#include <linux/mount.h>
#include <linux/module.h>
#include <linux/slab.h>
+#include <linux/err.h>
#include <linux/configfs.h>
#include "configfs_internal.h"
DECLARE_RWSEM(configfs_rename_sem);
+/*
+ * Protects mutations of configfs_dirent linkage together with proper i_mutex
+ * Also protects mutations of symlinks linkage to target configfs_dirent
+ * Mutators of configfs_dirent linkage must *both* have the proper inode locked
+ * and configfs_dirent_lock locked, in that order.
+ * This allows one to safely traverse configfs_dirent trees and symlinks without
+ * having to lock inodes.
+ *
+ * Protects setting of CONFIGFS_USET_DROPPING: checking the flag
+ * unlocked is not reliable unless in detach_groups() called from
+ * rmdir()/unregister() and from configfs_attach_group()
+ */
+DEFINE_SPINLOCK(configfs_dirent_lock);
static void configfs_d_iput(struct dentry * dentry,
struct inode * inode)
sd = kmem_cache_zalloc(configfs_dir_cachep, GFP_KERNEL);
if (!sd)
- return NULL;
+ return ERR_PTR(-ENOMEM);
atomic_set(&sd->s_count, 1);
INIT_LIST_HEAD(&sd->s_links);
INIT_LIST_HEAD(&sd->s_children);
- list_add(&sd->s_sibling, &parent_sd->s_children);
sd->s_element = element;
+ spin_lock(&configfs_dirent_lock);
+ if (parent_sd->s_type & CONFIGFS_USET_DROPPING) {
+ spin_unlock(&configfs_dirent_lock);
+ kmem_cache_free(configfs_dir_cachep, sd);
+ return ERR_PTR(-ENOENT);
+ }
+ list_add(&sd->s_sibling, &parent_sd->s_children);
+ spin_unlock(&configfs_dirent_lock);
return sd;
}
struct configfs_dirent * sd;
sd = configfs_new_dirent(parent_sd, element);
- if (!sd)
- return -ENOMEM;
+ if (IS_ERR(sd))
+ return PTR_ERR(sd);
sd->s_mode = mode;
sd->s_type = type;
return 0;
}
-static int init_file(struct inode * inode)
+static int configfs_init_file(struct inode * inode)
{
inode->i_size = PAGE_SIZE;
inode->i_fop = &configfs_file_operations;
} else {
struct configfs_dirent *sd = d->d_fsdata;
if (sd) {
+ spin_lock(&configfs_dirent_lock);
list_del_init(&sd->s_sibling);
+ spin_unlock(&configfs_dirent_lock);
configfs_put(sd);
}
}
else {
struct configfs_dirent *sd = dentry->d_fsdata;
if (sd) {
+ spin_lock(&configfs_dirent_lock);
list_del_init(&sd->s_sibling);
+ spin_unlock(&configfs_dirent_lock);
configfs_put(sd);
}
}
struct configfs_dirent * sd;
sd = d->d_fsdata;
+ spin_lock(&configfs_dirent_lock);
list_del_init(&sd->s_sibling);
+ spin_unlock(&configfs_dirent_lock);
configfs_put(sd);
if (d->d_inode)
simple_rmdir(parent->d_inode,d);
dentry->d_fsdata = configfs_get(sd);
sd->s_dentry = dentry;
- error = configfs_create(dentry, (attr->ca_mode & S_IALLUGO) | S_IFREG, init_file);
+ error = configfs_create(dentry, (attr->ca_mode & S_IALLUGO) | S_IFREG,
+ configfs_init_file);
if (error) {
configfs_put(sd);
return error;
/*
* Only subdirectories count here. Files (CONFIGFS_NOT_PINNED) are
- * attributes and are removed by rmdir(). We recurse, taking i_mutex
- * on all children that are candidates for default detach. If the
- * result is clean, then configfs_detach_group() will handle dropping
- * i_mutex. If there is an error, the caller will clean up the i_mutex
- * holders via configfs_detach_rollback().
+ * attributes and are removed by rmdir(). We recurse, setting
+ * CONFIGFS_USET_DROPPING on all children that are candidates for
+ * default detach.
+ * If there is an error, the caller will reset the flags via
+ * configfs_detach_rollback().
