xfs: remove subdirectories

Use the move from Linux 2.6 to Linux 3.x as an excuse to kill the
annoying subdirectories in the XFS source code.  Besides the large
amount of file rename the only changes are to the Makefile, a few
files including headers with the subdirectory prefix, and the binary
sysctl compat code that includes a header under fs/xfs/ from
kernel/.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>

1 files changed, 1876 insertions, 0 deletions

diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
new file mode 100644
index 000000000000..c57836dc778f
--- /dev/null
+++ b/fs/xfs/xfs_buf.c
@@ -0,0 +1,1876 @@
+/*
+ * Copyright (c) 2000-2006 Silicon Graphics, Inc.
+ * All Rights Reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms 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.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write the Free Software Foundation,
+ * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+#include "xfs.h"
+#include <linux/stddef.h>
+#include <linux/errno.h>
+#include <linux/gfp.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 <linux/kthread.h>
+#include <linux/migrate.h>
+#include <linux/backing-dev.h>
+#include <linux/freezer.h>
+
+#include "xfs_sb.h"
+#include "xfs_inum.h"
+#include "xfs_log.h"
+#include "xfs_ag.h"
+#include "xfs_mount.h"
+#include "xfs_trace.h"
+
+static kmem_zone_t *xfs_buf_zone;
+STATIC int xfsbufd(void *);
+STATIC void xfs_buf_delwri_queue(xfs_buf_t *, int);
+
+static struct workqueue_struct *xfslogd_workqueue;
+struct workqueue_struct *xfsdatad_workqueue;
+struct workqueue_struct *xfsconvertd_workqueue;
+
+#ifdef XFS_BUF_LOCK_TRACKING
+# define XB_SET_OWNER(bp)	((bp)->b_last_holder = current->pid)
+# define XB_CLEAR_OWNER(bp)	((bp)->b_last_holder = -1)
+# define XB_GET_OWNER(bp)	((bp)->b_last_holder)
+#else
+# define XB_SET_OWNER(bp)	do { } while (0)
+# define XB_CLEAR_OWNER(bp)	do { } while (0)
+# define XB_GET_OWNER(bp)	do { } while (0)
+#endif
+
+#define xb_to_gfp(flags) \
+	((((flags) & XBF_READ_AHEAD) ? __GFP_NORETRY : \
+	  ((flags) & XBF_DONT_BLOCK) ? GFP_NOFS : GFP_KERNEL) | __GFP_NOWARN)
+
+#define xb_to_km(flags) \
+	 (((flags) & XBF_DONT_BLOCK) ? KM_NOFS : KM_SLEEP)
+
+#define xfs_buf_allocate(flags) \
+	kmem_zone_alloc(xfs_buf_zone, xb_to_km(flags))
+#define xfs_buf_deallocate(bp) \
+	kmem_zone_free(xfs_buf_zone, (bp));
+
+static inline int
+xfs_buf_is_vmapped(
+	struct xfs_buf	*bp)
+{
+	/*
+	 * Return true if the buffer is vmapped.
+	 *
+	 * The XBF_MAPPED flag is set if the buffer should be mapped, but the
+	 * code is clever enough to know it doesn't have to map a single page,
+	 * so the check has to be both for XBF_MAPPED and bp->b_page_count > 1.
+	 */
+	return (bp->b_flags & XBF_MAPPED) && bp->b_page_count > 1;
+}
+
+static inline int
+xfs_buf_vmap_len(
+	struct xfs_buf	*bp)
+{
+	return (bp->b_page_count * PAGE_SIZE) - bp->b_offset;
+}
+
+/*
+ * xfs_buf_lru_add - add a buffer to the LRU.
+ *
+ * The LRU takes a new reference to the buffer so that it will only be freed
+ * once the shrinker takes the buffer off the LRU.
+ */
+STATIC void
+xfs_buf_lru_add(
+	struct xfs_buf	*bp)
+{
+	struct xfs_buftarg *btp = bp->b_target;
+
+	spin_lock(&btp->bt_lru_lock);
+	if (list_empty(&bp->b_lru)) {
+		atomic_inc(&bp->b_hold);
+		list_add_tail(&bp->b_lru, &btp->bt_lru);
+		btp->bt_lru_nr++;
+	}
+	spin_unlock(&btp->bt_lru_lock);
+}
+
+/*
+ * xfs_buf_lru_del - remove a buffer from the LRU
+ *
+ * The unlocked check is safe here because it only occurs when there are not
+ * b_lru_ref counts left on the inode under the pag->pag_buf_lock. it is there
+ * to optimise the shrinker removing the buffer from the LRU and calling
+ * xfs_buf_free(). i.e. it removes an unnecessary round trip on the
+ * bt_lru_lock.
+ */
+STATIC void
+xfs_buf_lru_del(
+	struct xfs_buf	*bp)
+{
+	struct xfs_buftarg *btp = bp->b_target;
+
+	if (list_empty(&bp->b_lru))
+		return;
+
+	spin_lock(&btp->bt_lru_lock);
+	if (!list_empty(&bp->b_lru)) {
+		list_del_init(&bp->b_lru);
+		btp->bt_lru_nr--;
+	}
+	spin_unlock(&btp->bt_lru_lock);
+}
+
+/*
+ * When we mark a buffer stale, we remove the buffer from the LRU and clear the
+ * b_lru_ref count so that the buffer is freed immediately when the buffer
+ * reference count falls to zero. If the buffer is already on the LRU, we need
+ * to remove the reference that LRU holds on the buffer.
+ *
+ * This prevents build-up of stale buffers on the LRU.
+ */
+void
+xfs_buf_stale(
+	struct xfs_buf	*bp)
+{
+	bp->b_flags |= XBF_STALE;
+	atomic_set(&(bp)->b_lru_ref, 0);
+	if (!list_empty(&bp->b_lru)) {
+		struct xfs_buftarg *btp = bp->b_target;
+
+		spin_lock(&btp->bt_lru_lock);
+		if (!list_empty(&bp->b_lru)) {
+			list_del_init(&bp->b_lru);
+			btp->bt_lru_nr--;
+			atomic_dec(&bp->b_hold);
+		}
+		spin_unlock(&btp->bt_lru_lock);
+	}
+	ASSERT(atomic_read(&bp->b_hold) >= 1);
+}
+
+STATIC void
+_xfs_buf_initialize(
+	xfs_buf_t		*bp,
+	xfs_buftarg_t		*target,
+	xfs_off_t		range_base,
+	size_t			range_length,
+	xfs_buf_flags_t		flags)
+{
+	/*
+	 * We don't want certain flags to appear in b_flags.
+	 */
+	flags &= ~(XBF_LOCK|XBF_MAPPED|XBF_DONT_BLOCK|XBF_READ_AHEAD);
+
+	memset(bp, 0, sizeof(xfs_buf_t));
+	atomic_set(&bp->b_hold, 1);
+	atomic_set(&bp->b_lru_ref, 1);
+	init_completion(&bp->b_iowait);
+	INIT_LIST_HEAD(&bp->b_lru);
+	INIT_LIST_HEAD(&bp->b_list);
+	RB_CLEAR_NODE(&bp->b_rbnode);
+	sema_init(&bp->b_sema, 0); /* held, no waiters */
+	XB_SET_OWNER(bp);
+	bp->b_target = target;
+	bp->b_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).
+	 */
+	bp->b_buffer_length = bp->b_count_desired = range_length;
+	bp->b_flags = flags;
+	bp->b_bn = XFS_BUF_DADDR_NULL;
+	atomic_set(&bp->b_pin_count, 0);
+	init_waitqueue_head(&bp->b_waiters);
+
+	XFS_STATS_INC(xb_create);
+
+	trace_xfs_buf_init(bp, _RET_IP_);
+}
+
+/*
+ *	Allocate a page array capable of holding a specified number
+ *	of pages, and point the page buf at it.
