Linux-2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!

1 files changed, 1980 insertions, 0 deletions

diff --git a/fs/xfs/linux-2.6/xfs_buf.c b/fs/xfs/linux-2.6/xfs_buf.c
new file mode 100644
index 00000000000..23e0eb67fc2
--- /dev/null
+++ b/fs/xfs/linux-2.6/xfs_buf.c
@@ -0,0 +1,1980 @@
+/*
+ * 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/bio.h>
+#include <linux/sysctl.h>
+#include <linux/proc_fs.h>
+#include <linux/workqueue.h>
+#include <linux/percpu.h>
+#include <linux/blkdev.h>
+#include <linux/hash.h>
+
+#include "xfs_linux.h"
+
+/*
+ * File wide globals
+ */
+
+STATIC kmem_cache_t *pagebuf_cache;
+STATIC kmem_shaker_t pagebuf_shake;
+STATIC int pagebuf_daemon_wakeup(int, unsigned int);
+STATIC void pagebuf_delwri_queue(xfs_buf_t *, int);
+STATIC struct workqueue_struct *pagebuf_logio_workqueue;
+STATIC struct workqueue_struct *pagebuf_dataio_workqueue;
+
+/*
+ * 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_NORETRY : \
+	  ((flags) & PBF_DONT_BLOCK) ? GFP_NOFS : GFP_KERNEL) | __GFP_NOWARN)
+
+#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));
+
+/*
+ * Page Region interfaces.
+ *
+ * For pages in filesystems where the blocksize is smaller than the
+ * pagesize, we use the page->private field (long) to hold a bitmap
+ * of uptodate regions within the page.
+ *
+ * Each such region is "bytes per page / bits per long" bytes long.
+ *
+ * NBPPR == number-of-bytes-per-page-region
+ * BTOPR == bytes-to-page-region (rounded up)
+ * BTOPRT == bytes-to-page-region-truncated (rounded down)
+ */
+#if (BITS_PER_LONG == 32)
+#define PRSHIFT		(PAGE_CACHE_SHIFT - 5)	/* (32 == 1<<5) */
+#elif (BITS_PER_LONG == 64)
+#define PRSHIFT		(PAGE_CACHE_SHIFT - 6)	/* (64 == 1<<6) */
+#else
+#error BITS_PER_LONG must be 32 or 64
+#endif
+#define NBPPR		(PAGE_CACHE_SIZE/BITS_PER_LONG)
+#define BTOPR(b)	(((unsigned int)(b) + (NBPPR - 1)) >> PRSHIFT)
+#define BTOPRT(b)	(((unsigned int)(b) >> PRSHIFT))
+
+STATIC unsigned long
+page_region_mask(
+	size_t		offset,
+	size_t		length)
+{
+	unsigned long	mask;
+	int		first, final;
+
+	first = BTOPR(offset);
+	final = BTOPRT(offset + length - 1);
+	first = min(first, final);
+
+	mask = ~0UL;
+	mask <<= BITS_PER_LONG - (final - first);
+	mask >>= BITS_PER_LONG - (final);
+
+	ASSERT(offset + length <= PAGE_CACHE_SIZE);
+	ASSERT((final - first) < BITS_PER_LONG && (final - first) >= 0);
+
+	return mask;
+}
+
+STATIC inline void
+set_page_region(
+	struct page	*page,
+	size_t		offset,
+	size_t		length)
+{
+	page->private |= page_region_mask(offset, length);
+	if (page->private == ~0UL)
+		SetPageUptodate(page);
+}
+
+STATIC inline int
+test_page_region(
+	struct page	*page,
+	size_t		offset,
+	size_t		length)
+{
+	unsigned long	mask = page_region_mask(offset, length);
+
+	return (mask && (page->private & mask) == mask);
+}
+
+/*
+ * 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 DEFINE_SPINLOCK(as_lock);
+
+/*
+ * 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 & ~__GFP_HIGH);
+	if (likely(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;
+	size_t			size = bp->pb_count_desired;
+	size_t			nbytes, offset;
+	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;
+
+	offset = bp->pb_offset;
+	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
+					"XFS: possible memory allocation "
+					"deadlock in %s (mode:0x%x)\n",
+					__FUNCTION__, gfp_mask);
+
+			XFS_STATS_INC(pb_page_retries);
+			pagebuf_daemon_wakeup(0, gfp_mask);
+			blk_congestion_wait(WRITE, HZ/50);
+			goto retry;
+		}
+
+		XFS_STATS_INC(pb_page_found);
+
+		nbytes = min_t(size_t, size, PAGE_CACHE_SIZE - offset);
+		size -= nbytes;
+
+		if (!PageUptodate(page)) {
+			page_count--;
+			if (blocksize >= PAGE_CACHE_SIZE) {
+				if (flags & PBF_READ)
+					bp->pb_locked = 1;
+			} else if (!PagePrivate(page)) {
+				if (test_page_region(page, offset, nbytes))
+					page_count++;
+			}
+		}
+
+		bp->pb_pages[i] = page;
+		offset = 0;
+	}
+
+	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;
+}
+
+/*
+ *	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.
