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Revert the recent hashing change, performance seemed to go way down in
certain benchmarks.  This is reverted to how it was, except the number
of hash buckets is larger than previously to attempt to account for the
workload Steve was originally targetting with that change.
Merge of 2.4.x-xfs:slinx:140053a by nathans.

/*
 * Copyright (c) 2000-2002 Silicon Graphics, Inc.  All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of version 2 of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 *
 * Further, this software is distributed without any warranty that it is
 * free of the rightful claim of any third person regarding infringement
 * or the like.	 Any license provided herein, whether implied or
 * otherwise, applies only to this software file.  Patent licenses, if
 * any, provided herein do not apply to combinations of this program with
 * other software, or any other product whatsoever.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write the Free Software Foundation, Inc., 59
 * Temple Place - Suite 330, Boston MA 02111-1307, USA.
 *
 * Contact information: Silicon Graphics, Inc., 1600 Amphitheatre Pkwy,
 * Mountain View, CA  94043, or:
 *
 * http://www.sgi.com
 *
 * For further information regarding this notice, see:
 *
 * http://oss.sgi.com/projects/GenInfo/SGIGPLNoticeExplan/
 */

/*
 * Written by Steve Lord, Jim Mostek, Russell Cattelan at SGI
 */

#ifndef __PAGE_BUF_H__
#define __PAGE_BUF_H__

#include <linux/version.h>
#include <linux/config.h>
#include <linux/list.h>
#include <linux/types.h>
#include <linux/spinlock.h>
#include <asm/system.h>
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/buffer_head.h>
#include <linux/uio.h>

/*
 * Turn this on to get pagebuf lock ownership
#define PAGEBUF_LOCK_TRACKING
*/

/*
 *	Base types
 */

/* daddr must be signed since -1 is used for bmaps that are not yet allocated */
typedef loff_t page_buf_daddr_t;

#define PAGE_BUF_DADDR_NULL ((page_buf_daddr_t) (-1LL))

typedef size_t page_buf_dsize_t;		/* size of buffer in blocks */

#define page_buf_ctob(pp)	((pp) * PAGE_CACHE_SIZE)
#define page_buf_btoc(dd)	(((dd) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT)
#define page_buf_btoct(dd)	((dd) >> PAGE_CACHE_SHIFT)
#define page_buf_poff(aa)	((aa) & ~PAGE_CACHE_MASK)

typedef enum page_buf_rw_e {
	PBRW_READ = 1,			/* transfer into target memory */
	PBRW_WRITE = 2,			/* transfer from target memory */
	PBRW_ZERO = 3			/* Zero target memory */
} page_buf_rw_t;

typedef enum {				/* pbm_flags values */
	PBMF_EOF =		0x01,	/* mapping contains EOF		*/
	PBMF_HOLE =		0x02,	/* mapping covers a hole	*/
	PBMF_DELAY =		0x04,	/* mapping covers delalloc region  */
	PBMF_UNWRITTEN =	0x20	/* mapping covers allocated	*/
					/* but uninitialized file data	*/
} bmap_flags_t;

typedef enum page_buf_flags_e {		/* pb_flags values */
	PBF_READ = (1 << 0),	/* buffer intended for reading from device */
	PBF_WRITE = (1 << 1),	/* buffer intended for writing to device   */
	PBF_MAPPED = (1 << 2),	/* buffer mapped (pb_addr valid)	   */
	PBF_PARTIAL = (1 << 3), /* buffer partially read		   */
	PBF_ASYNC = (1 << 4),	/* initiator will not wait for completion  */
	PBF_NONE = (1 << 5),	/* buffer not read at all		   */
	PBF_DELWRI = (1 << 6),	/* buffer has dirty pages		   */
	PBF_FREED = (1 << 7),	/* buffer has been freed and is invalid	   */
	PBF_SYNC = (1 << 8),	/* force updates to disk		   */
	PBF_MAPPABLE = (1 << 9),/* use directly-addressable pages	   */
	PBF_STALE = (1 << 10),	/* buffer has been staled, do not find it  */
	PBF_FS_MANAGED = (1 << 11), /* filesystem controls freeing memory  */

