include/linux/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
  17 struct 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  */
  28 struct 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  */
  41 static 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
  48 static inline void folio_batch_reinit(struct folio_batch *fbatch)
  49 {
  50         fbatch->nr = 0;
  51         fbatch->i = 0;
  52 }
  53
  54 static inline unsigned int folio_batch_count(struct folio_batch *fbatch)
  55 {
  56         return fbatch->nr;
  57 }
  58
  59 static inline unsigned int folio_batch_space(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  */
  74 static 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  */
  89 static 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
  96 void __folio_batch_release(struct folio_batch *pvec);
  97
  98 static inline void folio_batch_release(struct folio_batch *fbatch)
  99 {
 100         if (folio_batch_count(fbatch))
 101                 __folio_batch_release(fbatch);
 102 }
 103
 104 void folio_batch_remove_exceptionals(struct folio_batch *fbatch);
 105 #endif /* _LINUX_PAGEVEC_H */