ipc: fix wrong comments
This patch fixes the wrong / obsolete comments in the ipc code. Also adds
a missing lock around ipc_get_maxid() in shm_get_stat().
Signed-off-by: Nadia Derbey <Nadia.Derbey@bull.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/ipc/util.c b/ipc/util.c
index 49e75ef..fd29246 100644
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -194,7 +194,7 @@
* Requires ipc_ids.mutex locked.
* Returns the LOCKED pointer to the ipc structure if found or NULL
* if not.
- * If key is found ipc contains its ipc structure
+ * If key is found ipc points to the owning ipc structure
*/
static struct kern_ipc_perm *ipc_findkey(struct ipc_ids *ids, key_t key)
@@ -258,10 +258,10 @@
* @new: new IPC permission set
* @size: limit for the number of used ids
*
- * Add an entry 'new' to the IPC idr. The permissions object is
+ * Add an entry 'new' to the IPC ids idr. The permissions object is
* initialised and the first free entry is set up and the id assigned
- * is returned. The list is returned in a locked state on success.
- * On failure the list is not locked and -1 is returned.
+ * is returned. The 'new' entry is returned in a locked state on success.
+ * On failure the entry is not locked and -1 is returned.
*
* Called with ipc_ids.mutex held.
*/
@@ -270,10 +270,6 @@
{
int id, err;
- /*
- * rcu_dereference()() is not needed here since
- * ipc_ids.mutex is held
- */
if (size > IPCMNI)
size = IPCMNI;
@@ -303,12 +299,12 @@
/**
* ipcget_new - create a new ipc object
* @ns: namespace
- * @ids: identifer set
+ * @ids: IPC identifer set
* @ops: the actual creation routine to call
* @params: its parameters
*
- * This routine is called sys_msgget, sys_semget() and sys_shmget() when
- * the key is IPC_PRIVATE
+ * This routine is called by sys_msgget, sys_semget() and sys_shmget()
+ * when the key is IPC_PRIVATE.
*/
int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids,
struct ipc_ops *ops, struct ipc_params *params)
@@ -330,9 +326,16 @@
/**
* ipc_check_perms - check security and permissions for an IPC
* @ipcp: ipc permission set
- * @ids: identifer set
* @ops: the actual security routine to call
* @params: its parameters
+ *
+ * This routine is called by sys_msgget(), sys_semget() and sys_shmget()
+ * when the key is not IPC_PRIVATE and that key already exists in the
+ * ids IDR.
+ *
+ * On success, the IPC id is returned.
+ *
+ * It is called with ipc_ids.mutex and ipcp->lock held.
*/
static int ipc_check_perms(struct kern_ipc_perm *ipcp, struct ipc_ops *ops,
struct ipc_params *params)
@@ -353,12 +356,16 @@
/**
* ipcget_public - get an ipc object or create a new one
* @ns: namespace
- * @ids: identifer set
+ * @ids: IPC identifer set
* @ops: the actual creation routine to call
* @params: its parameters
*
- * This routine is called sys_msgget, sys_semget() and sys_shmget() when
- * the key is not IPC_PRIVATE
+ * This routine is called by sys_msgget, sys_semget() and sys_shmget()
+ * when the key is not IPC_PRIVATE.
+ * It adds a new entry if the key is not found and does some permission
+ * / security checkings if the key is found.
+ *
+ * On success, the ipc id is returned.
*/
int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids,
struct ipc_ops *ops, struct ipc_params *params)
@@ -389,6 +396,10 @@
if (ops->more_checks)
err = ops->more_checks(ipcp, params);
if (!err)
+ /*
+ * ipc_check_perms returns the IPC id on
+ * success
+ */
err = ipc_check_perms(ipcp, ops, params);
}
ipc_unlock(ipcp);
@@ -401,12 +412,9 @@
/**
* ipc_rmid - remove an IPC identifier
- * @ids: identifier set
- * @id: ipc perm structure containing the identifier to remove
+ * @ids: IPC identifier set
+ * @ipcp: ipc perm structure containing the identifier to remove
*
- * The identifier must be valid, and in use. The kernel will panic if
- * fed an invalid identifier. The entry is removed and internal
- * variables recomputed.
* ipc_ids.mutex and the spinlock for this ID are held before this
* function is called, and remain locked on the exit.
*/
@@ -558,10 +566,12 @@
*/
static void ipc_schedule_free(struct rcu_head *head)
{
- struct ipc_rcu_grace *grace =
- container_of(head, struct ipc_rcu_grace, rcu);
- struct ipc_rcu_sched *sched =
- container_of(&(grace->data[0]), struct ipc_rcu_sched, data[0]);
+ struct ipc_rcu_grace *grace;
+ struct ipc_rcu_sched *sched;
+
+ grace = container_of(head, struct ipc_rcu_grace, rcu);
+ sched = container_of(&(grace->data[0]), struct ipc_rcu_sched,
+ data[0]);
INIT_WORK(&sched->work, ipc_do_vfree);
schedule_work(&sched->work);
@@ -650,7 +660,7 @@
}
/**
- * ipc64_perm_to_ipc_perm - convert old ipc permissions to new
+ * ipc64_perm_to_ipc_perm - convert new ipc permissions to old
* @in: new style IPC permissions
* @out: old style IPC permissions
*
@@ -669,6 +679,18 @@
out->seq = in->seq;
}
+/**
+ * ipc_lock - Lock an ipc structure
+ * @ids: IPC identifier set
+ * @id: ipc id to look for
+ *
+ * Look for an id in the ipc ids idr and lock the associated ipc object.
+ *
+ * ipc_ids.mutex is not necessarily held before this function is called,
+ * that's why we enter a RCU read section.
+ * The ipc object is locked on exit.
+ */
+
struct kern_ipc_perm *ipc_lock(struct ipc_ids *ids, int id)
{
struct kern_ipc_perm *out;
@@ -771,8 +793,8 @@
}
/*
- * File positions: pos 0 -> header, pos n -> ipc id + 1.
- * SeqFile iterator: iterator value locked shp or SEQ_TOKEN_START.
+ * File positions: pos 0 -> header, pos n -> ipc id = n - 1.
+ * SeqFile iterator: iterator value locked ipc pointer or SEQ_TOKEN_START.
*/
static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
{
@@ -807,7 +829,7 @@
struct ipc_proc_iface *iface = iter->iface;
struct ipc_ids *ids;
- /* If we had a locked segment, release it */
+ /* If we had a locked structure, release it */
if (ipc && ipc != SEQ_START_TOKEN)
ipc_unlock(ipc);