stram.c

是关于linux2.5.1的完全源码

/*
 * arch/m68k/atari/stram.c: Functions for ST-RAM allocations
 *
 * Copyright 1994-97 Roman Hodek <[e-mail]>
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file COPYING in the main directory of this archive
 * for more details.
 */

#include <linux/config.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/kdev_t.h>
#include <linux/major.h>
#include <linux/init.h>
#include <linux/swap.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/pagemap.h>
#include <linux/shm.h>
#include <linux/bootmem.h>

#include <asm/setup.h>
#include <asm/machdep.h>
#include <asm/page.h>
#include <asm/pgtable.h>
#include <asm/atarihw.h>
#include <asm/atari_stram.h>
#include <asm/io.h>
#include <asm/semaphore.h>


#ifdef CONFIG_STRAM_SWAP
#define MAJOR_NR    Z2RAM_MAJOR
#define do_z2_request do_stram_request
#include <linux/blk.h>
#undef DEVICE_NAME
#define DEVICE_NAME	"stram"
#endif

#undef DEBUG

#ifdef DEBUG
#define	DPRINTK(fmt,args...) printk( fmt, ##args )
#else
#define DPRINTK(fmt,args...)
#endif

#if defined(CONFIG_PROC_FS) && defined(CONFIG_STRAM_PROC)
/* abbrev for the && above... */
#define DO_PROC
#include <linux/proc_fs.h>
#endif

/* Pre-swapping comments:
 *
 * ++roman:
 * 
 * New version of ST-Ram buffer allocation. Instead of using the
 * 1 MB - 4 KB that remain when the ST-Ram chunk starts at $1000
 * (1 MB granularity!), such buffers are reserved like this:
 *
 *  - If the kernel resides in ST-Ram anyway, we can take the buffer
 *    from behind the current kernel data space the normal way
 *    (incrementing start_mem).
 *    
 *  - If the kernel is in TT-Ram, stram_init() initializes start and
 *    end of the available region. Buffers are allocated from there
 *    and mem_init() later marks the such used pages as reserved.
 *    Since each TT-Ram chunk is at least 4 MB in size, I hope there
 *    won't be an overrun of the ST-Ram region by normal kernel data
 *    space.
 *    
 * For that, ST-Ram may only be allocated while kernel initialization
 * is going on, or exactly: before mem_init() is called. There is also
 * no provision now for freeing ST-Ram buffers. It seems that isn't
 * really needed.
 *
 */

/*
 * New Nov 1997: Use ST-RAM as swap space!
 *
 * In the past, there were often problems with modules that require ST-RAM
 * buffers. Such drivers have to use __get_dma_pages(), which unfortunately
 * often isn't very successful in allocating more than 1 page :-( [1] The net
 * result was that most of the time you couldn't insmod such modules (ataflop,
 * ACSI, SCSI on Falcon, Atari internal framebuffer, not to speak of acsi_slm,
 * which needs a 1 MB buffer... :-).
 *
 * To overcome this limitation, ST-RAM can now be turned into a very
 * high-speed swap space. If a request for an ST-RAM buffer comes, the kernel
 * now tries to unswap some pages on that swap device to make some free (and
 * contiguous) space. This works much better in comparison to
 * __get_dma_pages(), since used swap pages can be selectively freed by either
 * moving them to somewhere else in swap space, or by reading them back into
 * system memory. Ok, there operation of unswapping isn't really cheap (for
 * each page, one has to go through the page tables of all processes), but it
 * doesn't happen that often (only when allocation ST-RAM, i.e. when loading a
 * module that needs ST-RAM). But it at least makes it possible to load such
 * modules!
 *
 * It could also be that overall system performance increases a bit due to
 * ST-RAM swapping, since slow ST-RAM isn't used anymore for holding data or
 * executing code in. It's then just a (very fast, compared to disk) back
 * storage for not-so-often needed data. (But this effect must be compared
 * with the loss of total memory...) Don't know if the effect is already
 * visible on a TT, where the speed difference between ST- and TT-RAM isn't
 * that dramatic, but it should on machines where TT-RAM is really much faster
 * (e.g. Afterburner).
 * 
 *   [1]: __get_free_pages() does a fine job if you only want one page, but if
 * you want more (contiguous) pages, it can give you such a block only if
 * there's already a free one. The algorithm can't try to free buffers or swap
 * out something in order to make more free space, since all that page-freeing
 * mechanisms work "target-less", i.e. they just free something, but not in a
 * specific place. I.e., __get_free_pages() can't do anything to free
 * *adjacent* pages :-( This situation becomes even worse for DMA memory,
 * since the freeing algorithms are also blind to DMA capability of pages.
 */

