fs/erofs/zpvec.h

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2 /*
   3  * Copyright (C) 2018 HUAWEI, Inc.
   4  *             https://www.huawei.com/
   5  */
   6 #ifndef __EROFS_FS_ZPVEC_H
   7 #define __EROFS_FS_ZPVEC_H
   8
   9 #include "tagptr.h"
  10
  11 /* page type in pagevec for decompress subsystem */
  12 enum z_erofs_page_type {
  13         /* including Z_EROFS_VLE_PAGE_TAIL_EXCLUSIVE */
  14         Z_EROFS_PAGE_TYPE_EXCLUSIVE,
  15
  16         Z_EROFS_VLE_PAGE_TYPE_TAIL_SHARED,
  17
  18         Z_EROFS_VLE_PAGE_TYPE_HEAD,
  19         Z_EROFS_VLE_PAGE_TYPE_MAX
  20 };
  21
  22 extern void __compiletime_error("Z_EROFS_PAGE_TYPE_EXCLUSIVE != 0")
  23         __bad_page_type_exclusive(void);
  24
  25 /* pagevec tagged pointer */
  26 typedef tagptr2_t       erofs_vtptr_t;
  27
  28 /* pagevec collector */
  29 struct z_erofs_pagevec_ctor {
  30         struct page *curr, *next;
  31         erofs_vtptr_t *pages;
  32
  33         unsigned int nr, index;
  34 };
  35
  36 static inline void z_erofs_pagevec_ctor_exit(struct z_erofs_pagevec_ctor *ctor,
  37                                              bool atomic)
  38 {
  39         if (!ctor->curr)
  40                 return;
  41
  42         if (atomic)
  43                 kunmap_atomic(ctor->pages);
  44         else
  45                 kunmap(ctor->curr);
  46 }
  47
  48 static inline struct page *
  49 z_erofs_pagevec_ctor_next_page(struct z_erofs_pagevec_ctor *ctor,
  50                                unsigned int nr)
  51 {
  52         unsigned int index;
  53
  54         /* keep away from occupied pages */
  55         if (ctor->next)
  56                 return ctor->next;
  57
  58         for (index = 0; index < nr; ++index) {
  59                 const erofs_vtptr_t t = ctor->pages[index];
  60                 const unsigned int tags = tagptr_unfold_tags(t);
  61
  62                 if (tags == Z_EROFS_PAGE_TYPE_EXCLUSIVE)
  63                         return tagptr_unfold_ptr(t);
  64         }
  65         DBG_BUGON(nr >= ctor->nr);
  66         return NULL;
  67 }
  68
  69 static inline void
  70 z_erofs_pagevec_ctor_pagedown(struct z_erofs_pagevec_ctor *ctor,
  71                               bool atomic)
  72 {
  73         struct page *next = z_erofs_pagevec_ctor_next_page(ctor, ctor->nr);
  74
  75         z_erofs_pagevec_ctor_exit(ctor, atomic);
  76
  77         ctor->curr = next;
  78         ctor->next = NULL;
  79         ctor->pages = atomic ?
  80                 kmap_atomic(ctor->curr) : kmap(ctor->curr);
  81
  82         ctor->nr = PAGE_SIZE / sizeof(struct page *);
  83         ctor->index = 0;
  84 }
  85
  86 static inline void z_erofs_pagevec_ctor_init(struct z_erofs_pagevec_ctor *ctor,
  87                                              unsigned int nr,
  88                                              erofs_vtptr_t *pages,
  89                                              unsigned int i)
  90 {
  91         ctor->nr = nr;
  92         ctor->curr = ctor->next = NULL;
  93         ctor->pages = pages;
  94
  95         if (i >= nr) {
  96                 i -= nr;
  97                 z_erofs_pagevec_ctor_pagedown(ctor, false);
  98                 while (i > ctor->nr) {
  99                         i -= ctor->nr;
 100                         z_erofs_pagevec_ctor_pagedown(ctor, false);
 101                 }
 102         }
 103         ctor->next = z_erofs_pagevec_ctor_next_page(ctor, i);
 104         ctor->index = i;
 105 }
 106
 107 static inline bool z_erofs_pagevec_enqueue(struct z_erofs_pagevec_ctor *ctor,
 108                                            struct page *page,
 109                                            enum z_erofs_page_type type,
 110                                            bool pvec_safereuse)
 111 {
 112         if (!ctor->next) {
 113                 /* some pages cannot be reused as pvec safely without I/O */
 114                 if (type == Z_EROFS_PAGE_TYPE_EXCLUSIVE && !pvec_safereuse)
 115                         type = Z_EROFS_VLE_PAGE_TYPE_TAIL_SHARED;
 116
 117                 if (type != Z_EROFS_PAGE_TYPE_EXCLUSIVE &&
 118                     ctor->index + 1 == ctor->nr)
 119                         return false;
 120         }
 121
 122         if (ctor->index >= ctor->nr)
 123                 z_erofs_pagevec_ctor_pagedown(ctor, false);
 124
 125         /* exclusive page type must be 0 */
 126         if (Z_EROFS_PAGE_TYPE_EXCLUSIVE != (uintptr_t)NULL)
 127                 __bad_page_type_exclusive();
 128
 129         /* should remind that collector->next never equal to 1, 2 */
 130         if (type == (uintptr_t)ctor->next) {
 131                 ctor->next = page;
 132         }
 133         ctor->pages[ctor->index++] = tagptr_fold(erofs_vtptr_t, page, type);
 134         return true;
 135 }
 136
 137 static inline struct page *
 138 z_erofs_pagevec_dequeue(struct z_erofs_pagevec_ctor *ctor,
 139                         enum z_erofs_page_type *type)
 140 {
 141         erofs_vtptr_t t;
 142
 143         if (ctor->index >= ctor->nr) {
 144                 DBG_BUGON(!ctor->next);
 145                 z_erofs_pagevec_ctor_pagedown(ctor, true);
 146         }
 147
 148         t = ctor->pages[ctor->index];
 149
 150         *type = tagptr_unfold_tags(t);
 151
 152         /* should remind that collector->next never equal to 1, 2 */
 153         if (*type == (uintptr_t)ctor->next)
 154                 ctor->next = tagptr_unfold_ptr(t);
 155
 156         ctor->pages[ctor->index++] = tagptr_fold(erofs_vtptr_t, NULL, 0);
 157         return tagptr_unfold_ptr(t);
 158 }
 159 #endif