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sysfs, kernfs: revamp sysfs_dirent active_ref lockdep annotation
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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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Tejun Heo authored and Greg Kroah-Hartman committed Nov 30, 2013
1 parent 2b25a62 commit 517e64f
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Showing 4 changed files with 56 additions and 52 deletions.
4 changes: 2 additions & 2 deletions fs/sysfs/dir.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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;
}
Expand All @@ -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))
Expand Down
35 changes: 24 additions & 11 deletions fs/sysfs/file.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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;
}
Expand All @@ -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;
}
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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);
Expand All @@ -992,22 +997,24 @@ 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
* @size: size of the file
* @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;
Expand All @@ -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
Expand Down
32 changes: 1 addition & 31 deletions fs/sysfs/sysfs.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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.
*/
Expand Down
37 changes: 29 additions & 8 deletions include/linux/kernfs.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,7 @@
#include <linux/err.h>
#include <linux/list.h>
#include <linux/mutex.h>
#include <linux/lockdep.h>

struct file;
struct iattr;
Expand Down Expand Up @@ -62,18 +63,23 @@ 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

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);
Expand All @@ -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 *
Expand Down Expand Up @@ -131,6 +138,20 @@ kernfs_create_dir(struct sysfs_dirent *parent, const char *name, void *priv)
return kernfs_create_dir_ns(parent, name, priv, NULL);
}

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)
Expand Down

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