[PATCH 23/41] sysfs, kernfs: revamp sysfs_dirent active_ref lockdep annotation

Tejun Heo
2013-11-23T22:28:52Z

Currently, sysfs_dirent active_ref lockdep annotation uses
attribute->[s]key as the lockdep key, which forces
kernfs_create_file_ns() to assume that sysfs_dirent->priv is pointing
to a struct attribute which may not be true for non-sysfs users. This
patch restructures the lockdep annotation such that

* kernfs_ops contains lockdep_key which is used by default for files
created kernfs_create_file_ns().

* kernfs_create_file_ns_key() is introduced which takes an extra @key
argument. The created file will use the specified key for
active_ref lockdep annotation. If NULL is specified, lockdep for
the file is disabled.

* sysfs_add_file_mode_ns() is updated to use
kernfs_create_file_ns_key() with the appropriate key from the
attribute or NULL if ignore_lockdep is set.

This makes the lockdep annotation properly contained in kernfs while
allowing sysfs to cleanly keep its current behavior. This patch
doesn't introduce any behavior differences.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
fs/sysfs/dir.c | 4 ++--
fs/sysfs/file.c | 35 ++++++++++++++++++++++++-----------
fs/sysfs/sysfs.h | 32 +-------------------------------
include/linux/kernfs.h | 37 +++++++++++++++++++++++++++++--------
4 files changed, 56 insertions(+), 52 deletions(-)

diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index e88e9a9..8f2d577 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -150,7 +150,7 @@ struct sysfs_dirent *sysfs_get_active(struct sysfs_dirent *sd)
if (!atomic_inc_unless_negative(&sd->s_active))
return NULL;

- if (likely(!sysfs_ignore_lockdep(sd)))
+ if (sd->s_flags & SYSFS_FLAG_LOCKDEP)
rwsem_acquire_read(&sd->dep_map, 0, 1, _RET_IP_);
return sd;
}
@@ -169,7 +169,7 @@ void sysfs_put_active(struct sysfs_dirent *sd)
if (unlikely(!sd))
return;

- if (likely(!sysfs_ignore_lockdep(sd)))
+ if (sd->s_flags & SYSFS_FLAG_LOCKDEP)
rwsem_release(&sd->dep_map, 1, _RET_IP_);
v = atomic_dec_return(&sd->s_active);
if (likely(v != SD_DEACTIVATED_BIAS))
diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index a68cbef..e4eca28 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -58,7 +58,7 @@ static struct sysfs_open_file *sysfs_of(struct file *file)
*/
static const struct kernfs_ops *kernfs_ops(struct sysfs_dirent *sd)
{
- if (!sysfs_ignore_lockdep(sd))
+ if (sd->s_flags & SYSFS_FLAG_LOCKDEP)
lockdep_assert_held(sd);
return sd->s_attr.ops;
}
@@ -71,7 +71,7 @@ static const struct sysfs_ops *sysfs_file_ops(struct sysfs_dirent *sd)
{
struct kobject *kobj = sd->s_parent->priv;

- if (!sysfs_ignore_lockdep(sd))
+ if (sd->s_flags & SYSFS_FLAG_LOCKDEP)
lockdep_assert_held(sd);
return kobj->ktype ? kobj->ktype->sysfs_ops : NULL;
}
@@ -942,6 +942,7 @@ int sysfs_add_file_mode_ns(struct sysfs_dirent *dir_sd,
const struct attribute *attr, bool is_bin,
umode_t mode, const void *ns)
{
+ struct lock_class_key *key = NULL;
const struct kernfs_ops *ops;
struct sysfs_dirent *sd;
loff_t size;
@@ -981,8 +982,12 @@ int sysfs_add_file_mode_ns(struct sysfs_dirent *dir_sd,
size = battr->size;
}

- sd = kernfs_create_file_ns(dir_sd, attr->name, mode, size,
- ops, (void *)attr, ns);
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+ if (!attr->ignore_lockdep)
+ key = attr->key ?: (struct lock_class_key *)&attr->skey;
+#endif
+ sd = kernfs_create_file_ns_key(dir_sd, attr->name, mode, size,
+ ops, (void *)attr, ns, key);
if (IS_ERR(sd)) {
if (PTR_ERR(sd) == -EEXIST)
sysfs_warn_dup(dir_sd, attr->name);
@@ -992,7 +997,7 @@ int sysfs_add_file_mode_ns(struct sysfs_dirent *dir_sd,
}

/**
- * kernfs_create_file_ns - create a file
+ * kernfs_create_file_ns_key - create a file
* @parent: directory to create the file in
* @name: name of the file
* @mode: mode of the file
@@ -1000,14 +1005,16 @@ int sysfs_add_file_mode_ns(struct sysfs_dirent *dir_sd,
* @ops: kernfs operations for the file
* @priv: private data for the file
* @ns: optional namespace tag of the file
+ * @key: lockdep key for the file's active_ref, %NULL to disable lockdep
*
* Returns the created node on success, ERR_PTR() value on error.
*/
-struct sysfs_dirent *kernfs_create_file_ns(struct sysfs_dirent *parent,
- const char *name,
- umode_t mode, loff_t size,
- const struct kernfs_ops *ops,
- void *priv, const void *ns)
+struct sysfs_dirent *kernfs_create_file_ns_key(struct sysfs_dirent *parent,
+ const char *name,
+ umode_t mode, loff_t size,
+ const struct kernfs_ops *ops,
+ void *priv, const void *ns,
+ struct lock_class_key *key)
{
struct sysfs_addrm_cxt acxt;
struct sysfs_dirent *sd;
@@ -1022,7 +1029,13 @@ struct sysfs_dirent *kernfs_create_file_ns(struct sysfs_dirent *parent,
sd->s_attr.size = size;
sd->s_ns = ns;
sd->priv = priv;
- sysfs_dirent_init_lockdep(sd);
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+ if (key) {
+ lockdep_init_map(&sd->dep_map, "s_active", key, 0);
+ sd->s_flags |= SYSFS_FLAG_LOCKDEP;
+ }
+#endif

