[PATCH 56/61] sysfs: use sysfs_mutex to protect the sysfs_dirent tree

From: Greg Kroah-Hartman
Date: Wed Jul 11 2007 - 19:59:54 EST

From: Tejun Heo <htejun@xxxxxxxxx>

As kobj sysfs dentries and inodes are gonna be made reclaimable,
i_mutex can't be used to protect sysfs_dirent tree. Use sysfs_mutex
globally instead. As the whole tree is protected with sysfs_mutex,
there is no reason to keep sysfs_rename_sem. Drop it.

While at it, add docbook comments to functions which require
sysfs_mutex locking.

Signed-off-by: Tejun Heo <htejun@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
---
fs/sysfs/dir.c | 101 ++++++++++++++++++++++++++++++++++++---------------
fs/sysfs/file.c | 31 ++++++++--------
fs/sysfs/inode.c | 11 ++----
fs/sysfs/symlink.c | 51 +++++++++++++-------------
fs/sysfs/sysfs.h | 2 +-
5 files changed, 116 insertions(+), 80 deletions(-)

diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index 1b56434..9fc8558 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -14,7 +14,7 @@
#include <asm/semaphore.h>
#include "sysfs.h"

-DECLARE_RWSEM(sysfs_rename_sem);
+DEFINE_MUTEX(sysfs_mutex);
spinlock_t sysfs_assoc_lock = SPIN_LOCK_UNLOCKED;

static spinlock_t sysfs_ino_lock = SPIN_LOCK_UNLOCKED;
@@ -28,7 +28,7 @@ static DEFINE_IDA(sysfs_ino_ida);
* sd->s_parent->s_children.
*
* Locking:
- * mutex_lock(sd->s_parent->dentry->d_inode->i_mutex)
+ * mutex_lock(sysfs_mutex)
*/
static void sysfs_link_sibling(struct sysfs_dirent *sd)
{
@@ -47,7 +47,7 @@ static void sysfs_link_sibling(struct sysfs_dirent *sd)
* sd->s_parent->s_children.
*
* Locking:
- * mutex_lock(sd->s_parent->dentry->d_inode->i_mutex)
+ * mutex_lock(sysfs_mutex)
*/
static void sysfs_unlink_sibling(struct sysfs_dirent *sd)
{
@@ -215,6 +215,9 @@ void release_sysfs_dirent(struct sysfs_dirent * sd)
struct sysfs_dirent *parent_sd;

repeat:
+ /* Moving/renaming is always done while holding reference.
+ * sd->s_parent won't change beneath us.
+ */
parent_sd = sd->s_parent;

if (sysfs_type(sd) == SYSFS_KOBJ_LINK)
@@ -291,6 +294,17 @@ struct sysfs_dirent *sysfs_new_dirent(const char *name, umode_t mode, int type)
return NULL;
}

+/**
+ * sysfs_attach_dentry - associate sysfs_dirent with dentry
+ * @sd: target sysfs_dirent
+ * @dentry: dentry to associate
+ *
+ * Associate @sd with @dentry. This is protected by
+ * sysfs_assoc_lock to avoid race with sysfs_d_iput().
+ *
+ * LOCKING:
+ * mutex_lock(sysfs_mutex)
+ */
static void sysfs_attach_dentry(struct sysfs_dirent *sd, struct dentry *dentry)
{
dentry->d_op = &sysfs_dentry_ops;
@@ -304,6 +318,17 @@ static void sysfs_attach_dentry(struct sysfs_dirent *sd, struct dentry *dentry)
d_rehash(dentry);
}

