pagevec.h

  1/* SPDX-License-Identifier: GPL-2.0 */
  2/*
  3 * include/linux/pagevec.h
  4 *
  5 * In many places it is efficient to batch an operation up against multiple
  6 * folios.  A folio_batch is a container which is used for that.
  7 */
  8
  9#ifndef _LINUX_PAGEVEC_H
 10#define _LINUX_PAGEVEC_H
 11
 12#include <linux/types.h>
 13
 14/* 31 pointers + header align the folio_batch structure to a power of two */
 15#define PAGEVEC_SIZE	31
 16
 17struct folio;
 18
 19/**
 20 * struct folio_batch - A collection of folios.
 21 *
 22 * The folio_batch is used to amortise the cost of retrieving and
 23 * operating on a set of folios.  The order of folios in the batch may be
 24 * significant (eg delete_from_page_cache_batch()).  Some users of the
 25 * folio_batch store "exceptional" entries in it which can be removed
 26 * by calling folio_batch_remove_exceptionals().
 27 */
 28struct folio_batch {
 29	unsigned char nr;
 30	unsigned char i;
 31	bool percpu_pvec_drained;
 32	struct folio *folios[PAGEVEC_SIZE];
 33};
 34
 35/**
 36 * folio_batch_init() - Initialise a batch of folios
 37 * @fbatch: The folio batch.
 38 *
 39 * A freshly initialised folio_batch contains zero folios.
 40 */
 41static inline void folio_batch_init(struct folio_batch *fbatch)
 42{
 43	fbatch->nr = 0;
 44	fbatch->i = 0;
 45	fbatch->percpu_pvec_drained = false;
 46}
 47
 48static inline void folio_batch_reinit(struct folio_batch *fbatch)
 49{
 50	fbatch->nr = 0;
 51	fbatch->i = 0;
 52}
 53
 54static inline unsigned int folio_batch_count(const struct folio_batch *fbatch)
 55{
 56	return fbatch->nr;
 57}
 58
 59static inline unsigned int folio_batch_space(const struct folio_batch *fbatch)
 60{
 61	return PAGEVEC_SIZE - fbatch->nr;
 62}
 63
 64/**
 65 * folio_batch_add() - Add a folio to a batch.
 66 * @fbatch: The folio batch.
 67 * @folio: The folio to add.
 68 *
 69 * The folio is added to the end of the batch.
 70 * The batch must have previously been initialised using folio_batch_init().
 71 *
 72 * Return: The number of slots still available.
 73 */
 74static inline unsigned folio_batch_add(struct folio_batch *fbatch,
 75		struct folio *folio)
 76{
 77	fbatch->folios[fbatch->nr++] = folio;
 78	return folio_batch_space(fbatch);
 79}
 80
 81/**
 82 * folio_batch_next - Return the next folio to process.
 83 * @fbatch: The folio batch being processed.
 84 *
 85 * Use this function to implement a queue of folios.
 86 *
 87 * Return: The next folio in the queue, or NULL if the queue is empty.
 88 */
 89static inline struct folio *folio_batch_next(struct folio_batch *fbatch)
 90{
 91	if (fbatch->i == fbatch->nr)
 92		return NULL;
 93	return fbatch->folios[fbatch->i++];
 94}
 95
 96void __folio_batch_release(struct folio_batch *pvec);
 97
 98static inline void folio_batch_release(struct folio_batch *fbatch)
 99{
100	if (folio_batch_count(fbatch))
101		__folio_batch_release(fbatch);
102}
103
104void folio_batch_remove_exceptionals(struct folio_batch *fbatch);
105#endif /* _LINUX_PAGEVEC_H */