+ */
+STATIC int
+_xfs_buf_get_pages(
+	xfs_buf_t		*bp,
+	int			page_count,
+	xfs_buf_flags_t		flags)
+{
+	/* Make sure that we have a page list */
+	if (bp->b_pages == NULL) {
+		bp->b_offset = xfs_buf_poff(bp->b_file_offset);
+		bp->b_page_count = page_count;
+		if (page_count <= XB_PAGES) {
+			bp->b_pages = bp->b_page_array;
+		} else {
+			bp->b_pages = kmem_alloc(sizeof(struct page *) *
+					page_count, xb_to_km(flags));
+			if (bp->b_pages == NULL)
+				return -ENOMEM;
+		}
+		memset(bp->b_pages, 0, sizeof(struct page *) * page_count);
+	}
+	return 0;
+}
+
+/*
+ *	Frees b_pages if it was allocated.
+ */
+STATIC void
+_xfs_buf_free_pages(
+	xfs_buf_t	*bp)
+{
+	if (bp->b_pages != bp->b_page_array) {
+		kmem_free(bp->b_pages);
+		bp->b_pages = NULL;
+	}
+}
+
+/*
+ *	Releases the specified buffer.
+ *
+ * 	The modification state of any associated pages is left unchanged.
+ * 	The buffer most not be on any hash - use xfs_buf_rele instead for
+ * 	hashed and refcounted buffers
+ */
+void
+xfs_buf_free(
+	xfs_buf_t		*bp)
+{
+	trace_xfs_buf_free(bp, _RET_IP_);
+
+	ASSERT(list_empty(&bp->b_lru));
+
+	if (bp->b_flags & _XBF_PAGES) {
+		uint		i;
+
+		if (xfs_buf_is_vmapped(bp))
+			vm_unmap_ram(bp->b_addr - bp->b_offset,
+					bp->b_page_count);
+
+		for (i = 0; i < bp->b_page_count; i++) {
+			struct page	*page = bp->b_pages[i];
+
+			__free_page(page);
+		}
+	} else if (bp->b_flags & _XBF_KMEM)
+		kmem_free(bp->b_addr);
+	_xfs_buf_free_pages(bp);
+	xfs_buf_deallocate(bp);
+}
+
+/*
+ * Allocates all the pages for buffer in question and builds it's page list.
+ */
+STATIC int
+xfs_buf_allocate_memory(
+	xfs_buf_t		*bp,
+	uint			flags)
+{
+	size_t			size = bp->b_count_desired;
+	size_t			nbytes, offset;
+	gfp_t			gfp_mask = xb_to_gfp(flags);
+	unsigned short		page_count, i;
+	xfs_off_t		end;
+	int			error;
+
+	/*
+	 * for buffers that are contained within a single page, just allocate
+	 * the memory from the heap - there's no need for the complexity of
+	 * page arrays to keep allocation down to order 0.
+	 */
+	if (bp->b_buffer_length < PAGE_SIZE) {
+		bp->b_addr = kmem_alloc(bp->b_buffer_length, xb_to_km(flags));
+		if (!bp->b_addr) {
+			/* low memory - use alloc_page loop instead */
+			goto use_alloc_page;
+		}
+
+		if (((unsigned long)(bp->b_addr + bp->b_buffer_length - 1) &
+								PAGE_MASK) !=
+		    ((unsigned long)bp->b_addr & PAGE_MASK)) {
+			/* b_addr spans two pages - use alloc_page instead */
+			kmem_free(bp->b_addr);
+			bp->b_addr = NULL;
+			goto use_alloc_page;
+		}
+		bp->b_offset = offset_in_page(bp->b_addr);
+		bp->b_pages = bp->b_page_array;
+		bp->b_pages[0] = virt_to_page(bp->b_addr);
+		bp->b_page_count = 1;
+		bp->b_flags |= XBF_MAPPED | _XBF_KMEM;
+		return 0;
+	}
+
+use_alloc_page:
+	end = bp->b_file_offset + bp->b_buffer_length;
+	page_count = xfs_buf_btoc(end) - xfs_buf_btoct(bp->b_file_offset);
+	error = _xfs_buf_get_pages(bp, page_count, flags);
+	if (unlikely(error))
+		return error;
+
+	offset = bp->b_offset;
+	bp->b_flags |= _XBF_PAGES;
+
+	for (i = 0; i < bp->b_page_count; i++) {
+		struct page	*page;
+		uint		retries = 0;
+retry:
+		page = alloc_page(gfp_mask);
+		if (unlikely(page == NULL)) {
+			if (flags & XBF_READ_AHEAD) {
+				bp->b_page_count = i;
+				error = ENOMEM;
+				goto out_free_pages;
+			}
+
+			/*
+			 * 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))
+				xfs_err(NULL,
+		"possible memory allocation deadlock in %s (mode:0x%x)",
+					__func__, gfp_mask);
+
+			XFS_STATS_INC(xb_page_retries);
+			congestion_wait(BLK_RW_ASYNC, HZ/50);
+			goto retry;
+		}
+
+		XFS_STATS_INC(xb_page_found);
+
+		nbytes = min_t(size_t, size, PAGE_SIZE - offset);
+		size -= nbytes;
+		bp->b_pages[i] = page;
+		offset = 0;
+	}
+	return 0;
+
+out_free_pages:
+	for (i = 0; i < bp->b_page_count; i++)
+		__free_page(bp->b_pages[i]);
+	return error;
+}
+
+/*
+ *	Map buffer into kernel address-space if necessary.
+ */
+STATIC int
+_xfs_buf_map_pages(
+	xfs_buf_t		*bp,
+	uint			flags)
+{
+	ASSERT(bp->b_flags & _XBF_PAGES);
+	if (bp->b_page_count == 1) {
+		/* A single page buffer is always mappable */
+		bp->b_addr = page_address(bp->b_pages[0]) + bp->b_offset;
+		bp->b_flags |= XBF_MAPPED;
+	} else if (flags & XBF_MAPPED) {
+		int retried = 0;
+
+		do {
+			bp->b_addr = vm_map_ram(bp->b_pages, bp->b_page_count,
+						-1, PAGE_KERNEL);
+			if (bp->b_addr)
+				break;
+			vm_unmap_aliases();
+		} while (retried++ <= 1);
+
+		if (!bp->b_addr)
+			return -ENOMEM;
+		bp->b_addr += bp->b_offset;
+		bp->b_flags |= XBF_MAPPED;
+	}
+
+	return 0;
+}
+
+/*
+ *	Finding and Reading Buffers
+ */
+
+/*
+ *	Look 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 *
+_xfs_buf_find(
+	xfs_buftarg_t		*btp,	/* block device target		*/
+	xfs_off_t		ioff,	/* starting offset of range	*/
+	size_t			isize,	/* length of range		*/
+	xfs_buf_flags_t		flags,
+	xfs_buf_t		*new_bp)
+{
+	xfs_off_t		range_base;
+	size_t			range_length;
+	struct xfs_perag	*pag;
+	struct rb_node		**rbp;
+	struct rb_node		*parent;
+	xfs_buf_t		*bp;
+
+	range_base = (ioff << BBSHIFT);
+	range_length = (isize << BBSHIFT);
+
+	/* Check for IOs smaller than the sector size / not sector aligned */
+	ASSERT(!(range_length < (1 << btp->bt_sshift)));
+	ASSERT(!(range_base & (xfs_off_t)btp->bt_smask));
+
+	/* get tree root */
+	pag = xfs_perag_get(btp->bt_mount,
+				xfs_daddr_to_agno(btp->bt_mount, ioff));
+
+	/* walk tree */
+	spin_lock(&pag->pag_buf_lock);
+	rbp = &pag->pag_buf_tree.rb_node;
+	parent = NULL;
+	bp = NULL;
+	while (*rbp) {
+		parent = *rbp;
+		bp = rb_entry(parent, struct xfs_buf, b_rbnode);
+
+		if (range_base < bp->b_file_offset)
+			rbp = &(*rbp)->rb_left;
+		else if (range_base > bp->b_file_offset)
+			rbp = &(*rbp)->rb_right;
+		else {
+			/*
+			 * found a block offset match. If the range doesn't
+			 * match, the only way this is allowed is if the buffer
+			 * in the cache is stale and the transaction that made
+			 * it stale has not yet committed. i.e. we are
+			 * reallocating a busy extent. Skip this buffer and
+			 * continue searching to the right for an exact match.
