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Date: Thu, 6 Aug 2009 17:40:02 +0800
From: tom.leiming@...il.com
To: greg@...ah.com
Cc: linux-kernel@...r.kernel.org, kay.sievers@...y.org,
akpm@...ux-foundation.org, Ming Lei <tom.leiming@...il.com>
Subject: [PATCH 1/2] driver core: introduce devtmpfs_wait_for_dev() v1
From: Ming Lei <tom.leiming@...il.com>
This patch introduces devtmpfs_wait_for_dev(), which is based on devtmpfs
and can be used to remove polling for root device before mounting rootfs.
This patch also gives a generic and simple way to wait for a device in
kernel mode based on devtmpfs.
This version takes Kay Sievers's suggestion: pass relative path to
devtmpfs_wait_for_dev(), for devtmpfs has no clue where it is
mounted.
Signed-off-by: Ming Lei <tom.leiming@...il.com>
---
drivers/base/devtmpfs.c | 50 +++++++++++++++++++++++++++++++++++++++++++++++
include/linux/device.h | 7 ++++++
2 files changed, 57 insertions(+), 0 deletions(-)
diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c
index 51c410f..3a04252 100644
--- a/drivers/base/devtmpfs.c
+++ b/drivers/base/devtmpfs.c
@@ -30,6 +30,9 @@ static int dev_mount = 1;
static int dev_mount;
#endif
+static DECLARE_WAIT_QUEUE_HEAD(devtmpfs_waitqueue);
+
+
static int __init mount_param(char *str)
{
dev_mount = simple_strtoul(str, NULL, 0);
@@ -178,6 +181,10 @@ int devtmpfs_create_node(struct device *dev)
path_put(&nd.path);
out:
+ /*notify others that we have created a dev node*/
+ if (!err)
+ wake_up(&devtmpfs_waitqueue);
+
kfree(tmp);
revert_creds(curr_cred);
return err;
@@ -310,6 +317,49 @@ out:
return err;
}
+static int devtmpfs_query_dev(const char *nodename)
+{
+ const struct cred *curr_cred;
+ struct nameidata nd;
+ struct dentry *dentry;
+ int err;
+
+ if (!dev_mnt)
+ return -ENOENT;
+
+ curr_cred = override_creds(&init_cred);
+ err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,
+ nodename, LOOKUP_PARENT, &nd);
+ if (err)
+ goto out;
+
+ mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
+ dentry = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len);
+ if (!IS_ERR(dentry)) {
+ if (dentry->d_inode)
+ err = 0;
+ else
+ err = -ENOENT;
+ dput(dentry);
+ } else {
+ err = PTR_ERR(dentry);
+ }
+ mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
+
+ path_put(&nd.path);
+out:
+ revert_creds(curr_cred);
+ return err;
+}
+
+int devtmpfs_wait_for_dev(const char *dev_name, unsigned long seconds)
+{
+
+ return wait_event_timeout(devtmpfs_waitqueue,
+ devtmpfs_query_dev(dev_name) == 0,
+ seconds*HZ);
+}
+
/*
* If configured, or requested by the commandline, devtmpfs will be
* auto-mounted after the kernel mounted the root filesystem.
diff --git a/include/linux/device.h b/include/linux/device.h
index 65f5b5a..1fa1b19 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -557,10 +557,17 @@ extern void wait_for_device_probe(void);
extern int devtmpfs_create_node(struct device *dev);
extern int devtmpfs_delete_node(struct device *dev);
extern int devtmpfs_mount(const char *mountpoint);
+extern int devtmpfs_wait_for_dev(const char *dev_path,
+ unsigned long seconds);
#else
static inline int devtmpfs_create_node(struct device *dev) { return 0; }
static inline int devtmpfs_delete_node(struct device *dev) { return 0; }
static inline int devtmpfs_mount(const char *mountpoint) { return 0; }
+static inline int devtmpfs_wait_for_dev(const char *dev_path,
+ unsigned long seconds)
+{
+ return 0;
+}
#endif
/* drivers/base/power/shutdown.c */
--
1.6.0.GIT
--
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