Initial import

1 files changed, 1495 insertions, 0 deletions

diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c
new file mode 100644
index 000000000..61296ecbd
--- /dev/null
+++ b/fs/gfs2/bmap.c
@@ -0,0 +1,1495 @@
+/*
+ * Copyright (C) Sistina Software, Inc.  1997-2003 All rights reserved.
+ * Copyright (C) 2004-2006 Red Hat, Inc.  All rights reserved.
+ *
+ * This copyrighted material is made available to anyone wishing to use,
+ * modify, copy, or redistribute it subject to the terms and conditions
+ * of the GNU General Public License version 2.
+ */
+
+#include <linux/spinlock.h>
+#include <linux/completion.h>
+#include <linux/buffer_head.h>
+#include <linux/blkdev.h>
+#include <linux/gfs2_ondisk.h>
+#include <linux/crc32.h>
+
+#include "gfs2.h"
+#include "incore.h"
+#include "bmap.h"
+#include "glock.h"
+#include "inode.h"
+#include "meta_io.h"
+#include "quota.h"
+#include "rgrp.h"
+#include "log.h"
+#include "super.h"
+#include "trans.h"
+#include "dir.h"
+#include "util.h"
+#include "trace_gfs2.h"
+
+/* This doesn't need to be that large as max 64 bit pointers in a 4k
+ * block is 512, so __u16 is fine for that. It saves stack space to
+ * keep it small.
+ */
+struct metapath {
+	struct buffer_head *mp_bh[GFS2_MAX_META_HEIGHT];
+	__u16 mp_list[GFS2_MAX_META_HEIGHT];
+};
+
+struct strip_mine {
+	int sm_first;
+	unsigned int sm_height;
+};
+
+/**
+ * gfs2_unstuffer_page - unstuff a stuffed inode into a block cached by a page
+ * @ip: the inode
+ * @dibh: the dinode buffer
+ * @block: the block number that was allocated
+ * @page: The (optional) page. This is looked up if @page is NULL
+ *
+ * Returns: errno
+ */
+
+static int gfs2_unstuffer_page(struct gfs2_inode *ip, struct buffer_head *dibh,
+			       u64 block, struct page *page)
+{
+	struct inode *inode = &ip->i_inode;
+	struct buffer_head *bh;
+	int release = 0;
+
+	if (!page || page->index) {
+		page = find_or_create_page(inode->i_mapping, 0, GFP_NOFS);
+		if (!page)
+			return -ENOMEM;
+		release = 1;
+	}
+
+	if (!PageUptodate(page)) {
+		void *kaddr = kmap(page);
+		u64 dsize = i_size_read(inode);
+ 
+		if (dsize > (dibh->b_size - sizeof(struct gfs2_dinode)))
+			dsize = dibh->b_size - sizeof(struct gfs2_dinode);
+
+		memcpy(kaddr, dibh->b_data + sizeof(struct gfs2_dinode), dsize);
+		memset(kaddr + dsize, 0, PAGE_CACHE_SIZE - dsize);
+		kunmap(page);
+
+		SetPageUptodate(page);
+	}
+
+	if (!page_has_buffers(page))
+		create_empty_buffers(page, 1 << inode->i_blkbits,
+				     (1 << BH_Uptodate));
+
+	bh = page_buffers(page);
+
+	if (!buffer_mapped(bh))
+		map_bh(bh, inode->i_sb, block);
+
+	set_buffer_uptodate(bh);
+	if (!gfs2_is_jdata(ip))
+		mark_buffer_dirty(bh);
+	if (!gfs2_is_writeback(ip))
+		gfs2_trans_add_data(ip->i_gl, bh);
+
+	if (release) {
+		unlock_page(page);
+		page_cache_release(page);
+	}
+
+	return 0;
+}
+
+/**
+ * gfs2_unstuff_dinode - Unstuff a dinode when the data has grown too big
+ * @ip: The GFS2 inode to unstuff
+ * @page: The (optional) page. This is looked up if the @page is NULL
+ *
+ * This routine unstuffs a dinode and returns it to a "normal" state such
+ * that the height can be grown in the traditional way.
