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Date:	Sat,  7 Nov 2009 23:27:08 -0800
From:	"Eric W. Biederman" <ebiederm@...ssion.com>
To:	Greg Kroah-Hartman <gregkh@...e.de>
Cc:	Kay Sievers <kay.sievers@...y.org>, Greg KH <greg@...ah.com>,
	linux-kernel@...r.kernel.org, Tejun Heo <tj@...nel.org>,
	Cornelia Huck <cornelia.huck@...ibm.com>,
	linux-fsdevel@...r.kernel.org,
	Eric Dumazet <eric.dumazet@...il.com>,
	Benjamin LaHaise <bcrl@...et.ca>,
	Serge Hallyn <serue@...ibm.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"Eric W. Biederman" <ebiederm@...stanetworks.com>
Subject: [PATCH 10/15] sysfs: In sysfs_chmod_file lazily propagate the mode change.

From: Eric W. Biederman <ebiederm@...ssion.com>

Now that sysfs_getattr and sysfs_permission refresh the vfs
inode there is no need to immediatly push the mode change
into the vfs cache.  Reducing the amount of work needed and
simplifying the locking.

Acked-by: Tejun Heo <tj@...nel.org>
Acked-by: Serge Hallyn <serue@...ibm.com>
Signed-off-by: Eric W. Biederman <ebiederm@...stanetworks.com>
---
 fs/sysfs/file.c |   31 ++++++++-----------------------
 1 files changed, 8 insertions(+), 23 deletions(-)

diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index faa1a80..dc30d9e 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -579,38 +579,23 @@ EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
  */
 int sysfs_chmod_file(struct kobject *kobj, struct attribute *attr, mode_t mode)
 {
-	struct sysfs_dirent *victim_sd = NULL;
-	struct dentry *victim = NULL;
-	struct inode * inode;
+	struct sysfs_dirent *sd;
 	struct iattr newattrs;
 	int rc;
 
-	rc = -ENOENT;
-	victim_sd = sysfs_get_dirent(kobj->sd, attr->name);
-	if (!victim_sd)
-		goto out;
+	mutex_lock(&sysfs_mutex);
 
-	mutex_lock(&sysfs_rename_mutex);
-	victim = sysfs_get_dentry(victim_sd);
-	mutex_unlock(&sysfs_rename_mutex);
-	if (IS_ERR(victim)) {
-		rc = PTR_ERR(victim);
-		victim = NULL;
+	rc = -ENOENT;
+	sd = sysfs_find_dirent(kobj->sd, attr->name);
+	if (!sd)
 		goto out;
-	}
-
-	inode = victim->d_inode;
 
-	mutex_lock(&inode->i_mutex);
-
-	newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
+	newattrs.ia_mode = (mode & S_IALLUGO) | (sd->s_mode & ~S_IALLUGO);
 	newattrs.ia_valid = ATTR_MODE;
-	rc = sysfs_setattr(victim, &newattrs);
+	rc = sysfs_sd_setattr(sd, &newattrs);
 
-	mutex_unlock(&inode->i_mutex);
  out:
-	dput(victim);
-	sysfs_put(victim_sd);
+	mutex_unlock(&sysfs_mutex);
 	return rc;
 }
 EXPORT_SYMBOL_GPL(sysfs_chmod_file);
-- 
1.6.5.2.143.g8cc62

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