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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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