+ */
+xfs_buf_t *
+_pagebuf_find(
+	xfs_buftarg_t		*btp,	/* block device target		*/
+	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;
+	xfs_bufhash_t		*hash;
+	xfs_buf_t		*pb, *n;
+
+	range_base = (ioff << BBSHIFT);
+	range_length = (isize << BBSHIFT);
+
+	/* Check for IOs smaller than the sector size / not sector aligned */
+	ASSERT(!(range_length < (1 << btp->pbr_sshift)));
+	ASSERT(!(range_base & (loff_t)btp->pbr_smask));
+
+	hash = &btp->bt_hash[hash_long((unsigned long)ioff, btp->bt_hashshift)];
+
+	spin_lock(&hash->bh_lock);
+
+	list_for_each_entry_safe(pb, n, &hash->bh_list, pb_hash_list) {
+		ASSERT(btp == pb->pb_target);
+		if (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, &hash->bh_list);
+			goto found;
+		}
+	}
+
+	/* No match found */
+	if (new_pb) {
+		_pagebuf_initialize(new_pb, btp, range_base,
+				range_length, flags);
+		new_pb->pb_hash = hash;
+		list_add(&new_pb->pb_hash_list, &hash->bh_list);
+	} else {
+		XFS_STATS_INC(pb_miss_locked);
+	}
+
+	spin_unlock(&hash->bh_lock);
+	return new_pb;
+
+found:
+	spin_unlock(&hash->bh_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.
+	 */
+	if (down_trylock(&pb->pb_sema)) {
+		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);
+}
+
+/*
+ *	xfs_buf_get_flags assembles a buffer covering the specified range.
+ *
+ *	Storage in memory for all portions of the buffer will be allocated,
+ *	although backing storage may not be.
+ */
+xfs_buf_t *
+xfs_buf_get_flags(			/* 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 (error)
+			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 "%s: failed to map pages\n",
+					__FUNCTION__);
+			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;
+
+	PB_TRACE(pb, "get", (unsigned long)flags);
+	return pb;
+
+ no_buffer:
+	if (flags & (PBF_LOCK | PBF_TRYLOCK))
+		pagebuf_unlock(pb);
+	pagebuf_rele(pb);
+	return NULL;
+}
+
+xfs_buf_t *
+xfs_buf_read_flags(
+	xfs_buftarg_t		*target,
+	loff_t			ioff,
+	size_t			isize,
+	page_buf_flags_t	flags)
+{
+	xfs_buf_t		*pb;
+
+	flags |= PBF_READ;
+
+	pb = xfs_buf_get_flags(target, ioff, isize, flags);
+	if (pb) {
+		if (PBF_NOT_DONE(pb)) {
+			PB_TRACE(pb, "read", (unsigned long)flags);
+			XFS_STATS_INC(pb_get_read);
+			pagebuf_iostart(pb, flags);
+		} else if (flags & PBF_ASYNC) {
+			PB_TRACE(pb, "read_async", (unsigned long)flags);
+			/*
+			 * Read ahead call which is already satisfied,
+			 * drop the buffer
+			 */
+			goto no_buffer;
+		} else {
+			PB_TRACE(pb, "read_done", (unsigned long)flags);
+			/* We do not want read in the flags */
+			pb->pb_flags &= ~PBF_READ;
+		}
+	}
+
+	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;
+
+	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)
+{
+	struct backing_dev_info *bdi;
+
+	bdi = target->pbr_mapping->backing_dev_info;
+	if (bdi_read_congested(bdi))
+		return;
+
+	flags |= (PBF_TRYLOCK|PBF_ASYNC|PBF_READ_AHEAD);
+	xfs_buf_read_flags(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;
+
+	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)
+{
+	xfs_bufhash_t		*hash = pb->pb_hash;
+
+	PB_TRACE(pb, "rele", pb->pb_relse);
+
+	/*
+	 * pagebuf_lookup buffers are not hashed, not delayed write,
+	 * and don't have their own release routines.  Special case.