+			 */
+			if (bp->b_buffer_length != range_length) {
+				ASSERT(bp->b_flags & XBF_STALE);
+				rbp = &(*rbp)->rb_right;
+				continue;
+			}
+			atomic_inc(&bp->b_hold);
+			goto found;
+		}
+	}
+
+	/* No match found */
+	if (new_bp) {
+		_xfs_buf_initialize(new_bp, btp, range_base,
+				range_length, flags);
+		rb_link_node(&new_bp->b_rbnode, parent, rbp);
+		rb_insert_color(&new_bp->b_rbnode, &pag->pag_buf_tree);
+		/* the buffer keeps the perag reference until it is freed */
+		new_bp->b_pag = pag;
+		spin_unlock(&pag->pag_buf_lock);
+	} else {
+		XFS_STATS_INC(xb_miss_locked);
+		spin_unlock(&pag->pag_buf_lock);
+		xfs_perag_put(pag);
+	}
+	return new_bp;
+
+found:
+	spin_unlock(&pag->pag_buf_lock);
+	xfs_perag_put(pag);
+
+	if (!xfs_buf_trylock(bp)) {
+		if (flags & XBF_TRYLOCK) {
+			xfs_buf_rele(bp);
+			XFS_STATS_INC(xb_busy_locked);
+			return NULL;
+		}
+		xfs_buf_lock(bp);
+		XFS_STATS_INC(xb_get_locked_waited);
+	}
+
+	/*
+	 * if the buffer is stale, clear all the external state associated with
+	 * it. We need to keep flags such as how we allocated the buffer memory
+	 * intact here.
+	 */
+	if (bp->b_flags & XBF_STALE) {
+		ASSERT((bp->b_flags & _XBF_DELWRI_Q) == 0);
+		bp->b_flags &= XBF_MAPPED | _XBF_KMEM | _XBF_PAGES;
+	}
+
+	trace_xfs_buf_find(bp, flags, _RET_IP_);
+	XFS_STATS_INC(xb_get_locked);
+	return bp;
+}
+
+/*
+ *	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(
+	xfs_buftarg_t		*target,/* target for buffer		*/
+	xfs_off_t		ioff,	/* starting offset of range	*/
+	size_t			isize,	/* length of range		*/
+	xfs_buf_flags_t		flags)
+{
+	xfs_buf_t		*bp, *new_bp;
+	int			error = 0;
+
+	new_bp = xfs_buf_allocate(flags);
+	if (unlikely(!new_bp))
+		return NULL;
+
+	bp = _xfs_buf_find(target, ioff, isize, flags, new_bp);
+	if (bp == new_bp) {
+		error = xfs_buf_allocate_memory(bp, flags);
+		if (error)
+			goto no_buffer;
+	} else {
+		xfs_buf_deallocate(new_bp);
+		if (unlikely(bp == NULL))
+			return NULL;
+	}
+
+	if (!(bp->b_flags & XBF_MAPPED)) {
+		error = _xfs_buf_map_pages(bp, flags);
+		if (unlikely(error)) {
+			xfs_warn(target->bt_mount,
+				"%s: failed to map pages\n", __func__);
+			goto no_buffer;
+		}
+	}
+
+	XFS_STATS_INC(xb_get);
+
+	/*
+	 * Always fill in the block number now, the mapped cases can do
+	 * their own overlay of this later.
+	 */
+	bp->b_bn = ioff;
+	bp->b_count_desired = bp->b_buffer_length;
+
+	trace_xfs_buf_get(bp, flags, _RET_IP_);
+	return bp;
+
+ no_buffer:
+	if (flags & (XBF_LOCK | XBF_TRYLOCK))
+		xfs_buf_unlock(bp);
+	xfs_buf_rele(bp);
+	return NULL;
+}
+
+STATIC int
+_xfs_buf_read(
+	xfs_buf_t		*bp,
+	xfs_buf_flags_t		flags)
+{
+	int			status;
+
+	ASSERT(!(flags & (XBF_DELWRI|XBF_WRITE)));
+	ASSERT(bp->b_bn != XFS_BUF_DADDR_NULL);
+
+	bp->b_flags &= ~(XBF_WRITE | XBF_ASYNC | XBF_DELWRI | XBF_READ_AHEAD);
+	bp->b_flags |= flags & (XBF_READ | XBF_ASYNC | XBF_READ_AHEAD);
+
+	status = xfs_buf_iorequest(bp);
+	if (status || bp->b_error || (flags & XBF_ASYNC))
+		return status;
+	return xfs_buf_iowait(bp);
+}
+
+xfs_buf_t *
+xfs_buf_read(
+	xfs_buftarg_t		*target,
+	xfs_off_t		ioff,
+	size_t			isize,
+	xfs_buf_flags_t		flags)
+{
+	xfs_buf_t		*bp;
+
+	flags |= XBF_READ;
+
+	bp = xfs_buf_get(target, ioff, isize, flags);
+	if (bp) {
+		trace_xfs_buf_read(bp, flags, _RET_IP_);
+
+		if (!XFS_BUF_ISDONE(bp)) {
+			XFS_STATS_INC(xb_get_read);
+			_xfs_buf_read(bp, flags);
+		} else if (flags & XBF_ASYNC) {
+			/*
+			 * Read ahead call which is already satisfied,
+			 * drop the buffer
+			 */
+			goto no_buffer;
+		} else {
+			/* We do not want read in the flags */
+			bp->b_flags &= ~XBF_READ;
+		}
+	}
+
+	return bp;
+
+ no_buffer:
+	if (flags & (XBF_LOCK | XBF_TRYLOCK))
+		xfs_buf_unlock(bp);
+	xfs_buf_rele(bp);
+	return NULL;
+}
+
+/*
+ *	If we are not low on memory then do the readahead in a deadlock
+ *	safe manner.
+ */
+void
+xfs_buf_readahead(
+	xfs_buftarg_t		*target,
+	xfs_off_t		ioff,
+	size_t			isize)
+{
+	if (bdi_read_congested(target->bt_bdi))
+		return;
+
+	xfs_buf_read(target, ioff, isize,
+		     XBF_TRYLOCK|XBF_ASYNC|XBF_READ_AHEAD|XBF_DONT_BLOCK);
+}
+
+/*
+ * Read an uncached buffer from disk. Allocates and returns a locked
+ * buffer containing the disk contents or nothing.
+ */
+struct xfs_buf *
+xfs_buf_read_uncached(
+	struct xfs_mount	*mp,
+	struct xfs_buftarg	*target,
+	xfs_daddr_t		daddr,
+	size_t			length,
+	int			flags)
+{
+	xfs_buf_t		*bp;
+	int			error;
+
+	bp = xfs_buf_get_uncached(target, length, flags);
+	if (!bp)
+		return NULL;
+
+	/* set up the buffer for a read IO */
+	XFS_BUF_SET_ADDR(bp, daddr);
+	XFS_BUF_READ(bp);
+
+	xfsbdstrat(mp, bp);
+	error = xfs_buf_iowait(bp);
+	if (error || bp->b_error) {
+		xfs_buf_relse(bp);
+		return NULL;
+	}
+	return bp;
+}
+
+xfs_buf_t *
+xfs_buf_get_empty(
+	size_t			len,
+	xfs_buftarg_t		*target)
+{
+	xfs_buf_t		*bp;
+
+	bp = xfs_buf_allocate(0);
+	if (bp)
+		_xfs_buf_initialize(bp, target, 0, len, 0);
+	return bp;
+}
+
+/*
+ * Return a buffer allocated as an empty buffer and associated to external
+ * memory via xfs_buf_associate_memory() back to it's empty state.
