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kernfs: remove KERNFS_ACTIVE_REF and add kernfs_lockdep() 

There currently are two mechanisms gating active ref lockdep
annotations - KERNFS_LOCKDEP flag and KERNFS_ACTIVE_REF type mask.
The former disables lockdep annotations in kernfs_get/put_active()
while the latter disables all of kernfs_deactivate().

While KERNFS_ACTIVE_REF also behaves as an optimization to skip the
deactivation step for non-file nodes, the benefit is marginal and it
needlessly diverges code paths.  Let's drop KERNFS_ACTIVE_REF.

While at it, add a test helper kernfs_lockdep() to test KERNFS_LOCKDEP
flag so that it's more convenient and the related code can be compiled
out when not enabled.

v2: Refreshed on top of ("kernfs: make kernfs_deactivate() honor
    KERNFS_LOCKDEP flag").  As the earlier patch already added
    KERNFS_LOCKDEP tests to kernfs_deactivate(), those additions are
    dropped from this patch and the existing ones are simply converted
    to kernfs_lockdep().

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Tejun Heo 2014-02-03 14:02:59 -05:00 committed by Greg Kroah-Hartman
parent 988cd7afb3
commit 182fd64b66
2 changed files with 13 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
fs/kernfs/dir.c
View File

@ -22,6 +22,15 @@ DEFINE_MUTEX(kernfs_mutex);
#define rb_to_kn(X) rb_entry((X), struct kernfs_node, rb) #define rb_to_kn(X) rb_entry((X), struct kernfs_node, rb)
static bool kernfs_lockdep(struct kernfs_node *kn)
{
#ifdef CONFIG_DEBUG_LOCK_ALLOC
return kn->flags & KERNFS_LOCKDEP;
#else
return false;
#endif
}
/** /**
* kernfs_name_hash * kernfs_name_hash
* @name: Null terminated string to hash * @name: Null terminated string to hash
@ -144,7 +153,7 @@ struct kernfs_node *kernfs_get_active(struct kernfs_node *kn)
if (!atomic_inc_unless_negative(&kn->active)) if (!atomic_inc_unless_negative(&kn->active))
return NULL; return NULL;
if (kn->flags & KERNFS_LOCKDEP) if (kernfs_lockdep(kn))
rwsem_acquire_read(&kn->dep_map, 0, 1, _RET_IP_); rwsem_acquire_read(&kn->dep_map, 0, 1, _RET_IP_);
return kn; return kn;
} }
@ -164,7 +173,7 @@ void kernfs_put_active(struct kernfs_node *kn)
if (unlikely(!kn)) if (unlikely(!kn))
return; return;
if (kn->flags & KERNFS_LOCKDEP) if (kernfs_lockdep(kn))
rwsem_release(&kn->dep_map, 1, _RET_IP_); rwsem_release(&kn->dep_map, 1, _RET_IP_);
v = atomic_dec_return(&kn->active); v = atomic_dec_return(&kn->active);
if (likely(v != KN_DEACTIVATED_BIAS)) if (likely(v != KN_DEACTIVATED_BIAS))
@ -190,16 +199,13 @@ static void kernfs_deactivate(struct kernfs_node *kn)
lockdep_assert_held(&kernfs_mutex); lockdep_assert_held(&kernfs_mutex);
BUG_ON(!(kn->flags & KERNFS_REMOVED)); BUG_ON(!(kn->flags & KERNFS_REMOVED));
if (!(kernfs_type(kn) & KERNFS_ACTIVE_REF))
return;
/* only the first invocation on @kn should deactivate it */ /* only the first invocation on @kn should deactivate it */
if (atomic_read(&kn->active) >= 0) if (atomic_read(&kn->active) >= 0)
atomic_add(KN_DEACTIVATED_BIAS, &kn->active); atomic_add(KN_DEACTIVATED_BIAS, &kn->active);
mutex_unlock(&kernfs_mutex); mutex_unlock(&kernfs_mutex);
if (kn->flags & KERNFS_LOCKDEP) { if (kernfs_lockdep(kn)) {
rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_); rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_);
if (atomic_read(&kn->active) != KN_DEACTIVATED_BIAS) if (atomic_read(&kn->active) != KN_DEACTIVATED_BIAS)
lock_contended(&kn->dep_map, _RET_IP_); lock_contended(&kn->dep_map, _RET_IP_);
@ -209,7 +215,7 @@ static void kernfs_deactivate(struct kernfs_node *kn)
wait_event(root->deactivate_waitq, wait_event(root->deactivate_waitq,
atomic_read(&kn->active) == KN_DEACTIVATED_BIAS); atomic_read(&kn->active) == KN_DEACTIVATED_BIAS);
if (kn->flags & KERNFS_LOCKDEP) { if (kernfs_lockdep(kn)) {
lock_acquired(&kn->dep_map, _RET_IP_); lock_acquired(&kn->dep_map, _RET_IP_);
rwsem_release(&kn->dep_map, 1, _RET_IP_); rwsem_release(&kn->dep_map, 1, _RET_IP_);
} }

1
include/linux/kernfs.h
View File

@ -35,7 +35,6 @@ enum kernfs_node_type {
}; };
#define KERNFS_TYPE_MASK 0x000f #define KERNFS_TYPE_MASK 0x000f
#define KERNFS_ACTIVE_REF KERNFS_FILE
#define KERNFS_FLAG_MASK ~KERNFS_TYPE_MASK #define KERNFS_FLAG_MASK ~KERNFS_TYPE_MASK
enum kernfs_node_flag { enum kernfs_node_flag {