sysfs: use sysfs_mutex to protect the sysfs_dirent tree
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@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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 @@
* 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 @@
* 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 @@
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 @@
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 @@
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 @@
* 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 @@
* 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 *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 @@
}
/* 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 @@
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 @@
sysfs_instantiate(dentry, inode);
sysfs_attach_dentry(sd, dentry);
+ mutex_unlock(&sysfs_mutex);
+
return NULL;
}
@@ -526,17 +561,13 @@
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 @@
{
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 @@
} 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 @@
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 @@
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 @@
dput(new_dentry);
out_unlock:
mutex_unlock(&new_parent->d_inode->i_mutex);
- up_write(&sysfs_rename_sem);
return error;
}
@@ -717,12 +747,15 @@
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 @@
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_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 @@
i++;
/* fallthrough */
default:
+ mutex_lock(&sysfs_mutex);
+
pos = &parent_sd->s_children;
while (*pos != cursor)
pos = &(*pos)->s_sibling;
@@ -826,6 +861,8 @@
/* put cursor back in */
cursor->s_sibling = *pos;
*pos = cursor;
+
+ mutex_unlock(&sysfs_mutex);
}
return 0;
}
@@ -834,7 +871,6 @@
{
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 @@
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 @@
cursor->s_sibling = *pos;
*pos = cursor;
}
+
+ mutex_unlock(&sysfs_mutex);
}
- mutex_unlock(&dentry->d_inode->i_mutex);
+
return offset;
}
@@ -933,7 +972,9 @@
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);