[PATCH V4 04/12] kernfs: don't set dentry->d_fsdata

From: Shaohua Li
Date: Wed Jun 28 2017 - 12:30:20 EST

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From: Shaohua Li <shli@xxxxxx>

When working on adding exportfs operations in kernfs, I found it's hard
to initialize dentry->d_fsdata in the exportfs operations. Looks there
is no way to do it without race condition. Look at the kernfs code
closely, there is no point to set dentry->d_fsdata. inode->i_private
already points to kernfs_node, and we can get inode from a dentry. So
this patch just delete the d_fsdata usage.

Acked-by: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Shaohua Li <shli@xxxxxx>
---
fs/kernfs/dir.c | 25 +++++++++----------------
fs/kernfs/file.c | 6 +++---
fs/kernfs/inode.c | 6 +++---
fs/kernfs/kernfs-internal.h | 7 +++++++
fs/kernfs/mount.c | 8 ++------
fs/kernfs/symlink.c | 6 +++---
6 files changed, 27 insertions(+), 31 deletions(-)

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 7be37c8..b61a7ef 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -566,7 +566,7 @@ static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags)
if (d_really_is_negative(dentry))
goto out_bad_unlocked;

- kn = dentry->d_fsdata;
+ kn = kernfs_dentry_node(dentry);
mutex_lock(&kernfs_mutex);

/* The kernfs node has been deactivated */
@@ -574,7 +574,7 @@ static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags)
goto out_bad;

/* The kernfs node has been moved? */
- if (dentry->d_parent->d_fsdata != kn->parent)
+ if (kernfs_dentry_node(dentry->d_parent) != kn->parent)
goto out_bad;

/* The kernfs node has been renamed */
@@ -594,14 +594,8 @@ static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags)
return 0;
}

-static void kernfs_dop_release(struct dentry *dentry)
-{
- kernfs_put(dentry->d_fsdata);
-}
-
const struct dentry_operations kernfs_dops = {
.d_revalidate = kernfs_dop_revalidate,
- .d_release = kernfs_dop_release,
};

/**
@@ -617,8 +611,9 @@ const struct dentry_operations kernfs_dops = {
*/
struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry)
{
- if (dentry->d_sb->s_op == &kernfs_sops)
- return dentry->d_fsdata;
+ if (dentry->d_sb->s_op == &kernfs_sops &&
+ !d_really_is_negative(dentry))
+ return kernfs_dentry_node(dentry);
return NULL;
}

@@ -1056,7 +1051,7 @@ static struct dentry *kernfs_iop_lookup(struct inode *dir,
unsigned int flags)
{
struct dentry *ret;
- struct kernfs_node *parent = dentry->d_parent->d_fsdata;
+ struct kernfs_node *parent = dir->i_private;
struct kernfs_node *kn;
struct inode *inode;
const void *ns = NULL;
@@ -1073,8 +1068,6 @@ static struct dentry *kernfs_iop_lookup(struct inode *dir,
ret = NULL;
goto out_unlock;
}
- kernfs_get(kn);
- dentry->d_fsdata = kn;

/* attach dentry and inode */
inode = kernfs_get_inode(dir->i_sb, kn);
@@ -1111,7 +1104,7 @@ static int kernfs_iop_mkdir(struct inode *dir, struct dentry *dentry,

static int kernfs_iop_rmdir(struct inode *dir, struct dentry *dentry)
{
- struct kernfs_node *kn = dentry->d_fsdata;
+ struct kernfs_node *kn = kernfs_dentry_node(dentry);
struct kernfs_syscall_ops *scops = kernfs_root(kn)->syscall_ops;
int ret;

@@ -1131,7 +1124,7 @@ static int kernfs_iop_rename(struct inode *old_dir, struct dentry *old_dentry,
struct inode *new_dir, struct dentry *new_dentry,
unsigned int flags)
{
- struct kernfs_node *kn = old_dentry->d_fsdata;
+ struct kernfs_node *kn = kernfs_dentry_node(old_dentry);
struct kernfs_node *new_parent = new_dir->i_private;
struct kernfs_syscall_ops *scops = kernfs_root(kn)->syscall_ops;
int ret;
@@ -1644,7 +1637,7 @@ static struct kernfs_node *kernfs_dir_next_pos(const void *ns,
static int kernfs_fop_readdir(struct file *file, struct dir_context *ctx)
{
struct dentry *dentry = file->f_path.dentry;
- struct kernfs_node *parent = dentry->d_fsdata;
+ struct kernfs_node *parent = kernfs_dentry_node(dentry);
struct kernfs_node *pos = file->private_data;
const void *ns = NULL;

diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index ac2dfe0..7f90d4d 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -616,7 +616,7 @@ static void kernfs_put_open_node(struct kernfs_node *kn,

static int kernfs_fop_open(struct inode *inode, struct file *file)
{
- struct kernfs_node *kn = file->f_path.dentry->d_fsdata;
+ struct kernfs_node *kn = inode->i_private;
struct kernfs_root *root = kernfs_root(kn);
const struct kernfs_ops *ops;
struct kernfs_open_file *of;
@@ -768,7 +768,7 @@ static void kernfs_release_file(struct kernfs_node *kn,

static int kernfs_fop_release(struct inode *inode, struct file *filp)
{
- struct kernfs_node *kn = filp->f_path.dentry->d_fsdata;
+ struct kernfs_node *kn = inode->i_private;
struct kernfs_open_file *of = kernfs_of(filp);

