[PATCH 14/21] sysfs: implement kobj_sysfs_assoc_lock

From: Tejun Heo
Date: Sat Apr 28 2007 - 09:45:33 EST

kobj->dentry can go away anytime unless the user controls when the
associated sysfs node is deleted. This patch implements
kobj_sysfs_assoc_lock which protects kobj->dentry. This will be used
to maintain kobj based API when converting sysfs to use sysfs_dirent
tree instead of dentry/kobject.

Note that this lock belongs to kobject/driver-model not sysfs. Once
sysfs is converted to not use kobject in its interface, this can be
removed from sysfs.

This is in preparation of object reference simplification.

Signed-off-by: Tejun Heo <htejun@xxxxxxxxx>
fs/sysfs/dir.c | 8 +++++++-
fs/sysfs/sysfs.h | 1 +
2 files changed, 8 insertions(+), 1 deletions(-)

diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index 0050de9..2fddf8a 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -14,6 +14,7 @@
#include "sysfs.h"

+spinlock_t kobj_sysfs_assoc_lock = SPIN_LOCK_UNLOCKED;

static spinlock_t sysfs_ino_lock = SPIN_LOCK_UNLOCKED;
static DEFINE_IDA(sysfs_ino_ida);
@@ -408,8 +409,13 @@ static void __sysfs_remove_dir(struct dentry *dentry)

void sysfs_remove_dir(struct kobject * kobj)
- __sysfs_remove_dir(kobj->dentry);
+ struct dentry *d = kobj->dentry;
+ spin_lock(&kobj_sysfs_assoc_lock);
kobj->dentry = NULL;
+ spin_unlock(&kobj_sysfs_assoc_lock);
+ __sysfs_remove_dir(d);

int sysfs_rename_dir(struct kobject * kobj, struct dentry *new_parent,
diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
index 14ca866..e37b6e8 100644
--- a/fs/sysfs/sysfs.h
+++ b/fs/sysfs/sysfs.h
@@ -61,6 +61,7 @@ extern void sysfs_remove_subdir(struct dentry *);
extern void sysfs_drop_dentry(struct sysfs_dirent *sd, struct dentry *parent);
extern int sysfs_setattr(struct dentry *dentry, struct iattr *iattr);

+extern spinlock_t kobj_sysfs_assoc_lock;
extern struct rw_semaphore sysfs_rename_sem;
extern struct super_block * sysfs_sb;
extern const struct file_operations sysfs_dir_operations;

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