	/* flags used only as arguments to access routines */
	PBF_LOCK = (1 << 13),	/* lock requested			   */
	PBF_TRYLOCK = (1 << 14), /* lock requested, but do not wait	   */
	PBF_FILE_ALLOCATE = (1 << 15), /* allocate all file space	   */
	PBF_DONT_BLOCK = (1 << 16), /* do not block in current thread	   */
	PBF_DIRECT = (1 << 17),	/* direct I/O desired			   */
	PBF_FILE_UNWRITTEN = (1 << 18), /* convert unwritten extent space  */

	/* flags used only internally */
	_PBF_LOCKABLE = (1 << 19), /* page_buf_t may be locked		   */
	_PBF_ALL_PAGES_MAPPED = (1 << 21), /* all pages in range mapped	   */
	_PBF_ADDR_ALLOCATED = (1 << 22), /* pb_addr space was allocated	   */
	_PBF_MEM_ALLOCATED = (1 << 23), /* pb_mem+underlying pages alloc'd */

	PBF_FORCEIO = (1 << 24),
	PBF_FLUSH = (1 << 25),	/* flush disk write cache		   */
	PBF_READ_AHEAD = (1 << 26),

} page_buf_flags_t;

#define PBF_UPDATE (PBF_READ | PBF_WRITE)
#define PBF_NOT_DONE(pb) (((pb)->pb_flags & (PBF_PARTIAL|PBF_NONE)) != 0)
#define PBF_DONE(pb) (((pb)->pb_flags & (PBF_PARTIAL|PBF_NONE)) == 0)

#define PBR_SECTOR_ONLY	1	/* only use sector size buffer heads */
#define PBR_ALIGNED_ONLY 2	/* only use aligned I/O */

typedef struct pb_target {
	dev_t			pbr_dev;
	struct block_device	*pbr_bdev;
	struct address_space	*pbr_mapping;
	unsigned int		pbr_bsize;
	unsigned int		pbr_sshift;
	size_t			pbr_smask;
} pb_target_t;

/*
 *	page_buf_bmap_t:  File system I/O map
 *
 * The pbm_bn, pbm_offset and pbm_length fields are expressed in disk blocks.
 * The pbm_length field specifies the size of the underlying backing store
 * for the particular mapping.
 *
 * The pbm_bsize, pbm_size and pbm_delta fields are in bytes and indicate
 * the size of the mapping, the number of bytes that are valid to access
 * (read or write), and the offset into the mapping, given the offset
 * supplied to the file I/O map routine.  pbm_delta is the offset of the
 * desired data from the beginning of the mapping.
 *
 * When a request is made to read beyond the logical end of the object,
 * pbm_size may be set to 0, but pbm_offset and pbm_length should be set to
 * the actual amount of underlying storage that has been allocated, if any.
 */

typedef struct page_buf_bmap_s {
	page_buf_daddr_t pbm_bn;	/* block number in file system	    */
	pb_target_t	*pbm_target;	/* device to do I/O to		    */
	loff_t		pbm_offset;	/* byte offset of mapping in file   */
	size_t		pbm_delta;	/* offset of request into bmap	    */
	size_t		pbm_bsize;	/* size of this mapping in bytes    */
	bmap_flags_t	pbm_flags;	/* options flags for mapping	    */
} page_buf_bmap_t;

typedef page_buf_bmap_t pb_bmap_t;


/*
 *	page_buf_t:  Buffer structure for page cache-based buffers
 *
 * This buffer structure is used by the page cache buffer management routines
 * to refer to an assembly of pages forming a logical buffer.  The actual
 * I/O is performed with buffer_head or bio structures, as required by drivers,
 * for drivers which do not understand this structure. The buffer structure is
 * used on temporary basis only, and discarded when released.  
 *
 * The real data storage is recorded in the page cache.	 Metadata is
 * hashed to the inode for the block device on which the file system resides.
 * File data is hashed to the inode for the file.  Pages which are only
 * partially filled with data have bits set in their block_map entry
 * to indicate which disk blocks in the page are not valid.
 */

struct page_buf_s;
typedef void (*page_buf_iodone_t)(struct page_buf_s *);
			/* call-back function on I/O completion */
typedef void (*page_buf_relse_t)(struct page_buf_s *);
			/* call-back function on I/O completion */
typedef int (*page_buf_bdstrat_t)(struct page_buf_s *);

