Commit a38e4082 authored by Dave Chinner's avatar Dave Chinner Committed by Al Viro
Browse files

list: add a new LRU list type



Several subsystems use the same construct for LRU lists - a list head, a
spin lock and and item count.  They also use exactly the same code for
adding and removing items from the LRU.  Create a generic type for these
LRU lists.

This is the beginning of generic, node aware LRUs for shrinkers to work
with.

[glommer@openvz.org: enum defined constants for lru. Suggested by gthelen, don't relock over retry]
Signed-off-by: default avatarDave Chinner <dchinner@redhat.com>
Signed-off-by: default avatarGlauber Costa <glommer@openvz.org>
Reviewed-by: default avatarGreg Thelen <gthelen@google.com>
Acked-by: default avatarMel Gorman <mgorman@suse.de>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Cc: Arve Hjønnevåg <arve@android.com>
Cc: Carlos Maiolino <cmaiolino@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: David Rientjes <rientjes@google.com>
Cc: Gleb Natapov <gleb@redhat.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: J. Bruce Fields <bfields@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Kent Overstreet <koverstreet@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Steven Whitehouse <swhiteho@redhat.com>
Cc: Thomas Hellstrom <thellstrom@vmware.com>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 0a234c6d
/*
* Copyright (c) 2013 Red Hat, Inc. and Parallels Inc. All rights reserved.
* Authors: David Chinner and Glauber Costa
*
* Generic LRU infrastructure
*/
#ifndef _LRU_LIST_H
#define _LRU_LIST_H
#include <linux/list.h>
/* list_lru_walk_cb has to always return one of those */
enum lru_status {
LRU_REMOVED, /* item removed from list */
LRU_ROTATE, /* item referenced, give another pass */
LRU_SKIP, /* item cannot be locked, skip */
LRU_RETRY, /* item not freeable. May drop the lock
internally, but has to return locked. */
};
struct list_lru {
spinlock_t lock;
struct list_head list;
/* kept as signed so we can catch imbalance bugs */
long nr_items;
};
int list_lru_init(struct list_lru *lru);
/**
* list_lru_add: add an element to the lru list's tail
* @list_lru: the lru pointer
* @item: the item to be added.
*
* If the element is already part of a list, this function returns doing
* nothing. Therefore the caller does not need to keep state about whether or
* not the element already belongs in the list and is allowed to lazy update
* it. Note however that this is valid for *a* list, not *this* list. If
* the caller organize itself in a way that elements can be in more than
* one type of list, it is up to the caller to fully remove the item from
* the previous list (with list_lru_del() for instance) before moving it
* to @list_lru
*
* Return value: true if the list was updated, false otherwise
*/
bool list_lru_add(struct list_lru *lru, struct list_head *item);
/**
* list_lru_del: delete an element to the lru list
* @list_lru: the lru pointer
* @item: the item to be deleted.
*
* This function works analogously as list_lru_add in terms of list
* manipulation. The comments about an element already pertaining to
* a list are also valid for list_lru_del.
*
* Return value: true if the list was updated, false otherwise
*/
bool list_lru_del(struct list_lru *lru, struct list_head *item);
/**
* list_lru_count: return the number of objects currently held by @lru
* @lru: the lru pointer.
*
* Always return a non-negative number, 0 for empty lists. There is no
* guarantee that the list is not updated while the count is being computed.
* Callers that want such a guarantee need to provide an outer lock.
*/
static inline unsigned long list_lru_count(struct list_lru *lru)
{
return lru->nr_items;
}
typedef enum lru_status
(*list_lru_walk_cb)(struct list_head *item, spinlock_t *lock, void *cb_arg);
/**
* list_lru_walk: walk a list_lru, isolating and disposing freeable items.
* @lru: the lru pointer.
* @isolate: callback function that is resposible for deciding what to do with
* the item currently being scanned
* @cb_arg: opaque type that will be passed to @isolate
* @nr_to_walk: how many items to scan.
*