*/
-static int configfs_detach_prep(struct dentry *dentry)
+static int configfs_detach_prep(struct dentry *dentry, struct mutex **wait_mutex)
{
struct configfs_dirent *parent_sd = dentry->d_fsdata;
struct configfs_dirent *sd;
if (sd->s_type & CONFIGFS_NOT_PINNED)
continue;
if (sd->s_type & CONFIGFS_USET_DEFAULT) {
- mutex_lock(&sd->s_dentry->d_inode->i_mutex);
- /* Mark that we've taken i_mutex */
+ /* Abort if racing with mkdir() */
+ if (sd->s_type & CONFIGFS_USET_IN_MKDIR) {
+ if (wait_mutex)
+ *wait_mutex = &sd->s_dentry->d_inode->i_mutex;
+ return -EAGAIN;
+ }
+ /* Mark that we're trying to drop the group */
sd->s_type |= CONFIGFS_USET_DROPPING;
/*
* Yup, recursive. If there's a problem, blame
* deep nesting of default_groups
*/
- ret = configfs_detach_prep(sd->s_dentry);
+ ret = configfs_detach_prep(sd->s_dentry, wait_mutex);
if (!ret)
continue;
} else
}
/*
- * Walk the tree, dropping i_mutex wherever CONFIGFS_USET_DROPPING is
+ * Walk the tree, resetting CONFIGFS_USET_DROPPING wherever it was
* set.
*/
static void configfs_detach_rollback(struct dentry *dentry)
list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
if (sd->s_type & CONFIGFS_USET_DEFAULT) {
configfs_detach_rollback(sd->s_dentry);
-
- if (sd->s_type & CONFIGFS_USET_DROPPING) {
- sd->s_type &= ~CONFIGFS_USET_DROPPING;
- mutex_unlock(&sd->s_dentry->d_inode->i_mutex);
- }
+ sd->s_type &= ~CONFIGFS_USET_DROPPING;
}
}
}
list_for_each_entry_safe(sd, tmp, &parent_sd->s_children, s_sibling) {
if (!sd->s_element || !(sd->s_type & CONFIGFS_NOT_PINNED))
continue;
+ spin_lock(&configfs_dirent_lock);
list_del_init(&sd->s_sibling);
+ spin_unlock(&configfs_dirent_lock);
configfs_drop_dentry(sd, dentry);
configfs_put(sd);
}
child = sd->s_dentry;
+ mutex_lock(&child->d_inode->i_mutex);
+
configfs_detach_group(sd->s_element);
child->d_inode->i_flags |= S_DEAD;
- /*
- * From rmdir/unregister, a configfs_detach_prep() pass
- * has taken our i_mutex for us. Drop it.
- * From mkdir/register cleanup, there is no sem held.
- */
- if (sd->s_type & CONFIGFS_USET_DROPPING)
- mutex_unlock(&child->d_inode->i_mutex);
+ mutex_unlock(&child->d_inode->i_mutex);
d_delete(child);
dput(child);
* That said, taking our i_mutex is closer to mkdir
* emulation, and shouldn't hurt.
*/
- mutex_lock(&dentry->d_inode->i_mutex);
+ mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_CHILD);
for (i = 0; group->default_groups[i]; i++) {
new_group = group->default_groups[i];
group = NULL;
item = NULL;
if (type->ct_group_ops->make_group) {
- group = type->ct_group_ops->make_group(to_config_group(parent_item), name);
- if (group) {
+ ret = type->ct_group_ops->make_group(to_config_group(parent_item), name, &group);
+ if (!ret) {
link_group(to_config_group(parent_item), group);
item = &group->cg_item;
}
} else {
- item = type->ct_group_ops->make_item(to_config_group(parent_item), name);
- if (item)
+ ret = type->ct_group_ops->make_item(to_config_group(parent_item), name, &item);
+ if (!ret)
link_obj(parent_item, item);
}
mutex_unlock(&subsys->su_mutex);
kfree(name);
- if (!item) {
+ if (ret) {
/*
- * If item == NULL, then link_obj() was never called.
+ * If ret != 0, then link_obj() was never called.
* There are no extra references to clean up.