+	 */
+	if (unlikely(!hash)) {
+		ASSERT(!pb->pb_relse);
+		if (atomic_dec_and_test(&pb->pb_hold))
+			xfs_buf_free(pb);
+		return;
+	}
+
+	if (atomic_dec_and_lock(&pb->pb_hold, &hash->bh_lock)) {
+		int		do_free = 1;
+
+		if (pb->pb_relse) {
+			atomic_inc(&pb->pb_hold);
+			spin_unlock(&hash->bh_lock);
+			(*(pb->pb_relse)) (pb);
+			spin_lock(&hash->bh_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->bh_lock);
+			pagebuf_free(pb);
+		} else {
+			spin_unlock(&hash->bh_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);
+}
+
+#if defined(DEBUG) || defined(XFS_BLI_TRACE)
+/*
+ *	pagebuf_lock_value
+ *
+ *	Return lock value for a pagebuf
+ */
+int
+pagebuf_lock_value(
+	xfs_buf_t		*pb)
+{
+	return(atomic_read(&pb->pb_sema.count));
+}
+#endif
+
+/*
+ *	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))
+		blk_run_address_space(pb->pb_target->pbr_mapping);
+	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))
+			blk_run_address_space(pb->pb_target->pbr_mapping);
+		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.
+ */
+STATIC void
+pagebuf_iodone_work(
+	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) {
+			INIT_WORK(&pb->pb_iodone_work, pagebuf_iodone_work, pb);
+			queue_work(dataio ? pagebuf_dataio_workqueue :
+				pagebuf_logio_workqueue, &pb->pb_iodone_work);
+		} else {
+			pagebuf_iodone_work(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 routine for pagebuf_iorequest
+ */
+
+STATIC __inline__ int
+_pagebuf_iolocked(
+	xfs_buf_t		*pb)
+{
+	ASSERT(pb->pb_flags & (PBF_READ|PBF_WRITE));
+	if (pb->pb_flags & PBF_READ)
+		return pb->pb_locked;
+	return 0;
+}
+
+STATIC __inline__ void
+_pagebuf_iodone(
+	xfs_buf_t		*pb,
+	int			schedule)
+{
+	if (atomic_dec_and_test(&pb->pb_io_remaining) == 1) {
+		pb->pb_locked = 0;
+		pagebuf_iodone(pb, (pb->pb_flags & PBF_FS_DATAIOD), schedule);
+	}
+}
+
+STATIC int
+bio_end_io_pagebuf(
+	struct bio		*bio,
+	unsigned int		bytes_done,
+	int			error)
+{
+	xfs_buf_t		*pb = (xfs_buf_t *)bio->bi_private;
+	unsigned int		i, blocksize = pb->pb_target->pbr_bsize;
+	struct bio_vec		*bvec = bio->bi_io_vec;
+
+	if (bio->bi_size)
+		return 1;
+
+	if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
+		pb->pb_error = EIO;
+
+	for (i = 0; i < bio->bi_vcnt; i++, bvec++) {
+		struct page	*page = bvec->bv_page;
+
+		if (pb->pb_error) {
+			SetPageError(page);
+		} else if (blocksize == PAGE_CACHE_SIZE) {
+			SetPageUptodate(page);
+		} else if (!PagePrivate(page) &&
+				(pb->pb_flags & _PBF_PAGE_CACHE)) {
+			set_page_region(page, bvec->bv_offset, bvec->bv_len);
+		}
+
+		if (_pagebuf_iolocked(pb)) {
+			unlock_page(page);
+		}
+	}
+
+	_pagebuf_iodone(pb, 1);
+	bio_put(bio);
+	return 0;
+}
+
+STATIC void
+_pagebuf_ioapply(
+	xfs_buf_t		*pb)
+{
+	int			i, rw, map_i, total_nr_pages, nr_pages;
+	struct bio		*bio;
+	int			offset = pb->pb_offset;
+	int			size = pb->pb_count_desired;
+	sector_t		sector = pb->pb_bn;
+	unsigned int		blocksize = pb->pb_target->pbr_bsize;
+	int			locking = _pagebuf_iolocked(pb);
+
+	total_nr_pages = pb->pb_page_count;
+	map_i = 0;
+
+	if (pb->pb_flags & _PBF_RUN_QUEUES) {
+		pb->pb_flags &= ~_PBF_RUN_QUEUES;
+		rw = (pb->pb_flags & PBF_READ) ? READ_SYNC : WRITE_SYNC;
+	} else {
+		rw = (pb->pb_flags & PBF_READ) ? READ : WRITE;
+	}
+
+	/* Special code path for reading a sub page size pagebuf in --
+	 * we populate up the whole page, and hence the other metadata
+	 * in the same page.  This optimization is only valid when the
+	 * filesystem block size and the page size are equal.