#define PB_PAGES	4

typedef struct page_buf_s {
	struct semaphore	pb_sema;	/* semaphore for lockables  */
	unsigned long		pb_flushtime;	/* time to flush pagebuf    */
	atomic_t		pb_pin_count;	/* pin count		    */
	wait_queue_head_t	pb_waiters;	/* unpin waiters	    */
	struct list_head	pb_list;
	page_buf_flags_t	pb_flags;	/* status flags */
	struct list_head	pb_hash_list;
	struct pb_target	*pb_target;	/* logical object */
	atomic_t		pb_hold;	/* reference count */
	page_buf_daddr_t	pb_bn;		/* block number for I/O */
	loff_t			pb_file_offset; /* offset in file */
	size_t			pb_buffer_length; /* size of buffer in bytes */
	size_t			pb_count_desired; /* desired transfer size */
	void			*pb_addr;	/* virtual address of buffer */
	struct work_struct	pb_iodone_work;
	atomic_t		pb_io_remaining;/* #outstanding I/O requests */
	page_buf_iodone_t	pb_iodone;	/* I/O completion function */
	page_buf_relse_t	pb_relse;	/* releasing function */
	page_buf_bdstrat_t	pb_strat;	/* pre-write function */
	struct semaphore	pb_iodonesema;	/* Semaphore for I/O waiters */
	void			*pb_fspriv;
	void			*pb_fspriv2;
	void			*pb_fspriv3;
	unsigned short		pb_error;	/* error code on I/O */
	unsigned short		pb_page_count;	/* size of page array */
	unsigned short		pb_offset;	/* page offset in first page */
	unsigned char		pb_locked;	/* page array is locked */
	unsigned char		pb_hash_index;	/* hash table index	*/
	struct page		**pb_pages;	/* array of page pointers */
	struct page		*pb_page_array[PB_PAGES]; /* inline pages */
#ifdef PAGEBUF_LOCK_TRACKING
	int			pb_last_holder;
#endif
} page_buf_t;


/*
 * page_buf module entry points
 */

/* Finding and Reading Buffers */

extern page_buf_t *pagebuf_find(	/* find buffer for block if	*/
					/* the block is in memory	*/
		struct pb_target *,	/* inode for block		*/
		loff_t,			/* starting offset of range	*/
		size_t,			/* length of range		*/
		page_buf_flags_t);	/* PBF_LOCK			*/

extern page_buf_t *pagebuf_get(		/* allocate a buffer		*/
		struct pb_target *,	/* inode for buffer		*/
		loff_t,			/* starting offset of range	*/
		size_t,			/* length of range		*/
		page_buf_flags_t);	/* PBF_LOCK, PBF_READ,		*/
					/* PBF_ASYNC			*/	

extern page_buf_t *pagebuf_get_empty(	/* allocate pagebuf struct with */
					/*  no memory or disk address	*/
		struct pb_target *);	/* mount point "fake" inode	*/

extern page_buf_t *pagebuf_get_no_daddr(/* allocate pagebuf struct	*/
					/* without disk address		*/
		size_t len,
		struct pb_target *);	/* mount point "fake" inode	*/

extern int	pagebuf_associate_memory(
		page_buf_t *,
		void *,
		size_t);


extern void pagebuf_hold(		/* increment reference count	*/
		page_buf_t *);		/* buffer to hold		*/

extern void pagebuf_readahead(		/* read ahead into cache	*/
		struct pb_target  *,	/* target for buffer (or NULL)	*/
		loff_t,			/* starting offset of range	*/
		size_t,			/* length of range		*/
		page_buf_flags_t);	/* additional read flags	*/

