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path: root/fs/configfs/dir.c
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Diffstat (limited to 'fs/configfs/dir.c')
-rw-r--r--fs/configfs/dir.c159
1 files changed, 115 insertions, 44 deletions
diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
index a48dc7dd876..179589be063 100644
--- a/fs/configfs/dir.c
+++ b/fs/configfs/dir.c
@@ -30,11 +30,25 @@
#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)
@@ -74,13 +88,20 @@ static struct configfs_dirent *configfs_new_dirent(struct configfs_dirent * pare
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;
}
@@ -118,8 +139,8 @@ int configfs_make_dirent(struct configfs_dirent * parent_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;
@@ -173,7 +194,9 @@ static int create_dir(struct config_item * k, struct dentry * p,
} 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);
}
}
@@ -224,7 +247,9 @@ int configfs_create_link(struct configfs_symlink *sl,
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);
}
}
@@ -238,7 +263,9 @@ static void remove_dir(struct dentry * d)
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);
@@ -331,13 +358,13 @@ static struct dentry * configfs_lookup(struct inode *dir,
/*
* 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;
@@ -352,15 +379,20 @@ static int configfs_detach_prep(struct dentry *dentry)
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
@@ -374,7 +406,7 @@ out:
}
/*
- * 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)
@@ -385,11 +417,7 @@ 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;
}
}
}
@@ -410,7 +438,9 @@ static void detach_attrs(struct config_item * item)
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);
}
@@ -466,16 +496,12 @@ static void detach_groups(struct config_group *group)
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);
@@ -1001,9 +1027,10 @@ EXPORT_SYMBOL(configfs_undepend_item);
static int configfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
{
- int ret, module_got = 0;
- struct config_group *group;
- struct config_item *item;
+ int ret = 0;
+ int module_got = 0;
+ struct config_group *group = NULL;
+ struct config_item *item = NULL;
struct config_item *parent_item;
struct configfs_subsystem *subsys;
struct configfs_dirent *sd;
@@ -1044,28 +1071,32 @@ static int configfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
snprintf(name, dentry->d_name.len + 1, "%s", dentry->d_name.name);
mutex_lock(&subsys->su_mutex);
- 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) {
+ if (!group)
+ group = ERR_PTR(-ENOMEM);
+ if (!IS_ERR(group)) {
link_group(to_config_group(parent_item), group);
item = &group->cg_item;
- }
+ } else
+ ret = PTR_ERR(group);
} else {
item = type->ct_group_ops->make_item(to_config_group(parent_item), name);
- if (item)
+ if (!item)
+ item = ERR_PTR(-ENOMEM);
+ if (!IS_ERR(item))
link_obj(parent_item, item);
+ else
+ ret = PTR_ERR(item);
}
mutex_unlock(&subsys->su_mutex);
kfree(name);
- if (!item) {
+ if (ret) {
/*
* If item == NULL, then link_obj() was never called.
* There are no extra references to clean up.
*/
- ret = -ENOMEM;
goto out_put;
}
@@ -1093,11 +1124,26 @@ static int configfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
*/
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 */
@@ -1161,12 +1207,27 @@ static int configfs_rmdir(struct inode *dir, struct dentry *dentry)
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);
@@ -1258,7 +1319,7 @@ static int configfs_dir_open(struct inode *inode, struct file *file)
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;
}
@@ -1268,7 +1329,9 @@ static int configfs_dir_close(struct inode *inode, struct file *file)
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);
@@ -1308,7 +1371,9 @@ static int configfs_readdir(struct file * filp, void * dirent, filldir_t filldir
/* 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;
@@ -1331,7 +1396,9 @@ static int configfs_readdir(struct file * filp, void * dirent, filldir_t filldir
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++;
}
@@ -1362,6 +1429,7 @@ static loff_t configfs_dir_lseek(struct file * file, loff_t offset, int origin)
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) {
@@ -1373,6 +1441,7 @@ static loff_t configfs_dir_lseek(struct file * file, loff_t offset, int origin)
p = p->next;
}
list_add_tail(&cursor->s_sibling, p);
+ spin_unlock(&configfs_dirent_lock);
}
}
mutex_unlock(&dentry->d_inode->i_mutex);
@@ -1448,9 +1517,11 @@ void configfs_unregister_subsystem(struct configfs_subsystem *subsys)
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);
generated by cgit v1.2.3 (git 2.25.1) at 2024-12-25 11:05:31 +0000