Commit a4e8b912 authored by Tejun Heo's avatar Tejun Heo Committed by Greg Kroah-Hartman
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sysfs: move sysfs file poll implementation to sysfs_open_dirent 



Sysfs file poll implementation is scattered over sysfs and kobject.
Event numbering is done in sysfs_dirent but wait itself is done on
kobject.  This not only unecessarily bloats both kobject and
sysfs_dirent but is also buggy - if a sysfs_dirent is removed while
there still are pollers, the associaton betwen the kobject and
sysfs_dirent breaks and kobject may be freed with the pollers still
sleeping on it.

This patch moves whole poll implementation into sysfs_open_dirent.
Each time a sysfs_open_dirent is created, event number restarts from 1
and pollers sleep on sysfs_open_dirent.  As event sequence number is
meaningless without any open file and pollers should have open file
and thus sysfs_open_dirent, this ephemeral event counting works and is
a saner implementation.

This patch fixes the dnagling sleepers bug and reduces the sizes of
kobject and sysfs_dirent by one pointer.

Signed-off-by: default avatarTejun Heo <htejun@gmail.com>
Acked-by: default avatarCornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 85a4ffad

fs/sysfs/dir.c

+0 −1
Original line number Diff line number Diff line
@@ -318,7 +318,6 @@ struct sysfs_dirent *sysfs_new_dirent(const char *name, umode_t mode, int type) 


	atomic_set(&sd->s_count, 1);

	atomic_set(&sd->s_active, 0);

	atomic_set(&sd->s_event, 1);



	sd->s_name = name;

	sd->s_mode = mode;

fs/sysfs/file.c

+19 −6
Original line number Diff line number Diff line
@@ -62,6 +62,8 @@ static spinlock_t sysfs_open_dirent_lock = SPIN_LOCK_UNLOCKED; 


struct sysfs_open_dirent {

	atomic_t		refcnt;

	atomic_t		event;

	wait_queue_head_t	poll;

	struct list_head	buffers; /* goes through sysfs_buffer.list */

};
@@ -104,7 +106,7 @@ static int fill_read_buffer(struct dentry * dentry, struct sysfs_buffer * buffer 
	if (!sysfs_get_active_two(attr_sd))

		return -ENODEV;



	buffer->event = atomic_read(&attr_sd->s_event);

	buffer->event = atomic_read(&attr_sd->s_attr.open->event);

	count = ops->show(kobj, attr_sd->s_attr.attr, buffer->page);



	sysfs_put_active_two(attr_sd);
@@ -301,6 +303,8 @@ static int sysfs_get_open_dirent(struct sysfs_dirent *sd, 
		return -ENOMEM;



	atomic_set(&new_od->refcnt, 0);

	atomic_set(&new_od->event, 1);

	init_waitqueue_head(&new_od->poll);

	INIT_LIST_HEAD(&new_od->buffers);

	goto retry;

}
@@ -443,17 +447,17 @@ static unsigned int sysfs_poll(struct file *filp, poll_table *wait) 
{

	struct sysfs_buffer * buffer = filp->private_data;

	struct sysfs_dirent *attr_sd = filp->f_path.dentry->d_fsdata;

	struct kobject *kobj = attr_sd->s_parent->s_dir.kobj;

	struct sysfs_open_dirent *od = attr_sd->s_attr.open;



	/* need parent for the kobj, grab both */

	if (!sysfs_get_active_two(attr_sd))

		goto trigger;



	poll_wait(filp, &kobj->poll, wait);

	poll_wait(filp, &od->poll, wait);



	sysfs_put_active_two(attr_sd);



	if (buffer->event != atomic_read(&attr_sd->s_event))

	if (buffer->event != atomic_read(&od->event))

		goto trigger;



	return 0;
@@ -474,8 +478,17 @@ void sysfs_notify(struct kobject *k, char *dir, char *attr) 
	if (sd && attr)

		sd = sysfs_find_dirent(sd, attr);

	if (sd) {

		atomic_inc(&sd->s_event);

		wake_up_interruptible(&k->poll);

		struct sysfs_open_dirent *od;



		spin_lock(&sysfs_open_dirent_lock);



		od = sd->s_attr.open;

		if (od) {

			atomic_inc(&od->event);

			wake_up_interruptible(&od->poll);

		}



		spin_unlock(&sysfs_open_dirent_lock);

	}



	mutex_unlock(&sysfs_mutex);

fs/sysfs/sysfs.h

+0 −1
Original line number Diff line number Diff line
@@ -46,7 +46,6 @@ struct sysfs_dirent { 
	ino_t			s_ino;

	umode_t			s_mode;

	struct iattr		*s_iattr;

	atomic_t		s_event;

};



#define SD_DEACTIVATED_BIAS		INT_MIN

include/linux/kobject.h

+0 −1
Original line number Diff line number Diff line
@@ -66,7 +66,6 @@ struct kobject { 
	struct kset		* kset;

	struct kobj_type	* ktype;

	struct sysfs_dirent	* sd;

	wait_queue_head_t	poll;

};



extern int kobject_set_name(struct kobject *, const char *, ...)

lib/kobject.c

+0 −1
Original line number Diff line number Diff line
@@ -131,7 +131,6 @@ void kobject_init(struct kobject * kobj) 
		return;

	kref_init(&kobj->kref);

	INIT_LIST_HEAD(&kobj->entry);

	init_waitqueue_head(&kobj->poll);

	kobj->kset = kset_get(kobj->kset);

}

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