/* 1998-10-20: ++andreas
   unswap_by_move disabled because it does not handle swapped shm pages.
*/

/* 2000-05-01: ++andreas
   Integrated with bootmem.  Remove all traces of unswap_by_move.
*/

#ifdef CONFIG_STRAM_SWAP
#define ALIGN_IF_SWAP(x)	PAGE_ALIGN(x)
#else
#define ALIGN_IF_SWAP(x)	(x)
#endif

/* get index of swap page at address 'addr' */
#define SWAP_NR(addr)		(((addr) - swap_start) >> PAGE_SHIFT)

/* get address of swap page #'nr' */
#define SWAP_ADDR(nr)		(swap_start + ((nr) << PAGE_SHIFT))

/* get number of pages for 'n' bytes (already page-aligned) */
#define N_PAGES(n)			((n) >> PAGE_SHIFT)

/* The following two numbers define the maximum fraction of ST-RAM in total
 * memory, below that the kernel would automatically use ST-RAM as swap
 * space. This decision can be overriden with stram_swap= */
#define MAX_STRAM_FRACTION_NOM		1
#define MAX_STRAM_FRACTION_DENOM	3

/* Start and end (virtual) of ST-RAM */
static void *stram_start, *stram_end;

/* set after memory_init() executed and allocations via start_mem aren't
 * possible anymore */
static int mem_init_done = 0;

/* set if kernel is in ST-RAM */
static int kernel_in_stram;

typedef struct stram_block {
	struct stram_block *next;
	void *start;
	unsigned long size;
	unsigned flags;
	const char *owner;
} BLOCK;

/* values for flags field */
#define BLOCK_FREE		0x01	/* free structure in the BLOCKs pool */
#define BLOCK_KMALLOCED	0x02	/* structure allocated by kmalloc() */
#define BLOCK_GFP		0x08	/* block allocated with __get_dma_pages() */
#define BLOCK_INSWAP	0x10	/* block allocated in swap space */

/* list of allocated blocks */
static BLOCK *alloc_list = NULL;

/* We can't always use kmalloc() to allocate BLOCK structures, since
 * stram_alloc() can be called rather early. So we need some pool of
 * statically allocated structures. 20 of them is more than enough, so in most
 * cases we never should need to call kmalloc(). */
#define N_STATIC_BLOCKS	20
static BLOCK static_blocks[N_STATIC_BLOCKS];

#ifdef CONFIG_STRAM_SWAP
/* max. number of bytes to use for swapping
 *  0 = no ST-RAM swapping
 * -1 = do swapping (to whole ST-RAM) if it's less than MAX_STRAM_FRACTION of
 *      total memory
 */
static int max_swap_size = -1;

/* start and end of swapping area */
static void *swap_start, *swap_end;

/* The ST-RAM's swap info structure */
static struct swap_info_struct *stram_swap_info;

/* The ST-RAM's swap type */
static int stram_swap_type;

/* Semaphore for get_stram_region.  */
static DECLARE_MUTEX(stram_swap_sem);

/* major and minor device number of the ST-RAM device; for the major, we use
 * the same as Amiga z2ram, which is really similar and impossible on Atari,
 * and for the minor a relatively odd number to avoid the user creating and
 * using that device. */
#define	STRAM_MAJOR		Z2RAM_MAJOR
#define	STRAM_MINOR		13

/* Some impossible pointer value */
#define MAGIC_FILE_P	(struct file *)0xffffdead

