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![Dan Streetman](/assets/img/avatar_default.png)
Add plist_requeue(), which moves the specified plist_node after all other same-priority plist_nodes in the list. This is essentially an optimized plist_del() followed by plist_add(). This is needed by swap, which (with the next patch in this set) uses a plist of available swap devices. When a swap device (either a swap partition or swap file) are added to the system with swapon(), the device is added to a plist, ordered by the swap device's priority. When swap needs to allocate a page from one of the swap devices, it takes the page from the first swap device on the plist, which is the highest priority swap device. The swap device is left in the plist until all its pages are used, and then removed from the plist when it becomes full. However, as described in man 2 swapon, swap must allocate pages from swap devices with the same priority in round-robin order; to do this, on each swap page allocation, swap uses a page from the first swap device in the plist, and then calls plist_requeue() to move that swap device entry to after any other same-priority swap devices. The next swap page allocation will again use a page from the first swap device in the plist and requeue it, and so on, resulting in round-robin usage of equal-priority swap devices. Also add plist_test_requeue() test function, for use by plist_test() to test plist_requeue() function. Signed-off-by: Dan Streetman <ddstreet@ieee.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Peter Zijlstra <peterz@infradead.org> Acked-by: Mel Gorman <mgorman@suse.de> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Shaohua Li <shli@fusionio.com> Cc: Hugh Dickins <hughd@google.com> Cc: Dan Streetman <ddstreet@ieee.org> Cc: Michal Hocko <mhocko@suse.cz> Cc: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com> Cc: Weijie Yang <weijieut@gmail.com> Cc: Rik van Riel <riel@redhat.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Bob Liu <bob.liu@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
300 lines
8.7 KiB
C
300 lines
8.7 KiB
C
/*
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* Descending-priority-sorted double-linked list
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*
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* (C) 2002-2003 Intel Corp
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* Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>.
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*
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* 2001-2005 (c) MontaVista Software, Inc.
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* Daniel Walker <dwalker@mvista.com>
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*
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* (C) 2005 Thomas Gleixner <tglx@linutronix.de>
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*
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* Simplifications of the original code by
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* Oleg Nesterov <oleg@tv-sign.ru>
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*
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* Licensed under the FSF's GNU Public License v2 or later.
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*
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* Based on simple lists (include/linux/list.h).
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*
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* This is a priority-sorted list of nodes; each node has a
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* priority from INT_MIN (highest) to INT_MAX (lowest).
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*
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* Addition is O(K), removal is O(1), change of priority of a node is
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* O(K) and K is the number of RT priority levels used in the system.
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* (1 <= K <= 99)
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*
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* This list is really a list of lists:
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*
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* - The tier 1 list is the prio_list, different priority nodes.
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*
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* - The tier 2 list is the node_list, serialized nodes.
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*
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* Simple ASCII art explanation:
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*
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* pl:prio_list (only for plist_node)
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* nl:node_list
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* HEAD| NODE(S)
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* |
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* ||------------------------------------|
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* ||->|pl|<->|pl|<--------------->|pl|<-|
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* | |10| |21| |21| |21| |40| (prio)
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* | | | | | | | | | | |
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* | | | | | | | | | | |
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* |->|nl|<->|nl|<->|nl|<->|nl|<->|nl|<->|nl|<-|
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* |-------------------------------------------|
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*
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* The nodes on the prio_list list are sorted by priority to simplify
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* the insertion of new nodes. There are no nodes with duplicate
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* priorites on the list.
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*
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* The nodes on the node_list are ordered by priority and can contain
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* entries which have the same priority. Those entries are ordered
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* FIFO
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*
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* Addition means: look for the prio_list node in the prio_list
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* for the priority of the node and insert it before the node_list
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* entry of the next prio_list node. If it is the first node of
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* that priority, add it to the prio_list in the right position and
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* insert it into the serialized node_list list
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*
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* Removal means remove it from the node_list and remove it from
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* the prio_list if the node_list list_head is non empty. In case
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* of removal from the prio_list it must be checked whether other
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* entries of the same priority are on the list or not. If there
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* is another entry of the same priority then this entry has to
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* replace the removed entry on the prio_list. If the entry which
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* is removed is the only entry of this priority then a simple
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* remove from both list is sufficient.
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*
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* INT_MIN is the highest priority, 0 is the medium highest, INT_MAX
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* is lowest priority.
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*
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* No locking is done, up to the caller.
