drivers/xen/blkback/blkback-pagemap.c

   1 #include <linux/module.h>
   2 #include <linux/slab.h>
   3 #include "blkback-pagemap.h"
   4
   5 static int blkback_pagemap_size;
   6 static struct blkback_pagemap *blkback_pagemap;
   7
   8 static inline int
   9 blkback_pagemap_entry_clear(struct blkback_pagemap *map)
  10 {
  11         static struct blkback_pagemap zero;
  12         return !memcmp(map, &zero, sizeof(zero));
  13 }
  14
  15 int
  16 blkback_pagemap_init(int pages)
  17 {
  18         blkback_pagemap = kzalloc(pages * sizeof(struct blkback_pagemap),
  19                                   GFP_KERNEL);
  20         if (!blkback_pagemap)
  21                 return -ENOMEM;
  22
  23         blkback_pagemap_size = pages;
  24         return 0;
  25 }
  26 EXPORT_SYMBOL_GPL(blkback_pagemap_init);
  27
  28 void
  29 blkback_pagemap_set(int idx, struct page *page,
  30                     domid_t domid, busid_t busid, grant_ref_t gref)
  31 {
  32         struct blkback_pagemap *entry;
  33
  34         BUG_ON(!blkback_pagemap);
  35         BUG_ON(idx >= blkback_pagemap_size);
  36
  37         SetPageBlkback(page);
  38         set_page_private(page, idx);
  39
  40         entry = blkback_pagemap + idx;
  41         if (!blkback_pagemap_entry_clear(entry)) {
  42                 pr_emerg("overwriting pagemap %d: d %u b %u g %u\n",
  43                          idx, entry->domid, entry->busid, entry->gref);
  44                 BUG();
  45         }
  46
  47         entry->domid = domid;
  48         entry->busid = busid;
  49         entry->gref  = gref;
  50 }
  51 EXPORT_SYMBOL_GPL(blkback_pagemap_set);
  52
  53 void
  54 blkback_pagemap_clear(struct page *page)
  55 {
  56         int idx;
  57         struct blkback_pagemap *entry;
  58
  59         idx = (int)page_private(page);
  60
  61         BUG_ON(!blkback_pagemap);
  62         BUG_ON(!PageBlkback(page));
  63         BUG_ON(idx >= blkback_pagemap_size);
  64
  65         entry = blkback_pagemap + idx;
  66         if (blkback_pagemap_entry_clear(entry)) {
  67                 pr_emerg("clearing empty pagemap %d\n", idx);
  68                 BUG();
  69         }
  70
  71         memset(entry, 0, sizeof(*entry));
  72 }
  73 EXPORT_SYMBOL_GPL(blkback_pagemap_clear);
  74
  75 struct blkback_pagemap
  76 blkback_pagemap_read(struct page *page)
  77 {
  78         int idx;
  79         struct blkback_pagemap *entry;
  80
  81         idx = (int)page_private(page);
  82
  83         BUG_ON(!blkback_pagemap);
  84         BUG_ON(!PageBlkback(page));
  85         BUG_ON(idx >= blkback_pagemap_size);
  86
  87         entry = blkback_pagemap + idx;
  88         if (blkback_pagemap_entry_clear(entry)) {
  89                 pr_emerg("reading empty pagemap %d\n", idx);
  90                 BUG();
  91         }
  92
  93         return *entry;
  94 }
  95 EXPORT_SYMBOL(blkback_pagemap_read);
  96
  97 MODULE_LICENSE("Dual BSD/GPL");