#ifdef DO_PROC
static unsigned stat_swap_read = 0;
static unsigned stat_swap_write = 0;
static unsigned stat_swap_force = 0;
#endif /* DO_PROC */

#endif /* CONFIG_STRAM_SWAP */

/***************************** Prototypes *****************************/

#ifdef CONFIG_STRAM_SWAP
static int swap_init(void *start_mem, void *swap_data);
static void *get_stram_region( unsigned long n_pages );
static void free_stram_region( unsigned long offset, unsigned long n_pages
			       );
static int in_some_region(void *addr);
static unsigned long find_free_region( unsigned long n_pages, unsigned long
				       *total_free, unsigned long
				       *region_free );
static void do_stram_request(request_queue_t *);
static int stram_open( struct inode *inode, struct file *filp );
static int stram_release( struct inode *inode, struct file *filp );
#endif
static void reserve_region(void *start, void *end);
static BLOCK *add_region( void *addr, unsigned long size );
static BLOCK *find_region( void *addr );
static int remove_region( BLOCK *block );

/************************* End of Prototypes **************************/


/* ------------------------------------------------------------------------ */
/*							   Public Interface								*/
/* ------------------------------------------------------------------------ */

/*
 * This init function is called very early by atari/config.c
 * It initializes some internal variables needed for stram_alloc()
 */
void __init atari_stram_init(void)
{
	int i;

	/* initialize static blocks */
	for( i = 0; i < N_STATIC_BLOCKS; ++i )
		static_blocks[i].flags = BLOCK_FREE;

	/* determine whether kernel code resides in ST-RAM (then ST-RAM is the
	 * first memory block at virtual 0x0) */
	stram_start = phys_to_virt(0);
	kernel_in_stram = (stram_start == 0);

	for( i = 0; i < m68k_num_memory; ++i ) {
		if (m68k_memory[i].addr == 0) {
			/* skip first 2kB or page (supervisor-only!) */
			stram_end = stram_start + m68k_memory[i].size;
			return;
		}
	}
	/* Should never come here! (There is always ST-Ram!) */
	panic( "atari_stram_init: no ST-RAM found!" );
}


/*
 * This function is called from setup_arch() to reserve the pages needed for
 * ST-RAM management.
 */
void __init atari_stram_reserve_pages(void *start_mem)
{
#ifdef CONFIG_STRAM_SWAP
	/* if max_swap_size is negative (i.e. no stram_swap= option given),
	 * determine at run time whether to use ST-RAM swapping */
	if (max_swap_size < 0)
		/* Use swapping if ST-RAM doesn't make up more than MAX_STRAM_FRACTION
		 * of total memory. In that case, the max. size is set to 16 MB,
		 * because ST-RAM can never be bigger than that.
		 * Also, never use swapping on a Hades, there's no separate ST-RAM in
		 * that machine. */
		max_swap_size =
			(!MACH_IS_HADES &&
			 (N_PAGES(stram_end-stram_start)*MAX_STRAM_FRACTION_DENOM <=
			  (high_memory>>PAGE_SHIFT)*MAX_STRAM_FRACTION_NOM)) ? 16*1024*1024 : 0;
	DPRINTK( "atari_stram_reserve_pages: max_swap_size = %d\n", max_swap_size );
#endif

	/* always reserve first page of ST-RAM, the first 2 kB are
	 * supervisor-only! */
	if (!kernel_in_stram)
		reserve_bootmem (0, PAGE_SIZE);

#ifdef CONFIG_STRAM_SWAP
	{
		void *swap_data;

		start_mem = (void *) PAGE_ALIGN ((unsigned long) start_mem);
		/* determine first page to use as swap: if the kernel is
		   in TT-RAM, this is the first page of (usable) ST-RAM;
		   otherwise just use the end of kernel data (= start_mem) */
		swap_start = !kernel_in_stram ? stram_start + PAGE_SIZE : start_mem;
		/* decrement by one page, rest of kernel assumes that first swap page
		 * is always reserved and maybe doesn't handle SWP_ENTRY == 0
		 * correctly */
		swap_start -= PAGE_SIZE;
		swap_end = stram_end;
		if (swap_end-swap_start > max_swap_size)
			swap_end =  swap_start + max_swap_size;
		DPRINTK( "atari_stram_reserve_pages: swapping enabled; "
				 "swap=%p-%p\n", swap_start, swap_end);
		
