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: Tejun Heo <htejun@gmail.com>
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index 4ad9422..e301a12 100644 (file)
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -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;

diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index b13ba94..c05f961 100644 (file)
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -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);

diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
index 3adce7d..269c845 100644 (file)
--- a/fs/sysfs/sysfs.h
+++ b/fs/sysfs/sysfs.h
@@ -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

diff --git a/include/linux/kobject.h b/include/linux/kobject.h
index 0777b3f..a8a84fc 100644 (file)
--- a/include/linux/kobject.h
+++ b/include/linux/kobject.h
@@ -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 *, ...)

diff --git a/lib/kobject.c b/lib/kobject.c
index e8181d3..fc6db6b 100644 (file)
--- a/lib/kobject.c
+++ b/lib/kobject.c
@@ -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);
 }