+/**
+ * sysfs_attach_dirent - attach sysfs_dirent to its parent and dentry
+ * @sd: sysfs_dirent to attach
+ * @parent_sd: parent to attach to (optional)
+ * @dentry: dentry to be associated to @sd (optional)
+ *
+ * Attach @sd to @parent_sd and/or @dentry. Both are optional.
+ *
+ * LOCKING:
+ * mutex_lock(sysfs_mutex)
+ */
void sysfs_attach_dirent(struct sysfs_dirent *sd,
struct sysfs_dirent *parent_sd, struct dentry *dentry)
{
@@ -324,7 +349,7 @@ void sysfs_attach_dirent(struct sysfs_dirent *sd,
* Look for sysfs_dirent with name @name under @parent_sd.
*
* LOCKING:
- * mutex_lock(parent->i_mutex)
+ * mutex_lock(sysfs_mutex)
*
* RETURNS:
* Pointer to sysfs_dirent if found, NULL if not.
@@ -349,7 +374,7 @@ struct sysfs_dirent *sysfs_find_dirent(struct sysfs_dirent *parent_sd,
* it if found.
*
* LOCKING:
- * Kernel thread context (may sleep)
+ * Kernel thread context (may sleep). Grabs sysfs_mutex.
*
* RETURNS:
* Pointer to sysfs_dirent if found, NULL if not.
@@ -359,10 +384,10 @@ struct sysfs_dirent *sysfs_get_dirent(struct sysfs_dirent *parent_sd,
{
struct sysfs_dirent *sd;

- mutex_lock(&parent_sd->s_dentry->d_inode->i_mutex);
+ mutex_lock(&sysfs_mutex);
sd = sysfs_find_dirent(parent_sd, name);
sysfs_get(sd);
- mutex_unlock(&parent_sd->s_dentry->d_inode->i_mutex);
+ mutex_unlock(&sysfs_mutex);

return sd;
}
@@ -408,14 +433,20 @@ static int create_dir(struct kobject *kobj, struct sysfs_dirent *parent_sd,
}

/* link in */
+ mutex_lock(&sysfs_mutex);
+
error = -EEXIST;
- if (sysfs_find_dirent(parent_sd, name))
+ if (sysfs_find_dirent(parent_sd, name)) {
+ mutex_unlock(&sysfs_mutex);
goto out_iput;
+ }

sysfs_instantiate(dentry, inode);
inc_nlink(parent->d_inode);
sysfs_attach_dirent(sd, parent_sd, dentry);

+ mutex_unlock(&sysfs_mutex);
+
*p_sd = sd;
error = 0;
goto out_unlock; /* pin directory dentry in core */
@@ -493,6 +524,8 @@ static struct dentry * sysfs_lookup(struct inode *dir, struct dentry *dentry,
if (!inode)
return ERR_PTR(-ENOMEM);

+ mutex_lock(&sysfs_mutex);
+
if (inode->i_state & I_NEW) {
/* initialize inode according to type */
switch (sysfs_type(sd)) {
@@ -516,6 +549,8 @@ static struct dentry * sysfs_lookup(struct inode *dir, struct dentry *dentry,
sysfs_instantiate(dentry, inode);
sysfs_attach_dentry(sd, dentry);

+ mutex_unlock(&sysfs_mutex);
+
return NULL;
}

@@ -526,17 +561,13 @@ const struct inode_operations sysfs_dir_inode_operations = {

static void remove_dir(struct sysfs_dirent *sd)
{
- struct dentry *parent = sd->s_parent->s_dentry;
-
- mutex_lock(&parent->d_inode->i_mutex);
-
+ mutex_lock(&sysfs_mutex);
sysfs_unlink_sibling(sd);
sd->s_flags |= SYSFS_FLAG_REMOVED;
+ mutex_unlock(&sysfs_mutex);

pr_debug(" o %s removing done\n", sd->s_name);

- mutex_unlock(&parent->d_inode->i_mutex);
-
sysfs_drop_dentry(sd);
sysfs_deactivate(sd);
sysfs_put(sd);
@@ -552,15 +583,12 @@ static void __sysfs_remove_dir(struct sysfs_dirent *dir_sd)
{
struct sysfs_dirent *removed = NULL;
struct sysfs_dirent **pos;
- struct dentry *dir;

if (!dir_sd)
return;

- dir = dir_sd->s_dentry;
-
pr_debug("sysfs %s: removing dir\n", dir_sd->s_name);
- mutex_lock(&dir->d_inode->i_mutex);
+ mutex_lock(&sysfs_mutex);
pos = &dir_sd->s_children;
while (*pos) {
struct sysfs_dirent *sd = *pos;
@@ -573,7 +601,7 @@ static void __sysfs_remove_dir(struct sysfs_dirent *dir_sd)
} else
pos = &(*pos)->s_sibling;
}
- mutex_unlock(&dir->d_inode->i_mutex);
+ mutex_unlock(&sysfs_mutex);

while (removed) {
struct sysfs_dirent *sd = removed;
@@ -621,7 +649,6 @@ int sysfs_rename_dir(struct kobject *kobj, struct sysfs_dirent *new_parent_sd,
if (!new_parent_sd)
return -EFAULT;