/*
* sd->s_attr.ops is accesible only while holding active ref. We
diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
index c86456c..e93f8b8 100644
--- a/fs/sysfs/sysfs.h
+++ b/fs/sysfs/sysfs.h
@@ -92,43 +92,13 @@ struct sysfs_dirent {
#define SYSFS_FLAG_NS 0x0020
#define SYSFS_FLAG_HAS_SEQ_SHOW 0x0040
#define SYSFS_FLAG_HAS_MMAP 0x0080
+#define SYSFS_FLAG_LOCKDEP 0x0100

static inline unsigned int sysfs_type(struct sysfs_dirent *sd)
{
return sd->s_flags & SYSFS_TYPE_MASK;
}

-#ifdef CONFIG_DEBUG_LOCK_ALLOC
-
-#define sysfs_dirent_init_lockdep(sd) \
-do { \
- struct attribute *attr = sd->priv; \
- struct lock_class_key *key = attr->key; \
- if (!key) \
- key = &attr->skey; \
- \
- lockdep_init_map(&sd->dep_map, "s_active", key, 0); \
-} while (0)
-
-/* Test for attributes that want to ignore lockdep for read-locking */
-static inline bool sysfs_ignore_lockdep(struct sysfs_dirent *sd)
-{
- struct attribute *attr = sd->priv;
-
- return sysfs_type(sd) == SYSFS_KOBJ_ATTR && attr->ignore_lockdep;
-}
-
-#else
-
-#define sysfs_dirent_init_lockdep(sd) do {} while (0)
-
-static inline bool sysfs_ignore_lockdep(struct sysfs_dirent *sd)
-{
- return true;
-}
-
-#endif
-
/*
* Context structure to be used while adding/removing nodes.
*/
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index f20796e..105d09d 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -11,6 +11,7 @@
#include <linux/err.h>
#include <linux/list.h>
#include <linux/mutex.h>
+#include <linux/lockdep.h>

struct file;
struct iattr;
@@ -62,6 +63,10 @@ struct kernfs_ops {
loff_t off);

int (*mmap)(struct sysfs_open_file *of, struct vm_area_struct *vma);
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+ struct lock_class_key lockdep_key;
+#endif
};

#ifdef CONFIG_SYSFS
@@ -69,11 +74,12 @@ struct kernfs_ops {
struct sysfs_dirent *kernfs_create_dir_ns(struct sysfs_dirent *parent,
const char *name, void *priv,
const void *ns);
-struct sysfs_dirent *kernfs_create_file_ns(struct sysfs_dirent *parent,
- const char *name,
- umode_t mode, loff_t size,
- const struct kernfs_ops *ops,
- void *priv, const void *ns);
+struct sysfs_dirent *kernfs_create_file_ns_key(struct sysfs_dirent *parent,
+ const char *name,
+ umode_t mode, loff_t size,
+ const struct kernfs_ops *ops,
+ void *priv, const void *ns,
+ struct lock_class_key *key);
struct sysfs_dirent *kernfs_create_link(struct sysfs_dirent *parent,
const char *name,
struct sysfs_dirent *target);
@@ -94,9 +100,10 @@ kernfs_create_dir_ns(struct sysfs_dirent *parent, const char *name, void *priv,
{ return ERR_PTR(-ENOSYS); }

static inline struct sysfs_dirent *
-kernfs_create_file_ns(struct sysfs_dirent *parent, const char *name,
- umode_t mode, loff_t size, const struct kernfs_ops *ops,
- void *priv, const void *ns)
+kernfs_create_file_ns_key(struct sysfs_dirent *parent, const char *name,
+ umode_t mode, loff_t size,
+ const struct kernfs_ops *ops, void *priv,
+ const void *ns, struct lock_class_key *key)
{ return ERR_PTR(-ENOSYS); }

static inline struct sysfs_dirent *
@@ -132,6 +139,20 @@ kernfs_create_dir(struct sysfs_dirent *parent, const char *name, void *priv)
}

static inline struct sysfs_dirent *
+kernfs_create_file_ns(struct sysfs_dirent *parent, const char *name,
+ umode_t mode, loff_t size, const struct kernfs_ops *ops,
+ void *priv, const void *ns)
+{
+ struct lock_class_key *key = NULL;
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+ key = (struct lock_class_key *)&ops->lockdep_key;
+#endif
+ return kernfs_create_file_ns_key(parent, name, mode, size, ops, priv,
+ ns, key);
+}
+
+static inline struct sysfs_dirent *
kernfs_create_file(struct sysfs_dirent *parent, const char *name, umode_t mode,
loff_t size, const struct kernfs_ops *ops, void *priv)
{
--
1.8.4.2