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configfs: calculate the symlink target only once

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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Al Viro 2019-09-11 09:00:01 +02:00 committed by Christoph Hellwig
parent 2743c515a1
commit e9c03af21c
4 changed files with 75 additions and 173 deletions
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19
fs/configfs/configfs_internal.h
View File

@ -34,7 +34,7 @@ struct configfs_dirent {
int s_dependent_count;
struct list_head s_sibling;
struct list_head s_children;
struct list_head s_links;
int s_links;
void * s_element;
int s_type;
umode_t s_mode;
@ -84,7 +84,6 @@ extern int configfs_setattr(struct dentry *dentry, struct iattr *iattr);
extern struct dentry *configfs_pin_fs(void);
extern void configfs_release_fs(void);
extern struct rw_semaphore configfs_rename_sem;
extern const struct file_operations configfs_dir_operations;
extern const struct file_operations configfs_file_operations;
extern const struct file_operations configfs_bin_file_operations;
@ -97,14 +96,8 @@ extern int configfs_symlink(struct inode *dir, struct dentry *dentry,
const char *symname);
extern int configfs_unlink(struct inode *dir, struct dentry *dentry);
struct configfs_symlink {
struct list_head sl_list;
struct config_item *sl_target;
};
extern int configfs_create_link(struct configfs_symlink *sl,
struct dentry *parent,
struct dentry *dentry);
int configfs_create_link(struct configfs_dirent *target, struct dentry *parent,
struct dentry *dentry, char *body);
static inline struct config_item * to_item(struct dentry * dentry)
{
@ -132,11 +125,7 @@ static inline struct config_item *configfs_get_config_item(struct dentry *dentry
spin_lock(&dentry->d_lock);
if (!d_unhashed(dentry)) {
struct configfs_dirent * sd = dentry->d_fsdata;
if (sd->s_type & CONFIGFS_ITEM_LINK) {
struct configfs_symlink * sl = sd->s_element;
item = config_item_get(sl->sl_target);
} else
item = config_item_get(sd->s_element);
item = config_item_get(sd->s_element);
}
spin_unlock(&dentry->d_lock);

52
fs/configfs/dir.c
View File

@ -22,7 +22,6 @@
#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
@ -191,7 +190,6 @@ static struct configfs_dirent *configfs_new_dirent(struct configfs_dirent *paren
return ERR_PTR(-ENOMEM);
atomic_set(&sd->s_count, 1);
INIT_LIST_HEAD(&sd->s_links);
INIT_LIST_HEAD(&sd->s_children);
sd->s_element = element;
sd->s_type = type;
@ -353,17 +351,16 @@ int configfs_dirent_is_ready(struct configfs_dirent *sd)
return ret;
}
int configfs_create_link(struct configfs_symlink *sl,
struct dentry *parent,
struct dentry *dentry)
int configfs_create_link(struct configfs_dirent *target, struct dentry *parent,
struct dentry *dentry, char *body)
{
int err = 0;
umode_t mode = S_IFLNK | S_IRWXUGO;
struct configfs_dirent *p = parent->d_fsdata;
struct inode *inode;
err = configfs_make_dirent(p, dentry, sl, mode,
CONFIGFS_ITEM_LINK, p->s_frag);
err = configfs_make_dirent(p, dentry, target, mode, CONFIGFS_ITEM_LINK,
p->s_frag);
if (err)
return err;
@ -371,6 +368,7 @@ int configfs_create_link(struct configfs_symlink *sl,
if (IS_ERR(inode))
goto out_remove;
inode->i_link = body;
inode->i_op = &configfs_symlink_inode_operations;
d_instantiate(dentry, inode);
dget(dentry); /* pin link dentries in core */
@ -517,7 +515,7 @@ static int configfs_detach_prep(struct dentry *dentry, struct dentry **wait)
parent_sd->s_type |= CONFIGFS_USET_DROPPING;
ret = -EBUSY;
if (!list_empty(&parent_sd->s_links))
if (parent_sd->s_links)
goto out;
ret = 0;
@ -1575,44 +1573,6 @@ const struct inode_operations configfs_root_inode_operations = {
.setattr = configfs_setattr,
};
#if 0
int configfs_rename_dir(struct config_item * item, const char *new_name)
{
int error = 0;
struct dentry * new_dentry, * parent;
if (!strcmp(config_item_name(item), new_name))
return -EINVAL;
if (!item->parent)
return -EINVAL;
down_write(&configfs_rename_sem);
parent = item->parent->dentry;
inode_lock(d_inode(parent));
new_dentry = lookup_one_len(new_name, parent, strlen(new_name));
if (!IS_ERR(new_dentry)) {
if (d_really_is_negative(new_dentry)) {
error = config_item_set_name(item, "%s", new_name);
if (!error) {
d_add(new_dentry, NULL);
d_move(item->dentry, new_dentry);
}
else
d_delete(new_dentry);
} else
error = -EEXIST;
dput(new_dentry);
}
inode_unlock(d_inode(parent));
up_write(&configfs_rename_sem);
return error;
}
#endif
static int configfs_dir_open(struct inode *inode, struct file *file)
{
struct dentry * dentry = file->f_path.dentry;

