patch-2.4.27 linux-2.4.27/fs/xfs/linux-2.4/xfs_buf.c

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diff -urN linux-2.4.26/fs/xfs/linux-2.4/xfs_buf.c linux-2.4.27/fs/xfs/linux-2.4/xfs_buf.c
@@ -0,0 +1,2306 @@
+/*
+ * 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;
+
+	if (! (free = pb_resv_bh_cnt >= NR_RESERVED_BH)) {
+		spin_lock_irqsave(&pb_resv_bh_lock, flags);
+
+		if (! (free = pb_resv_bh_cnt >= NR_RESERVED_BH)) {
+			bh->b_pprev = &pb_resv_bh;
+			bh->b_next = pb_resv_bh;
+			pb_resv_bh = bh;
+			pb_resv_bh_cnt++;
+
+			if (waitqueue_active(&pb_resv_bh_wait)) {
+				wake_up(&pb_resv_bh_wait);
+			}
+		}
+
+		spin_unlock_irqrestore(&pb_resv_bh_lock, flags);
+	}
+	if (free) {
+		kmem_cache_free(bh_cachep, bh);
+	}
+}
+
+/*
+ *	Finding and Reading Buffers
+ */
+
+/*
+ *	_pagebuf_find
+ *
+ *	Looks up, and creates if absent, a lockable buffer for
+ *	a given range of an inode.  The buffer is returned
+ *	locked.	 If other overlapping buffers exist, they are
+ *	released before the new buffer is created and locked,
+ *	which may imply that this call will block until those buffers
+ *	are unlocked.  No I/O is implied by this call.
+ */
+STATIC xfs_buf_t *
+_pagebuf_find(				/* find buffer for block	*/
+	xfs_buftarg_t		*target,/* target for block		*/
+	loff_t			ioff,	/* starting offset of range	*/
+	size_t			isize,	/* length of range		*/
+	page_buf_flags_t	flags,	/* PBF_TRYLOCK			*/
+	xfs_buf_t		*new_pb)/* newly allocated buffer	*/
+{
+	loff_t			range_base;
+	size_t			range_length;
+	int			hval;
+	pb_hash_t		*h;
+	xfs_buf_t		*pb, *n;
+	int			not_locked;
+
+	range_base = (ioff << BBSHIFT);
+	range_length = (isize << BBSHIFT);
+
+	/* Ensure we never do IOs smaller than the sector size */
+	BUG_ON(range_length < (1 << target->pbr_sshift));
+
+	/* Ensure we never do IOs that are not sector aligned */
+	BUG_ON(range_base & (loff_t)target->pbr_smask);
+
+	hval = _bhash(target->pbr_bdev, range_base);
+	h = &pbhash[hval];
+
+	spin_lock(&h->pb_hash_lock);
+
+	list_for_each_entry_safe(pb, n, &h->pb_hash, pb_hash_list) {
+		if (pb->pb_target == target &&
+		    pb->pb_file_offset == range_base &&
+		    pb->pb_buffer_length == range_length) {
+			/* If we look at something bring it to the
+			 * front of the list for next time
+			 */
+			atomic_inc(&pb->pb_hold);
+			list_move(&pb->pb_hash_list, &h->pb_hash);
+			goto found;
+		}
+	}
+
+	/* No match found */
+	if (new_pb) {
+		_pagebuf_initialize(new_pb, target, range_base,
+				range_length, flags);
+		new_pb->pb_hash_index = hval;
+		list_add(&new_pb->pb_hash_list, &h->pb_hash);
+	} else {
+		XFS_STATS_INC(pb_miss_locked);
+	}
+
+	spin_unlock(&h->pb_hash_lock);
+	return (new_pb);
+
+found:
+	spin_unlock(&h->pb_hash_lock);
+
+	/* Attempt to get the semaphore without sleeping,
+	 * if this does not work then we need to drop the
+	 * spinlock and do a hard attempt on the semaphore.
+	 */
+	not_locked = down_trylock(&pb->pb_sema);
+	if (not_locked) {
+		if (!(flags & PBF_TRYLOCK)) {
+			/* wait for buffer ownership */
+			PB_TRACE(pb, "get_lock", 0);
+			pagebuf_lock(pb);
+			XFS_STATS_INC(pb_get_locked_waited);
+		} else {
+			/* We asked for a trylock and failed, no need
+			 * to look at file offset and length here, we
+			 * know that this pagebuf at least overlaps our
+			 * pagebuf and is locked, therefore our buffer
+			 * either does not exist, or is this buffer
+			 */
+
+			pagebuf_rele(pb);
+			XFS_STATS_INC(pb_busy_locked);
+			return (NULL);
+		}
+	} else {
+		/* trylock worked */
+		PB_SET_OWNER(pb);
+	}
+
+	if (pb->pb_flags & PBF_STALE)
+		pb->pb_flags &= PBF_MAPPED;
+	PB_TRACE(pb, "got_lock", 0);
+	XFS_STATS_INC(pb_get_locked);
+	return (pb);
+}
+
+
+/*
+ *	pagebuf_find
+ *
+ *	pagebuf_find returns a buffer matching the specified range of
+ *	data for the specified target, if any of the relevant blocks
+ *	are in memory.  The buffer may have unallocated holes, if
+ *	some, but not all, of the blocks are in memory.  Even where
+ *	pages are present in the buffer, not all of every page may be
+ *	valid.
+ */
+xfs_buf_t *
+pagebuf_find(				/* find buffer for block	*/
+					/* if the block is in memory	*/
+	xfs_buftarg_t		*target,/* target for block		*/
+	loff_t			ioff,	/* starting offset of range	*/
+	size_t			isize,	/* length of range		*/
+	page_buf_flags_t	flags)	/* PBF_TRYLOCK			*/
+{
+	return _pagebuf_find(target, ioff, isize, flags, NULL);
+}
+
+/*
+ *	pagebuf_get
+ *
+ *	pagebuf_get assembles a buffer covering the specified range.
+ *	Some or all of the blocks in the range may be valid.  Storage
+ *	in memory for all portions of the buffer will be allocated,
+ *	although backing storage may not be.  If PBF_READ is set in
+ *	flags, pagebuf_iostart is called also.
+ */
+xfs_buf_t *
+pagebuf_get(				/* allocate a buffer		*/
+	xfs_buftarg_t		*target,/* target for buffer		*/
+	loff_t			ioff,	/* starting offset of range	*/
+	size_t			isize,	/* length of range		*/
+	page_buf_flags_t	flags)	/* PBF_TRYLOCK			*/
+{
+	xfs_buf_t		*pb, *new_pb;
+	int			error = 0, i;
+
+	new_pb = pagebuf_allocate(flags);
+	if (unlikely(!new_pb))
+		return NULL;
+
+	pb = _pagebuf_find(target, ioff, isize, flags, new_pb);
+	if (pb == new_pb) {
+		error = _pagebuf_lookup_pages(pb, flags);
+		if (unlikely(error)) {
+			printk(KERN_WARNING
+			       "pagebuf_get: failed to lookup pages\n");
+			goto no_buffer;
+		}
+	} else {
+		pagebuf_deallocate(new_pb);
+		if (unlikely(pb == NULL))
+			return NULL;
+	}
+
+	for (i = 0; i < pb->pb_page_count; i++)
+		mark_page_accessed(pb->pb_pages[i]);
+
+	if (!(pb->pb_flags & PBF_MAPPED)) {
+		error = _pagebuf_map_pages(pb, flags);
+		if (unlikely(error)) {
+			printk(KERN_WARNING
+			       "pagebuf_get: failed to map pages\n");
+			goto no_buffer;
+		}
+	}
+
+	XFS_STATS_INC(pb_get);
+
+	/*
+	 * Always fill in the block number now, the mapped cases can do
+	 * their own overlay of this later.
