[email protected] wrote:
This patch adds the main containers framework - the container
filesystem, and the basic structures for tracking membership and
associating subsystem state objects to tasks.
[snip]
+*** notify_on_release is disabled in the current patch set. It may be
+*** reactivated in a future patch in a less-intrusive manner
+
Won't this break user space tools for cpusets?
[snip]
+See kernel/container.c for more details.
+
+Subsystems can take/release the container_mutex via the functions
+container_lock()/container_unlock(), and can
+take/release the callback_mutex via the functions
+container_lock()/container_unlock().
+
Hmm.. looks like a documentation error. Both mutex's are obtained through
container_lock/container_unlock ?
+Accessing a task's container pointer may be done in the following ways:
+- while holding container_mutex
+- while holding the task's alloc_lock (via task_lock())
+- inside an rcu_read_lock() section via rcu_dereference()
+
container_mutex() and task_lock() can be used for changing the pointer?
Could you please explain this a bit further.
[snip]
+int populate(struct container_subsys *ss, struct container *cont)
+LL=none
+
+Called after creation of a container to allow a subsystem to populate
+the container directory with file entries. The subsystem should make
+calls to container_add_file() with objects of type cftype (see
+include/linux/container.h for details). Note that although this
+method can return an error code, the error code is currently not
+always handled well.
We needed the equivalent of container_remove_file() to be called
if container_add_file() failed.
[snip]
+struct container {
+ unsigned long flags; /* "unsigned long" so bitops work */
+
+ /* count users of this container. >0 means busy, but doesn't
+ * necessarily indicate the number of tasks in the
+ * container */
+ atomic_t count;
+
+ /*
+ * We link our 'sibling' struct into our parent's 'children'.
+ * Our children link their 'sibling' into our 'children'.
+ */
+ struct list_head sibling; /* my parent's children */
+ struct list_head children; /* my children */
+
+ struct container *parent; /* my parent */
+ struct dentry *dentry; /* container fs entry */
+
+ /* Private pointers for each registered subsystem */
+ struct container_subsys_state *subsys[CONTAINER_SUBSYS_COUNT];
+
+ struct containerfs_root *root;
+ struct container *top_container;
+};
Can't we derive the top_container from containerfs_root?
+
+/* struct cftype:
+ *
+ * The files in the container filesystem mostly have a very simple read/write
+ * handling, some common function will take care of it. Nevertheless some cases
+ * (read tasks) are special and therefore I define this structure for every
+ * kind of file.
+ *
+ *
+ * When reading/writing to a file:
+ * - the container to use in file->f_dentry->d_parent->d_fsdata
+ * - the 'cftype' of the file is file->f_dentry->d_fsdata
+ */
+
+struct inode;
+#define MAX_CFTYPE_NAME 64
+struct cftype {
+ /* By convention, the name should begin with the name of the
+ * subsystem, followed by a period */
+ char name[MAX_CFTYPE_NAME];
+ int private;
+ int (*open) (struct inode *inode, struct file *file);
+ ssize_t (*read) (struct container *cont, struct cftype *cft,
+ struct file *file,
+ char __user *buf, size_t nbytes, loff_t *ppos);
+ u64 (*read_uint) (struct container *cont, struct cftype *cft);
Is this a new callback, a specialization of the read() callback?
+ ssize_t (*write) (struct container *cont, struct cftype *cft,
+ struct file *file,
+ const char __user *buf, size_t nbytes, loff_t *ppos);
+ int (*release) (struct inode *inode, struct file *file);
+};
+
[snip]
--
Warm Regards,
Balbir Singh
Linux Technology Center
IBM, ISTL
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