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configfs: new object reprsenting tree fragments
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Refcounted, hangs of configfs_dirent, created by operations that add
fragments to configfs tree (mkdir and configfs_register_{subsystem,group}).
Will be used in the next commit to provide exclusion between fragment
removal and ->show/->store calls.

Signed-off-by: Al Viro <[email protected]>
Signed-off-by: Christoph Hellwig <[email protected]>
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Al Viro authored and Christoph Hellwig committed Sep 2, 2019
1 parent f19e4ed commit 47320fb
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Showing 3 changed files with 97 additions and 27 deletions.
15 changes: 13 additions & 2 deletions fs/configfs/configfs_internal.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,15 @@
#include <linux/list.h>
#include <linux/spinlock.h>

struct configfs_fragment {
atomic_t frag_count;
struct rw_semaphore frag_sem;
bool frag_dead;
};

void put_fragment(struct configfs_fragment *);
struct configfs_fragment *get_fragment(struct configfs_fragment *);

struct configfs_dirent {
atomic_t s_count;
int s_dependent_count;
Expand All @@ -34,6 +43,7 @@ struct configfs_dirent {
#ifdef CONFIG_LOCKDEP
int s_depth;
#endif
struct configfs_fragment *s_frag;
};

#define CONFIGFS_ROOT 0x0001
Expand Down Expand Up @@ -61,8 +71,8 @@ extern int configfs_create(struct dentry *, umode_t mode, void (*init)(struct in
extern int configfs_create_file(struct config_item *, const struct configfs_attribute *);
extern int configfs_create_bin_file(struct config_item *,
const struct configfs_bin_attribute *);
extern int configfs_make_dirent(struct configfs_dirent *,
struct dentry *, void *, umode_t, int);
extern int configfs_make_dirent(struct configfs_dirent *, struct dentry *,
void *, umode_t, int, struct configfs_fragment *);
extern int configfs_dirent_is_ready(struct configfs_dirent *);

extern void configfs_hash_and_remove(struct dentry * dir, const char * name);
Expand Down Expand Up @@ -137,6 +147,7 @@ static inline void release_configfs_dirent(struct configfs_dirent * sd)
{
if (!(sd->s_type & CONFIGFS_ROOT)) {
kfree(sd->s_iattr);
put_fragment(sd->s_frag);
kmem_cache_free(configfs_dir_cachep, sd);
}
}
Expand Down
105 changes: 82 additions & 23 deletions fs/configfs/dir.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -151,11 +151,38 @@ configfs_adjust_dir_dirent_depth_after_populate(struct configfs_dirent *sd)

#endif /* CONFIG_LOCKDEP */

static struct configfs_fragment *new_fragment(void)
{
struct configfs_fragment *p;

p = kmalloc(sizeof(struct configfs_fragment), GFP_KERNEL);
if (p) {
atomic_set(&p->frag_count, 1);
init_rwsem(&p->frag_sem);
p->frag_dead = false;
}
return p;
}

void put_fragment(struct configfs_fragment *frag)
{
if (frag && atomic_dec_and_test(&frag->frag_count))
kfree(frag);
}

struct configfs_fragment *get_fragment(struct configfs_fragment *frag)
{
if (likely(frag))
atomic_inc(&frag->frag_count);
return frag;
}

/*
* Allocates a new configfs_dirent and links it to the parent configfs_dirent
*/
static struct configfs_dirent *configfs_new_dirent(struct configfs_dirent *parent_sd,
void *element, int type)
void *element, int type,
struct configfs_fragment *frag)
{
struct configfs_dirent * sd;

Expand All @@ -175,6 +202,7 @@ static struct configfs_dirent *configfs_new_dirent(struct configfs_dirent *paren
kmem_cache_free(configfs_dir_cachep, sd);
return ERR_PTR(-ENOENT);
}
sd->s_frag = get_fragment(frag);
list_add(&sd->s_sibling, &parent_sd->s_children);
spin_unlock(&configfs_dirent_lock);

Expand Down Expand Up @@ -209,11 +237,11 @@ static int configfs_dirent_exists(struct configfs_dirent *parent_sd,

int configfs_make_dirent(struct configfs_dirent * parent_sd,
struct dentry * dentry, void * element,
umode_t mode, int type)
umode_t mode, int type, struct configfs_fragment *frag)
{
struct configfs_dirent * sd;

sd = configfs_new_dirent(parent_sd, element, type);
sd = configfs_new_dirent(parent_sd, element, type, frag);
if (IS_ERR(sd))
return PTR_ERR(sd);