+	 */
+	pb->pb_bn = ioff;
+	pb->pb_count_desired = pb->pb_buffer_length;
+
+	if (flags & PBF_READ) {
+		if (PBF_NOT_DONE(pb)) {
+			PB_TRACE(pb, "get_read", (unsigned long)flags);
+			XFS_STATS_INC(pb_get_read);
+			pagebuf_iostart(pb, flags);
+		} else if (flags & PBF_ASYNC) {
+			PB_TRACE(pb, "get_read_async", (unsigned long)flags);
+			/*
+			 * Read ahead call which is already satisfied,
+			 * drop the buffer
+			 */
+			goto no_buffer;
+		} else {
+			PB_TRACE(pb, "get_read_done", (unsigned long)flags);
+			/* We do not want read in the flags */
+			pb->pb_flags &= ~PBF_READ;
+		}
+	} else {
+		PB_TRACE(pb, "get_write", (unsigned long)flags);
+	}
+
+	return pb;
+
+no_buffer:
+	if (flags & (PBF_LOCK | PBF_TRYLOCK))
+		pagebuf_unlock(pb);
+	pagebuf_rele(pb);
+	return NULL;
+}
+
+/*
+ * Create a skeletal pagebuf (no pages associated with it).
+ */
+xfs_buf_t *
+pagebuf_lookup(
+	xfs_buftarg_t		*target,
+	loff_t			ioff,
+	size_t			isize,
+	page_buf_flags_t	flags)
+{
+	xfs_buf_t		*pb;
+
+	flags |= _PBF_PRIVATE_BH;
+	pb = pagebuf_allocate(flags);
+	if (pb) {
+		_pagebuf_initialize(pb, target, ioff, isize, flags);
+	}
+	return pb;
+}
+
+/*
+ * If we are not low on memory then do the readahead in a deadlock
+ * safe manner.
+ */
+void
+pagebuf_readahead(
+	xfs_buftarg_t		*target,
+	loff_t			ioff,
+	size_t			isize,
+	page_buf_flags_t	flags)
+{
+	flags |= (PBF_TRYLOCK|PBF_READ|PBF_ASYNC|PBF_READ_AHEAD);
+	pagebuf_get(target, ioff, isize, flags);
+}
+
+xfs_buf_t *
+pagebuf_get_empty(
+	size_t			len,
+	xfs_buftarg_t		*target)
+{
+	xfs_buf_t		*pb;
+
+	pb = pagebuf_allocate(0);
+	if (pb)
+		_pagebuf_initialize(pb, target, 0, len, 0);
+	return pb;
+}
+
+static inline struct page *
+mem_to_page(
+	void			*addr)
+{
+	if (((unsigned long)addr < VMALLOC_START) ||
+	    ((unsigned long)addr >= VMALLOC_END)) {
+		return virt_to_page(addr);
+	} else {
+		return vmalloc_to_page(addr);
+	}
+}
+
+int
+pagebuf_associate_memory(
+	xfs_buf_t		*pb,
+	void			*mem,
+	size_t			len)
+{
+	int			rval;
+	int			i = 0;
+	size_t			ptr;
+	size_t			end, end_cur;
+	off_t			offset;
+	int			page_count;
+
+	page_count = PAGE_CACHE_ALIGN(len) >> PAGE_CACHE_SHIFT;
+	offset = (off_t) mem - ((off_t)mem & PAGE_CACHE_MASK);
+	if (offset && (len > PAGE_CACHE_SIZE))
+		page_count++;
+
+	/* Free any previous set of page pointers */
+	if (pb->pb_pages)
+		_pagebuf_free_pages(pb);
+
+	pb->pb_pages = NULL;
+	pb->pb_addr = mem;
+
+	rval = _pagebuf_get_pages(pb, page_count, 0);
+	if (rval)
+		return rval;
+
+	pb->pb_offset = offset;
+	ptr = (size_t) mem & PAGE_CACHE_MASK;
+	end = PAGE_CACHE_ALIGN((size_t) mem + len);
+	end_cur = end;
+	/* set up first page */
+	pb->pb_pages[0] = mem_to_page(mem);
+
+	ptr += PAGE_CACHE_SIZE;
+	pb->pb_page_count = ++i;
+	while (ptr < end) {
+		pb->pb_pages[i] = mem_to_page((void *)ptr);
+		pb->pb_page_count = ++i;
+		ptr += PAGE_CACHE_SIZE;
+	}
+	pb->pb_locked = 0;
+
+	pb->pb_count_desired = pb->pb_buffer_length = len;
+	pb->pb_flags |= PBF_MAPPED | _PBF_PRIVATE_BH;
+
+	return 0;
+}
+
+xfs_buf_t *
+pagebuf_get_no_daddr(
+	size_t			len,
+	xfs_buftarg_t		*target)
+{
+	size_t			malloc_len = len;
+	xfs_buf_t		*bp;
+	void			*data;
+	int			error;
+
+	bp = pagebuf_allocate(0);
+	if (unlikely(bp == NULL))
+		goto fail;
+	_pagebuf_initialize(bp, target, 0, len, PBF_FORCEIO);
+
+ try_again:
+	data = kmem_alloc(malloc_len, KM_SLEEP | KM_MAYFAIL);
+	if (unlikely(data == NULL))
+		goto fail_free_buf;
+
+	/* check whether alignment matches.. */
+	if ((__psunsigned_t)data !=
+	    ((__psunsigned_t)data & ~target->pbr_smask)) {
+		/* .. else double the size and try again */
+		kmem_free(data, malloc_len);
+		malloc_len <<= 1;
+		goto try_again;
+	}
+
+	error = pagebuf_associate_memory(bp, data, len);
+	if (error)
+		goto fail_free_mem;
+	bp->pb_flags |= _PBF_KMEM_ALLOC;
+
+	pagebuf_unlock(bp);
+
+	PB_TRACE(bp, "no_daddr", data);
+	return bp;
+ fail_free_mem:
+	kmem_free(data, malloc_len);
+ fail_free_buf:
+	pagebuf_free(bp);
+ fail:
+	return NULL;
+}
+
+/*
+ *	pagebuf_hold
+ *
+ *	Increment reference count on buffer, to hold the buffer concurrently
+ *	with another thread which may release (free) the buffer asynchronously.
+ *
+ *	Must hold the buffer already to call this function.
+ */
+void
+pagebuf_hold(
+	xfs_buf_t		*pb)
+{
+	atomic_inc(&pb->pb_hold);
+	PB_TRACE(pb, "hold", 0);
+}
+
+/*
+ *	pagebuf_rele
+ *
+ *	pagebuf_rele releases a hold on the specified buffer.  If the
+ *	the hold count is 1, pagebuf_rele calls pagebuf_free.