+ */
+void
+xfs_buf_set_empty(
+	struct xfs_buf		*bp,
+	size_t			len)
+{
+	if (bp->b_pages)
+		_xfs_buf_free_pages(bp);
+
+	bp->b_pages = NULL;
+	bp->b_page_count = 0;
+	bp->b_addr = NULL;
+	bp->b_file_offset = 0;
+	bp->b_buffer_length = bp->b_count_desired = len;
+	bp->b_bn = XFS_BUF_DADDR_NULL;
+	bp->b_flags &= ~XBF_MAPPED;
+}
+
+static inline struct page *
+mem_to_page(
+	void			*addr)
+{
+	if ((!is_vmalloc_addr(addr))) {
+		return virt_to_page(addr);
+	} else {
+		return vmalloc_to_page(addr);
+	}
+}
+
+int
+xfs_buf_associate_memory(
+	xfs_buf_t		*bp,
+	void			*mem,
+	size_t			len)
+{
+	int			rval;
+	int			i = 0;
+	unsigned long		pageaddr;
+	unsigned long		offset;
+	size_t			buflen;
+	int			page_count;
+
+	pageaddr = (unsigned long)mem & PAGE_MASK;
+	offset = (unsigned long)mem - pageaddr;
+	buflen = PAGE_ALIGN(len + offset);
+	page_count = buflen >> PAGE_SHIFT;
+
+	/* Free any previous set of page pointers */
+	if (bp->b_pages)
+		_xfs_buf_free_pages(bp);
+
+	bp->b_pages = NULL;
+	bp->b_addr = mem;
+
+	rval = _xfs_buf_get_pages(bp, page_count, XBF_DONT_BLOCK);
+	if (rval)
+		return rval;
+
+	bp->b_offset = offset;
+
+	for (i = 0; i < bp->b_page_count; i++) {
+		bp->b_pages[i] = mem_to_page((void *)pageaddr);
+		pageaddr += PAGE_SIZE;
+	}
+
+	bp->b_count_desired = len;
+	bp->b_buffer_length = buflen;
+	bp->b_flags |= XBF_MAPPED;
+
+	return 0;
+}
+
+xfs_buf_t *
+xfs_buf_get_uncached(
+	struct xfs_buftarg	*target,
+	size_t			len,
+	int			flags)
+{
+	unsigned long		page_count = PAGE_ALIGN(len) >> PAGE_SHIFT;
+	int			error, i;
+	xfs_buf_t		*bp;
+
+	bp = xfs_buf_allocate(0);
+	if (unlikely(bp == NULL))
+		goto fail;
+	_xfs_buf_initialize(bp, target, 0, len, 0);
+
+	error = _xfs_buf_get_pages(bp, page_count, 0);
+	if (error)
+		goto fail_free_buf;
+
+	for (i = 0; i < page_count; i++) {
+		bp->b_pages[i] = alloc_page(xb_to_gfp(flags));
+		if (!bp->b_pages[i])
+			goto fail_free_mem;
+	}
+	bp->b_flags |= _XBF_PAGES;
+
+	error = _xfs_buf_map_pages(bp, XBF_MAPPED);
+	if (unlikely(error)) {
+		xfs_warn(target->bt_mount,
+			"%s: failed to map pages\n", __func__);
+		goto fail_free_mem;
+	}
+
+	trace_xfs_buf_get_uncached(bp, _RET_IP_);
+	return bp;
+
+ fail_free_mem:
+	while (--i >= 0)
+		__free_page(bp->b_pages[i]);
+	_xfs_buf_free_pages(bp);
+ fail_free_buf:
+	xfs_buf_deallocate(bp);
+ fail:
+	return NULL;
+}
+
+/*
+ *	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
+xfs_buf_hold(
+	xfs_buf_t		*bp)
+{
+	trace_xfs_buf_hold(bp, _RET_IP_);
+	atomic_inc(&bp->b_hold);
+}
+
+/*
+ *	Releases a hold on the specified buffer.  If the
+ *	the hold count is 1, calls xfs_buf_free.
+ */
+void
+xfs_buf_rele(
+	xfs_buf_t		*bp)
+{
+	struct xfs_perag	*pag = bp->b_pag;
+
+	trace_xfs_buf_rele(bp, _RET_IP_);
+
+	if (!pag) {
+		ASSERT(list_empty(&bp->b_lru));
+		ASSERT(RB_EMPTY_NODE(&bp->b_rbnode));
+		if (atomic_dec_and_test(&bp->b_hold))
+			xfs_buf_free(bp);
+		return;
+	}
+
+	ASSERT(!RB_EMPTY_NODE(&bp->b_rbnode));
+
+	ASSERT(atomic_read(&bp->b_hold) > 0);
+	if (atomic_dec_and_lock(&bp->b_hold, &pag->pag_buf_lock)) {
+		if (!(bp->b_flags & XBF_STALE) &&
+			   atomic_read(&bp->b_lru_ref)) {
+			xfs_buf_lru_add(bp);
+			spin_unlock(&pag->pag_buf_lock);
+		} else {
+			xfs_buf_lru_del(bp);
+			ASSERT(!(bp->b_flags & (XBF_DELWRI|_XBF_DELWRI_Q)));
+			rb_erase(&bp->b_rbnode, &pag->pag_buf_tree);
+			spin_unlock(&pag->pag_buf_lock);
+			xfs_perag_put(pag);
+			xfs_buf_free(bp);
+		}
+	}
+}
+
+
+/*
+ *	Lock a buffer object, if it is not already locked.
+ *
+ *	If we come across a stale, pinned, locked buffer, we know that we are
+ *	being asked to lock a buffer that has been reallocated. Because it is
+ *	pinned, we know that the log has not been pushed to disk and hence it
+ *	will still be locked.  Rather than continuing to have trylock attempts
+ *	fail until someone else pushes the log, push it ourselves before
+ *	returning.  This means that the xfsaild will not get stuck trying
+ *	to push on stale inode buffers.
+ */
+int
+xfs_buf_trylock(
+	struct xfs_buf		*bp)
+{
+	int			locked;
+
+	locked = down_trylock(&bp->b_sema) == 0;
+	if (locked)
+		XB_SET_OWNER(bp);
+	else if (atomic_read(&bp->b_pin_count) && (bp->b_flags & XBF_STALE))
+		xfs_log_force(bp->b_target->bt_mount, 0);
+
+	trace_xfs_buf_trylock(bp, _RET_IP_);
+	return locked;
+}
+
+/*
+ *	Lock a buffer object.
+ *
+ *	If we come across a stale, pinned, locked buffer, we know that we
+ *	are being asked to lock a buffer that has been reallocated. Because
+ *	it is pinned, we know that the log has not been pushed to disk and
+ *	hence it will still be locked. Rather than sleeping until someone
+ *	else pushes the log, push it ourselves before trying to get the lock.
+ */
+void
+xfs_buf_lock(
+	struct xfs_buf		*bp)
+{
+	trace_xfs_buf_lock(bp, _RET_IP_);
+
+	if (atomic_read(&bp->b_pin_count) && (bp->b_flags & XBF_STALE))
+		xfs_log_force(bp->b_target->bt_mount, 0);
+	down(&bp->b_sema);
+	XB_SET_OWNER(bp);
+
+	trace_xfs_buf_lock_done(bp, _RET_IP_);
+}
+
+/*
+ *	Releases the lock on the buffer object.