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*
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*/
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#ifndef _LINUX_PLIST_H_
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#define _LINUX_PLIST_H_
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#include <linux/kernel.h>
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#include <linux/list.h>
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struct plist_head {
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struct list_head node_list;
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};
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struct plist_node {
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int prio;
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struct list_head prio_list;
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struct list_head node_list;
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};
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/**
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* PLIST_HEAD_INIT - static struct plist_head initializer
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* @head: struct plist_head variable name
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*/
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#define PLIST_HEAD_INIT(head) \
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{ \
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.node_list = LIST_HEAD_INIT((head).node_list) \
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}
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/**
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* PLIST_HEAD - declare and init plist_head
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* @head: name for struct plist_head variable
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*/
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#define PLIST_HEAD(head) \
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struct plist_head head = PLIST_HEAD_INIT(head)
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/**
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* PLIST_NODE_INIT - static struct plist_node initializer
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* @node: struct plist_node variable name
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* @__prio: initial node priority
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*/
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#define PLIST_NODE_INIT(node, __prio) \
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{ \
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.prio = (__prio), \
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.prio_list = LIST_HEAD_INIT((node).prio_list), \
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.node_list = LIST_HEAD_INIT((node).node_list), \
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}
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/**
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* plist_head_init - dynamic struct plist_head initializer
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* @head: &struct plist_head pointer
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*/
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static inline void
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plist_head_init(struct plist_head *head)
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{
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INIT_LIST_HEAD(&head->node_list);
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}
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/**
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* plist_node_init - Dynamic struct plist_node initializer
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* @node: &struct plist_node pointer
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* @prio: initial node priority
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*/
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static inline void plist_node_init(struct plist_node *node, int prio)
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{
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node->prio = prio;
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INIT_LIST_HEAD(&node->prio_list);
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INIT_LIST_HEAD(&node->node_list);
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}
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extern void plist_add(struct plist_node *node, struct plist_head *head);
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extern void plist_del(struct plist_node *node, struct plist_head *head);
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extern void plist_requeue(struct plist_node *node, struct plist_head *head);
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/**
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* plist_for_each - iterate over the plist
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* @pos: the type * to use as a loop counter
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* @head: the head for your list
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*/
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#define plist_for_each(pos, head) \
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list_for_each_entry(pos, &(head)->node_list, node_list)
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/**
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* plist_for_each_continue - continue iteration over the plist
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* @pos: the type * to use as a loop cursor
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* @head: the head for your list
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*
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* Continue to iterate over plist, continuing after the current position.
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*/
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#define plist_for_each_continue(pos, head) \
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list_for_each_entry_continue(pos, &(head)->node_list, node_list)
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/**
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* plist_for_each_safe - iterate safely over a plist of given type
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* @pos: the type * to use as a loop counter
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* @n: another type * to use as temporary storage
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* @head: the head for your list
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*
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* Iterate over a plist of given type, safe against removal of list entry.
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*/
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#define plist_for_each_safe(pos, n, head) \
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list_for_each_entry_safe(pos, n, &(head)->node_list, node_list)
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/**
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* plist_for_each_entry - iterate over list of given type
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* @pos: the type * to use as a loop counter
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* @head: the head for your list
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* @mem: the name of the list_struct within the struct
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*/
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#define plist_for_each_entry(pos, head, mem) \
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list_for_each_entry(pos, &(head)->node_list, mem.node_list)
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/**
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* plist_for_each_entry_continue - continue iteration over list of given type
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* @pos: the type * to use as a loop cursor
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* @head: the head for your list
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* @m: the name of the list_struct within the struct
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*
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* Continue to iterate over list of given type, continuing after
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* the current position.
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*/
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#define plist_for_each_entry_continue(pos, head, m) \
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list_for_each_entry_continue(pos, &(head)->node_list, m.node_list)
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/**
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* plist_for_each_entry_safe - iterate safely over list of given type
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* @pos: the type * to use as a loop counter
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* @n: another type * to use as temporary storage
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* @head: the head for your list
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* @m: the name of the list_struct within the struct
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*
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* Iterate over list of given type, safe against removal of list entry.
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*/
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#define plist_for_each_entry_safe(pos, n, head, m) \
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list_for_each_entry_safe(pos, n, &(head)->node_list, m.node_list)
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/**
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* plist_head_empty - return !0 if a plist_head is empty
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* @head: &struct plist_head pointer
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*/
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static inline int plist_head_empty(const struct plist_head *head)
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{
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return list_empty(&head->node_list);
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}
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/**
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* plist_node_empty - return !0 if plist_node is not on a list
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* @node: &struct plist_node pointer
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*/
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static inline int plist_node_empty(const struct plist_node *node)
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{
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return list_empty(&node->node_list);
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}
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/* All functions below assume the plist_head is not empty. */
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/**
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* plist_first_entry - get the struct for the first entry
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* @head: the &struct plist_head pointer
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* @type: the type of the struct this is embedded in
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* @member: the name of the list_struct within the struct
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*/
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#ifdef CONFIG_DEBUG_PI_LIST
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# define plist_first_entry(head, type, member) \
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({ \
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WARN_ON(plist_head_empty(head)); \
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container_of(plist_first(head), type, member); \
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})
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#else
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# define plist_first_entry(head, type, member) \
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container_of(plist_first(head), type, member)
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#endif
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/**
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* plist_last_entry - get the struct for the last entry
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* @head: the &struct plist_head pointer
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* @type: the type of the struct this is embedded in
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* @member: the name of the list_struct within the struct
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*/
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#ifdef CONFIG_DEBUG_PI_LIST
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# define plist_last_entry(head, type, member) \
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({ \
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WARN_ON(plist_head_empty(head)); \
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container_of(plist_last(head), type, member); \
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})
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#else
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# define plist_last_entry(head, type, member) \
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container_of(plist_last(head), type, member)
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#endif
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/**
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* plist_next - get the next entry in list
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* @pos: the type * to cursor
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*/
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#define plist_next(pos) \
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list_next_entry(pos, node_list)
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/**
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* plist_prev - get the prev entry in list
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* @pos: the type * to cursor
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*/
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#define plist_prev(pos) \
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list_prev_entry(pos, node_list)
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/**
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* plist_first - return the first node (and thus, highest priority)
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* @head: the &struct plist_head pointer
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*
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* Assumes the plist is _not_ empty.
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*/
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static inline struct plist_node *plist_first(const struct plist_head *head)
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{
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return list_entry(head->node_list.next,
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struct plist_node, node_list);
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}
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/**
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* plist_last - return the last node (and thus, lowest priority)
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* @head: the &struct plist_head pointer
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*
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* Assumes the plist is _not_ empty.
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*/
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static inline struct plist_node *plist_last(const struct plist_head *head)
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{
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return list_entry(head->node_list.prev,
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struct plist_node, node_list);
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}
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#endif
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