+ */
+void
+pagebuf_rele(
+	xfs_buf_t		*pb)
+{
+	pb_hash_t		*hash = pb_hash(pb);
+
+	PB_TRACE(pb, "rele", pb->pb_relse);
+
+	if (atomic_dec_and_lock(&pb->pb_hold, &hash->pb_hash_lock)) {
+		int		do_free = 1;
+
+		if (pb->pb_relse) {
+			atomic_inc(&pb->pb_hold);
+			spin_unlock(&hash->pb_hash_lock);
+			(*(pb->pb_relse)) (pb);
+			spin_lock(&hash->pb_hash_lock);
+			do_free = 0;
+		}
+
+		if (pb->pb_flags & PBF_DELWRI) {
+			pb->pb_flags |= PBF_ASYNC;
+			atomic_inc(&pb->pb_hold);
+			pagebuf_delwri_queue(pb, 0);
+			do_free = 0;
+		} else if (pb->pb_flags & PBF_FS_MANAGED) {
+			do_free = 0;
+		}
+
+		if (do_free) {
+			list_del_init(&pb->pb_hash_list);
+			spin_unlock(&hash->pb_hash_lock);
+			xfs_buf_free(pb);
+		} else {
+			spin_unlock(&hash->pb_hash_lock);
+		}
+	}
+}
+
+
+/*
+ *	Mutual exclusion on buffers.  Locking model:
+ *
+ *	Buffers associated with inodes for which buffer locking
+ *	is not enabled are not protected by semaphores, and are
+ *	assumed to be exclusively owned by the caller.  There is a
+ *	spinlock in the buffer, used by the caller when concurrent
+ *	access is possible.
+ */
+
+/*
+ *	pagebuf_cond_lock
+ *
+ *	pagebuf_cond_lock locks a buffer object, if it is not already locked.
+ *	Note that this in no way
+ *	locks the underlying pages, so it is only useful for synchronizing
+ *	concurrent use of page buffer objects, not for synchronizing independent
+ *	access to the underlying pages.
+ */
+int
+pagebuf_cond_lock(			/* lock buffer, if not locked	*/
+					/* returns -EBUSY if locked)	*/
+	xfs_buf_t		*pb)
+{
+	int			locked;
+
+	locked = down_trylock(&pb->pb_sema) == 0;
+	if (locked) {
+		PB_SET_OWNER(pb);
+	}
+	PB_TRACE(pb, "cond_lock", (long)locked);
+	return(locked ? 0 : -EBUSY);
+}
+
+/*
+ *	pagebuf_lock_value
+ *
+ *	Return lock value for a pagebuf
+ */
+int
+pagebuf_lock_value(
+	xfs_buf_t		*pb)
+{
+	return(atomic_read(&pb->pb_sema.count));
+}
+
+/*
+ *	pagebuf_lock
+ *
+ *	pagebuf_lock locks a buffer object.  Note that this in no way
+ *	locks the underlying pages, so it is only useful for synchronizing
+ *	concurrent use of page buffer objects, not for synchronizing independent
+ *	access to the underlying pages.
+ */
+int
+pagebuf_lock(
+	xfs_buf_t		*pb)
+{
+	PB_TRACE(pb, "lock", 0);
+	if (atomic_read(&pb->pb_io_remaining))
+		run_task_queue(&tq_disk);
+	down(&pb->pb_sema);
+	PB_SET_OWNER(pb);
+	PB_TRACE(pb, "locked", 0);
+	return 0;
+}
+
+/*
+ *	pagebuf_unlock
+ *
+ *	pagebuf_unlock releases the lock on the buffer object created by
+ *	pagebuf_lock or pagebuf_cond_lock (not any
+ *	pinning of underlying pages created by pagebuf_pin).
+ */
+void
+pagebuf_unlock(				/* unlock buffer		*/
+	xfs_buf_t		*pb)	/* buffer to unlock		*/
+{
+	PB_CLEAR_OWNER(pb);
+	up(&pb->pb_sema);
+	PB_TRACE(pb, "unlock", 0);
+}
+
+
+/*
+ *	Pinning Buffer Storage in Memory
+ */
+
+/*
+ *	pagebuf_pin
+ *
+ *	pagebuf_pin locks all of the memory represented by a buffer in
+ *	memory.  Multiple calls to pagebuf_pin and pagebuf_unpin, for
+ *	the same or different buffers affecting a given page, will
+ *	properly count the number of outstanding "pin" requests.  The
+ *	buffer may be released after the pagebuf_pin and a different
+ *	buffer used when calling pagebuf_unpin, if desired.
+ *	pagebuf_pin should be used by the file system when it wants be
+ *	assured that no attempt will be made to force the affected
+ *	memory to disk.	 It does not assure that a given logical page
+ *	will not be moved to a different physical page.
+ */
+void
+pagebuf_pin(
+	xfs_buf_t		*pb)
+{
+	atomic_inc(&pb->pb_pin_count);
+	PB_TRACE(pb, "pin", (long)pb->pb_pin_count.counter);
+}
+
+/*
+ *	pagebuf_unpin
+ *
+ *	pagebuf_unpin reverses the locking of memory performed by
+ *	pagebuf_pin.  Note that both functions affected the logical
+ *	pages associated with the buffer, not the buffer itself.
+ */
+void
+pagebuf_unpin(
+	xfs_buf_t		*pb)
+{
+	if (atomic_dec_and_test(&pb->pb_pin_count)) {
+		wake_up_all(&pb->pb_waiters);
+	}
+	PB_TRACE(pb, "unpin", (long)pb->pb_pin_count.counter);
+}
+
+int
+pagebuf_ispin(
+	xfs_buf_t		*pb)
+{
+	return atomic_read(&pb->pb_pin_count);
+}
+
+/*
+ *	pagebuf_wait_unpin
+ *
+ *	pagebuf_wait_unpin waits until all of the memory associated
+ *	with the buffer is not longer locked in memory.  It returns
+ *	immediately if none of the affected pages are locked.
+ */
+static inline void
+_pagebuf_wait_unpin(
+	xfs_buf_t		*pb)
+{
+	DECLARE_WAITQUEUE	(wait, current);
+
+	if (atomic_read(&pb->pb_pin_count) == 0)
+		return;
+
+	add_wait_queue(&pb->pb_waiters, &wait);
+	for (;;) {
+		set_current_state(TASK_UNINTERRUPTIBLE);
+		if (atomic_read(&pb->pb_pin_count) == 0)
+			break;
+		if (atomic_read(&pb->pb_io_remaining))
+			run_task_queue(&tq_disk);
+		schedule();
+	}
+	remove_wait_queue(&pb->pb_waiters, &wait);
+	set_current_state(TASK_RUNNING);
+}
+
+
+/*
+ *	Buffer Utility Routines
+ */
+
+/*
+ *	pagebuf_iodone
+ *
+ *	pagebuf_iodone marks a buffer for which I/O is in progress
+ *	done with respect to that I/O.	The pb_iodone routine, if
+ *	present, will be called as a side-effect.
+ */
+void
+pagebuf_iodone_sched(
+	void			*v)
+{
+	xfs_buf_t		*bp = (xfs_buf_t *)v;
+
+	if (bp->pb_iodone)
+		(*(bp->pb_iodone))(bp);
+	else if (bp->pb_flags & PBF_ASYNC)
+		xfs_buf_relse(bp);
+}
+
+void
+pagebuf_iodone(
+	xfs_buf_t		*pb,
+	int			dataio,
+	int			schedule)
+{
+	pb->pb_flags &= ~(PBF_READ | PBF_WRITE);
+	if (pb->pb_error == 0) {
+		pb->pb_flags &= ~(PBF_PARTIAL | PBF_NONE);
+	}
+
+	PB_TRACE(pb, "iodone", pb->pb_iodone);
+
+	if ((pb->pb_iodone) || (pb->pb_flags & PBF_ASYNC)) {
+		if (schedule) {
+			int	daemon = CPU_TO_DAEMON(smp_processor_id());
+
+			INIT_TQUEUE(&pb->pb_iodone_sched,
+				pagebuf_iodone_sched, (void *)pb);
+			queue_task(&pb->pb_iodone_sched, dataio ?
