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sysfs: add sysfs_dirent->s_parent

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Add sysfs_dirent->s_parent.  With this patch, each sd points to and
holds a reference to its parent.  This allows walking sysfs tree
without referencing sd->s_dentry which can go away anytime if the user
doesn't control when it's deleted.

sd->s_parent is initialized and parent is referenced in
sysfs_attach_dirent().  Reference to parent is released when the sd is
released, so as long as reference to a sd is held, s_parent can be
followed.

dentry walk in sysfs_readdir() is convereted to s_parent walk.

This will be used to reimplement symlink such that it uses only
sysfs_dirent tree.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Tejun Heo 2007-06-14 03:45:14 +09:00 committed by Greg Kroah-Hartman
parent a26cd7226c
commit 13b3086d2e
3 changed files with 25 additions and 7 deletions
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30
fs/sysfs/dir.c
View File

@ -47,6 +47,11 @@ static void sysfs_free_ino(ino_t ino)
void release_sysfs_dirent(struct sysfs_dirent * sd)
{
struct sysfs_dirent *parent_sd;
repeat:
parent_sd = sd->s_parent;
if (sd->s_type & SYSFS_KOBJ_LINK) {
struct sysfs_symlink * sl = sd->s_element;
kfree(sl->link_name);
@ -56,6 +61,10 @@ void release_sysfs_dirent(struct sysfs_dirent * sd)
kfree(sd->s_iattr);
sysfs_free_ino(sd->s_ino);
kmem_cache_free(sysfs_dir_cachep, sd);
sd = parent_sd;
if (sd && atomic_dec_and_test(&sd->s_count))
goto repeat;
}
static void sysfs_d_iput(struct dentry * dentry, struct inode * inode)
@ -119,8 +128,10 @@ void sysfs_attach_dirent(struct sysfs_dirent *sd,
dentry->d_op = &sysfs_dentry_ops;
}
if (parent_sd)
if (parent_sd) {
sd->s_parent = sysfs_get(parent_sd);
list_add(&sd->s_sibling, &parent_sd->s_children);
}
}
/*
@ -571,7 +582,10 @@ static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir)
i++;
/* fallthrough */
case 1:
ino = parent_ino(dentry);
if (parent_sd->s_parent)
ino = parent_sd->s_parent->s_ino;
else
ino = parent_sd->s_ino;
if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)
break;
filp->f_pos++;
@ -688,13 +702,13 @@ int sysfs_make_shadowed_dir(struct kobject *kobj,
struct dentry *sysfs_create_shadow_dir(struct kobject *kobj)
{
struct dentry *dir = kobj->dentry;
struct inode *inode = dir->d_inode;
struct dentry *parent = dir->d_parent;
struct sysfs_dirent *parent_sd = parent->d_fsdata;
struct dentry *shadow;
struct sysfs_dirent *sd;
struct dentry *parent, *dir, *shadow;
struct inode *inode;
dir = kobj->dentry;
inode = dir->d_inode;
parent = dir->d_parent;
shadow = ERR_PTR(-EINVAL);
if (!sysfs_is_shadowed_inode(inode))
goto out;
@ -706,6 +720,8 @@ struct dentry *sysfs_create_shadow_dir(struct kobject *kobj)
sd = sysfs_new_dirent(kobj, inode->i_mode, SYSFS_DIR);
if (!sd)
goto nomem;
/* point to parent_sd but don't attach to it */
sd->s_parent = sysfs_get(parent_sd);
sysfs_attach_dirent(sd, NULL, shadow);
d_instantiate(shadow, igrab(inode));

1
fs/sysfs/mount.c
View File

@ -28,6 +28,7 @@ static const struct super_operations sysfs_ops = {
};
static struct sysfs_dirent sysfs_root = {
.s_count = ATOMIC_INIT(1),
.s_sibling = LIST_HEAD_INIT(sysfs_root.s_sibling),
.s_children = LIST_HEAD_INIT(sysfs_root.s_children),
.s_element = NULL,

1
fs/sysfs/sysfs.h
View File

@ -1,5 +1,6 @@
struct sysfs_dirent {
atomic_t s_count;
struct sysfs_dirent * s_parent;
struct list_head s_sibling;
struct list_head s_children;
void * s_element;