if (kn->flags & KERNFS_HAS_RELEASE) {
@@ -835,7 +835,7 @@ void kernfs_drain_open_files(struct kernfs_node *kn)
static unsigned int kernfs_fop_poll(struct file *filp, poll_table *wait)
{
struct kernfs_open_file *of = kernfs_of(filp);
- struct kernfs_node *kn = filp->f_path.dentry->d_fsdata;
+ struct kernfs_node *kn = kernfs_dentry_node(filp->f_path.dentry);
struct kernfs_open_node *on = kn->attr.open;

if (!kernfs_get_active(kn))
diff --git a/fs/kernfs/inode.c b/fs/kernfs/inode.c
index 79cdae4..4c8b510 100644
--- a/fs/kernfs/inode.c
+++ b/fs/kernfs/inode.c
@@ -112,7 +112,7 @@ int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
int kernfs_iop_setattr(struct dentry *dentry, struct iattr *iattr)
{
struct inode *inode = d_inode(dentry);
- struct kernfs_node *kn = dentry->d_fsdata;
+ struct kernfs_node *kn = inode->i_private;
int error;

if (!kn)
@@ -154,7 +154,7 @@ static int kernfs_node_setsecdata(struct kernfs_iattrs *attrs, void **secdata,

ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size)
{
- struct kernfs_node *kn = dentry->d_fsdata;
+ struct kernfs_node *kn = kernfs_dentry_node(dentry);
struct kernfs_iattrs *attrs;

attrs = kernfs_iattrs(kn);
@@ -203,8 +203,8 @@ static void kernfs_refresh_inode(struct kernfs_node *kn, struct inode *inode)
int kernfs_iop_getattr(const struct path *path, struct kstat *stat,
u32 request_mask, unsigned int query_flags)
{
- struct kernfs_node *kn = path->dentry->d_fsdata;
struct inode *inode = d_inode(path->dentry);
+ struct kernfs_node *kn = inode->i_private;

mutex_lock(&kernfs_mutex);
kernfs_refresh_inode(kn, inode);
diff --git a/fs/kernfs/kernfs-internal.h b/fs/kernfs/kernfs-internal.h
index e9c226f..0f260dc 100644
--- a/fs/kernfs/kernfs-internal.h
+++ b/fs/kernfs/kernfs-internal.h
@@ -70,6 +70,13 @@ struct kernfs_super_info {
};
#define kernfs_info(SB) ((struct kernfs_super_info *)(SB->s_fs_info))

+static inline struct kernfs_node *kernfs_dentry_node(struct dentry *dentry)
+{
+ if (d_really_is_negative(dentry))
+ return NULL;
+ return d_inode(dentry)->i_private;
+}
+
extern const struct super_operations kernfs_sops;
extern struct kmem_cache *kernfs_node_cache;

diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c
index 69c48be..acd5426 100644
--- a/fs/kernfs/mount.c
+++ b/fs/kernfs/mount.c
@@ -33,7 +33,7 @@ static int kernfs_sop_remount_fs(struct super_block *sb, int *flags, char *data)

static int kernfs_sop_show_options(struct seq_file *sf, struct dentry *dentry)
{
- struct kernfs_root *root = kernfs_root(dentry->d_fsdata);
+ struct kernfs_root *root = kernfs_root(kernfs_dentry_node(dentry));
struct kernfs_syscall_ops *scops = root->syscall_ops;

if (scops && scops->show_options)
@@ -43,7 +43,7 @@ static int kernfs_sop_show_options(struct seq_file *sf, struct dentry *dentry)

static int kernfs_sop_show_path(struct seq_file *sf, struct dentry *dentry)
{
- struct kernfs_node *node = dentry->d_fsdata;
+ struct kernfs_node *node = kernfs_dentry_node(dentry);
struct kernfs_root *root = kernfs_root(node);
struct kernfs_syscall_ops *scops = root->syscall_ops;

@@ -176,8 +176,6 @@ static int kernfs_fill_super(struct super_block *sb, unsigned long magic)
pr_debug("%s: could not get root dentry!\n", __func__);
return -ENOMEM;
}
- kernfs_get(info->root->kn);
- root->d_fsdata = info->root->kn;
sb->s_root = root;
sb->s_d_op = &kernfs_dops;
return 0;
@@ -283,7 +281,6 @@ struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags,
void kernfs_kill_sb(struct super_block *sb)
{
struct kernfs_super_info *info = kernfs_info(sb);
- struct kernfs_node *root_kn = sb->s_root->d_fsdata;

mutex_lock(&kernfs_mutex);
list_del(&info->node);
@@ -295,7 +292,6 @@ void kernfs_kill_sb(struct super_block *sb)
*/
kill_anon_super(sb);
kfree(info);
- kernfs_put(root_kn);
}

/**
diff --git a/fs/kernfs/symlink.c b/fs/kernfs/symlink.c
index 1684af4..08ccabd 100644
--- a/fs/kernfs/symlink.c
+++ b/fs/kernfs/symlink.c
@@ -98,9 +98,9 @@ static int kernfs_get_target_path(struct kernfs_node *parent,
return 0;
}

-static int kernfs_getlink(struct dentry *dentry, char *path)
+static int kernfs_getlink(struct inode *inode, char *path)
{
- struct kernfs_node *kn = dentry->d_fsdata;
+ struct kernfs_node *kn = inode->i_private;
struct kernfs_node *parent = kn->parent;
struct kernfs_node *target = kn->symlink.target_kn;
int error;
@@ -124,7 +124,7 @@ static const char *kernfs_iop_get_link(struct dentry *dentry,
body = kzalloc(PAGE_SIZE, GFP_KERNEL);
if (!body)
return ERR_PTR(-ENOMEM);
- error = kernfs_getlink(dentry, body);
+ error = kernfs_getlink(inode, body);
if (unlikely(error < 0)) {
kfree(body);
return ERR_PTR(error);
--
2.9.3

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