Viewing file:  highmem.c (10.18 KB) -rw-r--r--
Select action/file-type:
 (+) |  (+) |  (+) | Code (+) | Session (+) |  (+) | SDB (+) |  (+) |  (+) |  (+) |  (+) |  (+) |
/*
* High memory handling common code and variables.
*
* (C) 1999 Andrea Arcangeli, SuSE GmbH, andrea@suse.de
* Gerhard Wichert, Siemens AG, Gerhard.Wichert@pdb.siemens.de
*
*
* Redesigned the x86 32-bit VM architecture to deal with
* 64-bit physical space. With current x86 CPUs this
* means up to 64 Gigabytes physical RAM.
*
* Rewrote high memory support to move the page cache into
* high memory. Implemented permanent (schedulable) kmaps
* based on Linus' idea.
*
* Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
*/
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/swap.h>
#include <linux/slab.h>
/*
* Virtual_count is not a pure "count".
* 0 means that it is not mapped, and has not been mapped
* since a TLB flush - it is usable.
* 1 means that there are no users, but it has been mapped
* since the last TLB flush - so we can't use it.
* n means that there are (n-1) current users of it.
*/
static int pkmap_count[LAST_PKMAP];
static unsigned int last_pkmap_nr;
static spinlock_t kmap_lock __cacheline_aligned_in_smp = SPIN_LOCK_UNLOCKED;
pte_t * pkmap_page_table;
static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);
static void flush_all_zero_pkmaps(void)
{
int i;
flush_cache_all();
for (i = 0; i < LAST_PKMAP; i++) {
struct page *page;
/*
* zero means we don't have anything to do,
* >1 means that it is still in use. Only
* a count of 1 means that it is free but
* needs to be unmapped
*/
if (pkmap_count[i] != 1)
continue;
pkmap_count[i] = 0;
/* sanity check */
if (pte_none(pkmap_page_table[i]))
BUG();
/*
* Don't need an atomic fetch-and-clear op here;
* no-one has the page mapped, and cannot get at
* its virtual address (and hence PTE) without first
* getting the kmap_lock (which is held here).
* So no dangers, even with speculative execution.
*/
page = pte_page(pkmap_page_table[i]);
pte_clear(&pkmap_page_table[i]);
page->virtual = NULL;
}
flush_tlb_all();
}
static inline unsigned long map_new_virtual(struct page *page)
{
unsigned long vaddr;
int count;
start:
count = LAST_PKMAP;
/* Find an empty entry */
for (;;) {
last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;
if (!last_pkmap_nr) {
flush_all_zero_pkmaps();
count = LAST_PKMAP;
}
if (!pkmap_count[last_pkmap_nr])
break; /* Found a usable entry */
if (--count)
continue;
/*
* Sleep for somebody else to unmap their entries
*/
{
DECLARE_WAITQUEUE(wait, current);
current->state = TASK_UNINTERRUPTIBLE;
add_wait_queue(&pkmap_map_wait, &wait);
spin_unlock(&kmap_lock);
schedule();
remove_wait_queue(&pkmap_map_wait, &wait);
spin_lock(&kmap_lock);
/* Somebody else might have mapped it while we slept */
if (page->virtual)
return (unsigned long) page->virtual;
/* Re-start */
goto start;
}
}
vaddr = PKMAP_ADDR(last_pkmap_nr);
set_pte(&(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot));
pkmap_count[last_pkmap_nr] = 1;
page->virtual = (void *) vaddr;
return vaddr;
}
void *kmap_high(struct page *page)
{
unsigned long vaddr;
/*
* For highmem pages, we can't trust "virtual" until
* after we have the lock.
*
* We cannot call this from interrupts, as it may block
*/
spin_lock(&kmap_lock);
vaddr = (unsigned long) page->virtual;
if (!vaddr)
vaddr = map_new_virtual(page);
pkmap_count[PKMAP_NR(vaddr)]++;
if (pkmap_count[PKMAP_NR(vaddr)] < 2)
BUG();
spin_unlock(&kmap_lock);
return (void*) vaddr;
}
void kunmap_high(struct page *page)
{
unsigned long vaddr;
unsigned long nr;
int need_wakeup;
spin_lock(&kmap_lock);
vaddr = (unsigned long) page->virtual;
if (!vaddr)
BUG();
nr = PKMAP_NR(vaddr);
/*
* A count must never go down to zero
* without a TLB flush!