+				&pagebuf_dataiodone_tq[daemon] :
+				&pagebuf_logiodone_tq[daemon]);
+			wake_up(dataio ?
+				&pagebuf_dataiodone_wait[daemon] :
+				&pagebuf_logiodone_wait[daemon]);
+		} else {
+			pagebuf_iodone_sched(pb);
+		}
+	} else {
+		up(&pb->pb_iodonesema);
+	}
+}
+
+/*
+ *	pagebuf_ioerror
+ *
+ *	pagebuf_ioerror sets the error code for a buffer.
+ */
+void
+pagebuf_ioerror(			/* mark/clear buffer error flag */
+	xfs_buf_t		*pb,	/* buffer to mark		*/
+	int			error)	/* error to store (0 if none)	*/
+{
+	ASSERT(error >= 0 && error <= 0xffff);
+	pb->pb_error = (unsigned short)error;
+	PB_TRACE(pb, "ioerror", (unsigned long)error);
+}
+
+/*
+ *	pagebuf_iostart
+ *
+ *	pagebuf_iostart initiates I/O on a buffer, based on the flags supplied.
+ *	If necessary, it will arrange for any disk space allocation required,
+ *	and it will break up the request if the block mappings require it.
+ *	The pb_iodone routine in the buffer supplied will only be called
+ *	when all of the subsidiary I/O requests, if any, have been completed.
+ *	pagebuf_iostart calls the pagebuf_ioinitiate routine or
+ *	pagebuf_iorequest, if the former routine is not defined, to start
+ *	the I/O on a given low-level request.
+ */
+int
+pagebuf_iostart(			/* start I/O on a buffer	  */
+	xfs_buf_t		*pb,	/* buffer to start		  */
+	page_buf_flags_t	flags)	/* PBF_LOCK, PBF_ASYNC, PBF_READ, */
+					/* PBF_WRITE, PBF_DELWRI,	  */
+					/* PBF_DONT_BLOCK		  */
+{
+	int			status = 0;
+
+	PB_TRACE(pb, "iostart", (unsigned long)flags);
+
+	if (flags & PBF_DELWRI) {
+		pb->pb_flags &= ~(PBF_READ | PBF_WRITE | PBF_ASYNC);
+		pb->pb_flags |= flags & (PBF_DELWRI | PBF_ASYNC);
+		pagebuf_delwri_queue(pb, 1);
+		return status;
+	}
+
+	pb->pb_flags &= ~(PBF_READ | PBF_WRITE | PBF_ASYNC | PBF_DELWRI | \
+			PBF_READ_AHEAD | _PBF_RUN_QUEUES);
+	pb->pb_flags |= flags & (PBF_READ | PBF_WRITE | PBF_ASYNC | \
+			PBF_READ_AHEAD | _PBF_RUN_QUEUES);
+
+	BUG_ON(pb->pb_bn == XFS_BUF_DADDR_NULL);
+
+	/* For writes allow an alternate strategy routine to precede
+	 * the actual I/O request (which may not be issued at all in
+	 * a shutdown situation, for example).
+	 */
+	status = (flags & PBF_WRITE) ?
+		pagebuf_iostrategy(pb) : pagebuf_iorequest(pb);
+
+	/* Wait for I/O if we are not an async request.
+	 * Note: async I/O request completion will release the buffer,
+	 * and that can already be done by this point.  So using the
+	 * buffer pointer from here on, after async I/O, is invalid.
+	 */
+	if (!status && !(flags & PBF_ASYNC))
+		status = pagebuf_iowait(pb);
+
+	return status;
+}
+
+
+/*
+ * Helper routines for pagebuf_iorequest (pagebuf I/O completion)
+ */
+
+STATIC __inline__ int
+_pagebuf_iolocked(
+	xfs_buf_t		*pb)
+{
+	ASSERT(pb->pb_flags & (PBF_READ|PBF_WRITE));
+	if (pb->pb_target->pbr_bsize < PAGE_CACHE_SIZE)
+		return pb->pb_locked;
+	if (pb->pb_flags & PBF_READ)
+		return pb->pb_locked;
+	return (pb->pb_flags & _PBF_PAGE_CACHE);
+}
+
+STATIC void
+_pagebuf_iodone(
+	xfs_buf_t		*pb,
+	int			schedule)
+{
+	int			i;
+
+	if (atomic_dec_and_test(&pb->pb_io_remaining) != 1)
+		return;
+
+	if (_pagebuf_iolocked(pb))
+		for (i = 0; i < pb->pb_page_count; i++)
+			unlock_page(pb->pb_pages[i]);
+	pb->pb_locked = 0;
+	pagebuf_iodone(pb, (pb->pb_flags & PBF_FS_DATAIOD), schedule);
+}
+
+STATIC void
+_end_io_pagebuf(
+	struct buffer_head	*bh,
+	int			uptodate,
+	int			fullpage)
+{
+	struct page		*page = bh->b_page;
+	xfs_buf_t		*pb = (xfs_buf_t *)bh->b_private;
+
+	mark_buffer_uptodate(bh, uptodate);
+	put_bh(bh);
+
+	if (!uptodate) {
+		SetPageError(page);
+		pb->pb_error = EIO;
+	}
+
+	if (fullpage) {
+		unlock_buffer(bh);
+		_pagebuf_free_bh(bh);
+		if (!PageError(page))
+			SetPageUptodate(page);
+	} else {
+		static spinlock_t page_uptodate_lock = SPIN_LOCK_UNLOCKED;
+		struct buffer_head *bp;
+		unsigned long flags;
+
+		ASSERT(PageLocked(page));
+		spin_lock_irqsave(&page_uptodate_lock, flags);
+		clear_buffer_async(bh);
+		unlock_buffer(bh);
+		for (bp = bh->b_this_page; bp != bh; bp = bp->b_this_page) {
+			if (buffer_locked(bp)) {
+				if (buffer_async(bp))
+					break;
+			} else if (!buffer_uptodate(bp))
+				break;
+		}
+		spin_unlock_irqrestore(&page_uptodate_lock, flags);
+		if (bp == bh && !PageError(page))
+			SetPageUptodate(page);
+	}
+
+	_pagebuf_iodone(pb, 1);
+}
+
+STATIC void
+_pagebuf_end_io_complete_pages(
+	struct buffer_head	*bh,
+	int			uptodate)
+{
+	_end_io_pagebuf(bh, uptodate, 1);
+}
+
+STATIC void
+_pagebuf_end_io_partial_pages(
+	struct buffer_head	*bh,
+	int			uptodate)
+{
+	_end_io_pagebuf(bh, uptodate, 0);
+}
+
+/*
+ *	Handling of buftargs.