+	 */
+	if ((pb->pb_buffer_length < PAGE_CACHE_SIZE) &&
+	    (pb->pb_flags & PBF_READ) && locking &&
+	    (blocksize == PAGE_CACHE_SIZE)) {
+		bio = bio_alloc(GFP_NOIO, 1);
+
+		bio->bi_bdev = pb->pb_target->pbr_bdev;
+		bio->bi_sector = sector - (offset >> BBSHIFT);
+		bio->bi_end_io = bio_end_io_pagebuf;
+		bio->bi_private = pb;
+
+		bio_add_page(bio, pb->pb_pages[0], PAGE_CACHE_SIZE, 0);
+		size = 0;
+
+		atomic_inc(&pb->pb_io_remaining);
+
+		goto submit_io;
+	}
+
+	/* Lock down the pages which we need to for the request */
+	if (locking && (pb->pb_flags & PBF_WRITE) && (pb->pb_locked == 0)) {
+		for (i = 0; size; i++) {
+			int		nbytes = PAGE_CACHE_SIZE - offset;
+			struct page	*page = pb->pb_pages[i];
+
+			if (nbytes > size)
+				nbytes = size;
+
+			lock_page(page);
+
+			size -= nbytes;
+			offset = 0;
+		}
+		offset = pb->pb_offset;
+		size = pb->pb_count_desired;
+	}
+
+next_chunk:
+	atomic_inc(&pb->pb_io_remaining);
+	nr_pages = BIO_MAX_SECTORS >> (PAGE_SHIFT - BBSHIFT);
+	if (nr_pages > total_nr_pages)
+		nr_pages = total_nr_pages;
+
+	bio = bio_alloc(GFP_NOIO, nr_pages);
+	bio->bi_bdev = pb->pb_target->pbr_bdev;
+	bio->bi_sector = sector;
+	bio->bi_end_io = bio_end_io_pagebuf;
+	bio->bi_private = pb;
+
+	for (; size && nr_pages; nr_pages--, map_i++) {
+		int	nbytes = PAGE_CACHE_SIZE - offset;
+
+		if (nbytes > size)
+			nbytes = size;
+
+		if (bio_add_page(bio, pb->pb_pages[map_i],
+					nbytes, offset) < nbytes)
+			break;
+
+		offset = 0;
+		sector += nbytes >> BBSHIFT;
+		size -= nbytes;
+		total_nr_pages--;
+	}
+
+submit_io:
+	if (likely(bio->bi_size)) {
+		submit_bio(rw, bio);
+		if (size)
+			goto next_chunk;
+	} else {
+		bio_put(bio);
+		pagebuf_ioerror(pb, EIO);
+	}
+}
+
+/*
+ *	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))
+		blk_run_address_space(pb->pb_target->pbr_mapping);
+	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;
+	}
+}
+
+/*
+ *	Handling of buftargs.
+ */
+
+/*
+ * Wait for any bufs with callbacks that have been submitted but
+ * have not yet returned... walk the hash list for the target.
+ */
+void
+xfs_wait_buftarg(
+	xfs_buftarg_t	*btp)
+{
+	xfs_buf_t	*bp, *n;
+	xfs_bufhash_t	*hash;
+	uint		i;
+
+	for (i = 0; i < (1 << btp->bt_hashshift); i++) {
+		hash = &btp->bt_hash[i];
+again:
+		spin_lock(&hash->bh_lock);
+		list_for_each_entry_safe(bp, n, &hash->bh_list, pb_hash_list) {
+			ASSERT(btp == bp->pb_target);
+			if (!(bp->pb_flags & PBF_FS_MANAGED)) {
+				spin_unlock(&hash->bh_lock);
+				delay(100);
+				goto again;
+			}
+		}
+		spin_unlock(&hash->bh_lock);
+	}
+}
+
+/*
+ * Allocate buffer hash table for a given target.
+ * For devices containing metadata (i.e. not the log/realtime devices)
+ * we need to allocate a much larger hash table.