*/
need_wakeup = 0;
switch (--pkmap_count[nr]) {
case 0:
BUG();
case 1:
/*
* Avoid an unnecessary wake_up() function call.
* The common case is pkmap_count[] == 1, but
* no waiters.
* The tasks queued in the wait-queue are guarded
* by both the lock in the wait-queue-head and by
* the kmap_lock. As the kmap_lock is held here,
* no need for the wait-queue-head's lock. Simply
* test if the queue is empty.
*/
need_wakeup = waitqueue_active(&pkmap_map_wait);
}
spin_unlock(&kmap_lock);
/* do wake-up, if needed, race-free outside of the spin lock */
if (need_wakeup)
wake_up(&pkmap_map_wait);
}
#define POOL_SIZE 32
/*
* This lock gets no contention at all, normally.
*/
static spinlock_t emergency_lock = SPIN_LOCK_UNLOCKED;
int nr_emergency_pages;
static LIST_HEAD(emergency_pages);
int nr_emergency_bhs;
static LIST_HEAD(emergency_bhs);
/*
* Simple bounce buffer support for highmem pages.
* This will be moved to the block layer in 2.5.
*/
static inline void copy_from_high_bh (struct buffer_head *to,
struct buffer_head *from)
{
struct page *p_from;
char *vfrom;
p_from = from->b_page;
vfrom = kmap_atomic(p_from, KM_USER0);
memcpy(to->b_data, vfrom + bh_offset(from), to->b_size);
kunmap_atomic(vfrom, KM_USER0);
}
static inline void copy_to_high_bh_irq (struct buffer_head *to,
struct buffer_head *from)
{
struct page *p_to;
char *vto;
unsigned long flags;
p_to = to->b_page;
__save_flags(flags);
__cli();
vto = kmap_atomic(p_to, KM_BOUNCE_READ);
memcpy(vto + bh_offset(to), from->b_data, to->b_size);
kunmap_atomic(vto, KM_BOUNCE_READ);
__restore_flags(flags);
}
static inline void bounce_end_io (struct buffer_head *bh, int uptodate)
{
struct page *page;
struct buffer_head *bh_orig = (struct buffer_head *)(bh->b_private);
unsigned long flags;
bh_orig->b_end_io(bh_orig, uptodate);
page = bh->b_page;
spin_lock_irqsave(&emergency_lock, flags);
if (nr_emergency_pages >= POOL_SIZE)
__free_page(page);
else {
/*
* We are abusing page->list to manage
* the highmem emergency pool:
*/
list_add(&page->list, &emergency_pages);
nr_emergency_pages++;
}
if (nr_emergency_bhs >= POOL_SIZE) {
#ifdef HIGHMEM_DEBUG
/* Don't clobber the constructed slab cache */
init_waitqueue_head(&bh->b_wait);
#endif
kmem_cache_free(bh_cachep, bh);
} else {
/*
* Ditto in the bh case, here we abuse b_inode_buffers:
*/
list_add(&bh->b_inode_buffers, &emergency_bhs);
nr_emergency_bhs++;
}
spin_unlock_irqrestore(&emergency_lock, flags);
}
static __init int init_emergency_pool(void)
{
struct sysinfo i;
si_meminfo(&i);
si_swapinfo(&i);
if (!i.totalhigh)
return 0;
spin_lock_irq(&emergency_lock);
while (nr_emergency_pages < POOL_SIZE) {
struct page * page = alloc_page(GFP_ATOMIC);
if (!page) {
printk("couldn't refill highmem emergency pages");
break;
}
list_add(&page->list, &emergency_pages);
nr_emergency_pages++;
}
while (nr_emergency_bhs < POOL_SIZE) {
struct buffer_head * bh = kmem_cache_alloc(bh_cachep, SLAB_ATOMIC);
if (!bh) {
printk("couldn't refill highmem emergency bhs");
break;
}
list_add(&bh->b_inode_buffers, &emergency_bhs);
nr_emergency_bhs++;
}
spin_unlock_irq(&emergency_lock);
printk("allocated %d pages and %d bhs reserved for the highmem bounces\n",
nr_emergency_pages, nr_emergency_bhs);
return 0;
}
__initcall(init_emergency_pool);
static void bounce_end_io_write (struct buffer_head *bh, int uptodate)
{
bounce_end_io(bh, uptodate);
}
static void bounce_end_io_read (struct buffer_head *bh, int uptodate)
{
struct buffer_head *bh_orig = (struct buffer_head *)(bh->b_private);
if (uptodate)
copy_to_high_bh_irq(bh_orig, bh);
bounce_end_io(bh, uptodate);
}
struct page *alloc_bounce_page (void)
{
struct list_head *tmp;
struct page *page;
page = alloc_page(GFP_NOHIGHIO);
if (page)
return page;
/*
* No luck. First, kick the VM so it doesnt idle around while
* we are using up our emergency rations.
