xfs_buf.c

linux-2.4.29操作系统的源码

/*
 * Copyright (c) 2000-2004 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/
 */

/*
 *	The xfs_buf.c code provides an abstract buffer cache model on top
 *	of the Linux page cache.  Cached metadata blocks for a file system
 *	are hashed to the inode for the block device.  xfs_buf.c assembles
 *	buffers (xfs_buf_t) on demand to aggregate such cached pages for I/O.
 *
 *      Written by Steve Lord, Jim Mostek, Russell Cattelan
 *		    and Rajagopal Ananthanarayanan ("ananth") at SGI.
 *
 */

#include <linux/stddef.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/pagemap.h>
#include <linux/init.h>
#include <linux/vmalloc.h>
#include <linux/blkdev.h>
#include <linux/locks.h>
#include <linux/sysctl.h>
#include <linux/proc_fs.h>

#include "xfs_linux.h"

#define BN_ALIGN_MASK	((1 << (PAGE_CACHE_SHIFT - BBSHIFT)) - 1)

#ifndef GFP_READAHEAD
#define GFP_READAHEAD	0
#endif

/*
 * A backport of the 2.5 scheduler is used by many vendors of 2.4-based
 * distributions.
 * We can only guess it's presences by the lack of the SCHED_YIELD flag.
 * If the heuristic doesn't work, change this define by hand.
 */
#ifndef SCHED_YIELD
#define __HAVE_NEW_SCHEDULER	1
#endif

/*
 * cpumask_t is used for supporting NR_CPUS > BITS_PER_LONG.
 * If support for this is present, migrate_to_cpu exists and provides
 * a wrapper around the set_cpus_allowed routine.
 */
#ifdef copy_cpumask
#define __HAVE_CPUMASK_T	1
#endif

#ifndef __HAVE_CPUMASK_T
# ifndef __HAVE_NEW_SCHEDULER
#  define migrate_to_cpu(cpu)	\
	do { current->cpus_allowed = 1UL << (cpu); } while (0)
# else
#  define migrate_to_cpu(cpu)	\
	set_cpus_allowed(current, 1UL << (cpu))
# endif
#endif

#ifndef VM_MAP
#define VM_MAP	VM_ALLOC
#endif

/*
 * File wide globals
 */

STATIC kmem_cache_t *pagebuf_cache;
STATIC kmem_shaker_t pagebuf_shake;

#define MAX_IO_DAEMONS		NR_CPUS
#define CPU_TO_DAEMON(cpu)	(cpu)
STATIC int pb_logio_daemons[MAX_IO_DAEMONS];
STATIC struct list_head pagebuf_logiodone_tq[MAX_IO_DAEMONS];
STATIC wait_queue_head_t pagebuf_logiodone_wait[MAX_IO_DAEMONS];
STATIC int pb_dataio_daemons[MAX_IO_DAEMONS];
STATIC struct list_head pagebuf_dataiodone_tq[MAX_IO_DAEMONS];
STATIC wait_queue_head_t pagebuf_dataiodone_wait[MAX_IO_DAEMONS];

/*
 * For pre-allocated buffer head pool
 */

#define NR_RESERVED_BH	64
static wait_queue_head_t	pb_resv_bh_wait;
static spinlock_t		pb_resv_bh_lock = SPIN_LOCK_UNLOCKED;
struct buffer_head		*pb_resv_bh = NULL;	/* list of bh */
int				pb_resv_bh_cnt = 0;	/* # of bh available */

STATIC void _pagebuf_ioapply(xfs_buf_t *);
STATIC int pagebuf_daemon_wakeup(int, unsigned int);
STATIC void pagebuf_delwri_queue(xfs_buf_t *, int);
STATIC void pagebuf_runall_queues(struct list_head[]);

/*
 * Pagebuf debugging
 */

#ifdef PAGEBUF_TRACE
void
pagebuf_trace(
	xfs_buf_t	*pb,
	char		*id,
	void		*data,
	void		*ra)
{
	ktrace_enter(pagebuf_trace_buf,
		pb, id,
		(void *)(unsigned long)pb->pb_flags,
		(void *)(unsigned long)pb->pb_hold.counter,
		(void *)(unsigned long)pb->pb_sema.count.counter,
		(void *)current,
		data, ra,
		(void *)(unsigned long)((pb->pb_file_offset>>32) & 0xffffffff),
		(void *)(unsigned long)(pb->pb_file_offset & 0xffffffff),
		(void *)(unsigned long)pb->pb_buffer_length,
		NULL, NULL, NULL, NULL, NULL);
}
ktrace_t *pagebuf_trace_buf;
#define PAGEBUF_TRACE_SIZE	4096
#define PB_TRACE(pb, id, data)	\
	pagebuf_trace(pb, id, (void *)data, (void *)__builtin_return_address(0))
#else
#define PB_TRACE(pb, id, data)	do { } while (0)
#endif