+ *	If the buffer is marked delwri but is not queued, do so before we
+ *	unlock the buffer as we need to set flags correctly.  We also need to
+ *	take a reference for the delwri queue because the unlocker is going to
+ *	drop their's and they don't know we just queued it.
+ */
+void
+xfs_buf_unlock(
+	struct xfs_buf		*bp)
+{
+	if ((bp->b_flags & (XBF_DELWRI|_XBF_DELWRI_Q)) == XBF_DELWRI) {
+		atomic_inc(&bp->b_hold);
+		bp->b_flags |= XBF_ASYNC;
+		xfs_buf_delwri_queue(bp, 0);
+	}
+
+	XB_CLEAR_OWNER(bp);
+	up(&bp->b_sema);
+
+	trace_xfs_buf_unlock(bp, _RET_IP_);
+}
+
+STATIC void
+xfs_buf_wait_unpin(
+	xfs_buf_t		*bp)
+{
+	DECLARE_WAITQUEUE	(wait, current);
+
+	if (atomic_read(&bp->b_pin_count) == 0)
+		return;
+
+	add_wait_queue(&bp->b_waiters, &wait);
+	for (;;) {
+		set_current_state(TASK_UNINTERRUPTIBLE);
+		if (atomic_read(&bp->b_pin_count) == 0)
+			break;
+		io_schedule();
+	}
+	remove_wait_queue(&bp->b_waiters, &wait);
+	set_current_state(TASK_RUNNING);
+}
+
+/*
+ *	Buffer Utility Routines
+ */
+
+STATIC void
+xfs_buf_iodone_work(
+	struct work_struct	*work)
+{
+	xfs_buf_t		*bp =
+		container_of(work, xfs_buf_t, b_iodone_work);
+
+	if (bp->b_iodone)
+		(*(bp->b_iodone))(bp);
+	else if (bp->b_flags & XBF_ASYNC)
+		xfs_buf_relse(bp);
+}
+
+void
+xfs_buf_ioend(
+	xfs_buf_t		*bp,
+	int			schedule)
+{
+	trace_xfs_buf_iodone(bp, _RET_IP_);
+
+	bp->b_flags &= ~(XBF_READ | XBF_WRITE | XBF_READ_AHEAD);
+	if (bp->b_error == 0)
+		bp->b_flags |= XBF_DONE;
+
+	if ((bp->b_iodone) || (bp->b_flags & XBF_ASYNC)) {
+		if (schedule) {
+			INIT_WORK(&bp->b_iodone_work, xfs_buf_iodone_work);
+			queue_work(xfslogd_workqueue, &bp->b_iodone_work);
+		} else {
+			xfs_buf_iodone_work(&bp->b_iodone_work);
+		}
+	} else {
+		complete(&bp->b_iowait);
+	}
+}
+
+void
+xfs_buf_ioerror(
+	xfs_buf_t		*bp,
+	int			error)
+{
+	ASSERT(error >= 0 && error <= 0xffff);
+	bp->b_error = (unsigned short)error;
+	trace_xfs_buf_ioerror(bp, error, _RET_IP_);
+}
+
+int
+xfs_bwrite(
+	struct xfs_mount	*mp,
+	struct xfs_buf		*bp)
+{
+	int			error;
+
+	bp->b_flags |= XBF_WRITE;
+	bp->b_flags &= ~(XBF_ASYNC | XBF_READ);
+
+	xfs_buf_delwri_dequeue(bp);
+	xfs_bdstrat_cb(bp);
+
+	error = xfs_buf_iowait(bp);
+	if (error)
+		xfs_force_shutdown(mp, SHUTDOWN_META_IO_ERROR);
+	xfs_buf_relse(bp);
+	return error;
+}
+
+void
+xfs_bdwrite(
+	void			*mp,
+	struct xfs_buf		*bp)
+{
+	trace_xfs_buf_bdwrite(bp, _RET_IP_);
+
+	bp->b_flags &= ~XBF_READ;
+	bp->b_flags |= (XBF_DELWRI | XBF_ASYNC);
+
+	xfs_buf_delwri_queue(bp, 1);
+}
+
+/*
+ * Called when we want to stop a buffer from getting written or read.
+ * We attach the EIO error, muck with its flags, and call xfs_buf_ioend
+ * so that the proper iodone callbacks get called.
+ */
+STATIC int
+xfs_bioerror(
+	xfs_buf_t *bp)
+{
+#ifdef XFSERRORDEBUG
+	ASSERT(XFS_BUF_ISREAD(bp) || bp->b_iodone);
+#endif
+
+	/*
+	 * No need to wait until the buffer is unpinned, we aren't flushing it.
+	 */
+	xfs_buf_ioerror(bp, EIO);
+
+	/*
+	 * We're calling xfs_buf_ioend, so delete XBF_DONE flag.
+	 */
+	XFS_BUF_UNREAD(bp);
+	XFS_BUF_UNDELAYWRITE(bp);
+	XFS_BUF_UNDONE(bp);
+	XFS_BUF_STALE(bp);
+
+	xfs_buf_ioend(bp, 0);
+
+	return EIO;
+}
+
+/*
+ * Same as xfs_bioerror, except that we are releasing the buffer
+ * here ourselves, and avoiding the xfs_buf_ioend call.
+ * This is meant for userdata errors; metadata bufs come with
+ * iodone functions attached, so that we can track down errors.
+ */
+STATIC int
+xfs_bioerror_relse(
+	struct xfs_buf	*bp)
+{
+	int64_t		fl = bp->b_flags;
+	/*
+	 * No need to wait until the buffer is unpinned.
+	 * We aren't flushing it.
+	 *
+	 * chunkhold expects B_DONE to be set, whether
+	 * we actually finish the I/O or not. We don't want to
+	 * change that interface.
+	 */
+	XFS_BUF_UNREAD(bp);
+	XFS_BUF_UNDELAYWRITE(bp);
+	XFS_BUF_DONE(bp);
+	XFS_BUF_STALE(bp);
+	bp->b_iodone = NULL;
+	if (!(fl & XBF_ASYNC)) {
+		/*
+		 * Mark b_error and B_ERROR _both_.
+		 * Lot's of chunkcache code assumes that.
+		 * There's no reason to mark error for
+		 * ASYNC buffers.
+		 */
+		xfs_buf_ioerror(bp, EIO);
+		XFS_BUF_FINISH_IOWAIT(bp);
+	} else {
+		xfs_buf_relse(bp);
+	}
+
+	return EIO;
+}
+
+
+/*
+ * All xfs metadata buffers except log state machine buffers
+ * get this attached as their b_bdstrat callback function.
+ * This is so that we can catch a buffer
+ * after prematurely unpinning it to forcibly shutdown the filesystem.
+ */
+int
+xfs_bdstrat_cb(
+	struct xfs_buf	*bp)
+{
+	if (XFS_FORCED_SHUTDOWN(bp->b_target->bt_mount)) {
+		trace_xfs_bdstrat_shut(bp, _RET_IP_);
+		/*
+		 * Metadata write that didn't get logged but
+		 * written delayed anyway. These aren't associated
+		 * with a transaction, and can be ignored.
+		 */
+		if (!bp->b_iodone && !XFS_BUF_ISREAD(bp))
+			return xfs_bioerror_relse(bp);
+		else
+			return xfs_bioerror(bp);
+	}
+
+	xfs_buf_iorequest(bp);
+	return 0;
+}
+
+/*
+ * Wrapper around bdstrat so that we can stop data from going to disk in case
+ * we are shutting down the filesystem.  Typically user data goes thru this
+ * path; one of the exceptions is the superblock.