- down_write(&sysfs_rename_sem);
mutex_lock(&new_parent->d_inode->i_mutex);

new_dentry = lookup_one_len(new_name, new_parent, strlen(new_name));
@@ -661,12 +688,16 @@ int sysfs_rename_dir(struct kobject *kobj, struct sysfs_dirent *new_parent_sd,
d_add(new_dentry, NULL);
d_move(sd->s_dentry, new_dentry);

+ mutex_lock(&sysfs_mutex);
+
sysfs_unlink_sibling(sd);
sysfs_get(new_parent_sd);
sysfs_put(sd->s_parent);
sd->s_parent = new_parent_sd;
sysfs_link_sibling(sd);

+ mutex_unlock(&sysfs_mutex);
+
error = 0;
goto out_unlock;

@@ -678,7 +709,6 @@ int sysfs_rename_dir(struct kobject *kobj, struct sysfs_dirent *new_parent_sd,
dput(new_dentry);
out_unlock:
mutex_unlock(&new_parent->d_inode->i_mutex);
- up_write(&sysfs_rename_sem);
return error;
}

@@ -717,12 +747,15 @@ again:
dput(new_dentry);

/* Remove from old parent's list and insert into new parent's list. */
+ mutex_lock(&sysfs_mutex);
+
sysfs_unlink_sibling(sd);
sysfs_get(new_parent_sd);
sysfs_put(sd->s_parent);
sd->s_parent = new_parent_sd;
sysfs_link_sibling(sd);

+ mutex_unlock(&sysfs_mutex);
out:
mutex_unlock(&new_parent_dentry->d_inode->i_mutex);
mutex_unlock(&old_parent_dentry->d_inode->i_mutex);
@@ -736,11 +769,12 @@ static int sysfs_dir_open(struct inode *inode, struct file *file)
struct sysfs_dirent * parent_sd = dentry->d_fsdata;
struct sysfs_dirent * sd;

- mutex_lock(&dentry->d_inode->i_mutex);
sd = sysfs_new_dirent("_DIR_", 0, 0);
- if (sd)
+ if (sd) {
+ mutex_lock(&sysfs_mutex);
sysfs_attach_dirent(sd, parent_sd, NULL);
- mutex_unlock(&dentry->d_inode->i_mutex);
+ mutex_unlock(&sysfs_mutex);
+ }

file->private_data = sd;
return sd ? 0 : -ENOMEM;
@@ -748,12 +782,11 @@ static int sysfs_dir_open(struct inode *inode, struct file *file)

static int sysfs_dir_close(struct inode *inode, struct file *file)
{
- struct dentry * dentry = file->f_path.dentry;
struct sysfs_dirent * cursor = file->private_data;

- mutex_lock(&dentry->d_inode->i_mutex);
+ mutex_lock(&sysfs_mutex);
sysfs_unlink_sibling(cursor);
- mutex_unlock(&dentry->d_inode->i_mutex);
+ mutex_unlock(&sysfs_mutex);

release_sysfs_dirent(cursor);

@@ -794,6 +827,8 @@ static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir)
i++;
/* fallthrough */
default:
+ mutex_lock(&sysfs_mutex);
+
pos = &parent_sd->s_children;
while (*pos != cursor)
pos = &(*pos)->s_sibling;
@@ -826,6 +861,8 @@ static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir)
/* put cursor back in */
cursor->s_sibling = *pos;
*pos = cursor;
+
+ mutex_unlock(&sysfs_mutex);
}
return 0;
}
@@ -834,7 +871,6 @@ static loff_t sysfs_dir_lseek(struct file * file, loff_t offset, int origin)
{
struct dentry * dentry = file->f_path.dentry;

- mutex_lock(&dentry->d_inode->i_mutex);
switch (origin) {
case 1:
offset += file->f_pos;
@@ -842,10 +878,11 @@ static loff_t sysfs_dir_lseek(struct file * file, loff_t offset, int origin)
if (offset >= 0)
break;
default:
- mutex_unlock(&file->f_path.dentry->d_inode->i_mutex);
return -EINVAL;
}
if (offset != file->f_pos) {
+ mutex_lock(&sysfs_mutex);
+
file->f_pos = offset;
if (file->f_pos >= 2) {
struct sysfs_dirent *sd = dentry->d_fsdata;
@@ -866,8 +903,10 @@ static loff_t sysfs_dir_lseek(struct file * file, loff_t offset, int origin)
cursor->s_sibling = *pos;
*pos = cursor;
}
+
+ mutex_unlock(&sysfs_mutex);
}
- mutex_unlock(&dentry->d_inode->i_mutex);
+
return offset;
}

@@ -933,7 +972,9 @@ struct sysfs_dirent *sysfs_create_shadow_dir(struct kobject *kobj)
sd->s_elem.dir.kobj = kobj;
/* point to parent_sd but don't attach to it */
sd->s_parent = sysfs_get(parent_sd);
+ mutex_lock(&sysfs_mutex);
sysfs_attach_dirent(sd, NULL, shadow);
+ mutex_unlock(&sysfs_mutex);

d_instantiate(shadow, igrab(inode));
inc_nlink(inode);
diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index 20703b9..d0deed3 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -415,29 +415,28 @@ const struct file_operations sysfs_file_operations = {
int sysfs_add_file(struct sysfs_dirent *dir_sd, const struct attribute *attr,
int type)
{
- struct dentry *dir = dir_sd->s_dentry;
umode_t mode = (attr->mode & S_IALLUGO) | S_IFREG;
struct sysfs_dirent *sd;
- int error = 0;

- mutex_lock(&dir->d_inode->i_mutex);
+ sd = sysfs_new_dirent(attr->name, mode, type);
+ if (!sd)
+ return -ENOMEM;
+ sd->s_elem.attr.attr = (void *)attr;

- if (sysfs_find_dirent(dir_sd, attr->name)) {
- error = -EEXIST;
- goto out_unlock;
- }
+ mutex_lock(&sysfs_mutex);

- sd = sysfs_new_dirent(attr->name, mode, type);
- if (!sd) {
- error = -ENOMEM;
- goto out_unlock;
+ if (!sysfs_find_dirent(dir_sd, attr->name)) {
+ sysfs_attach_dirent(sd, dir_sd, NULL);
+ sd = NULL;
}
- sd->s_elem.attr.attr = (void *)attr;
- sysfs_attach_dirent(sd, dir_sd, NULL);

- out_unlock:
- mutex_unlock(&dir->d_inode->i_mutex);
- return error;
+ mutex_unlock(&sysfs_mutex);
+
+ if (sd) {
+ sysfs_put(sd);
+ return -EEXIST;
+ }
+ return 0;
}


diff --git a/fs/sysfs/inode.c b/fs/sysfs/inode.c
index e4c2393..d439c0b 100644
--- a/fs/sysfs/inode.c
+++ b/fs/sysfs/inode.c
@@ -277,20 +277,14 @@ void sysfs_drop_dentry(struct sysfs_dirent *sd)

int sysfs_hash_and_remove(struct sysfs_dirent *dir_sd, const char *name)
{
- struct dentry *dir;
struct sysfs_dirent **pos, *sd;
int found = 0;

if (!dir_sd)
return -ENOENT;

- dir = dir_sd->s_dentry;
+ mutex_lock(&sysfs_mutex);

- if (dir->d_inode == NULL)
- /* no inode means this hasn't been made visible yet */
- return -ENOENT;
-
- mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_PARENT);
for (pos = &dir_sd->s_children; *pos; pos = &(*pos)->s_sibling) {
sd = *pos;

@@ -304,7 +298,8 @@ int sysfs_hash_and_remove(struct sysfs_dirent *dir_sd, const char *name)
break;
}
}
- mutex_unlock(&dir->d_inode->i_mutex);
+
+ mutex_unlock(&sysfs_mutex);

if (!found)
return -ENOENT;
diff --git a/fs/sysfs/symlink.c b/fs/sysfs/symlink.c
index cbd95a4..683316f 100644
--- a/fs/sysfs/symlink.c
+++ b/fs/sysfs/symlink.c
@@ -44,20 +44,6 @@ static void fill_object_path(struct sysfs_dirent *sd, char *buffer, int length)
}
}

-static int sysfs_add_link(struct sysfs_dirent * parent_sd, const char * name,
- struct sysfs_dirent * target_sd)
-{
- struct sysfs_dirent * sd;
-
- sd = sysfs_new_dirent(name, S_IFLNK|S_IRWXUGO, SYSFS_KOBJ_LINK);
- if (!sd)
- return -ENOMEM;
-
- sd->s_elem.symlink.target_sd = target_sd;
- sysfs_attach_dirent(sd, parent_sd, NULL);
- return 0;
-}
-
/**
* sysfs_create_link - create symlink between two objects.
* @kobj: object whose directory we're creating the link in.
@@ -68,7 +54,8 @@ int sysfs_create_link(struct kobject * kobj, struct kobject * target, const char
{
struct sysfs_dirent *parent_sd = NULL;
struct sysfs_dirent *target_sd = NULL;
- int error = -EEXIST;
+ struct sysfs_dirent *sd = NULL;
+ int error;

BUG_ON(!name);

@@ -78,8 +65,9 @@ int sysfs_create_link(struct kobject * kobj, struct kobject * target, const char
} else
parent_sd = kobj->sd;

+ error = -EFAULT;
if (!parent_sd)
- return -EFAULT;
+ goto out_put;

/* target->sd can go away beneath us but is protected with
* sysfs_assoc_lock. Fetch target_sd from it.
@@ -89,17 +77,30 @@ int sysfs_create_link(struct kobject * kobj, struct kobject * target, const char
target_sd = sysfs_get(target->sd);
spin_unlock(&sysfs_assoc_lock);

+ error = -ENOENT;
if (!target_sd)
- return -ENOENT;
+ goto out_put;
+
+ error = -ENOMEM;
+ sd = sysfs_new_dirent(name, S_IFLNK|S_IRWXUGO, SYSFS_KOBJ_LINK);
+ if (!sd)
+ goto out_put;
+ sd->s_elem.symlink.target_sd = target_sd;

- mutex_lock(&parent_sd->s_dentry->d_inode->i_mutex);
- if (!sysfs_find_dirent(parent_sd, name))
- error = sysfs_add_link(parent_sd, name, target_sd);
- mutex_unlock(&parent_sd->s_dentry->d_inode->i_mutex);
+ mutex_lock(&sysfs_mutex);
+ error = -EEXIST;
+ if (sysfs_find_dirent(parent_sd, name))
+ goto out_unlock;
+ sysfs_attach_dirent(sd, parent_sd, NULL);
+ mutex_unlock(&sysfs_mutex);

- if (error)
- sysfs_put(target_sd);
+ return 0;

+ out_unlock:
+ mutex_unlock(&sysfs_mutex);
+ out_put:
+ sysfs_put(target_sd);
+ sysfs_put(sd);
return error;
}

@@ -144,9 +145,9 @@ static int sysfs_getlink(struct dentry *dentry, char * path)
struct sysfs_dirent *target_sd = sd->s_elem.symlink.target_sd;
int error;

- down_read(&sysfs_rename_sem);
+ mutex_lock(&sysfs_mutex);
error = sysfs_get_target_path(parent_sd, target_sd, path);
- up_read(&sysfs_rename_sem);
+ mutex_unlock(&sysfs_mutex);

return error;
}
diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
index 4572677..2605161 100644
--- a/fs/sysfs/sysfs.h
+++ b/fs/sysfs/sysfs.h
@@ -82,7 +82,7 @@ extern void sysfs_drop_dentry(struct sysfs_dirent *sd);
extern int sysfs_setattr(struct dentry *dentry, struct iattr *iattr);

extern spinlock_t sysfs_assoc_lock;
-extern struct rw_semaphore sysfs_rename_sem;
+extern struct mutex sysfs_mutex;
extern struct super_block * sysfs_sb;
extern const struct file_operations sysfs_dir_operations;
extern const struct file_operations sysfs_file_operations;
--
1.5.2.2

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