#ifdef PAGEBUF_LOCK_TRACKING
# define PB_SET_OWNER(pb)	((pb)->pb_last_holder = current->pid)
# define PB_CLEAR_OWNER(pb)	((pb)->pb_last_holder = -1)
# define PB_GET_OWNER(pb)	((pb)->pb_last_holder)
#else
# define PB_SET_OWNER(pb)	do { } while (0)
# define PB_CLEAR_OWNER(pb)	do { } while (0)
# define PB_GET_OWNER(pb)	do { } while (0)
#endif

/*
 * Pagebuf allocation / freeing.
 */

#define pb_to_gfp(flags) \
	(((flags) & PBF_READ_AHEAD) ? GFP_READAHEAD : \
	 ((flags) & PBF_DONT_BLOCK) ? GFP_NOFS : GFP_KERNEL)

#define pb_to_km(flags) \
	 (((flags) & PBF_DONT_BLOCK) ? KM_NOFS : KM_SLEEP)


#define pagebuf_allocate(flags) \
	kmem_zone_alloc(pagebuf_cache, pb_to_km(flags))
#define pagebuf_deallocate(pb) \
	kmem_zone_free(pagebuf_cache, (pb));

/*
 * Pagebuf hashing
 */

#define NBITS	8
#define NHASH	(1<<NBITS)

typedef struct {
	struct list_head	pb_hash;
	spinlock_t		pb_hash_lock;
} pb_hash_t;

STATIC pb_hash_t	pbhash[NHASH];
#define pb_hash(pb)	&pbhash[pb->pb_hash_index]

STATIC int
_bhash(
	struct block_device *bdev,
	loff_t		base)
{
	int		bit, hval;

	base >>= 9;
	base ^= (unsigned long)bdev / L1_CACHE_BYTES;
	for (bit = hval = 0; base && bit < sizeof(base) * 8; bit += NBITS) {
		hval ^= (int)base & (NHASH-1);
		base >>= NBITS;
	}
	return hval;
}

/*
 * Mapping of multi-page buffers into contiguous virtual space
 */

typedef struct a_list {
	void		*vm_addr;
	struct a_list	*next;
} a_list_t;

STATIC a_list_t		*as_free_head;
STATIC int		as_list_len;
STATIC spinlock_t	as_lock = SPIN_LOCK_UNLOCKED;

/*
 * Try to batch vunmaps because they are costly.
 */
STATIC void
free_address(
	void		*addr)
{
	a_list_t	*aentry;

	aentry = kmalloc(sizeof(a_list_t), GFP_ATOMIC);
	if (aentry) {
		spin_lock(&as_lock);
		aentry->next = as_free_head;
		aentry->vm_addr = addr;
		as_free_head = aentry;
		as_list_len++;
		spin_unlock(&as_lock);
	} else {
		vunmap(addr);
	}
}

STATIC void
purge_addresses(void)
{
	a_list_t	*aentry, *old;

	if (as_free_head == NULL)
		return;

	spin_lock(&as_lock);
	aentry = as_free_head;
	as_free_head = NULL;
	as_list_len = 0;
	spin_unlock(&as_lock);

	while ((old = aentry) != NULL) {
		vunmap(aentry->vm_addr);
		aentry = aentry->next;
		kfree(old);
	}
}

/*
 *	Internal pagebuf object manipulation
 */

STATIC void
_pagebuf_initialize(
	xfs_buf_t		*pb,
	xfs_buftarg_t		*target,
	loff_t			range_base,
	size_t			range_length,
	page_buf_flags_t	flags)
{
	/*
	 * We don't want certain flags to appear in pb->pb_flags.
	 */
	flags &= ~(PBF_LOCK|PBF_MAPPED|PBF_DONT_BLOCK|PBF_READ_AHEAD);

	memset(pb, 0, sizeof(xfs_buf_t));
	atomic_set(&pb->pb_hold, 1);
	init_MUTEX_LOCKED(&pb->pb_iodonesema);
	INIT_LIST_HEAD(&pb->pb_list);
	INIT_LIST_HEAD(&pb->pb_hash_list);
	init_MUTEX_LOCKED(&pb->pb_sema); /* held, no waiters */
	PB_SET_OWNER(pb);
	pb->pb_target = target;
	pb->pb_file_offset = range_base;
	/*
	 * Set buffer_length and count_desired to the same value initially.
	 * I/O routines should use count_desired, which will be the same in
	 * most cases but may be reset (e.g. XFS recovery).
	 */
	pb->pb_buffer_length = pb->pb_count_desired = range_length;
	pb->pb_flags = flags | PBF_NONE;
	pb->pb_bn = XFS_BUF_DADDR_NULL;
	atomic_set(&pb->pb_pin_count, 0);
	init_waitqueue_head(&pb->pb_waiters);

