sysfs: Support sysfs_notify from atomic context with new sysfs_notify_dirent
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>
diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index aedaeba..53bc7fc 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -636,6 +636,7 @@
return sd;
}
+EXPORT_SYMBOL_GPL(sysfs_get_dirent);
static int create_dir(struct kobject *kobj, struct sysfs_dirent *parent_sd,
const char *name, struct sysfs_dirent **p_sd)
diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index ce8339c..d0d79e6 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -453,6 +453,22 @@
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 @@
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);
}
diff --git a/fs/sysfs/mount.c b/fs/sysfs/mount.c
index 14f0023..ab343e3 100644
--- a/fs/sysfs/mount.c
+++ b/fs/sysfs/mount.c
@@ -16,6 +16,7 @@
#include <linux/mount.h>
#include <linux/pagemap.h>
#include <linux/init.h>
+#include <linux/module.h>
#include "sysfs.h"
@@ -115,3 +116,17 @@
sysfs_dir_cachep = NULL;
goto out;
}
+
+#undef sysfs_get
+struct sysfs_dirent *sysfs_get(struct sysfs_dirent *sd)
+{
+ return __sysfs_get(sd);
+}
+EXPORT_SYMBOL_GPL(sysfs_get);
+
+#undef sysfs_put
+void sysfs_put(struct sysfs_dirent *sd)
+{
+ __sysfs_put(sd);
+}
+EXPORT_SYMBOL_GPL(sysfs_put);
diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
index a5db496..93c6d6b 100644
--- a/fs/sysfs/sysfs.h
+++ b/fs/sysfs/sysfs.h
@@ -124,7 +124,7 @@
struct sysfs_dirent **p_sd);
void sysfs_remove_subdir(struct sysfs_dirent *sd);
-static inline struct sysfs_dirent *sysfs_get(struct sysfs_dirent *sd)
+static inline struct sysfs_dirent *__sysfs_get(struct sysfs_dirent *sd)
{
if (sd) {
WARN_ON(!atomic_read(&sd->s_count));
@@ -132,12 +132,14 @@
}
return sd;
}
+#define sysfs_get(sd) __sysfs_get(sd)
-static inline void sysfs_put(struct sysfs_dirent *sd)
+static inline void __sysfs_put(struct sysfs_dirent *sd)
{
if (sd && atomic_dec_and_test(&sd->s_count))
release_sysfs_dirent(sd);
}
+#define sysfs_put(sd) __sysfs_put(sd)
/*
* inode.c