+ */
+
+void
+xfs_free_buftarg(
+	xfs_buftarg_t		*btp,
+	int			external)
+{
+	xfs_flush_buftarg(btp, 1);
+	if (external)
+		xfs_blkdev_put(btp->pbr_bdev);
+	kmem_free(btp, sizeof(*btp));
+}
+
+void
+xfs_incore_relse(
+	xfs_buftarg_t		*btp,
+	int			delwri_only,
+	int			wait)
+{
+	destroy_buffers(btp->pbr_kdev);
+	truncate_inode_pages(btp->pbr_mapping, 0LL);
+}
+
+void
+xfs_setsize_buftarg(
+	xfs_buftarg_t		*btp,
+	unsigned int		blocksize,
+	unsigned int		sectorsize)
+{
+	btp->pbr_bsize = blocksize;
+	btp->pbr_sshift = ffs(sectorsize) - 1;
+	btp->pbr_smask = sectorsize - 1;
+
+	if (set_blocksize(btp->pbr_kdev, sectorsize)) {
+		printk(KERN_WARNING
+			"XFS: Cannot set_blocksize to %u on device 0x%x\n",
+			sectorsize, kdev_t_to_nr(btp->pbr_kdev));
+	}
+}
+
+xfs_buftarg_t *
+xfs_alloc_buftarg(
+	struct block_device	*bdev)
+{
+	xfs_buftarg_t		*btp;
+
+	btp = kmem_zalloc(sizeof(*btp), KM_SLEEP);
+
+	btp->pbr_dev =  bdev->bd_dev;
+	btp->pbr_kdev = to_kdev_t(btp->pbr_dev);
+	btp->pbr_bdev = bdev;
+	btp->pbr_mapping = bdev->bd_inode->i_mapping;
+	xfs_setsize_buftarg(btp, PAGE_CACHE_SIZE,
+			    get_hardsect_size(btp->pbr_kdev));
+
+	switch (MAJOR(btp->pbr_dev)) {
+	case MD_MAJOR:
+	case EVMS_MAJOR:
+		btp->pbr_flags = PBR_ALIGNED_ONLY;
+		break;
+	case LVM_BLK_MAJOR:
+		btp->pbr_flags = PBR_SECTOR_ONLY;
+		break;
+	}
+
+	return btp;
+}
+
+/*
+ * Initiate I/O on part of a page we are interested in
+ */
+STATIC int
+_pagebuf_page_io(
+	struct page		*page,	/* Page structure we are dealing with */
+	xfs_buftarg_t		*pbr,	/* device parameters (bsz, ssz, dev) */
+	xfs_buf_t		*pb,	/* pagebuf holding it, can be NULL */
+	xfs_daddr_t		bn,	/* starting block number */
+	size_t			pg_offset,	/* starting offset in page */
+	size_t			pg_length,	/* count of data to process */
+	int			rw,	/* read/write operation */
+	int			flush)
+{
+	size_t			sector;
+	size_t			blk_length = 0;
+	struct buffer_head	*bh, *head, *bufferlist[MAX_BUF_PER_PAGE];
+	int			sector_shift = pbr->pbr_sshift;
+	int			i = 0, cnt = 0;
+	int			public_bh = 0;
+	int			multi_ok;
+
+	if ((pbr->pbr_bsize < PAGE_CACHE_SIZE) &&
+	    !(pb->pb_flags & _PBF_PRIVATE_BH)) {
+		int		cache_ok;
+
+		cache_ok = !((pb->pb_flags & PBF_FORCEIO) || (rw == WRITE));
+		public_bh = multi_ok = 1;
+		sector = 1 << sector_shift;
+
+		ASSERT(PageLocked(page));
+		if (!page_has_buffers(page))
+			create_empty_buffers(page, pbr->pbr_kdev, sector);
+
+		i = sector >> BBSHIFT;
+		bn -= (pg_offset >> BBSHIFT);
+
+		/* Find buffer_heads belonging to just this pagebuf */
+		bh = head = page_buffers(page);
+		do {
+			if (buffer_uptodate(bh) && cache_ok)
+				continue;
+			if (blk_length < pg_offset)
+				continue;
+			if (blk_length >= pg_offset + pg_length)
+				break;
+
+			lock_buffer(bh);
+			get_bh(bh);
+			bh->b_size = sector;
+			bh->b_blocknr = bn;
+			bufferlist[cnt++] = bh;
+
+		} while ((bn += i),
+			 (blk_length += sector),
+			  (bh = bh->b_this_page) != head);
+
+		goto request;
+	}
+
+	/* Calculate the block offsets and length we will be using */
+	if (pg_offset) {
+		size_t		block_offset;
+
+		block_offset = pg_offset >> sector_shift;
+		block_offset = pg_offset - (block_offset << sector_shift);
+		blk_length = (pg_length + block_offset + pbr->pbr_smask) >>
+								sector_shift;
+	} else {
+		blk_length = (pg_length + pbr->pbr_smask) >> sector_shift;
+	}
+
+	/* This will attempt to make a request bigger than the sector
+	 * size if we are well aligned.
+	 */
+	switch (pb->pb_target->pbr_flags) {
+	case 0:
+		sector = blk_length << sector_shift;
+		blk_length = 1;
+		break;
+	case PBR_ALIGNED_ONLY:
+		if ((pg_offset == 0) && (pg_length == PAGE_CACHE_SIZE) &&
+		    (((unsigned int) bn) & BN_ALIGN_MASK) == 0) {
+			sector = blk_length << sector_shift;
+			blk_length = 1;
+			break;
+		}
+	case PBR_SECTOR_ONLY:
+		/* Fallthrough, same as default */
+	default:
+		sector = 1 << sector_shift;
+	}
+
+	/* If we are doing I/O larger than the bh->b_size field then
+	 * we need to split this request up.
+	 */
+	while (sector > ((1ULL << NBBY * sizeof(bh->b_size)) - 1)) {
+		sector >>= 1;
+		blk_length++;
+	}
+
+	multi_ok = (blk_length != 1);
+	i = sector >> BBSHIFT;
+
+	for (; blk_length > 0; bn += i, blk_length--, pg_offset += sector) {
+		bh = kmem_cache_alloc(bh_cachep, SLAB_NOFS);
+		if (!bh)
+			bh = _pagebuf_get_prealloc_bh();
+		memset(bh, 0, sizeof(*bh));
+		bh->b_blocknr = bn;
+		bh->b_size = sector;
+		bh->b_dev = pbr->pbr_kdev;
+		set_buffer_locked(bh);
+		set_bh_page(bh, page, pg_offset);
+		init_waitqueue_head(&bh->b_wait);
+		atomic_set(&bh->b_count, 1);
+		bufferlist[cnt++] = bh;
+	}
+
+request:
+	if (cnt) {
+		void	(*callback)(struct buffer_head *, int);
+
+		callback = (multi_ok && public_bh) ?
+				_pagebuf_end_io_partial_pages :
+				_pagebuf_end_io_complete_pages;
+
+		/* Account for additional buffers in progress */
+		atomic_add(cnt, &pb->pb_io_remaining);
+
+#ifdef RQ_WRITE_ORDERED
+		if (flush)
+			set_bit(BH_Ordered_Flush, &bufferlist[cnt-1]->b_state);
+#endif
+
+		for (i = 0; i < cnt; i++) {
+			bh = bufferlist[i];
+			init_buffer(bh, callback, pb);
+			bh->b_rdev = bh->b_dev;
+			bh->b_rsector = bh->b_blocknr;
+			set_buffer_mapped(bh);
+			set_buffer_async(bh);
+			set_buffer_req(bh);
+			if (rw == WRITE)
+				set_buffer_uptodate(bh);
+			generic_make_request(rw, bh);
+		}
+		return 0;
+	}
+
+	/*
+	 * We have no I/O to submit, let the caller know that
+	 * we have skipped over this page entirely.