+ */
+void
+xfsbdstrat(
+	struct xfs_mount	*mp,
+	struct xfs_buf		*bp)
+{
+	if (XFS_FORCED_SHUTDOWN(mp)) {
+		trace_xfs_bdstrat_shut(bp, _RET_IP_);
+		xfs_bioerror_relse(bp);
+		return;
+	}
+
+	xfs_buf_iorequest(bp);
+}
+
+STATIC void
+_xfs_buf_ioend(
+	xfs_buf_t		*bp,
+	int			schedule)
+{
+	if (atomic_dec_and_test(&bp->b_io_remaining) == 1)
+		xfs_buf_ioend(bp, schedule);
+}
+
+STATIC void
+xfs_buf_bio_end_io(
+	struct bio		*bio,
+	int			error)
+{
+	xfs_buf_t		*bp = (xfs_buf_t *)bio->bi_private;
+
+	xfs_buf_ioerror(bp, -error);
+
+	if (!error && xfs_buf_is_vmapped(bp) && (bp->b_flags & XBF_READ))
+		invalidate_kernel_vmap_range(bp->b_addr, xfs_buf_vmap_len(bp));
+
+	_xfs_buf_ioend(bp, 1);
+	bio_put(bio);
+}
+
+STATIC void
+_xfs_buf_ioapply(
+	xfs_buf_t		*bp)
+{
+	int			rw, map_i, total_nr_pages, nr_pages;
+	struct bio		*bio;
+	int			offset = bp->b_offset;
+	int			size = bp->b_count_desired;
+	sector_t		sector = bp->b_bn;
+
+	total_nr_pages = bp->b_page_count;
+	map_i = 0;
+
+	if (bp->b_flags & XBF_WRITE) {
+		if (bp->b_flags & XBF_SYNCIO)
+			rw = WRITE_SYNC;
+		else
+			rw = WRITE;
+		if (bp->b_flags & XBF_FUA)
+			rw |= REQ_FUA;
+		if (bp->b_flags & XBF_FLUSH)
+			rw |= REQ_FLUSH;
+	} else if (bp->b_flags & XBF_READ_AHEAD) {
+		rw = READA;
+	} else {
+		rw = READ;
+	}
+
+	/* we only use the buffer cache for meta-data */
+	rw |= REQ_META;
+
+next_chunk:
+	atomic_inc(&bp->b_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 = bp->b_target->bt_bdev;
+	bio->bi_sector = sector;
+	bio->bi_end_io = xfs_buf_bio_end_io;
+	bio->bi_private = bp;
+
+
+	for (; size && nr_pages; nr_pages--, map_i++) {
+		int	rbytes, nbytes = PAGE_SIZE - offset;
+
+		if (nbytes > size)
+			nbytes = size;
+
+		rbytes = bio_add_page(bio, bp->b_pages[map_i], nbytes, offset);
+		if (rbytes < nbytes)
+			break;
+
+		offset = 0;
+		sector += nbytes >> BBSHIFT;
+		size -= nbytes;
+		total_nr_pages--;
+	}
+
+	if (likely(bio->bi_size)) {
+		if (xfs_buf_is_vmapped(bp)) {
+			flush_kernel_vmap_range(bp->b_addr,
+						xfs_buf_vmap_len(bp));
+		}
+		submit_bio(rw, bio);
+		if (size)
+			goto next_chunk;
+	} else {
+		xfs_buf_ioerror(bp, EIO);
+		bio_put(bio);
+	}
+}
+
+int
+xfs_buf_iorequest(
+	xfs_buf_t		*bp)
+{
+	trace_xfs_buf_iorequest(bp, _RET_IP_);
+
+	if (bp->b_flags & XBF_DELWRI) {
+		xfs_buf_delwri_queue(bp, 1);
+		return 0;
+	}
+
+	if (bp->b_flags & XBF_WRITE) {
+		xfs_buf_wait_unpin(bp);
+	}
+
+	xfs_buf_hold(bp);
+
+	/* 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 xfs_buf_ioend too early.
+	 */
+	atomic_set(&bp->b_io_remaining, 1);
+	_xfs_buf_ioapply(bp);
+	_xfs_buf_ioend(bp, 0);
+
+	xfs_buf_rele(bp);
+	return 0;
+}
+
+/*
+ *	Waits for I/O to complete on the buffer supplied.
+ *	It returns immediately if no I/O is pending.
+ *	It returns the I/O error code, if any, or 0 if there was no error.
+ */
+int
+xfs_buf_iowait(
+	xfs_buf_t		*bp)
+{
+	trace_xfs_buf_iowait(bp, _RET_IP_);
+
+	wait_for_completion(&bp->b_iowait);
+
+	trace_xfs_buf_iowait_done(bp, _RET_IP_);
+	return bp->b_error;
+}
+
+xfs_caddr_t
+xfs_buf_offset(
+	xfs_buf_t		*bp,
+	size_t			offset)
+{
+	struct page		*page;
+
+	if (bp->b_flags & XBF_MAPPED)
+		return bp->b_addr + offset;
+
+	offset += bp->b_offset;
+	page = bp->b_pages[offset >> PAGE_SHIFT];
+	return (xfs_caddr_t)page_address(page) + (offset & (PAGE_SIZE-1));
+}
+
+/*
+ *	Move data into or out of a buffer.
+ */
+void
+xfs_buf_iomove(
+	xfs_buf_t		*bp,	/* buffer to process		*/
+	size_t			boff,	/* starting buffer offset	*/
+	size_t			bsize,	/* length to copy		*/
+	void			*data,	/* data address			*/
+	xfs_buf_rw_t		mode)	/* read/write/zero flag		*/
+{
+	size_t			bend, cpoff, csize;
+	struct page		*page;
+
+	bend = boff + bsize;
+	while (boff < bend) {
+		page = bp->b_pages[xfs_buf_btoct(boff + bp->b_offset)];
+		cpoff = xfs_buf_poff(boff + bp->b_offset);
+		csize = min_t(size_t,
+			      PAGE_SIZE-cpoff, bp->b_count_desired-boff);
+
+		ASSERT(((csize + cpoff) <= PAGE_SIZE));
+
+		switch (mode) {
+		case XBRW_ZERO:
+			memset(page_address(page) + cpoff, 0, csize);
+			break;
+		case XBRW_READ:
+			memcpy(data, page_address(page) + cpoff, csize);
+			break;
+		case XBRW_WRITE:
+			memcpy(page_address(page) + cpoff, data, csize);
+		}
+
+		boff += csize;
+		data += csize;
+	}
+}
+
+/*
+ *	Handling of buffer targets (buftargs).
+ */
+
+/*
+ * Wait for any bufs with callbacks that have been submitted but have not yet
+ * returned. These buffers will have an elevated hold count, so wait on those
+ * while freeing all the buffers only held by the LRU.
+ */
+void
+xfs_wait_buftarg(
+	struct xfs_buftarg	*btp)
+{
+	struct xfs_buf		*bp;
+
+restart:
+	spin_lock(&btp->bt_lru_lock);
+	while (!list_empty(&btp->bt_lru)) {
+		bp = list_first_entry(&btp->bt_lru, struct xfs_buf, b_lru);
+		if (atomic_read(&bp->b_hold) > 1) {
+			spin_unlock(&btp->bt_lru_lock);
+			delay(100);
+			goto restart;
+		}
+		/*
+		 * clear the LRU reference count so the bufer doesn't get
+		 * ignored in xfs_buf_rele().