Expand Down Expand Up @@ -260,7 +288,8 @@ static void init_symlink(struct inode * inode)
* until it is validated by configfs_dir_set_ready()
*/

static int configfs_create_dir(struct config_item *item, struct dentry *dentry)
static int configfs_create_dir(struct config_item *item, struct dentry *dentry,
struct configfs_fragment *frag)
{
int error;
umode_t mode = S_IFDIR| S_IRWXU | S_IRUGO | S_IXUGO;
Expand All @@ -273,7 +302,8 @@ static int configfs_create_dir(struct config_item *item, struct dentry *dentry)
return error;

error = configfs_make_dirent(p->d_fsdata, dentry, item, mode,
CONFIGFS_DIR | CONFIGFS_USET_CREATING);
CONFIGFS_DIR | CONFIGFS_USET_CREATING,
frag);
if (unlikely(error))
return error;

Expand Down Expand Up @@ -338,9 +368,10 @@ int configfs_create_link(struct configfs_symlink *sl,
{
int err = 0;
umode_t mode = S_IFLNK | S_IRWXUGO;
struct configfs_dirent *p = parent->d_fsdata;

err = configfs_make_dirent(parent->d_fsdata, dentry, sl, mode,
CONFIGFS_ITEM_LINK);
err = configfs_make_dirent(p, dentry, sl, mode,
CONFIGFS_ITEM_LINK, p->s_frag);
if (!err) {
err = configfs_create(dentry, mode, init_symlink);
if (err) {
Expand Down Expand Up @@ -599,7 +630,8 @@ static int populate_attrs(struct config_item *item)

static int configfs_attach_group(struct config_item *parent_item,
struct config_item *item,
struct dentry *dentry);
struct dentry *dentry,
struct configfs_fragment *frag);
static void configfs_detach_group(struct config_item *item);

static void detach_groups(struct config_group *group)
Expand Down Expand Up @@ -647,7 +679,8 @@ static void detach_groups(struct config_group *group)
* try using vfs_mkdir. Just a thought.
*/
static int create_default_group(struct config_group *parent_group,
struct config_group *group)
struct config_group *group,
struct configfs_fragment *frag)
{
int ret;
struct configfs_dirent *sd;
Expand All @@ -663,7 +696,7 @@ static int create_default_group(struct config_group *parent_group,
d_add(child, NULL);

ret = configfs_attach_group(&parent_group->cg_item,
&group->cg_item, child);
&group->cg_item, child, frag);
if (!ret) {
sd = child->d_fsdata;
sd->s_type |= CONFIGFS_USET_DEFAULT;
Expand All @@ -677,13 +710,14 @@ static int create_default_group(struct config_group *parent_group,
return ret;
}

static int populate_groups(struct config_group *group)
static int populate_groups(struct config_group *group,
struct configfs_fragment *frag)
{
struct config_group *new_group;
int ret = 0;

list_for_each_entry(new_group, &group->default_groups, group_entry) {
ret = create_default_group(group, new_group);
ret = create_default_group(group, new_group, frag);
if (ret) {
detach_groups(group);
break;
Expand Down Expand Up @@ -797,11 +831,12 @@ static void link_group(struct config_group *parent_group, struct config_group *g
*/
static int configfs_attach_item(struct config_item *parent_item,
struct config_item *item,
struct dentry *dentry)
struct dentry *dentry,
struct configfs_fragment *frag)
{
int ret;

ret = configfs_create_dir(item, dentry);
ret = configfs_create_dir(item, dentry, frag);
if (!ret) {
ret = populate_attrs(item);
if (ret) {
Expand Down Expand Up @@ -831,12 +866,13 @@ static void configfs_detach_item(struct config_item *item)

static int configfs_attach_group(struct config_item *parent_item,
struct config_item *item,
struct dentry *dentry)
struct dentry *dentry,
struct configfs_fragment *frag)
{
int ret;
struct configfs_dirent *sd;

ret = configfs_attach_item(parent_item, item, dentry);
ret = configfs_attach_item(parent_item, item, dentry, frag);
if (!ret) {
sd = dentry->d_fsdata;
sd->s_type |= CONFIGFS_USET_DIR;
Expand All @@ -852,7 +888,7 @@ static int configfs_attach_group(struct config_item *parent_item,
*/
inode_lock_nested(d_inode(dentry), I_MUTEX_CHILD);
configfs_adjust_dir_dirent_depth_before_populate(sd);
ret = populate_groups(to_config_group(item));
ret = populate_groups(to_config_group(item), frag);
if (ret) {
configfs_detach_item(item);
d_inode(dentry)->i_flags |= S_DEAD;
Expand Down Expand Up @@ -1247,6 +1283,7 @@ static int configfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode
struct configfs_dirent *sd;
const struct config_item_type *type;
struct module *subsys_owner = NULL, *new_item_owner = NULL;
struct configfs_fragment *frag;
char *name;

sd = dentry->d_parent->d_fsdata;
Expand All @@ -1265,6 +1302,12 @@ static int configfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode
goto out;
}

frag = new_fragment();
if (!frag) {
ret = -ENOMEM;
goto out;
}

/* Get a working ref for the duration of this function */
parent_item = configfs_get_config_item(dentry->d_parent);
type = parent_item->ci_type;
Expand Down Expand Up @@ -1367,9 +1410,9 @@ static int configfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode
spin_unlock(&configfs_dirent_lock);

if (group)
ret = configfs_attach_group(parent_item, item, dentry);
ret = configfs_attach_group(parent_item, item, dentry, frag);
else
ret = configfs_attach_item(parent_item, item, dentry);
ret = configfs_attach_item(parent_item, item, dentry, frag);

spin_lock(&configfs_dirent_lock);
sd->s_type &= ~CONFIGFS_USET_IN_MKDIR;
Expand Down Expand Up @@ -1406,6 +1449,7 @@ static int configfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode
* reference.
*/
config_item_put(parent_item);
put_fragment(frag);

out:
return ret;
Expand Down Expand Up @@ -1574,7 +1618,7 @@ static int configfs_dir_open(struct inode *inode, struct file *file)
*/
err = -ENOENT;
if (configfs_dirent_is_ready(parent_sd)) {
file->private_data = configfs_new_dirent(parent_sd, NULL, 0);
file->private_data = configfs_new_dirent(parent_sd, NULL, 0, NULL);
if (IS_ERR(file->private_data))
err = PTR_ERR(file->private_data);
else
Expand Down Expand Up @@ -1732,29 +1776,36 @@ int configfs_register_group(struct config_group *parent_group,
{
struct configfs_subsystem *subsys = parent_group->cg_subsys;
struct dentry *parent;
struct configfs_fragment *frag;
int ret;

frag = new_fragment();
if (!frag)
return -ENOMEM;

mutex_lock(&subsys->su_mutex);
link_group(parent_group, group);
mutex_unlock(&subsys->su_mutex);

parent = parent_group->cg_item.ci_dentry;

inode_lock_nested(d_inode(parent), I_MUTEX_PARENT);
ret = create_default_group(parent_group, group);
ret = create_default_group(parent_group, group, frag);
if (ret)
goto err_out;

spin_lock(&configfs_dirent_lock);
configfs_dir_set_ready(group->cg_item.ci_dentry->d_fsdata);
spin_unlock(&configfs_dirent_lock);
inode_unlock(d_inode(parent));
put_fragment(frag);
return 0;
err_out:
inode_unlock(d_inode(parent));
mutex_lock(&subsys->su_mutex);
unlink_group(group);
mutex_unlock(&subsys->su_mutex);
put_fragment(frag);
return ret;
}
EXPORT_SYMBOL(configfs_register_group);
Expand Down Expand Up @@ -1842,10 +1893,17 @@ int configfs_register_subsystem(struct configfs_subsystem *subsys)
struct dentry *dentry;
struct dentry *root;
struct configfs_dirent *sd;
struct configfs_fragment *frag;

frag = new_fragment();
if (!frag)
return -ENOMEM;

root = configfs_pin_fs();
if (IS_ERR(root))
if (IS_ERR(root)) {
put_fragment(frag);
return PTR_ERR(root);
}

if (!group->cg_item.ci_name)
group->cg_item.ci_name = group->cg_item.ci_namebuf;
Expand All @@ -1861,7 +1919,7 @@ int configfs_register_subsystem(struct configfs_subsystem *subsys)
d_add(dentry, NULL);

err = configfs_attach_group(sd->s_element, &group->cg_item,
dentry);
dentry, frag);
if (err) {
BUG_ON(d_inode(dentry));
d_drop(dentry);
Expand All @@ -1879,6 +1937,7 @@ int configfs_register_subsystem(struct configfs_subsystem *subsys)
unlink_group(group);
configfs_release_fs();
}
put_fragment(frag);

return err;
}
Expand Down
4 changes: 2 additions & 2 deletions fs/configfs/file.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -488,7 +488,7 @@ int configfs_create_file(struct config_item * item, const struct configfs_attrib

inode_lock_nested(d_inode(dir), I_MUTEX_NORMAL);
error = configfs_make_dirent(parent_sd, NULL, (void *) attr, mode,
CONFIGFS_ITEM_ATTR);
CONFIGFS_ITEM_ATTR, parent_sd->s_frag);
inode_unlock(d_inode(dir));

return error;
Expand All @@ -510,7 +510,7 @@ int configfs_create_bin_file(struct config_item *item,

inode_lock_nested(dir->d_inode, I_MUTEX_NORMAL);
error = configfs_make_dirent(parent_sd, NULL, (void *) bin_attr, mode,
CONFIGFS_ITEM_BIN_ATTR);
CONFIGFS_ITEM_BIN_ATTR, parent_sd->s_frag);
inode_unlock(dir->d_inode);

return error;
Expand Down

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