+	 */
+	return 1;
+}
+
+STATIC void
+_pagebuf_page_apply(
+	xfs_buf_t		*pb,
+	loff_t			offset,
+	struct page		*page,
+	size_t			pg_offset,
+	size_t			pg_length,
+	int			last)
+{
+	xfs_daddr_t		bn = pb->pb_bn;
+	xfs_buftarg_t		*pbr = pb->pb_target;
+	loff_t			pb_offset;
+	int			status, locking;
+
+	ASSERT(page);
+	ASSERT(pb->pb_flags & (PBF_READ|PBF_WRITE));
+
+	if ((pbr->pbr_bsize == PAGE_CACHE_SIZE) &&
+	    (pb->pb_buffer_length < PAGE_CACHE_SIZE) &&
+	    (pb->pb_flags & PBF_READ) && pb->pb_locked) {
+		bn -= (pb->pb_offset >> BBSHIFT);
+		pg_offset = 0;
+		pg_length = PAGE_CACHE_SIZE;
+	} else {
+		pb_offset = offset - pb->pb_file_offset;
+		if (pb_offset) {
+			bn += (pb_offset + BBMASK) >> BBSHIFT;
+		}
+	}
+
+	locking = _pagebuf_iolocked(pb);
+	if (pb->pb_flags & PBF_WRITE) {
+		if (locking && !pb->pb_locked)
+			lock_page(page);
+		status = _pagebuf_page_io(page, pbr, pb, bn,
+				pg_offset, pg_length, WRITE,
+				last && (pb->pb_flags & PBF_FLUSH));
+	} else {
+		status = _pagebuf_page_io(page, pbr, pb, bn,
+				pg_offset, pg_length, READ, 0);
+	}
+	if (status && locking && !(pb->pb_target->pbr_bsize < PAGE_CACHE_SIZE))
+		unlock_page(page);
+}
+
+/*
+ *	pagebuf_iorequest -- the core I/O request routine.
+ */
+int
+pagebuf_iorequest(			/* start real I/O		*/
+	xfs_buf_t		*pb)	/* buffer to convey to device	*/
+{
+	PB_TRACE(pb, "iorequest", 0);
+
+	if (pb->pb_flags & PBF_DELWRI) {
+		pagebuf_delwri_queue(pb, 1);
+		return 0;
+	}
+
+	if (pb->pb_flags & PBF_WRITE) {
+		_pagebuf_wait_unpin(pb);
+	}
+
+	pagebuf_hold(pb);
+
+	/* Set the count to 1 initially, this will stop an I/O
+	 * completion callout which happens before we have started
+	 * all the I/O from calling pagebuf_iodone too early.
+	 */
+	atomic_set(&pb->pb_io_remaining, 1);
+	_pagebuf_ioapply(pb);
+	_pagebuf_iodone(pb, 0);
+
+	pagebuf_rele(pb);
+	return 0;
+}
+
+/*
+ *	pagebuf_iowait
+ *
+ *	pagebuf_iowait waits for I/O to complete on the buffer supplied.
+ *	It returns immediately if no I/O is pending.  In any case, it returns
+ *	the error code, if any, or 0 if there is no error.
+ */
+int
+pagebuf_iowait(
+	xfs_buf_t		*pb)
+{
+	PB_TRACE(pb, "iowait", 0);
+	if (atomic_read(&pb->pb_io_remaining))
+		run_task_queue(&tq_disk);
+	if ((pb->pb_flags & PBF_FS_DATAIOD))
+		pagebuf_runall_queues(pagebuf_dataiodone_tq);
+	down(&pb->pb_iodonesema);
+	PB_TRACE(pb, "iowaited", (long)pb->pb_error);
+	return pb->pb_error;
+}
+
+caddr_t
+pagebuf_offset(
+	xfs_buf_t		*pb,
+	size_t			offset)
+{
+	struct page		*page;
+
+	offset += pb->pb_offset;
+
+	page = pb->pb_pages[offset >> PAGE_CACHE_SHIFT];
+	return (caddr_t) page_address(page) + (offset & (PAGE_CACHE_SIZE - 1));
+}
+
+/*
+ *	pagebuf_iomove
+ *
+ *	Move data into or out of a buffer.
+ */
+void
+pagebuf_iomove(
+	xfs_buf_t		*pb,	/* buffer to process		*/
+	size_t			boff,	/* starting buffer offset	*/
+	size_t			bsize,	/* length to copy		*/
+	caddr_t			data,	/* data address			*/
+	page_buf_rw_t		mode)	/* read/write flag		*/
+{
+	size_t			bend, cpoff, csize;
+	struct page		*page;
+
+	bend = boff + bsize;
+	while (boff < bend) {
+		page = pb->pb_pages[page_buf_btoct(boff + pb->pb_offset)];
+		cpoff = page_buf_poff(boff + pb->pb_offset);
+		csize = min_t(size_t,
+			      PAGE_CACHE_SIZE-cpoff, pb->pb_count_desired-boff);
+
+		ASSERT(((csize + cpoff) <= PAGE_CACHE_SIZE));
+
+		switch (mode) {
+		case PBRW_ZERO:
+			memset(page_address(page) + cpoff, 0, csize);
+			break;
+		case PBRW_READ:
+			memcpy(data, page_address(page) + cpoff, csize);
+			break;
+		case PBRW_WRITE:
+			memcpy(page_address(page) + cpoff, data, csize);
+		}
+
+		boff += csize;
+		data += csize;
+	}
+}
+
+/*
+ *	_pagebuf_ioapply
+ *
+ *	Applies _pagebuf_page_apply to each page of the xfs_buf_t.
+ */
+STATIC void
+_pagebuf_ioapply(			/* apply function to pages	*/
+	xfs_buf_t		*pb)	/* buffer to examine		*/
+{
+	int			index;
+	loff_t			buffer_offset = pb->pb_file_offset;
+	size_t			buffer_len = pb->pb_count_desired;
+	size_t			page_offset, len;
+	size_t			cur_offset, cur_len;
+
+	cur_offset = pb->pb_offset;
+	cur_len = buffer_len;
+
+	if (!pb->pb_locked && !(pb->pb_flags & PBF_DIRECTIO) &&
+	    (pb->pb_target->pbr_bsize < PAGE_CACHE_SIZE)) {
+		for (index = 0; index < pb->pb_page_count; index++)
+			lock_page(pb->pb_pages[index]);
+		pb->pb_locked = 1;
+	}
+
+	for (index = 0; index < pb->pb_page_count; index++) {
+		if (cur_len == 0)
+			break;
+		if (cur_offset >= PAGE_CACHE_SIZE) {
+			cur_offset -= PAGE_CACHE_SIZE;
+			continue;
+		}
+
+		page_offset = cur_offset;
+		cur_offset = 0;
+
+		len = PAGE_CACHE_SIZE - page_offset;
+		if (len > cur_len)
+			len = cur_len;
+		cur_len -= len;
+
+		_pagebuf_page_apply(pb, buffer_offset,
+				pb->pb_pages[index], page_offset, len,
+				index + 1 == pb->pb_page_count);
+		buffer_offset += len;
+		buffer_len -= len;
+	}
+
+	/*
+	 * Run the block device task queue here, while we have
+	 * a hold on the pagebuf (important to have that hold).
+	 */
+	if (pb->pb_flags & _PBF_RUN_QUEUES) {
+		pb->pb_flags &= ~_PBF_RUN_QUEUES;
+		if (atomic_read(&pb->pb_io_remaining) > 1)
+			run_task_queue(&tq_disk);
+	}
+}
+
+
+/*
+ * Delayed write buffer list handling
+ */
+
+STATIC LIST_HEAD(pbd_delwrite_queue);
+STATIC spinlock_t pbd_delwrite_lock = SPIN_LOCK_UNLOCKED;
+
+STATIC void
+pagebuf_delwri_queue(
+	xfs_buf_t		*pb,
+	int			unlock)
+{
+	PB_TRACE(pb, "delwri_q", (long)unlock);
+	ASSERT(pb->pb_flags & PBF_DELWRI);
+
+	spin_lock(&pbd_delwrite_lock);
+	/* If already in the queue, dequeue and place at tail */
+	if (!list_empty(&pb->pb_list)) {
+		if (unlock)
+			atomic_dec(&pb->pb_hold);
+		list_del(&pb->pb_list);
+	}
+
+	list_add_tail(&pb->pb_list, &pbd_delwrite_queue);
+	pb->pb_queuetime = jiffies;
+	spin_unlock(&pbd_delwrite_lock);
+
+	if (unlock)
+		pagebuf_unlock(pb);
+}
+
+void
+pagebuf_delwri_dequeue(
+	xfs_buf_t		*pb)
+{
+	int			dequeued = 0;
+
+	spin_lock(&pbd_delwrite_lock);
+	if ((pb->pb_flags & PBF_DELWRI) && !list_empty(&pb->pb_list)) {
+		list_del_init(&pb->pb_list);
+		dequeued = 1;
+	}
+	pb->pb_flags &= ~PBF_DELWRI;
+	spin_unlock(&pbd_delwrite_lock);
+
+	if (dequeued)
+		pagebuf_rele(pb);
+
+	PB_TRACE(pb, "delwri_dq", (long)dequeued);
+}
+
+
+/*
+ * The pagebuf iodone daemons
+ */
+
+STATIC int
+pagebuf_iodone_daemon(
+	void			*__bind_cpu,
+	const char		*name,
+	int			pagebuf_daemons[],
+	struct list_head	pagebuf_iodone_tq[],
+	wait_queue_head_t	pagebuf_iodone_wait[])
+{
+	int			bind_cpu, cpu;
+	DECLARE_WAITQUEUE	(wait, current);
+
+	bind_cpu = (int) (long)__bind_cpu;
+	cpu = CPU_TO_DAEMON(cpu_logical_map(bind_cpu));
+
+	/*  Set up the thread  */
+	daemonize();
+
+	/* Avoid signals */
+	sigmask_lock();
+	sigfillset(&current->blocked);
+	__recalc_sigpending(current);
+	sigmask_unlock();
+
+	/* Migrate to the right CPU */
+	migrate_to_cpu(cpu);
+#ifdef __HAVE_NEW_SCHEDULER
+	if (smp_processor_id() != cpu)
+		BUG();
+#else
+	while (smp_processor_id() != cpu)
+		schedule();
+#endif
+
+	sprintf(current->comm, "%s/%d", name, bind_cpu);
+	INIT_LIST_HEAD(&pagebuf_iodone_tq[cpu]);
+	init_waitqueue_head(&pagebuf_iodone_wait[cpu]);
+	__set_current_state(TASK_INTERRUPTIBLE);
+	mb();
+
+	pagebuf_daemons[cpu] = 1;
+
+	for (;;) {
+		add_wait_queue(&pagebuf_iodone_wait[cpu], &wait);
+
+		if (TQ_ACTIVE(pagebuf_iodone_tq[cpu]))
+			__set_task_state(current, TASK_RUNNING);
+		schedule();
+		remove_wait_queue(&pagebuf_iodone_wait[cpu], &wait);
+		run_task_queue(&pagebuf_iodone_tq[cpu]);
+		if (pagebuf_daemons[cpu] == 0)
+			break;
+		__set_current_state(TASK_INTERRUPTIBLE);
+	}
+
+	pagebuf_daemons[cpu] = -1;
+	wake_up_interruptible(&pagebuf_iodone_wait[cpu]);
+	return 0;
+}
+
+STATIC void
+pagebuf_runall_queues(
+	struct list_head	pagebuf_iodone_tq[])
+{
+	int	pcpu, cpu;
+
+	for (cpu = 0; cpu < min(smp_num_cpus, MAX_IO_DAEMONS); cpu++) {
+		pcpu = CPU_TO_DAEMON(cpu_logical_map(cpu));
+
+		run_task_queue(&pagebuf_iodone_tq[pcpu]);
+	}
+}
+
+STATIC int
+pagebuf_logiodone_daemon(
+	void			*__bind_cpu)
+{
+	return pagebuf_iodone_daemon(__bind_cpu, "xfslogd", pb_logio_daemons,
+			pagebuf_logiodone_tq, pagebuf_logiodone_wait);
+}
+
+STATIC int
+pagebuf_dataiodone_daemon(
+	void			*__bind_cpu)
+{
+	return pagebuf_iodone_daemon(__bind_cpu, "xfsdatad", pb_dataio_daemons,
+			pagebuf_dataiodone_tq, pagebuf_dataiodone_wait);
+}
+
+
+/* Defines for pagebuf daemon */
+STATIC DECLARE_COMPLETION(pagebuf_daemon_done);
+STATIC struct task_struct *pagebuf_daemon_task;
+STATIC int pagebuf_daemon_active;
+STATIC int force_flush;
+
+
+STATIC int
+pagebuf_daemon_wakeup(
+	int			priority,
+	unsigned int		mask)
+{
+	force_flush = 1;
+	barrier();
+	wake_up_process(pagebuf_daemon_task);
+	return 0;
+}
+
+STATIC int
+pagebuf_daemon(
+	void			*data)
+{
+	struct list_head	tmp;
+	unsigned long		age;
+	xfs_buf_t		*pb, *n;
+	int			count;
+
+	/*  Set up the thread  */
+	daemonize();
+
+	/* Mark it active */
+	pagebuf_daemon_task = current;
+	pagebuf_daemon_active = 1;
+	barrier();
+
+	/* Avoid signals */
+	sigmask_lock();
+	sigfillset(&current->blocked);
+	__recalc_sigpending(current);
+	sigmask_unlock();
+
+	strcpy(current->comm, "xfsbufd");
+	current->flags |= PF_MEMALLOC;
+
+	INIT_LIST_HEAD(&tmp);
+	do {
+		set_current_state(TASK_INTERRUPTIBLE);
+		schedule_timeout((xfs_buf_timer_centisecs * HZ) / 100);
+
+		count = 0;
+		age = (xfs_buf_age_centisecs * HZ) / 100;
+		spin_lock(&pbd_delwrite_lock);
+		list_for_each_entry_safe(pb, n, &pbd_delwrite_queue, pb_list) {
+			PB_TRACE(pb, "walkq1", (long)pagebuf_ispin(pb));
+			ASSERT(pb->pb_flags & PBF_DELWRI);
+
+			if (!pagebuf_ispin(pb) && !pagebuf_cond_lock(pb)) {
+				if (!force_flush &&
+				    time_before(jiffies,
+						pb->pb_queuetime + age)) {
+					pagebuf_unlock(pb);
+					break;
+				}
+
+				pb->pb_flags &= ~PBF_DELWRI;
+				pb->pb_flags |= PBF_WRITE;
+				list_move(&pb->pb_list, &tmp);
+				count++;
+			}
+		}
+		spin_unlock(&pbd_delwrite_lock);
+
+		while (!list_empty(&tmp)) {
+			pb = list_entry(tmp.next, xfs_buf_t, pb_list);
+			list_del_init(&pb->pb_list);
+			pagebuf_iostrategy(pb);
+		}
+
+		if (as_list_len > 0)
+			purge_addresses();
+		if (count)
+			run_task_queue(&tq_disk);
+
+		force_flush = 0;
+	} while (pagebuf_daemon_active);
+
+	complete_and_exit(&pagebuf_daemon_done, 0);
+}
+
+/*
+ * Go through all incore buffers, and release buffers if they belong to
+ * the given device. This is used in filesystem error handling to
+ * preserve the consistency of its metadata.