*/
- ret = -ENOMEM;
goto out_put;
}
*/
module_got = 1;
+ /*
+ * Make racing rmdir() fail if it did not tag parent with
+ * CONFIGFS_USET_DROPPING
+ * Note: if CONFIGFS_USET_DROPPING is already set, attach_group() will
+ * fail and let rmdir() terminate correctly
+ */
+ spin_lock(&configfs_dirent_lock);
+ /* This will make configfs_detach_prep() fail */
+ sd->s_type |= CONFIGFS_USET_IN_MKDIR;
+ spin_unlock(&configfs_dirent_lock);
+
if (group)
ret = configfs_attach_group(parent_item, item, dentry);
else
ret = configfs_attach_item(parent_item, item, dentry);
+ spin_lock(&configfs_dirent_lock);
+ sd->s_type &= ~CONFIGFS_USET_IN_MKDIR;
+ spin_unlock(&configfs_dirent_lock);
+
out_unlink:
if (ret) {
/* Tear down everything we built up */
return -EINVAL;
}
- ret = configfs_detach_prep(dentry);
- if (ret) {
- configfs_detach_rollback(dentry);
- config_item_put(parent_item);
- return ret;
- }
+ spin_lock(&configfs_dirent_lock);
+ do {
+ struct mutex *wait_mutex;
+
+ ret = configfs_detach_prep(dentry, &wait_mutex);
+ if (ret) {
+ configfs_detach_rollback(dentry);
+ spin_unlock(&configfs_dirent_lock);
+ if (ret != -EAGAIN) {
+ config_item_put(parent_item);
+ return ret;
+ }
+
+ /* Wait until the racing operation terminates */
+ mutex_lock(wait_mutex);
+ mutex_unlock(wait_mutex);
+
+ spin_lock(&configfs_dirent_lock);
+ }
+ } while (ret == -EAGAIN);
+ spin_unlock(&configfs_dirent_lock);
/* Get a working ref for the duration of this function */
item = configfs_get_config_item(dentry);
file->private_data = configfs_new_dirent(parent_sd, NULL);
mutex_unlock(&dentry->d_inode->i_mutex);
- return file->private_data ? 0 : -ENOMEM;
+ return IS_ERR(file->private_data) ? PTR_ERR(file->private_data) : 0;
}
struct configfs_dirent * cursor = file->private_data;
mutex_lock(&dentry->d_inode->i_mutex);
+ spin_lock(&configfs_dirent_lock);
list_del_init(&cursor->s_sibling);
+ spin_unlock(&configfs_dirent_lock);
mutex_unlock(&dentry->d_inode->i_mutex);
release_configfs_dirent(cursor);
/* fallthrough */
default:
if (filp->f_pos == 2) {
+ spin_lock(&configfs_dirent_lock);
list_move(q, &parent_sd->s_children);
+ spin_unlock(&configfs_dirent_lock);
}
for (p=q->next; p!= &parent_sd->s_children; p=p->next) {
struct configfs_dirent *next;
dt_type(next)) < 0)
return 0;
+ spin_lock(&configfs_dirent_lock);
list_move(q, p);
+ spin_unlock(&configfs_dirent_lock);
p = q;
filp->f_pos++;
}
struct list_head *p;
loff_t n = file->f_pos - 2;
+ spin_lock(&configfs_dirent_lock);
list_del(&cursor->s_sibling);
p = sd->s_children.next;
while (n && p != &sd->s_children) {
p = p->next;
}
list_add_tail(&cursor->s_sibling, p);
+ spin_unlock(&configfs_dirent_lock);
}
}
mutex_unlock(&dentry->d_inode->i_mutex);
sd = configfs_sb->s_root->d_fsdata;
link_group(to_config_group(sd->s_element), group);
- mutex_lock(&configfs_sb->s_root->d_inode->i_mutex);
+ mutex_lock_nested(&configfs_sb->s_root->d_inode->i_mutex,
+ I_MUTEX_PARENT);
name.name = group->cg_item.ci_name;
name.len = strlen(name.name);
mutex_lock_nested(&configfs_sb->s_root->d_inode->i_mutex,
I_MUTEX_PARENT);
mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_CHILD);
- if (configfs_detach_prep(dentry)) {
+ spin_lock(&configfs_dirent_lock);
+ if (configfs_detach_prep(dentry, NULL)) {
printk(KERN_ERR "configfs: Tried to unregister non-empty subsystem!\n");
}
+ spin_unlock(&configfs_dirent_lock);
configfs_detach_group(&group->cg_item);
dentry->d_inode->i_flags |= S_DEAD;
mutex_unlock(&dentry->d_inode->i_mutex);
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff