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sysfs: Support sysfs_notify from atomic context with new sysfs_notify_dirent

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Support sysfs_notify from atomic context with new sysfs_notify_dirent

sysfs_notify currently takes sysfs_mutex.
This means that it cannot be called in atomic context.
sysfs_mutex  is sometimes held over a malloc (sysfs_rename_dir)
so it can block on low memory.

In md I want to be able to notify on a sysfs attribute from
atomic context, and I don't want to block on low memory because I
could be in the writeout path for freeing memory.

So:
 - export the "sysfs_dirent" structure along with sysfs_get, sysfs_put
   and sysfs_get_dirent so I can get the sysfs_dirent that I want to
   notify on and hold it in an md structure.
 - split sysfs_notify_dirent out of sysfs_notify so the sysfs_dirent
   can be notified on with no blocking (just a spinlock).

Signed-off-by: Neil Brown <neilb@suse.de>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Neil Brown 2008-07-16 08:58:04 +10:00 • committed by Greg Kroah-Hartman
parent ec748fa9ed
commit f1282c844e
5 changed files with 62 additions and 18 deletions
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31
fs/sysfs/file.c
View file

@ -453,6 +453,22 @@ static unsigned int sysfs_poll(struct file *filp, poll_table *wait)
return POLLERR|POLLPRI;
}
void sysfs_notify_dirent(struct sysfs_dirent *sd)
{
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);
}
EXPORT_SYMBOL_GPL(sysfs_notify_dirent);
void sysfs_notify(struct kobject *k, char *dir, char *attr)
{
struct sysfs_dirent *sd = k->sd;
@ -463,19 +479,8 @@ void sysfs_notify(struct kobject *k, char *dir, char *attr)
sd = sysfs_find_dirent(sd, dir);
if (sd && attr)
sd = sysfs_find_dirent(sd, attr);
if (sd) {
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);
}
if (sd)
sysfs_notify_dirent(sd);
mutex_unlock(&sysfs_mutex);
}