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  * pages.  A pagevec is a multipage container which is used for that.
7  */
8 
9 #ifndef _LINUX_PAGEVEC_H
10 #define _LINUX_PAGEVEC_H
11 
12 #include <linux/xarray.h>
13 
14 /* 15 pointers + header align the pagevec structure to a power of two */
15 #define PAGEVEC_SIZE	15
16 
17 struct page;
18 struct folio;
19 struct address_space;
20 
21 /* Layout must match folio_batch */
22 struct pagevec {
23 	unsigned char nr;
24 	bool percpu_pvec_drained;
25 	struct page *pages[PAGEVEC_SIZE];
26 };
27 
28 void __pagevec_release(struct pagevec *pvec);
29 
pagevec_init(struct pagevec * pvec)30 static inline void pagevec_init(struct pagevec *pvec)
31 {
32 	pvec->nr = 0;
33 	pvec->percpu_pvec_drained = false;
34 }
35 
pagevec_reinit(struct pagevec * pvec)36 static inline void pagevec_reinit(struct pagevec *pvec)
37 {
38 	pvec->nr = 0;
39 }
40 
pagevec_count(struct pagevec * pvec)41 static inline unsigned pagevec_count(struct pagevec *pvec)
42 {
43 	return pvec->nr;
44 }
45 
pagevec_space(struct pagevec * pvec)46 static inline unsigned pagevec_space(struct pagevec *pvec)
47 {
48 	return PAGEVEC_SIZE - pvec->nr;
49 }
50 
51 /*
52  * Add a page to a pagevec.  Returns the number of slots still available.
53  */
pagevec_add(struct pagevec * pvec,struct page * page)54 static inline unsigned pagevec_add(struct pagevec *pvec, struct page *page)
55 {
56 	pvec->pages[pvec->nr++] = page;
57 	return pagevec_space(pvec);
58 }
59 
pagevec_release(struct pagevec * pvec)60 static inline void pagevec_release(struct pagevec *pvec)
61 {
62 	if (pagevec_count(pvec))
63 		__pagevec_release(pvec);
64 }
65 
66 /**
67  * struct folio_batch - A collection of folios.
68  *
69  * The folio_batch is used to amortise the cost of retrieving and
70  * operating on a set of folios.  The order of folios in the batch may be
71  * significant (eg delete_from_page_cache_batch()).  Some users of the
72  * folio_batch store "exceptional" entries in it which can be removed
73  * by calling folio_batch_remove_exceptionals().
74  */
75 struct folio_batch {
76 	unsigned char nr;
77 	bool percpu_pvec_drained;
78 	struct folio *folios[PAGEVEC_SIZE];
79 };
80 
81 /* Layout must match pagevec */
82 static_assert(sizeof(struct pagevec) == sizeof(struct folio_batch));
83 static_assert(offsetof(struct pagevec, pages) ==
84 		offsetof(struct folio_batch, folios));
85 
86 /**
87  * folio_batch_init() - Initialise a batch of folios
88  * @fbatch: The folio batch.
89  *
90  * A freshly initialised folio_batch contains zero folios.
91  */
folio_batch_init(struct folio_batch * fbatch)92 static inline void folio_batch_init(struct folio_batch *fbatch)
93 {
94 	fbatch->nr = 0;
95 	fbatch->percpu_pvec_drained = false;
96 }
97 
folio_batch_reinit(struct folio_batch * fbatch)98 static inline void folio_batch_reinit(struct folio_batch *fbatch)
99 {
100 	fbatch->nr = 0;
101 }
102 
folio_batch_count(struct folio_batch * fbatch)103 static inline unsigned int folio_batch_count(struct folio_batch *fbatch)
104 {
105 	return fbatch->nr;
106 }
107 
fbatch_space(struct folio_batch * fbatch)108 static inline unsigned int fbatch_space(struct folio_batch *fbatch)
109 {
110 	return PAGEVEC_SIZE - fbatch->nr;
111 }
112 
113 /**
114  * folio_batch_add() - Add a folio to a batch.
115  * @fbatch: The folio batch.
116  * @folio: The folio to add.
117  *
118  * The folio is added to the end of the batch.
119  * The batch must have previously been initialised using folio_batch_init().
120  *
121  * Return: The number of slots still available.
122  */
folio_batch_add(struct folio_batch * fbatch,struct folio * folio)123 static inline unsigned folio_batch_add(struct folio_batch *fbatch,
124 		struct folio *folio)
125 {
126 	fbatch->folios[fbatch->nr++] = folio;
127 	return fbatch_space(fbatch);
128 }
129 
folio_batch_release(struct folio_batch * fbatch)130 static inline void folio_batch_release(struct folio_batch *fbatch)
131 {
132 	pagevec_release((struct pagevec *)fbatch);
133 }
134 
135 void folio_batch_remove_exceptionals(struct folio_batch *fbatch);
136 #endif /* _LINUX_PAGEVEC_H */
137