/* Writing and Releasing Buffers */

extern void pagebuf_free(		/* deallocate a buffer		*/
		page_buf_t *);		/* buffer to deallocate		*/

extern void pagebuf_rele(		/* release hold on a buffer	*/
		page_buf_t *);		/* buffer to release		*/

/* Locking and Unlocking Buffers */

extern int pagebuf_cond_lock(		/* lock buffer, if not locked	*/
					/* (returns -EBUSY if locked)	*/
		page_buf_t *);		/* buffer to lock		*/

extern int pagebuf_lock_value(		/* return count on lock		*/
		page_buf_t *);		/* buffer to check		*/

extern int pagebuf_lock(		/* lock buffer			*/
		page_buf_t *);		/* buffer to lock		*/

extern void pagebuf_unlock(		/* unlock buffer		*/
		page_buf_t *);		/* buffer to unlock		*/

/* Buffer Utility Routines */
static inline int pagebuf_geterror(page_buf_t *pb)
{
	return (pb ? pb->pb_error : ENOMEM);
}

extern void pagebuf_iodone(		/* mark buffer I/O complete	*/
		page_buf_t *,		/* buffer to mark		*/
		int);			/* run completion locally, or in
					 * a helper thread. 		*/

extern void pagebuf_ioerror(		/* mark buffer in error (or not) */
		page_buf_t *,		/* buffer to mark		*/
		unsigned int);		/* error to store (0 if none)	*/

extern int pagebuf_iostart(		/* start I/O on a buffer	*/
		page_buf_t *,		/* buffer to start		*/
		page_buf_flags_t);	/* PBF_LOCK, PBF_ASYNC,		*/
					/* PBF_READ, PBF_WRITE,		*/
					/* PBF_DELWRI, PBF_SYNC		*/

extern int pagebuf_iorequest(		/* start real I/O		*/
		page_buf_t *);		/* buffer to convey to device	*/

	/*
	 * pagebuf_iorequest is the core I/O request routine.
	 * It assumes that the buffer is well-formed and
	 * mapped and ready for physical I/O, unlike
	 * pagebuf_iostart() and pagebuf_iophysio().  Those
	 * routines call the inode pagebuf_ioinitiate routine to start I/O,
	 * if it is present, or else call pagebuf_iorequest()
	 * directly if the inode pagebuf_ioinitiate routine is not present.
	 */

extern int pagebuf_iowait(		/* wait for buffer I/O done	*/
		page_buf_t *);		/* buffer to wait on		*/

extern caddr_t	pagebuf_offset(page_buf_t *, size_t);

extern void pagebuf_iomove(		/* move data in/out of pagebuf	*/
		page_buf_t *,		/* buffer to manipulate		*/
		size_t,			/* starting buffer offset	*/
		size_t,			/* length in buffer		*/
		caddr_t,		/* data pointer			*/
		page_buf_rw_t);		/* direction			*/

/* Pinning Buffer Storage in Memory */

extern void pagebuf_pin(		/* pin buffer in memory		*/
		page_buf_t *);		/* buffer to pin		*/

extern void pagebuf_unpin(		/* unpin buffered data		*/
		page_buf_t *);		/* buffer to unpin		*/

extern int pagebuf_ispin( page_buf_t *); /* check if pagebuf is pinned	*/

/* Reading and writing pages */

extern void pagebuf_delwri_dequeue(page_buf_t *);

#define PBDF_WAIT    0x01
#define PBDF_TRYLOCK 0x02
extern void pagebuf_delwri_flush(
		struct pb_target *,
		unsigned long,
		int *);

extern int pagebuf_init(void);
extern void pagebuf_terminate(void);

static __inline__ int __pagebuf_iorequest(page_buf_t *pb)
{
	if (pb->pb_strat)
		return pb->pb_strat(pb);
	return pagebuf_iorequest(pb);
}

static __inline__ void pagebuf_run_queues(page_buf_t *pb)
{
	if (!pb || atomic_read(&pb->pb_io_remaining))
		blk_run_queues();
}

#endif /* __PAGE_BUF_H__ */