+ */
+STATIC void
+xfs_alloc_bufhash(
+	xfs_buftarg_t		*btp,
+	int			external)
+{
+	unsigned int		i;
+
+	btp->bt_hashshift = external ? 3 : 8;	/* 8 or 256 buckets */
+	btp->bt_hashmask = (1 << btp->bt_hashshift) - 1;
+	btp->bt_hash = kmem_zalloc((1 << btp->bt_hashshift) *
+					sizeof(xfs_bufhash_t), KM_SLEEP);
+	for (i = 0; i < (1 << btp->bt_hashshift); i++) {
+		spin_lock_init(&btp->bt_hash[i].bh_lock);
+		INIT_LIST_HEAD(&btp->bt_hash[i].bh_list);
+	}
+}
+
+STATIC void
+xfs_free_bufhash(
+	xfs_buftarg_t		*btp)
+{
+	kmem_free(btp->bt_hash,
+			(1 << btp->bt_hashshift) * sizeof(xfs_bufhash_t));
+	btp->bt_hash = NULL;
+}
+
+void
+xfs_free_buftarg(
+	xfs_buftarg_t		*btp,
+	int			external)
+{
+	xfs_flush_buftarg(btp, 1);
+	if (external)
+		xfs_blkdev_put(btp->pbr_bdev);
+	xfs_free_bufhash(btp);
+	iput(btp->pbr_mapping->host);
+	kmem_free(btp, sizeof(*btp));
+}
+
+void
+xfs_incore_relse(
+	xfs_buftarg_t		*btp,
+	int			delwri_only,
+	int			wait)
+{
+	invalidate_bdev(btp->pbr_bdev, 1);
+	truncate_inode_pages(btp->pbr_mapping, 0LL);
+}
+
+STATIC int
+xfs_setsize_buftarg_flags(
+	xfs_buftarg_t		*btp,
+	unsigned int		blocksize,
+	unsigned int		sectorsize,
+	int			verbose)
+{
+	btp->pbr_bsize = blocksize;
+	btp->pbr_sshift = ffs(sectorsize) - 1;
+	btp->pbr_smask = sectorsize - 1;
+
+	if (set_blocksize(btp->pbr_bdev, sectorsize)) {
+		printk(KERN_WARNING
+			"XFS: Cannot set_blocksize to %u on device %s\n",
+			sectorsize, XFS_BUFTARG_NAME(btp));
+		return EINVAL;
+	}
+
+	if (verbose &&
+	    (PAGE_CACHE_SIZE / BITS_PER_LONG) > sectorsize) {
+		printk(KERN_WARNING
+			"XFS: %u byte sectors in use on device %s.  "
+			"This is suboptimal; %u or greater is ideal.\n",
+			sectorsize, XFS_BUFTARG_NAME(btp),
+			(unsigned int)PAGE_CACHE_SIZE / BITS_PER_LONG);
+	}
+
+	return 0;
+}
+
+/*
+* When allocating the initial buffer target we have not yet
+* read in the superblock, so don't know what sized sectors
+* are being used is at this early stage.  Play safe.
+*/
+STATIC int
+xfs_setsize_buftarg_early(
+	xfs_buftarg_t		*btp,
+	struct block_device	*bdev)
+{
+	return xfs_setsize_buftarg_flags(btp,
+			PAGE_CACHE_SIZE, bdev_hardsect_size(bdev), 0);
+}
+
+int
+xfs_setsize_buftarg(
+	xfs_buftarg_t		*btp,
+	unsigned int		blocksize,
+	unsigned int		sectorsize)
+{
+	return xfs_setsize_buftarg_flags(btp, blocksize, sectorsize, 1);
+}
+
+STATIC int
+xfs_mapping_buftarg(
+	xfs_buftarg_t		*btp,
+	struct block_device	*bdev)
+{
+	struct backing_dev_info	*bdi;
+	struct inode		*inode;
+	struct address_space	*mapping;
+	static struct address_space_operations mapping_aops = {
+		.sync_page = block_sync_page,
+	};
+
+	inode = new_inode(bdev->bd_inode->i_sb);
+	if (!inode) {
+		printk(KERN_WARNING
+			"XFS: Cannot allocate mapping inode for device %s\n",
+			XFS_BUFTARG_NAME(btp));
+		return ENOMEM;
+	}
+	inode->i_mode = S_IFBLK;
+	inode->i_bdev = bdev;
+	inode->i_rdev = bdev->bd_dev;
+	bdi = blk_get_backing_dev_info(bdev);
+	if (!bdi)
+		bdi = &default_backing_dev_info;
+	mapping = &inode->i_data;
+	mapping->a_ops = &mapping_aops;
+	mapping->backing_dev_info = bdi;
+	mapping_set_gfp_mask(mapping, GFP_NOFS);
+	btp->pbr_mapping = mapping;
