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831058dec3
Move the bounce buffer code from mm/highmem.c to mm/bounce.c so that it can be more easily disabled when the block layer is disabled. !!!NOTE!!! There may be a bug in this code: Should init_emergency_pool() be contingent on CONFIG_HIGHMEM? Signed-Off-By: David Howells <dhowells@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
335 lines
7.8 KiB
C
335 lines
7.8 KiB
C
/*
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* High memory handling common code and variables.
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*
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* (C) 1999 Andrea Arcangeli, SuSE GmbH, andrea@suse.de
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* Gerhard Wichert, Siemens AG, Gerhard.Wichert@pdb.siemens.de
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*
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*
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* Redesigned the x86 32-bit VM architecture to deal with
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* 64-bit physical space. With current x86 CPUs this
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* means up to 64 Gigabytes physical RAM.
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*
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* Rewrote high memory support to move the page cache into
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* high memory. Implemented permanent (schedulable) kmaps
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* based on Linus' idea.
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*
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* Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
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*/
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#include <linux/mm.h>
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#include <linux/module.h>
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#include <linux/swap.h>
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#include <linux/bio.h>
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#include <linux/pagemap.h>
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#include <linux/mempool.h>
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#include <linux/blkdev.h>
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#include <linux/init.h>
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#include <linux/hash.h>
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#include <linux/highmem.h>
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#include <linux/blktrace_api.h>
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#include <asm/tlbflush.h>
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/*
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* Virtual_count is not a pure "count".
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* 0 means that it is not mapped, and has not been mapped
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* since a TLB flush - it is usable.
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* 1 means that there are no users, but it has been mapped
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* since the last TLB flush - so we can't use it.
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* n means that there are (n-1) current users of it.
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*/
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#ifdef CONFIG_HIGHMEM
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unsigned long totalhigh_pages __read_mostly;
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unsigned int nr_free_highpages (void)
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{
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pg_data_t *pgdat;
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unsigned int pages = 0;
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for_each_online_pgdat(pgdat)
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pages += pgdat->node_zones[ZONE_HIGHMEM].free_pages;
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return pages;
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}
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static int pkmap_count[LAST_PKMAP];
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static unsigned int last_pkmap_nr;
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static __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock);
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pte_t * pkmap_page_table;
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static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);
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static void flush_all_zero_pkmaps(void)
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{
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int i;
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flush_cache_kmaps();
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for (i = 0; i < LAST_PKMAP; i++) {
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struct page *page;
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/*
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* zero means we don't have anything to do,
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* >1 means that it is still in use. Only
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* a count of 1 means that it is free but
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* needs to be unmapped
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*/
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if (pkmap_count[i] != 1)
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continue;
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pkmap_count[i] = 0;
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/* sanity check */
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BUG_ON(pte_none(pkmap_page_table[i]));
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/*
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* Don't need an atomic fetch-and-clear op here;
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* no-one has the page mapped, and cannot get at
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* its virtual address (and hence PTE) without first
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* getting the kmap_lock (which is held here).
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* So no dangers, even with speculative execution.
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*/
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page = pte_page(pkmap_page_table[i]);
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pte_clear(&init_mm, (unsigned long)page_address(page),
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&pkmap_page_table[i]);
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set_page_address(page, NULL);
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}
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flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
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}
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static inline unsigned long map_new_virtual(struct page *page)
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{
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unsigned long vaddr;
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int count;
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start:
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count = LAST_PKMAP;
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/* Find an empty entry */
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for (;;) {
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last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;
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if (!last_pkmap_nr) {
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flush_all_zero_pkmaps();
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count = LAST_PKMAP;
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}
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if (!pkmap_count[last_pkmap_nr])
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break; /* Found a usable entry */
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if (--count)
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continue;
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/*
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* Sleep for somebody else to unmap their entries
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*/
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{
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DECLARE_WAITQUEUE(wait, current);
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__set_current_state(TASK_UNINTERRUPTIBLE);
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add_wait_queue(&pkmap_map_wait, &wait);
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spin_unlock(&kmap_lock);
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schedule();
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remove_wait_queue(&pkmap_map_wait, &wait);
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spin_lock(&kmap_lock);
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/* Somebody else might have mapped it while we slept */
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if (page_address(page))
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return (unsigned long)page_address(page);
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/* Re-start */
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goto start;
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}
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}
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vaddr = PKMAP_ADDR(last_pkmap_nr);
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set_pte_at(&init_mm, vaddr,
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&(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot));
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pkmap_count[last_pkmap_nr] = 1;
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set_page_address(page, (void *)vaddr);
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return vaddr;
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}
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void fastcall *kmap_high(struct page *page)
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{
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unsigned long vaddr;
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/*
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* For highmem pages, we can't trust "virtual" until
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* after we have the lock.
