od->realfile, ctx);
+
+ if (!od->cache) {
+ struct ovl_dir_cache *cache;
+
+ cache = ovl_cache_get(dentry);
+ if (IS_ERR(cache))
+ return PTR_ERR(cache);
+
+ od->cache = cache;
+ ovl_seek_cursor(od, ctx->pos);
+ }
+
+ while (od->cursor.l_node.next != &od->cache->entries) {
+ struct ovl_cache_entry *p;
+
+ p = list_entry(od->cursor.l_node.next, struct ovl_cache_entry, l_node);
+ /* Skip cursors */
+ if (!p->is_cursor) {
+ if (!p->is_whiteout) {
+ if (!dir_emit(ctx, p->name, p->len, p->ino, p->type))
+ break;
+ }
+ ctx->pos++;
+ }
+ list_move(&od->cursor.l_node, &p->l_node);
+ }
+ return 0;
+}
+
+static loff_t ovl_dir_llseek(struct file *file, loff_t offset, int origin)
+{
+ loff_t res;
+ struct ovl_dir_file *od = file->private_data;
+
+ mutex_lock(&file_inode(file)->i_mutex);
+ if (!file->f_pos)
+ ovl_dir_reset(file);
+
+ if (od->is_real) {
+ res = vfs_llseek(od->realfile, offset, origin);
+ file->f_pos = od->realfile->f_pos;
+ } else {
+ res = -EINVAL;
+
+ switch (origin) {
+ case SEEK_CUR:
+ offset += file->f_pos;
+ break;
+ case SEEK_SET:
+ break;
+ default:
+ goto out_unlock;
+ }
+ if (offset < 0)
+ goto out_unlock;
+
+ if (offset != file->f_pos) {
+ file->f_pos = offset;
+ if (od->cache)
+ ovl_seek_cursor(od, offset);
+ }
+ res = offset;
+ }
+out_unlock:
+ mutex_unlock(&file_inode(file)->i_mutex);
+
+ return res;
+}
+
+static int ovl_dir_fsync(struct file *file, loff_t start, loff_t end,
+ int datasync)
+{
+ struct ovl_dir_file *od = file->private_data;
+ struct dentry *dentry = file->f_path.dentry;
+ struct file *realfile = od->realfile;
+
+ /*
+ * Need to check if we started out being a lower dir, but got copied up
+ */
+ if (!od->is_upper && ovl_path_type(dentry) == OVL_PATH_MERGE) {
+ struct inode *inode = file_inode(file);
+
+ realfile =lockless_dereference(od->upperfile);
+ if (!realfile) {
+ struct path upperpath;
+
+ ovl_path_upper(dentry, &upperpath);
+ realfile = ovl_path_open(&upperpath, O_RDONLY);
+ smp_mb__before_spinlock();
+ mutex_lock(&inode->i_mutex);
+ if (!od->upperfile) {
+ if (IS_ERR(realfile)) {
+ mutex_unlock(&inode->i_mutex);
+ return PTR_ERR(realfile);
+ }
+ od->upperfile = realfile;
+ } else {
+ /* somebody has beaten us to it */
+ if (!IS_ERR(realfile))
+ fput(realfile);
+ realfile = od->upperfile;
+ }
+ mutex_unlock(&inode->i_mutex);
+ }
+ }
+
+ return vfs_fsync_range(realfile, start, end, datasync);
+}
+
+static int ovl_dir_release(struct inode *inode, struct file *file)
+{
+ struct ovl_dir_file *od = file->private_data;
+
+ if (od->cache) {
+ mutex_lock(&inode->i_mutex);
+ ovl_cache_put(od, file->f_path.dentry);
+ mutex_unlock(&inode->i_mutex);
+ }
+ fput(od->realfile);
+ if (od->upperfile)
+ fput(od->upperfile);
+ kfree(od);
+
+ return 0;
+}
+
+static int ovl_dir_open(struct inode *inode, struct file *file)
+{
+ struct path realpath;
+ struct file *realfile;
+ struct ovl_dir_file *od;
+ enum ovl_path_type type;
+
+ od = kzalloc(sizeof(struct ovl_dir_file), GFP_KERNEL);
+ if (!od)
+ return -ENOMEM;
+
+ type = ovl_path_real(file->f_path.dentry, &realpath);
+ realfile = ovl_path_open(&realpath, file->f_flags);
+ if (IS_ERR(realfile)) {
+ kfree(od);
+ return PTR_ERR(realfile);
+ }
+ INIT_LIST_HEAD(&od->cursor.l_node);
+ od->realfile = realfile;
+ od->is_real = (type != OVL_PATH_MERGE);
+ od->is_upper = (type != OVL_PATH_LOWER);
+ od->cursor.is_cursor = true;
+ file->private_data = od;
+
+ return 0;
+}
+
+const struct file_operations ovl_dir_operations = {
+ .read = generic_read_dir,
+ .open = ovl_dir_open,
+ .iterate = ovl_iterate,
+ .llseek = ovl_dir_llseek,
+ .fsync = ovl_dir_fsync,
+ .release = ovl_dir_release,
+};
+
+int ovl_check_empty_dir(struct dentry *dentry, struct list_head *list)
+{
+ int err;
+ struct path lowerpath;
+ struct path upperpath;
+ struct ovl_cache_entry *p;
+
+ ovl_path_upper(dentry, &upperpath);
+ ovl_path_lower(dentry, &lowerpath);
+
+ err = ovl_dir_read_merged(&upperpath, &lowerpath, 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;
+
+ 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);
+}
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