+		 */
+		atomic_set(&bp->b_lru_ref, 0);
+		spin_unlock(&btp->bt_lru_lock);
+		xfs_buf_rele(bp);
+		spin_lock(&btp->bt_lru_lock);
+	}
+	spin_unlock(&btp->bt_lru_lock);
+}
+
+int
+xfs_buftarg_shrink(
+	struct shrinker		*shrink,
+	struct shrink_control	*sc)
+{
+	struct xfs_buftarg	*btp = container_of(shrink,
+					struct xfs_buftarg, bt_shrinker);
+	struct xfs_buf		*bp;
+	int nr_to_scan = sc->nr_to_scan;
+	LIST_HEAD(dispose);
+
+	if (!nr_to_scan)
+		return btp->bt_lru_nr;
+
+	spin_lock(&btp->bt_lru_lock);
+	while (!list_empty(&btp->bt_lru)) {
+		if (nr_to_scan-- <= 0)
+			break;
+
+		bp = list_first_entry(&btp->bt_lru, struct xfs_buf, b_lru);
+
+		/*
+		 * Decrement the b_lru_ref count unless the value is already
+		 * zero. If the value is already zero, we need to reclaim the
+		 * buffer, otherwise it gets another trip through the LRU.
+		 */
+		if (!atomic_add_unless(&bp->b_lru_ref, -1, 0)) {
+			list_move_tail(&bp->b_lru, &btp->bt_lru);
+			continue;
+		}
+
+		/*
+		 * remove the buffer from the LRU now to avoid needing another
+		 * lock round trip inside xfs_buf_rele().
+		 */
+		list_move(&bp->b_lru, &dispose);
+		btp->bt_lru_nr--;
+	}
+	spin_unlock(&btp->bt_lru_lock);
+
+	while (!list_empty(&dispose)) {
+		bp = list_first_entry(&dispose, struct xfs_buf, b_lru);
+		list_del_init(&bp->b_lru);
+		xfs_buf_rele(bp);
+	}
+
+	return btp->bt_lru_nr;
+}
+
+void
+xfs_free_buftarg(
+	struct xfs_mount	*mp,
+	struct xfs_buftarg	*btp)
+{
+	unregister_shrinker(&btp->bt_shrinker);
+
+	xfs_flush_buftarg(btp, 1);
+	if (mp->m_flags & XFS_MOUNT_BARRIER)
+		xfs_blkdev_issue_flush(btp);
+
+	kthread_stop(btp->bt_task);
+	kmem_free(btp);
+}
+
+STATIC int
+xfs_setsize_buftarg_flags(
+	xfs_buftarg_t		*btp,
+	unsigned int		blocksize,
+	unsigned int		sectorsize,
+	int			verbose)
+{
+	btp->bt_bsize = blocksize;
+	btp->bt_sshift = ffs(sectorsize) - 1;
+	btp->bt_smask = sectorsize - 1;
+
+	if (set_blocksize(btp->bt_bdev, sectorsize)) {
+		xfs_warn(btp->bt_mount,
+			"Cannot set_blocksize to %u on device %s\n",
+			sectorsize, xfs_buf_target_name(btp));
+		return EINVAL;
+	}
+
+	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_SIZE, bdev_logical_block_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_alloc_delwrite_queue(
+	xfs_buftarg_t		*btp,
+	const char		*fsname)
+{
+	INIT_LIST_HEAD(&btp->bt_delwrite_queue);
+	spin_lock_init(&btp->bt_delwrite_lock);
+	btp->bt_flags = 0;
+	btp->bt_task = kthread_run(xfsbufd, btp, "xfsbufd/%s", fsname);
+	if (IS_ERR(btp->bt_task))
+		return PTR_ERR(btp->bt_task);
+	return 0;
+}
+
+xfs_buftarg_t *
+xfs_alloc_buftarg(
+	struct xfs_mount	*mp,
+	struct block_device	*bdev,
+	int			external,
+	const char		*fsname)
+{
+	xfs_buftarg_t		*btp;
+
+	btp = kmem_zalloc(sizeof(*btp), KM_SLEEP);
+
+	btp->bt_mount = mp;
+	btp->bt_dev =  bdev->bd_dev;
+	btp->bt_bdev = bdev;
+	btp->bt_bdi = blk_get_backing_dev_info(bdev);
+	if (!btp->bt_bdi)
+		goto error;
+
+	INIT_LIST_HEAD(&btp->bt_lru);
+	spin_lock_init(&btp->bt_lru_lock);
+	if (xfs_setsize_buftarg_early(btp, bdev))
+		goto error;
+	if (xfs_alloc_delwrite_queue(btp, fsname))
+		goto error;
+	btp->bt_shrinker.shrink = xfs_buftarg_shrink;
+	btp->bt_shrinker.seeks = DEFAULT_SEEKS;
+	register_shrinker(&btp->bt_shrinker);
+	return btp;
+
+error:
+	kmem_free(btp);
+	return NULL;
+}
+
+
+/*
+ *	Delayed write buffer handling
+ */
+STATIC void
+xfs_buf_delwri_queue(
+	xfs_buf_t		*bp,
+	int			unlock)
+{
+	struct list_head	*dwq = &bp->b_target->bt_delwrite_queue;
+	spinlock_t		*dwlk = &bp->b_target->bt_delwrite_lock;
+
+	trace_xfs_buf_delwri_queue(bp, _RET_IP_);
+
+	ASSERT((bp->b_flags&(XBF_DELWRI|XBF_ASYNC)) == (XBF_DELWRI|XBF_ASYNC));
+
+	spin_lock(dwlk);
+	/* If already in the queue, dequeue and place at tail */
+	if (!list_empty(&bp->b_list)) {
+		ASSERT(bp->b_flags & _XBF_DELWRI_Q);
+		if (unlock)
+			atomic_dec(&bp->b_hold);
+		list_del(&bp->b_list);
+	}
+
+	if (list_empty(dwq)) {
+		/* start xfsbufd as it is about to have something to do */
+		wake_up_process(bp->b_target->bt_task);
+	}
+
+	bp->b_flags |= _XBF_DELWRI_Q;
+	list_add_tail(&bp->b_list, dwq);
+	bp->b_queuetime = jiffies;
+	spin_unlock(dwlk);
+
+	if (unlock)
+		xfs_buf_unlock(bp);
+}
+
+void
+xfs_buf_delwri_dequeue(
+	xfs_buf_t		*bp)
+{
+	spinlock_t		*dwlk = &bp->b_target->bt_delwrite_lock;
+	int			dequeued = 0;
+
+	spin_lock(dwlk);
+	if ((bp->b_flags & XBF_DELWRI) && !list_empty(&bp->b_list)) {
+		ASSERT(bp->b_flags & _XBF_DELWRI_Q);
+		list_del_init(&bp->b_list);
+		dequeued = 1;
+	}
+	bp->b_flags &= ~(XBF_DELWRI|_XBF_DELWRI_Q);
+	spin_unlock(dwlk);
+
+	if (dequeued)
+		xfs_buf_rele(bp);
+
+	trace_xfs_buf_delwri_dequeue(bp, _RET_IP_);
+}
+
+/*
+ * If a delwri buffer needs to be pushed before it has aged out, then promote
+ * it to the head of the delwri queue so that it will be flushed on the next
+ * xfsbufd run. We do this by resetting the queuetime of the buffer to be older
+ * than the age currently needed to flush the buffer. Hence the next time the
+ * xfsbufd sees it is guaranteed to be considered old enough to flush.
+ */
+void
+xfs_buf_delwri_promote(
+	struct xfs_buf	*bp)
+{
+	struct xfs_buftarg *btp = bp->b_target;
+	long		age = xfs_buf_age_centisecs * msecs_to_jiffies(10) + 1;
+
+	ASSERT(bp->b_flags & XBF_DELWRI);
+	ASSERT(bp->b_flags & _XBF_DELWRI_Q);
+
+	/*
+	 * Check the buffer age before locking the delayed write queue as we
+	 * don't need to promote buffers that are already past the flush age.