*/
wakeup_bdflush();
repeat_alloc:
/*
* Try to allocate from the emergency pool.
*/
tmp = &emergency_pages;
spin_lock_irq(&emergency_lock);
if (!list_empty(tmp)) {
page = list_entry(tmp->next, struct page, list);
list_del(tmp->next);
nr_emergency_pages--;
}
spin_unlock_irq(&emergency_lock);
if (page)
return page;
/* we need to wait I/O completion */
run_task_queue(&tq_disk);
current->policy |= SCHED_YIELD;
__set_current_state(TASK_RUNNING);
schedule();
goto repeat_alloc;
}
struct buffer_head *alloc_bounce_bh (void)
{
struct list_head *tmp;
struct buffer_head *bh;
bh = kmem_cache_alloc(bh_cachep, SLAB_NOHIGHIO);
if (bh)
return bh;
/*
* No luck. First, kick the VM so it doesnt idle around while
* we are using up our emergency rations.
*/
wakeup_bdflush();
repeat_alloc:
/*
* Try to allocate from the emergency pool.
*/
tmp = &emergency_bhs;
spin_lock_irq(&emergency_lock);
if (!list_empty(tmp)) {
bh = list_entry(tmp->next, struct buffer_head, b_inode_buffers);
list_del(tmp->next);
nr_emergency_bhs--;
}
spin_unlock_irq(&emergency_lock);
if (bh)
return bh;
/* we need to wait I/O completion */
run_task_queue(&tq_disk);
current->policy |= SCHED_YIELD;
__set_current_state(TASK_RUNNING);
schedule();
goto repeat_alloc;
}
struct buffer_head * create_bounce(int rw, struct buffer_head * bh_orig)
{
struct page *page;
struct buffer_head *bh;
if (!PageHighMem(bh_orig->b_page))
return bh_orig;
bh = alloc_bounce_bh();
/*
* This is wasteful for 1k buffers, but this is a stopgap measure
* and we are being ineffective anyway. This approach simplifies
* things immensly. On boxes with more than 4GB RAM this should
* not be an issue anyway.
*/
page = alloc_bounce_page();
set_bh_page(bh, page, 0);
bh->b_next = NULL;
bh->b_blocknr = bh_orig->b_blocknr;
bh->b_size = bh_orig->b_size;
bh->b_list = -1;
bh->b_dev = bh_orig->b_dev;
bh->b_count = bh_orig->b_count;
bh->b_rdev = bh_orig->b_rdev;
bh->b_state = bh_orig->b_state;
#ifdef HIGHMEM_DEBUG
bh->b_flushtime = jiffies;
bh->b_next_free = NULL;
bh->b_prev_free = NULL;
/* bh->b_this_page */
bh->b_reqnext = NULL;
bh->b_pprev = NULL;
#endif
/* bh->b_page */
if (rw == WRITE) {
bh->b_end_io = bounce_end_io_write;
copy_from_high_bh(bh, bh_orig);
} else
bh->b_end_io = bounce_end_io_read;
bh->b_private = (void *)bh_orig;
bh->b_rsector = bh_orig->b_rsector;
#ifdef HIGHMEM_DEBUG
memset(&bh->b_wait, -1, sizeof(bh->b_wait));
#endif
return bh;
}
|