+	return 0;
+}
+
+xfs_buftarg_t *
+xfs_alloc_buftarg(
+	struct block_device	*bdev,
+	int			external)
+{
+	xfs_buftarg_t		*btp;
+
+	btp = kmem_zalloc(sizeof(*btp), KM_SLEEP);
+
+	btp->pbr_dev =  bdev->bd_dev;
+	btp->pbr_bdev = bdev;
+	if (xfs_setsize_buftarg_early(btp, bdev))
+		goto error;
+	if (xfs_mapping_buftarg(btp, bdev))
+		goto error;
+	xfs_alloc_bufhash(btp, external);
+	return btp;
+
+error:
+	kmem_free(btp, sizeof(*btp));
+	return NULL;
+}
+
+
+/*
+ * Pagebuf delayed write buffer handling
+ */
+
+STATIC LIST_HEAD(pbd_delwrite_queue);
+STATIC DEFINE_SPINLOCK(pbd_delwrite_lock);
+
+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);
+}
+
+STATIC void
+pagebuf_runall_queues(
+	struct workqueue_struct	*queue)
+{
+	flush_workqueue(queue);
+}
+
+/* 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_buftarg_t		*target;
+	xfs_buf_t		*pb, *n;
+
+	/*  Set up the thread  */
+	daemonize("xfsbufd");
+	current->flags |= PF_MEMALLOC;
+
+	pagebuf_daemon_task = current;
+	pagebuf_daemon_active = 1;
+	barrier();
+
+	INIT_LIST_HEAD(&tmp);
+	do {
+		try_to_freeze(PF_FREEZE);
+
+		set_current_state(TASK_INTERRUPTIBLE);
+		schedule_timeout((xfs_buf_timer_centisecs * HZ) / 100);
+
+		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);
+			}
+		}
+		spin_unlock(&pbd_delwrite_lock);
+
+		while (!list_empty(&tmp)) {
+			pb = list_entry(tmp.next, xfs_buf_t, pb_list);
+			target = pb->pb_target;
+
+			list_del_init(&pb->pb_list);
+			pagebuf_iostrategy(pb);
+
+			blk_run_address_space(target->pbr_mapping);
+		}
+
+		if (as_list_len > 0)
+			purge_addresses();
+
+		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;
+
+	pagebuf_runall_queues(pagebuf_dataio_workqueue);
+	pagebuf_runall_queues(pagebuf_logio_workqueue);
+
+	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);
+	}
+
+	/*
+	 * 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);
+	}
+
+	if (wait)
+		blk_run_address_space(target->pbr_mapping);
+
+	return pincount;
+}
+
+STATIC int
+pagebuf_daemon_start(void)
+{
+	int		rval;
+
+	pagebuf_logio_workqueue = create_workqueue("xfslogd");
+	if (!pagebuf_logio_workqueue)
+		return -ENOMEM;
+
+	pagebuf_dataio_workqueue = create_workqueue("xfsdatad");
+	if (!pagebuf_dataio_workqueue) {
+		destroy_workqueue(pagebuf_logio_workqueue);
+		return -ENOMEM;
+	}
+
+	rval = kernel_thread(pagebuf_daemon, NULL, CLONE_FS|CLONE_FILES);
+	if (rval < 0) {
+		destroy_workqueue(pagebuf_logio_workqueue);
+		destroy_workqueue(pagebuf_dataio_workqueue);
+	}
+
+	return rval;
+}
+
+/*
+ * pagebuf_daemon_stop
+ *
+ * Note: do not mark as __exit, it is called from pagebuf_terminate.
+ */
+STATIC void
+pagebuf_daemon_stop(void)
+{
+	pagebuf_daemon_active = 0;
+	barrier();
+	wait_for_completion(&pagebuf_daemon_done);
+
+	destroy_workqueue(pagebuf_logio_workqueue);
+	destroy_workqueue(pagebuf_dataio_workqueue);
+}
+
+/*
+ *	Initialization and Termination
+ */
+
+int __init
+pagebuf_init(void)
+{
+	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");
+		pagebuf_terminate();
+		return -ENOMEM;
+	}
+
+#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;
+	}
+
+	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);
+}