[Patch] cpusets: fix race in cpuset_add_file()

[Simon Derr]

Hi,

This patch fixes a missing down()/up() pair in cpuset_add_file().

Without this patch, sometimes it is possible to have two duplicate 
dentries for a single file of a cpuset, with one of them being invalid, 
and thus the file is present but cannot be opened...

Something like:

# cd /dev/cpuset/foo
# ls
ls: cpus: No such file or directory



The patch also removes comments that
1/are now bogus with this fix applied
2/were not respected anyway



Signed-off-by: Simon Derr <simon.derr@xxxxxxxx>

Index: mm4/kernel/cpuset.c
===================================================================
--- mm4.orig/kernel/cpuset.c	2004-09-13 09:43:02.000000000 +0200
+++ mm4/kernel/cpuset.c	2004-09-16 15:46:21.847401360 +0200
@@ -956,13 +956,12 @@ static int cpuset_create_dir(struct cpus
 	return error;
 }

-/* MUST be called with dir->d_inode->i_sem held */
-
 static int cpuset_add_file(struct dentry *dir, const struct cftype *cft)
 {
 	struct dentry *dentry;
 	int error;

+	down(&dir->d_inode->i_sem);
 	dentry = cpuset_get_dentry(dir, cft->name);
 	if (!IS_ERR(dentry)) {
 		error = cpuset_create_file(dentry, 0644 | S_IFREG);
@@ -971,6 +970,7 @@ static int cpuset_add_file(struct dentry
 		dput(dentry);
 	} else
 		error = PTR_ERR(dentry);
+	up(&dir->d_inode->i_sem);
 	return error;
 }

@@ -1162,7 +1162,6 @@ static struct cftype cft_notify_on_relea
 	.private = FILE_NOTIFY_ON_RELEASE,
 };

-/* MUST be called with ->d_inode->i_sem held */
 static int cpuset_populate_dir(struct dentry *cs_dentry)
 {
 	int err;
-
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