+	 */
+	if (bp->b_queuetime < jiffies - age)
+		return;
+	bp->b_queuetime = jiffies - age;
+	spin_lock(&btp->bt_delwrite_lock);
+	list_move(&bp->b_list, &btp->bt_delwrite_queue);
+	spin_unlock(&btp->bt_delwrite_lock);
+}
+
+STATIC void
+xfs_buf_runall_queues(
+	struct workqueue_struct	*queue)
+{
+	flush_workqueue(queue);
+}
+
+/*
+ * Move as many buffers as specified to the supplied list
+ * idicating if we skipped any buffers to prevent deadlocks.
+ */
+STATIC int
+xfs_buf_delwri_split(
+	xfs_buftarg_t	*target,
+	struct list_head *list,
+	unsigned long	age)
+{
+	xfs_buf_t	*bp, *n;
+	struct list_head *dwq = &target->bt_delwrite_queue;
+	spinlock_t	*dwlk = &target->bt_delwrite_lock;
+	int		skipped = 0;
+	int		force;
+
+	force = test_and_clear_bit(XBT_FORCE_FLUSH, &target->bt_flags);
+	INIT_LIST_HEAD(list);
+	spin_lock(dwlk);
+	list_for_each_entry_safe(bp, n, dwq, b_list) {
+		ASSERT(bp->b_flags & XBF_DELWRI);
+
+		if (!xfs_buf_ispinned(bp) && xfs_buf_trylock(bp)) {
+			if (!force &&
+			    time_before(jiffies, bp->b_queuetime + age)) {
+				xfs_buf_unlock(bp);
+				break;
+			}
+
+			bp->b_flags &= ~(XBF_DELWRI | _XBF_DELWRI_Q);
+			bp->b_flags |= XBF_WRITE;
+			list_move_tail(&bp->b_list, list);
+			trace_xfs_buf_delwri_split(bp, _RET_IP_);
+		} else
+			skipped++;
+	}
+	spin_unlock(dwlk);
+
+	return skipped;
+
+}
+
+/*
+ * Compare function is more complex than it needs to be because
+ * the return value is only 32 bits and we are doing comparisons
+ * on 64 bit values
+ */
+static int
+xfs_buf_cmp(
+	void		*priv,
+	struct list_head *a,
+	struct list_head *b)
+{
+	struct xfs_buf	*ap = container_of(a, struct xfs_buf, b_list);
+	struct xfs_buf	*bp = container_of(b, struct xfs_buf, b_list);
+	xfs_daddr_t		diff;
+
+	diff = ap->b_bn - bp->b_bn;
+	if (diff < 0)
+		return -1;
+	if (diff > 0)
+		return 1;
+	return 0;
+}
+
+STATIC int
+xfsbufd(
+	void		*data)
+{
+	xfs_buftarg_t   *target = (xfs_buftarg_t *)data;
+
+	current->flags |= PF_MEMALLOC;
+
+	set_freezable();
+
+	do {
+		long	age = xfs_buf_age_centisecs * msecs_to_jiffies(10);
+		long	tout = xfs_buf_timer_centisecs * msecs_to_jiffies(10);
+		struct list_head tmp;
+		struct blk_plug plug;
+
+		if (unlikely(freezing(current))) {
+			set_bit(XBT_FORCE_SLEEP, &target->bt_flags);
+			refrigerator();
+		} else {
+			clear_bit(XBT_FORCE_SLEEP, &target->bt_flags);
+		}
+
+		/* sleep for a long time if there is nothing to do. */
+		if (list_empty(&target->bt_delwrite_queue))
+			tout = MAX_SCHEDULE_TIMEOUT;
+		schedule_timeout_interruptible(tout);
+
+		xfs_buf_delwri_split(target, &tmp, age);
+		list_sort(NULL, &tmp, xfs_buf_cmp);
+
+		blk_start_plug(&plug);
+		while (!list_empty(&tmp)) {
+			struct xfs_buf *bp;
+			bp = list_first_entry(&tmp, struct xfs_buf, b_list);
+			list_del_init(&bp->b_list);
+			xfs_bdstrat_cb(bp);
+		}
+		blk_finish_plug(&plug);
+	} while (!kthread_should_stop());
+
+	return 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)
+{
+	xfs_buf_t	*bp;
+	int		pincount = 0;
+	LIST_HEAD(tmp_list);
+	LIST_HEAD(wait_list);
+	struct blk_plug plug;
+
+	xfs_buf_runall_queues(xfsconvertd_workqueue);
+	xfs_buf_runall_queues(xfsdatad_workqueue);
+	xfs_buf_runall_queues(xfslogd_workqueue);
+
+	set_bit(XBT_FORCE_FLUSH, &target->bt_flags);
+	pincount = xfs_buf_delwri_split(target, &tmp_list, 0);
+
+	/*
+	 * Dropped the delayed write list lock, now walk the temporary list.
+	 * All I/O is issued async and then if we need to wait for completion
+	 * we do that after issuing all the IO.
+	 */
+	list_sort(NULL, &tmp_list, xfs_buf_cmp);
+
+	blk_start_plug(&plug);
+	while (!list_empty(&tmp_list)) {
+		bp = list_first_entry(&tmp_list, struct xfs_buf, b_list);
+		ASSERT(target == bp->b_target);
+		list_del_init(&bp->b_list);
+		if (wait) {
+			bp->b_flags &= ~XBF_ASYNC;
+			list_add(&bp->b_list, &wait_list);
+		}
+		xfs_bdstrat_cb(bp);
+	}
+	blk_finish_plug(&plug);
+
+	if (wait) {
+		/* Wait for IO to complete. */
+		while (!list_empty(&wait_list)) {
+			bp = list_first_entry(&wait_list, struct xfs_buf, b_list);
+
+			list_del_init(&bp->b_list);
+			xfs_buf_iowait(bp);
+			xfs_buf_relse(bp);
+		}
+	}
+
+	return pincount;
+}
+
+int __init
+xfs_buf_init(void)
+{
+	xfs_buf_zone = kmem_zone_init_flags(sizeof(xfs_buf_t), "xfs_buf",
+						KM_ZONE_HWALIGN, NULL);
+	if (!xfs_buf_zone)
+		goto out;
+
+	xfslogd_workqueue = alloc_workqueue("xfslogd",
+					WQ_MEM_RECLAIM | WQ_HIGHPRI, 1);
+	if (!xfslogd_workqueue)
+		goto out_free_buf_zone;
+
+	xfsdatad_workqueue = alloc_workqueue("xfsdatad", WQ_MEM_RECLAIM, 1);
+	if (!xfsdatad_workqueue)
+		goto out_destroy_xfslogd_workqueue;
+
+	xfsconvertd_workqueue = alloc_workqueue("xfsconvertd",
+						WQ_MEM_RECLAIM, 1);
+	if (!xfsconvertd_workqueue)
+		goto out_destroy_xfsdatad_workqueue;
+
+	return 0;
+
+ out_destroy_xfsdatad_workqueue:
+	destroy_workqueue(xfsdatad_workqueue);
+ out_destroy_xfslogd_workqueue:
+	destroy_workqueue(xfslogd_workqueue);
+ out_free_buf_zone:
+	kmem_zone_destroy(xfs_buf_zone);
+ out:
+	return -ENOMEM;
+}
+
+void
+xfs_buf_terminate(void)
+{
+	destroy_workqueue(xfsconvertd_workqueue);
+	destroy_workqueue(xfsdatad_workqueue);
+	destroy_workqueue(xfslogd_workqueue);
+	kmem_zone_destroy(xfs_buf_zone);
+}
+
+#ifdef CONFIG_KDB_MODULES
+struct list_head *
+xfs_get_buftarg_list(void)
+{
+	return &xfs_buftarg_list;
+}
+#endif