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Subject[PATCH 14/33] task-containersv11-basic-task-container-framework-containers-fix-refcount-bug
Fix a reference counting bug in cgroupfs

As part of the extraction of cpusetfs to cgroupfs, a call to
cpuset_get_dentry() was lost (justified by the fact that the dentry in
question was now being passed down by the caller). Since
cpuset_get_dentry() called lookup_one_len(), this resulted in a reference
count being missed from the directory dentry.

This patch removes cgroup_get_dentry() and replaces it with direct calls
to lookup_one_len(); the initialization of cgroupfs dentry ops is done
now in cgroup_create_file() at dentry creation time.

Signed-off-by: Paul Menage <menage@google.com>

---
kernel/cgroup.c | 24 +++++++-----------------
1 file changed, 7 insertions(+), 17 deletions(-)
Index: linux-2.6.23-rc4-mm1-new/kernel/cgroup.c
===================================================================
--- linux-2.6.23-rc4-mm1-new.orig/kernel/cgroup.c
+++ linux-2.6.23-rc4-mm1-new/kernel/cgroup.c
@@ -604,19 +604,6 @@ static void cgroup_diput(struct dentry *
iput(inode);
}

-static struct dentry *cgroup_get_dentry(struct dentry *parent,
- const char *name)
-{
- struct dentry *d = lookup_one_len(name, parent, strlen(name));
- static struct dentry_operations cgroup_dops = {
- .d_iput = cgroup_diput,
- };
-
- if (!IS_ERR(d))
- d->d_op = &cgroup_dops;
- return d;
-}
-
static void remove_dir(struct dentry *d)
{
struct dentry *parent = dget(d->d_parent);
@@ -1507,6 +1494,10 @@ static struct inode_operations cgroup_di
static int cgroup_create_file(struct dentry *dentry, int mode,
struct super_block *sb)
{
+ static struct dentry_operations cgroup_dops = {
+ .d_iput = cgroup_diput,
+ };
+
struct inode *inode;

if (!dentry)
@@ -1532,7 +1523,7 @@ static int cgroup_create_file(struct den
inode->i_size = 0;
inode->i_fop = &cgroup_file_operations;
}
-
+ dentry->d_op = &cgroup_dops;
d_instantiate(dentry, inode);
dget(dentry); /* Extra count - pin the dentry in core */
return 0;
@@ -1553,13 +1544,12 @@ static int cgroup_create_dir(struct cgro
int error = 0;

parent = cont->parent->dentry;
- if (IS_ERR(dentry))
- return PTR_ERR(dentry);
error = cgroup_create_file(dentry, S_IFDIR | mode, cont->root->sb);
if (!error) {
dentry->d_fsdata = cont;
inc_nlink(parent->d_inode);
cont->dentry = dentry;
+ dget(dentry);
}
dput(dentry);

@@ -1581,7 +1571,7 @@ int cgroup_add_file(struct cgroup *cont,
}
strcat(name, cft->name);
BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex));
- dentry = cgroup_get_dentry(dir, name);
+ dentry = lookup_one_len(name, dir, strlen(name));
if (!IS_ERR(dentry)) {
error = cgroup_create_file(dentry, 0644 | S_IFREG,
cont->root->sb);
--
-
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