9
fs/configfs/mount.c
View File

@ -28,9 +28,18 @@ static struct vfsmount *configfs_mount = NULL;
struct kmem_cache *configfs_dir_cachep;
static int configfs_mnt_count = 0;
static void configfs_free_inode(struct inode *inode)
{
if (S_ISLNK(inode->i_mode))
kfree(inode->i_link);
free_inode_nonrcu(inode);
}
static const struct super_operations configfs_ops = {
.statfs = simple_statfs,
.drop_inode = generic_delete_inode,
.free_inode = configfs_free_inode,
};
static struct config_group configfs_root_group = {

168
fs/configfs/symlink.c
View File

@ -55,41 +55,63 @@ static void fill_item_path(struct config_item * item, char * buffer, int length)
}
}
static int configfs_get_target_path(struct config_item *item,
struct config_item *target, char *path)
{
int depth, size;
char *s;
depth = item_depth(item);
size = item_path_length(target) + depth * 3 - 1;
if (size > PATH_MAX)
return -ENAMETOOLONG;
pr_debug("%s: depth = %d, size = %d\n", __func__, depth, size);
for (s = path; depth--; s += 3)
strcpy(s,"../");
fill_item_path(target, path, size);
pr_debug("%s: path = '%s'\n", __func__, path);
return 0;
}
static int create_link(struct config_item *parent_item,
struct config_item *item,
struct dentry *dentry)
{
struct configfs_dirent *target_sd = item->ci_dentry->d_fsdata;
struct configfs_symlink *sl;
char *body;
int ret;
ret = -ENOENT;
if (!configfs_dirent_is_ready(target_sd))
goto out;
ret = -ENOMEM;
sl = kmalloc(sizeof(struct configfs_symlink), GFP_KERNEL);
if (sl) {
spin_lock(&configfs_dirent_lock);
if (target_sd->s_type & CONFIGFS_USET_DROPPING) {
spin_unlock(&configfs_dirent_lock);
kfree(sl);
return -ENOENT;
}
sl->sl_target = config_item_get(item);
list_add(&sl->sl_list, &target_sd->s_links);
spin_unlock(&configfs_dirent_lock);
ret = configfs_create_link(sl, parent_item->ci_dentry,
dentry);
if (ret) {
spin_lock(&configfs_dirent_lock);
list_del_init(&sl->sl_list);
spin_unlock(&configfs_dirent_lock);
config_item_put(item);
kfree(sl);
}
}
return -ENOENT;
out:
body = kzalloc(PAGE_SIZE, GFP_KERNEL);
if (!body)
return -ENOMEM;
configfs_get(target_sd);
spin_lock(&configfs_dirent_lock);
if (target_sd->s_type & CONFIGFS_USET_DROPPING) {
spin_unlock(&configfs_dirent_lock);
configfs_put(target_sd);
kfree(body);
return -ENOENT;
}
target_sd->s_links++;
spin_unlock(&configfs_dirent_lock);
ret = configfs_get_target_path(item, item, body);
if (!ret)
ret = configfs_create_link(target_sd, parent_item->ci_dentry,
dentry, body);
if (ret) {
spin_lock(&configfs_dirent_lock);
target_sd->s_links--;
spin_unlock(&configfs_dirent_lock);
configfs_put(target_sd);
kfree(body);
}
return ret;
}
@ -131,9 +153,8 @@ int configfs_symlink(struct inode *dir, struct dentry *dentry, const char *symna
* Fake invisibility if dir belongs to a group/default groups hierarchy
* being attached
*/
ret = -ENOENT;
if (!configfs_dirent_is_ready(sd))
goto out;
return -ENOENT;
parent_item = configfs_get_config_item(dentry->d_parent);
type = parent_item->ci_type;