* This function will scan all elements in a particular list_lru, calling the
* @isolate callback for each of those items, along with the current list
* spinlock and a caller-provided opaque. The @isolate callback can choose to
* drop the lock internally, but *must* return with the lock held. The callback
* will return an enum lru_status telling the list_lru infrastructure what to
* do with the object being scanned.
*
* Please note that nr_to_walk does not mean how many objects will be freed,
* just how many objects will be scanned.
*
* Return value: the number of objects effectively removed from the LRU.
*/
unsigned long list_lru_walk(struct list_lru *lru, list_lru_walk_cb isolate,
void *cb_arg, unsigned long nr_to_walk);
typedef void (*list_lru_dispose_cb)(struct list_head *dispose_list);
/**
* list_lru_dispose_all: forceably flush all elements in an @lru
* @lru: the lru pointer
* @dispose: callback function to be called for each lru list.
*
* This function will forceably isolate all elements into the dispose list, and
* call the @dispose callback to flush the list. Please note that the callback
* should expect items in any state, clean or dirty, and be able to flush all of
* them.
*
* Return value: how many objects were freed. It should be equal to all objects
* in the list_lru.
*/
unsigned long
list_lru_dispose_all(struct list_lru *lru, list_lru_dispose_cb dispose);
#endif /* _LRU_LIST_H */
......@@ -17,7 +17,7 @@ obj-y := filemap.o mempool.o oom_kill.o fadvise.o \
util.o mmzone.o vmstat.o backing-dev.o \
mm_init.o mmu_context.o percpu.o slab_common.o \
compaction.o balloon_compaction.o \
interval_tree.o $(mmu-y)
interval_tree.o list_lru.o $(mmu-y)
obj-y += init-mm.o
......
/*
* Copyright (c) 2013 Red Hat, Inc. and Parallels Inc. All rights reserved.
* Authors: David Chinner and Glauber Costa
*
* Generic LRU infrastructure
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/list_lru.h>
bool list_lru_add(struct list_lru *lru, struct list_head *item)
{
spin_lock(&lru->lock);
if (list_empty(item)) {
list_add_tail(item, &lru->list);
lru->nr_items++;
spin_unlock(&lru->lock);
return true;
}
spin_unlock(&lru->lock);
return false;
}
EXPORT_SYMBOL_GPL(list_lru_add);
bool list_lru_del(struct list_lru *lru, struct list_head *item)
{
spin_lock(&lru->lock);
if (!list_empty(item)) {
list_del_init(item);
lru->nr_items--;
spin_unlock(&lru->lock);
return true;
}
spin_unlock(&lru->lock);
return false;
}
EXPORT_SYMBOL_GPL(list_lru_del);
unsigned long list_lru_walk(struct list_lru *lru, list_lru_walk_cb isolate,
void *cb_arg, unsigned long nr_to_walk)
{
struct list_head *item, *n;
unsigned long removed = 0;
/*
* If we don't keep state of at which pass we are, we can loop at
* LRU_RETRY, since we have no guarantees that the caller will be able
* to do something other than retry on the next pass. We handle this by
* allowing at most one retry per object. This should not be altered
* by any condition other than LRU_RETRY.
*/
bool first_pass = true;
spin_lock(&lru->lock);
restart:
list_for_each_safe(item, n, &lru->list) {
enum lru_status ret;
ret = isolate(item, &lru->lock, cb_arg);
switch (ret) {
case LRU_REMOVED:
lru->nr_items--;
removed++;
break;
case LRU_ROTATE:
list_move_tail(item, &lru->list);
break;
case LRU_SKIP:
break;
case LRU_RETRY:
if (!first_pass) {
first_pass = true;
break;
}
first_pass = false;
goto restart;
default:
BUG();
}
if (nr_to_walk-- == 0)
break;
}
spin_unlock(&lru->lock);
return removed;
}
EXPORT_SYMBOL_GPL(list_lru_walk);
unsigned long list_lru_dispose_all(struct list_lru *lru,
list_lru_dispose_cb dispose)
{
unsigned long disposed = 0;
LIST_HEAD(dispose_list);
spin_lock(&lru->lock);
while (!list_empty(&lru->list)) {
list_splice_init(&lru->list, &dispose_list);
disposed += lru->nr_items;
lru->nr_items = 0;
spin_unlock(&lru->lock);
dispose(&dispose_list);
spin_lock(&lru->lock);
}
spin_unlock(&lru->lock);
return disposed;
}
int list_lru_init(struct list_lru *lru)
{
spin_lock_init(&lru->lock);
INIT_LIST_HEAD(&lru->list);
lru->nr_items = 0;
return 0;
}
EXPORT_SYMBOL_GPL(list_lru_init);
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