fs/relayfs/buffers.c

   1 /*
   2  * RelayFS buffer management code.
   3  *
   4  * Copyright (C) 2002-2005 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp
   5  * Copyright (C) 1999-2005 - Karim Yaghmour (karim@opersys.com)
   6  *
   7  * This file is released under the GPL.
   8  */
   9
  10 #include <linux/module.h>
  11 #include <linux/vmalloc.h>
  12 #include <linux/mm.h>
  13 #include <linux/relayfs_fs.h>
  14 #include "relay.h"
  15 #include "buffers.h"
  16
  17 /*
  18  * close() vm_op implementation for relayfs file mapping.
  19  */
  20 static void relay_file_mmap_close(struct vm_area_struct *vma)
  21 {
  22         struct rchan_buf *buf = vma->vm_private_data;
  23         buf->chan->cb->buf_unmapped(buf, vma->vm_file);
  24 }
  25
  26 /*
  27  * nopage() vm_op implementation for relayfs file mapping.
  28  */
  29 static struct page *relay_buf_nopage(struct vm_area_struct *vma,
  30                                      unsigned long address,
  31                                      int *type)
  32 {
  33         struct page *page;
  34         struct rchan_buf *buf = vma->vm_private_data;
  35         unsigned long offset = address - vma->vm_start;
  36
  37         if (address > vma->vm_end)
  38                 return NOPAGE_SIGBUS; /* Disallow mremap */
  39         if (!buf)
  40                 return NOPAGE_OOM;
  41
  42         page = vmalloc_to_page(buf->start + offset);
  43         if (!page)
  44                 return NOPAGE_OOM;
  45         get_page(page);
  46
  47         if (type)
  48                 *type = VM_FAULT_MINOR;
  49
  50         return page;
  51 }
  52
  53 /*
  54  * vm_ops for relay file mappings.
  55  */
  56 static struct vm_operations_struct relay_file_mmap_ops = {
  57         .nopage = relay_buf_nopage,
  58         .close = relay_file_mmap_close,
  59 };
  60
  61 /**
  62  *      relay_mmap_buf: - mmap channel buffer to process address space
  63  *      @buf: relay channel buffer
  64  *      @vma: vm_area_struct describing memory to be mapped
  65  *
  66  *      Returns 0 if ok, negative on error
  67  *
  68  *      Caller should already have grabbed mmap_sem.
  69  */
  70 int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma)
  71 {
  72         unsigned long length = vma->vm_end - vma->vm_start;
  73         struct file *filp = vma->vm_file;
  74
  75         if (!buf)
  76                 return -EBADF;
  77
  78         if (length != (unsigned long)buf->chan->alloc_size)
  79                 return -EINVAL;
  80
  81         vma->vm_ops = &relay_file_mmap_ops;
  82         vma->vm_private_data = buf;
  83         buf->chan->cb->buf_mapped(buf, filp);
  84
  85         return 0;
  86 }
  87
  88 /**
  89  *      relay_alloc_buf - allocate a channel buffer
  90  *      @buf: the buffer struct
  91  *      @size: total size of the buffer
  92  *
  93  *      Returns a pointer to the resulting buffer, NULL if unsuccessful
  94  */
  95 static void *relay_alloc_buf(struct rchan_buf *buf, unsigned long size)
  96 {
  97         void *mem;
  98         unsigned int i, j, n_pages;
  99
 100         size = PAGE_ALIGN(size);
 101         n_pages = size >> PAGE_SHIFT;
 102
 103         buf->page_array = kcalloc(n_pages, sizeof(struct page *), GFP_KERNEL);
 104         if (!buf->page_array)
 105                 return NULL;
 106
 107         for (i = 0; i < n_pages; i++) {
 108                 buf->page_array[i] = alloc_page(GFP_KERNEL);
 109                 if (unlikely(!buf->page_array[i]))
 110                         goto depopulate;
 111         }
 112         mem = vmap(buf->page_array, n_pages, VM_MAP, PAGE_KERNEL);
 113         if (!mem)
 114                 goto depopulate;
 115
 116         memset(mem, 0, size);
 117         buf->page_count = n_pages;
 118         return mem;
 119
 120 depopulate:
 121         for (j = 0; j < i; j++)
 122                 __free_page(buf->page_array[j]);
 123         kfree(buf->page_array);
 124         return NULL;
 125 }
 126
 127 /**
 128  *      relay_create_buf - allocate and initialize a channel buffer
 129  *      @alloc_size: size of the buffer to allocate
 130  *      @n_subbufs: number of sub-buffers in the channel
 131  *
 132  *      Returns channel buffer if successful, NULL otherwise
 133  */
 134 struct rchan_buf *relay_create_buf(struct rchan *chan)
 135 {
 136         struct rchan_buf *buf = kcalloc(1, sizeof(struct rchan_buf), GFP_KERNEL);
 137         if (!buf)
 138                 return NULL;
 139
 140         buf->padding = kmalloc(chan->n_subbufs * sizeof(size_t *), GFP_KERNEL);
 141         if (!buf->padding)
 142                 goto free_buf;
 143
 144         buf->start = relay_alloc_buf(buf, chan->alloc_size);
 145         if (!buf->start)
 146                 goto free_buf;
 147
 148         buf->chan = chan;
 149         kref_get(&buf->chan->kref);
 150         return buf;
 151
 152 free_buf:
 153         kfree(buf->padding);
 154         kfree(buf);
 155         return NULL;
 156 }
 157
 158 /**
 159  *      relay_destroy_buf - destroy an rchan_buf struct and associated buffer
 160  *      @buf: the buffer struct
 161  */
 162 void relay_destroy_buf(struct rchan_buf *buf)
 163 {
 164         struct rchan *chan = buf->chan;
 165         unsigned int i;
 166
 167         if (likely(buf->start)) {
 168                 vunmap(buf->start);
 169                 for (i = 0; i < buf->page_count; i++)
 170                         __free_page(buf->page_array[i]);
 171                 kfree(buf->page_array);
 172         }
 173         kfree(buf->padding);
 174         kfree(buf);
 175         kref_put(&chan->kref, relay_destroy_channel);
 176 }
 177
 178 /**
 179  *      relay_remove_buf - remove a channel buffer
 180  *
 181  *      Removes the file from the relayfs fileystem, which also frees the
 182  *      rchan_buf_struct and the channel buffer.  Should only be called from
 183  *      kref_put().
 184  */
 185 void relay_remove_buf(struct kref *kref)
 186 {
 187         struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref);
 188         buf->chan->cb->remove_buf_file(buf->dentry);
 189         relay_destroy_buf(buf);
 190 }