	XFS_STATS_INC(pb_create);
	PB_TRACE(pb, "initialize", target);
}

/*
 * Allocate a page array capable of holding a specified number
 * of pages, and point the page buf at it.
 */
STATIC int
_pagebuf_get_pages(
	xfs_buf_t		*pb,
	int			page_count,
	page_buf_flags_t	flags)
{
	/* Make sure that we have a page list */
	if (pb->pb_pages == NULL) {
		pb->pb_offset = page_buf_poff(pb->pb_file_offset);
		pb->pb_page_count = page_count;
		if (page_count <= PB_PAGES) {
			pb->pb_pages = pb->pb_page_array;
		} else {
			pb->pb_pages = kmem_alloc(sizeof(struct page *) *
					page_count, pb_to_km(flags));
			if (pb->pb_pages == NULL)
				return -ENOMEM;
		}
		memset(pb->pb_pages, 0, sizeof(struct page *) * page_count);
	}
	return 0;
}

/*
 *	Frees pb_pages if it was malloced.
 */
STATIC void
_pagebuf_free_pages(
	xfs_buf_t	*bp)
{
	if (bp->pb_pages != bp->pb_page_array) {
		kmem_free(bp->pb_pages,
			  bp->pb_page_count * sizeof(struct page *));
	}
}

/*
 *	Releases the specified buffer.
 *
 * 	The modification state of any associated pages is left unchanged.
 * 	The buffer most not be on any hash - use pagebuf_rele instead for
 * 	hashed and refcounted buffers
 */
void
pagebuf_free(
	xfs_buf_t		*bp)
{
	PB_TRACE(bp, "free", 0);

	ASSERT(list_empty(&bp->pb_hash_list));

	if (bp->pb_flags & _PBF_PAGE_CACHE) {
		uint		i;

		if ((bp->pb_flags & PBF_MAPPED) && (bp->pb_page_count > 1))
			free_address(bp->pb_addr - bp->pb_offset);

		for (i = 0; i < bp->pb_page_count; i++)
			page_cache_release(bp->pb_pages[i]);
		_pagebuf_free_pages(bp);
	} else if (bp->pb_flags & _PBF_KMEM_ALLOC) {
		 /*
		  * XXX(hch): bp->pb_count_desired might be incorrect (see
		  * pagebuf_associate_memory for details), but fortunately
		  * the Linux version of kmem_free ignores the len argument..
		  */
		kmem_free(bp->pb_addr, bp->pb_count_desired);
		_pagebuf_free_pages(bp);
	}

	pagebuf_deallocate(bp);
}

/*
 *	Finds all pages for buffer in question and builds it's page list.
 */
STATIC int
_pagebuf_lookup_pages(
	xfs_buf_t		*bp,
	uint			flags)
{
	struct address_space	*mapping = bp->pb_target->pbr_mapping;
	size_t			blocksize = bp->pb_target->pbr_bsize;
	int			gfp_mask = pb_to_gfp(flags);
	unsigned short		page_count, i;
	pgoff_t			first;
	loff_t			end;
	int			error;

	end = bp->pb_file_offset + bp->pb_buffer_length;
	page_count = page_buf_btoc(end) - page_buf_btoct(bp->pb_file_offset);

	error = _pagebuf_get_pages(bp, page_count, flags);
	if (unlikely(error))
		return error;
	bp->pb_flags |= _PBF_PAGE_CACHE;

	first = bp->pb_file_offset >> PAGE_CACHE_SHIFT;

	for (i = 0; i < bp->pb_page_count; i++) {
		struct page	*page;
		uint		retries = 0;

	      retry:
		page = find_or_create_page(mapping, first + i, gfp_mask);
		if (unlikely(page == NULL)) {
			if (flags & PBF_READ_AHEAD) {
				bp->pb_page_count = i;
				for (i = 0; i < bp->pb_page_count; i++)
					unlock_page(bp->pb_pages[i]);
				return -ENOMEM;
			}

			/*
			 * This could deadlock.
			 *
			 * But until all the XFS lowlevel code is revamped to
			 * handle buffer allocation failures we can't do much.
			 */
			if (!(++retries % 100))
				printk(KERN_ERR
					"possible deadlock in %s (mode:0x%x)\n",
					__FUNCTION__, gfp_mask);