		/* reserve some amount of memory for maintainance of
		 * swapping itself: one page for each 2048 (PAGE_SIZE/2)
		 * swap pages. (2 bytes for each page) */
		swap_data = start_mem;
		start_mem += ((SWAP_NR(swap_end) + PAGE_SIZE/2 - 1)
			      >> (PAGE_SHIFT-1)) << PAGE_SHIFT;
		/* correct swap_start if necessary */
		if (swap_start + PAGE_SIZE == swap_data)
			swap_start = start_mem - PAGE_SIZE;
		
		if (!swap_init( start_mem, swap_data )) {
			printk( KERN_ERR "ST-RAM swap space initialization failed\n" );
			max_swap_size = 0;
			return;
		}
		/* reserve region for swapping meta-data */
		reserve_region(swap_data, start_mem);
		/* reserve swapping area itself */
		reserve_region(swap_start + PAGE_SIZE, swap_end);

		/*
		 * If the whole ST-RAM is used for swapping, there are no allocatable
		 * dma pages left. But unfortunately, some shared parts of the kernel
		 * (particularily the SCSI mid-level) call __get_dma_pages()
		 * unconditionally :-( These calls then fail, and scsi.c even doesn't
		 * check for NULL return values and just crashes. The quick fix for
		 * this (instead of doing much clean up work in the SCSI code) is to
		 * pretend all pages are DMA-able by setting mach_max_dma_address to
		 * ULONG_MAX. This doesn't change any functionality so far, since
		 * get_dma_pages() shouldn't be used on Atari anyway anymore (better
		 * use atari_stram_alloc()), and the Atari SCSI drivers don't need DMA
		 * memory. But unfortunately there's now no kind of warning (even not
		 * a NULL return value) if you use get_dma_pages() nevertheless :-(
		 * You just will get non-DMA-able memory...
		 */
		mach_max_dma_address = 0xffffffff;
	}
#endif
}

void atari_stram_mem_init_hook (void)
{
	mem_init_done = 1;
}


/*
 * This is main public interface: somehow allocate a ST-RAM block
 * There are three strategies:
 * 
 *  - If we're before mem_init(), we have to make a static allocation. The
 *    region is taken in the kernel data area (if the kernel is in ST-RAM) or
 *    from the start of ST-RAM (if the kernel is in TT-RAM) and added to the
 *    rsvd_stram_* region. The ST-RAM is somewhere in the middle of kernel
 *    address space in the latter case.
 * 
 *  - If mem_init() already has been called and ST-RAM swapping is enabled,
 *    try to get the memory from the (pseudo) swap-space, either free already
 *    or by moving some other pages out of the swap.
 *
 *  - If mem_init() already has been called, and ST-RAM swapping is not
 *    enabled, the only possibility is to try with __get_dma_pages(). This has
 *    the disadvantage that it's very hard to get more than 1 page, and it is
 *    likely to fail :-(
 * 
 */
void *atari_stram_alloc(long size, const char *owner)
{
	void *addr = NULL;
	BLOCK *block;
	int flags;

	DPRINTK("atari_stram_alloc(size=%08lx,owner=%s)\n", size, owner);

	size = ALIGN_IF_SWAP(size);
	DPRINTK( "atari_stram_alloc: rounded size = %08lx\n", size );
#ifdef CONFIG_STRAM_SWAP
	if (max_swap_size) {
		/* If swapping is active: make some free space in the swap
		   "device". */
		DPRINTK( "atari_stram_alloc: after mem_init, swapping ok, "
				 "calling get_region\n" );
		addr = get_stram_region( N_PAGES(size) );
		flags = BLOCK_INSWAP;
	}
	else
#endif
	if (!mem_init_done)
		return alloc_bootmem_low(size);
	else {
		/* After mem_init() and no swapping: can only resort to