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authorDave Chinner <dchinner@redhat.com>2013-08-28 10:17:58 +1000
committerAl Viro <viro@zeniv.linux.org.uk>2013-09-10 18:56:30 -0400
commita38e40824844a5ec85f3ea95632be953477d2afa (patch)
tree5f5df05ea253689cd515ef0ce47c6baf2210f094 /include/linux/list_lru.h
parent0a234c6dcb79a270803f5c9773ed650b78730962 (diff)
downloadop-kernel-dev-a38e40824844a5ec85f3ea95632be953477d2afa.zip
op-kernel-dev-a38e40824844a5ec85f3ea95632be953477d2afa.tar.gz
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: Dave Chinner <dchinner@redhat.com> Signed-off-by: Glauber Costa <glommer@openvz.org> Reviewed-by: Greg Thelen <gthelen@google.com> Acked-by: Mel 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: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'include/linux/list_lru.h')
-rw-r--r--include/linux/list_lru.h115
1 files changed, 115 insertions, 0 deletions
diff --git a/include/linux/list_lru.h b/include/linux/list_lru.h
new file mode 100644
index 0000000..1a548b0
--- /dev/null
+++ b/include/linux/list_lru.h
@@ -0,0 +1,115 @@
+/*
+ * 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 */
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