			XFS_STATS_INC(pb_page_retries);
			pagebuf_daemon_wakeup(0, gfp_mask);
			set_current_state(TASK_UNINTERRUPTIBLE);
			schedule_timeout(10);
			goto retry;
		}

		XFS_STATS_INC(pb_page_found);

		/* if we need to do I/O on a page record the fact */
		if (!Page_Uptodate(page)) {
			page_count--;
			if (blocksize == PAGE_CACHE_SIZE && (flags & PBF_READ))
				bp->pb_locked = 1;
		}

		bp->pb_pages[i] = page;
	}

	if (!bp->pb_locked) {
		for (i = 0; i < bp->pb_page_count; i++)
			unlock_page(bp->pb_pages[i]);
	}

	if (page_count) {
		/* if we have any uptodate pages, mark that in the buffer */
		bp->pb_flags &= ~PBF_NONE;

		/* if some pages aren't uptodate, mark that in the buffer */
		if (page_count != bp->pb_page_count)
			bp->pb_flags |= PBF_PARTIAL;
	}

	PB_TRACE(bp, "lookup_pages", (long)page_count);
	return error;
}

/*
 *	Map buffer into kernel address-space if nessecary.
 */
STATIC int
_pagebuf_map_pages(
	xfs_buf_t		*bp,
	uint			flags)
{
	/* A single page buffer is always mappable */
	if (bp->pb_page_count == 1) {
		bp->pb_addr = page_address(bp->pb_pages[0]) + bp->pb_offset;
		bp->pb_flags |= PBF_MAPPED;
	} else if (flags & PBF_MAPPED) {
		if (as_list_len > 64)
			purge_addresses();
		bp->pb_addr = vmap(bp->pb_pages, bp->pb_page_count,
				VM_MAP, PAGE_KERNEL);
		if (unlikely(bp->pb_addr == NULL))
			return -ENOMEM;
		bp->pb_addr += bp->pb_offset;
		bp->pb_flags |= PBF_MAPPED;
	}

	return 0;
}

/*
 *	Pre-allocation of a pool of buffer heads for use in
 *	low-memory situations.
 */

/*
 *	_pagebuf_prealloc_bh
 *
 *	Pre-allocate a pool of "count" buffer heads at startup.
 *	Puts them on a list at "pb_resv_bh"
 *	Returns number of bh actually allocated to pool.
 */
STATIC int
_pagebuf_prealloc_bh(
	int			count)
{
	struct buffer_head	*bh;
	int			i;

	for (i = 0; i < count; i++) {
		bh = kmem_cache_alloc(bh_cachep, SLAB_KERNEL);
		if (!bh)
			break;
		bh->b_pprev = &pb_resv_bh;
		bh->b_next = pb_resv_bh;
		pb_resv_bh = bh;
		pb_resv_bh_cnt++;
	}
	return i;
}

/*
 *	_pagebuf_get_prealloc_bh
 *
 *	Get one buffer head from our pre-allocated pool.
 *	If pool is empty, sleep 'til one comes back in.
 *	Returns aforementioned buffer head.
 */
STATIC struct buffer_head *
_pagebuf_get_prealloc_bh(void)
{
	unsigned long		flags;
	struct buffer_head	*bh;
	DECLARE_WAITQUEUE	(wait, current);

	spin_lock_irqsave(&pb_resv_bh_lock, flags);

	if (pb_resv_bh_cnt < 1) {
		add_wait_queue(&pb_resv_bh_wait, &wait);
		do {
			set_current_state(TASK_UNINTERRUPTIBLE);
			spin_unlock_irqrestore(&pb_resv_bh_lock, flags);
			run_task_queue(&tq_disk);
			schedule();
			spin_lock_irqsave(&pb_resv_bh_lock, flags);
		} while (pb_resv_bh_cnt < 1);
		__set_current_state(TASK_RUNNING);
		remove_wait_queue(&pb_resv_bh_wait, &wait);
	}

	BUG_ON(pb_resv_bh_cnt < 1);
	BUG_ON(!pb_resv_bh);

	bh = pb_resv_bh;
	pb_resv_bh = bh->b_next;
	pb_resv_bh_cnt--;

	spin_unlock_irqrestore(&pb_resv_bh_lock, flags);
	return bh;
}

/*
 *	_pagebuf_free_bh
 *
 *	Take care of buffer heads that we're finished with.
 *	Call this instead of just kmem_cache_free(bh_cachep, bh)
 *	when you're done with a bh.
 *
 *	If our pre-allocated pool is full, just free the buffer head.
 *	Otherwise, put it back in the pool, and wake up anybody
 *	waiting for one.
 */
STATIC inline void
_pagebuf_free_bh(
	struct buffer_head	*bh)
{
	unsigned long		flags;
	int			free;