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*
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* We cannot call this from interrupts, as it may block
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*/
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spin_lock(&kmap_lock);
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vaddr = (unsigned long)page_address(page);
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if (!vaddr)
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vaddr = map_new_virtual(page);
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pkmap_count[PKMAP_NR(vaddr)]++;
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BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2);
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spin_unlock(&kmap_lock);
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return (void*) vaddr;
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}
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EXPORT_SYMBOL(kmap_high);
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void fastcall kunmap_high(struct page *page)
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{
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unsigned long vaddr;
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unsigned long nr;
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int need_wakeup;
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spin_lock(&kmap_lock);
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vaddr = (unsigned long)page_address(page);
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BUG_ON(!vaddr);
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nr = PKMAP_NR(vaddr);
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/*
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* A count must never go down to zero
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* without a TLB flush!
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*/
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need_wakeup = 0;
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switch (--pkmap_count[nr]) {
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case 0:
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BUG();
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case 1:
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/*
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* Avoid an unnecessary wake_up() function call.
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* The common case is pkmap_count[] == 1, but
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* no waiters.
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* The tasks queued in the wait-queue are guarded
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* by both the lock in the wait-queue-head and by
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* the kmap_lock. As the kmap_lock is held here,
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* no need for the wait-queue-head's lock. Simply
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* test if the queue is empty.
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*/
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need_wakeup = waitqueue_active(&pkmap_map_wait);
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}
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spin_unlock(&kmap_lock);
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/* do wake-up, if needed, race-free outside of the spin lock */
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if (need_wakeup)
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wake_up(&pkmap_map_wait);
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}
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EXPORT_SYMBOL(kunmap_high);
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#endif
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#if defined(HASHED_PAGE_VIRTUAL)
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#define PA_HASH_ORDER 7
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/*
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* Describes one page->virtual association
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*/
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struct page_address_map {
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struct page *page;
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void *virtual;
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struct list_head list;
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};
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/*
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* page_address_map freelist, allocated from page_address_maps.
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*/
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static struct list_head page_address_pool; /* freelist */
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static spinlock_t pool_lock; /* protects page_address_pool */
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/*
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* Hash table bucket
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*/
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static struct page_address_slot {
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struct list_head lh; /* List of page_address_maps */
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spinlock_t lock; /* Protect this bucket's list */
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} ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER];
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static struct page_address_slot *page_slot(struct page *page)
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{
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return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)];
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}
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void *page_address(struct page *page)
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{
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unsigned long flags;
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void *ret;
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struct page_address_slot *pas;
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if (!PageHighMem(page))
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return lowmem_page_address(page);
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pas = page_slot(page);
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ret = NULL;
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spin_lock_irqsave(&pas->lock, flags);
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if (!list_empty(&pas->lh)) {
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struct page_address_map *pam;
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list_for_each_entry(pam, &pas->lh, list) {
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if (pam->page == page) {
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ret = pam->virtual;
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goto done;
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}
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}
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}
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done:
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spin_unlock_irqrestore(&pas->lock, flags);
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return ret;
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}
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EXPORT_SYMBOL(page_address);
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void set_page_address(struct page *page, void *virtual)
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{
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unsigned long flags;
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struct page_address_slot *pas;
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struct page_address_map *pam;
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BUG_ON(!PageHighMem(page));
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pas = page_slot(page);
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if (virtual) { /* Add */
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BUG_ON(list_empty(&page_address_pool));
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spin_lock_irqsave(&pool_lock, flags);
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pam = list_entry(page_address_pool.next,
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struct page_address_map, list);
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list_del(&pam->list);
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spin_unlock_irqrestore(&pool_lock, flags);
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pam->page = page;
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pam->virtual = virtual;
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spin_lock_irqsave(&pas->lock, flags);
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list_add_tail(&pam->list, &pas->lh);
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spin_unlock_irqrestore(&pas->lock, flags);
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} else { /* Remove */
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spin_lock_irqsave(&pas->lock, flags);
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list_for_each_entry(pam, &pas->lh, list) {
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if (pam->page == page) {
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list_del(&pam->list);
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spin_unlock_irqrestore(&pas->lock, flags);
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spin_lock_irqsave(&pool_lock, flags);
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list_add_tail(&pam->list, &page_address_pool);
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spin_unlock_irqrestore(&pool_lock, flags);
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goto done;
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}
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}
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spin_unlock_irqrestore(&pas->lock, flags);
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}
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done:
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return;
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}
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static struct page_address_map page_address_maps[LAST_PKMAP];
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void __init page_address_init(void)
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{
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int i;
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INIT_LIST_HEAD(&page_address_pool);
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for (i = 0; i < ARRAY_SIZE(page_address_maps); i++)
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list_add(&page_address_maps[i].list, &page_address_pool);
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for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) {
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INIT_LIST_HEAD(&page_address_htable[i].lh);
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spin_lock_init(&page_address_htable[i].lock);
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}
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spin_lock_init(&pool_lock);
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}
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#endif /* defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL) */
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