/*
* Create the appropriate buffers when given a page for data area and
* the size of each buffer.. Use the bh->b_this_page linked list to
* follow the buffers created. Return NULL if unable to create more
* buffers.
*/
static struct buffer_head * create_buffers(unsigned long page, unsigned long size)
{
struct buffer_head *bh, *head;
unsigned long offset;
head = NULL;
offset = PAGE_SIZE;
while ((offset -= size) < PAGE_SIZE) {
bh = get_unused_buffer_head();
if (!bh)
goto no_grow;
bh->b_this_page = head;
head = bh;
bh->b_data = (char *) (page+offset);
bh->b_size = size;
}
return head;
/*
* In case anything failed, we just free everything we got.
*/
no_grow:
bh = head;
while (bh) {
head = bh;
bh = bh->b_this_page;
put_unused_buffer_head(head);
}
return NULL;
}
/*
* Try to increase the number of buffers available: the size argument
* is used to determine what kind of buffers we want. Currently only
* 1024-byte buffers are supported by the rest of the system, but I
* think this will change eventually.
*/
void grow_buffers(int size)
{
unsigned long page;
int i;
struct buffer_head *bh, *tmp;
if ((size & 511) || (size > 4096)) {
printk("grow_buffers: size = %d\n",size);
return;
}
page = get_free_page(GFP_BUFFER);
if (!page)
return;
tmp = NULL;
i = 0;
for (i = 0 ; i+size <= 4096 ; i += size) {
bh = get_unused_buffer_head();
if (!bh)
goto no_grow;
bh->b_this_page = tmp;
tmp = bh;
bh->b_data = (char * ) (page+i);
bh->b_size = size;
}
tmp = bh;
while (1) {
if (free_list) {
tmp->b_next_free = free_list;
tmp->b_prev_free = free_list->b_prev_free;
free_list->b_prev_free->b_next_free = tmp;
free_list->b_prev_free = tmp;
} else {
tmp->b_prev_free = tmp;
tmp->b_next_free = tmp;
}
free_list = tmp;
++nr_buffers;
if (tmp->b_this_page)
tmp = tmp->b_this_page;
else
break;
}
tmp->b_this_page = bh;
return;
/*
* In case anything failed, we just free everything we got.
*/
no_grow:
bh = tmp;
while (bh) {
tmp = bh;
bh = bh->b_this_page;
put_unused_buffer_head(tmp);
}
free_page(page);
}