+ */
+int
+xfs_flush_buftarg(
+	xfs_buftarg_t		*target,
+	int			wait)
+{
+	struct list_head	tmp;
+	xfs_buf_t		*pb, *n;
+	int			pincount = 0;
+	int			flush_cnt = 0;
+
+	pagebuf_runall_queues(pagebuf_dataiodone_tq);
+	pagebuf_runall_queues(pagebuf_logiodone_tq);
+
+	INIT_LIST_HEAD(&tmp);
+	spin_lock(&pbd_delwrite_lock);
+	list_for_each_entry_safe(pb, n, &pbd_delwrite_queue, pb_list) {
+
+		if (pb->pb_target != target)
+			continue;
+
+		ASSERT(pb->pb_flags & PBF_DELWRI);
+		PB_TRACE(pb, "walkq2", (long)pagebuf_ispin(pb));
+		if (pagebuf_ispin(pb)) {
+			pincount++;
+			continue;
+		}
+
+		pb->pb_flags &= ~PBF_DELWRI;
+		pb->pb_flags |= PBF_WRITE;
+		list_move(&pb->pb_list, &tmp);
+	}
+	spin_unlock(&pbd_delwrite_lock);
+
+	/*
+	 * Dropped the delayed write list lock, now walk the temporary list
+	 */
+	list_for_each_entry_safe(pb, n, &tmp, pb_list) {
+
+		if (wait)
+			pb->pb_flags &= ~PBF_ASYNC;
+		else
+			list_del_init(&pb->pb_list);
+
+		pagebuf_lock(pb);
+		pagebuf_iostrategy(pb);
+
+		if (++flush_cnt > 32) {
+			run_task_queue(&tq_disk);
+			flush_cnt = 0;
+		}
+	}
+
+	run_task_queue(&tq_disk);
+
+	/*
+	 * Remaining list items must be flushed before returning
+	 */
+	while (!list_empty(&tmp)) {
+		pb = list_entry(tmp.next, xfs_buf_t, pb_list);
+
+		list_del_init(&pb->pb_list);
+		
+		xfs_iowait(pb);
+		xfs_buf_relse(pb);
+	}
+
+	return pincount;
+}
+
+STATIC int
+pagebuf_daemon_start(void)
+{
+	int		cpu, pcpu;
+
+	kernel_thread(pagebuf_daemon, NULL, CLONE_FS|CLONE_FILES|CLONE_VM);
+
+	for (cpu = 0; cpu < min(smp_num_cpus, MAX_IO_DAEMONS); cpu++) {
+		pcpu = CPU_TO_DAEMON(cpu_logical_map(cpu));
+
+		if (kernel_thread(pagebuf_logiodone_daemon,
+				(void *)(long) cpu,
+				CLONE_FS|CLONE_FILES|CLONE_VM) < 0) {
+			printk("pagebuf_logiodone daemon failed to start\n");
+		} else {
+			while (!pb_logio_daemons[pcpu])
+				yield();
+		}
+	}
+	for (cpu = 0; cpu < min(smp_num_cpus, MAX_IO_DAEMONS); cpu++) {
+		pcpu = CPU_TO_DAEMON(cpu_logical_map(cpu));
+
+		if (kernel_thread(pagebuf_dataiodone_daemon,
+				(void *)(long) cpu,
+				CLONE_FS|CLONE_FILES|CLONE_VM) < 0) {
+			printk("pagebuf_dataiodone daemon failed to start\n");
+		} else {
+			while (!pb_dataio_daemons[pcpu])
+				yield();
+		}
+	}
+	return 0;
+}
+
+/*
+ * pagebuf_daemon_stop
+ *
+ * Note: do not mark as __exit, it is called from pagebuf_terminate.
+ */
+STATIC void
+pagebuf_daemon_stop(void)
+{
+	int		cpu, pcpu;
+
+	pagebuf_daemon_active = 0;
+	barrier();
+	wait_for_completion(&pagebuf_daemon_done);
+
+	for (pcpu = 0; pcpu < min(smp_num_cpus, MAX_IO_DAEMONS); pcpu++) {
+		cpu = CPU_TO_DAEMON(cpu_logical_map(pcpu));
+
+		pb_logio_daemons[cpu] = 0;
+		wake_up(&pagebuf_logiodone_wait[cpu]);
+		wait_event_interruptible(pagebuf_logiodone_wait[cpu],
+				pb_logio_daemons[cpu] == -1);
+
+		pb_dataio_daemons[cpu] = 0;
+		wake_up(&pagebuf_dataiodone_wait[cpu]);
+		wait_event_interruptible(pagebuf_dataiodone_wait[cpu],
+				pb_dataio_daemons[cpu] == -1);
+	}
+}
+
+/*
+ *	Initialization and Termination
+ */
+
+int __init
+pagebuf_init(void)
+{
+	int			i;
+
+	pagebuf_cache = kmem_cache_create("xfs_buf_t", sizeof(xfs_buf_t), 0,
+			SLAB_HWCACHE_ALIGN, NULL, NULL);
+	if (pagebuf_cache == NULL) {
+		printk("XFS: couldn't init xfs_buf_t cache\n");
+		return -ENOMEM;
+	}
+
+	if (_pagebuf_prealloc_bh(NR_RESERVED_BH) < NR_RESERVED_BH) {
+		printk("XFS: couldn't allocate %d reserved buffers\n",
+			NR_RESERVED_BH);
+		kmem_zone_destroy(pagebuf_cache);
+		return -ENOMEM;
+	}
+	init_waitqueue_head(&pb_resv_bh_wait);
+
+#ifdef PAGEBUF_TRACE
+	pagebuf_trace_buf = ktrace_alloc(PAGEBUF_TRACE_SIZE, KM_SLEEP);
+#endif
+
+	pagebuf_daemon_start();
+
+	pagebuf_shake = kmem_shake_register(pagebuf_daemon_wakeup);
+	if (pagebuf_shake == NULL) {
+		pagebuf_terminate();
+		return -ENOMEM;
+	}
+
+	for (i = 0; i < NHASH; i++) {
+		spin_lock_init(&pbhash[i].pb_hash_lock);
+		INIT_LIST_HEAD(&pbhash[i].pb_hash);
+	}
+
+	return 0;
+}
+
+/*
+ *	pagebuf_terminate.
+ *
+ *	Note: do not mark as __exit, this is also called from the __init code.
+ */
+void
+pagebuf_terminate(void)
+{
+	pagebuf_daemon_stop();
+
+#ifdef PAGEBUF_TRACE
+	ktrace_free(pagebuf_trace_buf);
+#endif
+
+	kmem_zone_destroy(pagebuf_cache);
+	kmem_shake_deregister(pagebuf_shake);
+}
FUNET's LINUX-ADM group, linux-adm@nic.funet.fi
TCL-scripts by Sam Shen (who was at: slshen@lbl.gov)