@ -193,15 +214,12 @@ int configfs_symlink(struct inode *dir, struct dentry *dentry, const char *symna
out_put:
config_item_put(parent_item);
out:
return ret;
}
int configfs_unlink(struct inode *dir, struct dentry *dentry)
{
struct configfs_dirent *sd = dentry->d_fsdata;
struct configfs_symlink *sl;
struct configfs_dirent *sd = dentry->d_fsdata, *target_sd;
struct config_item *parent_item;
const struct config_item_type *type;
int ret;
@ -210,7 +228,7 @@ int configfs_unlink(struct inode *dir, struct dentry *dentry)
if (!(sd->s_type & CONFIGFS_ITEM_LINK))
goto out;
sl = sd->s_element;
target_sd = sd->s_element;
parent_item = configfs_get_config_item(dentry->d_parent);
type = parent_item->ci_type;
@ -224,21 +242,18 @@ int configfs_unlink(struct inode *dir, struct dentry *dentry)
/*
* drop_link() must be called before
* list_del_init(&sl->sl_list), so that the order of
* decrementing target's ->s_links, so that the order of
* drop_link(this, target) and drop_item(target) is preserved.
*/
if (type && type->ct_item_ops &&
type->ct_item_ops->drop_link)
type->ct_item_ops->drop_link(parent_item,
sl->sl_target);
target_sd->s_element);
spin_lock(&configfs_dirent_lock);
list_del_init(&sl->sl_list);
target_sd->s_links--;
spin_unlock(&configfs_dirent_lock);
/* Put reference from create_link() */
config_item_put(sl->sl_target);
kfree(sl);
configfs_put(target_sd);
config_item_put(parent_item);
@ -248,79 +263,8 @@ int configfs_unlink(struct inode *dir, struct dentry *dentry)
return ret;
}
static int configfs_get_target_path(struct config_item * item, struct config_item * target,
char *path)
{
char * s;
int depth, size;
depth = item_depth(item);
size = item_path_length(target) + depth * 3 - 1;
if (size > PATH_MAX)
return -ENAMETOOLONG;
pr_debug("%s: depth = %d, size = %d\n", __func__, depth, size);
for (s = path; depth--; s += 3)
strcpy(s,"../");
fill_item_path(target, path, size);
pr_debug("%s: path = '%s'\n", __func__, path);
return 0;
}
static int configfs_getlink(struct dentry *dentry, char * path)
{
struct config_item *item, *target_item;
int error = 0;
item = configfs_get_config_item(dentry->d_parent);
if (!item)
return -EINVAL;
target_item = configfs_get_config_item(dentry);
if (!target_item) {
config_item_put(item);
return -EINVAL;
}
down_read(&configfs_rename_sem);
error = configfs_get_target_path(item, target_item, path);
up_read(&configfs_rename_sem);
config_item_put(item);
config_item_put(target_item);
return error;
}
static const char *configfs_get_link(struct dentry *dentry,
struct inode *inode,
struct delayed_call *done)
{
char *body;
int error;
if (!dentry)
return ERR_PTR(-ECHILD);
body = kzalloc(PAGE_SIZE, GFP_KERNEL);
if (!body)
return ERR_PTR(-ENOMEM);
error = configfs_getlink(dentry, body);
if (!error) {
set_delayed_call(done, kfree_link, body);
return body;
}
kfree(body);
return ERR_PTR(error);
}
const struct inode_operations configfs_symlink_inode_operations = {
.get_link = configfs_get_link,
.get_link = simple_get_link,
.setattr = configfs_setattr,
};