+ *
+ * Returns: errno
+ */
+
+int gfs2_unstuff_dinode(struct gfs2_inode *ip, struct page *page)
+{
+	struct buffer_head *bh, *dibh;
+	struct gfs2_dinode *di;
+	u64 block = 0;
+	int isdir = gfs2_is_dir(ip);
+	int error;
+
+	down_write(&ip->i_rw_mutex);
+
+	error = gfs2_meta_inode_buffer(ip, &dibh);
+	if (error)
+		goto out;
+
+	if (i_size_read(&ip->i_inode)) {
+		/* Get a free block, fill it with the stuffed data,
+		   and write it out to disk */
+
+		unsigned int n = 1;
+		error = gfs2_alloc_blocks(ip, &block, &n, 0, NULL);
+		if (error)
+			goto out_brelse;
+		if (isdir) {
+			gfs2_trans_add_unrevoke(GFS2_SB(&ip->i_inode), block, 1);
+			error = gfs2_dir_get_new_buffer(ip, block, &bh);
+			if (error)
+				goto out_brelse;
+			gfs2_buffer_copy_tail(bh, sizeof(struct gfs2_meta_header),
+					      dibh, sizeof(struct gfs2_dinode));
+			brelse(bh);
+		} else {
+			error = gfs2_unstuffer_page(ip, dibh, block, page);
+			if (error)
+				goto out_brelse;
+		}
+	}
+
+	/*  Set up the pointer to the new block  */
+
+	gfs2_trans_add_meta(ip->i_gl, dibh);
+	di = (struct gfs2_dinode *)dibh->b_data;
+	gfs2_buffer_clear_tail(dibh, sizeof(struct gfs2_dinode));
+
+	if (i_size_read(&ip->i_inode)) {
+		*(__be64 *)(di + 1) = cpu_to_be64(block);
+		gfs2_add_inode_blocks(&ip->i_inode, 1);
+		di->di_blocks = cpu_to_be64(gfs2_get_inode_blocks(&ip->i_inode));
+	}
+
+	ip->i_height = 1;
+	di->di_height = cpu_to_be16(1);
+
+out_brelse:
+	brelse(dibh);
+out:
+	up_write(&ip->i_rw_mutex);
+	return error;
+}
+
+
+/**
+ * find_metapath - Find path through the metadata tree
+ * @sdp: The superblock
+ * @mp: The metapath to return the result in
+ * @block: The disk block to look up
+ * @height: The pre-calculated height of the metadata tree
+ *
+ *   This routine returns a struct metapath structure that defines a path
+ *   through the metadata of inode "ip" to get to block "block".
+ *
+ *   Example:
+ *   Given:  "ip" is a height 3 file, "offset" is 101342453, and this is a
+ *   filesystem with a blocksize of 4096.
+ *
+ *   find_metapath() would return a struct metapath structure set to:
+ *   mp_offset = 101342453, mp_height = 3, mp_list[0] = 0, mp_list[1] = 48,
+ *   and mp_list[2] = 165.
+ *
+ *   That means that in order to get to the block containing the byte at
+ *   offset 101342453, we would load the indirect block pointed to by pointer
+ *   0 in the dinode.  We would then load the indirect block pointed to by
+ *   pointer 48 in that indirect block.  We would then load the data block
+ *   pointed to by pointer 165 in that indirect block.
+ *
+ *             ----------------------------------------
+ *             | Dinode |                             |
+ *             |        |                            4|
+ *             |        |0 1 2 3 4 5                 9|
+ *             |        |                            6|
+ *             ----------------------------------------
+ *                       |
+ *                       |
+ *                       V
+ *             ----------------------------------------
+ *             | Indirect Block                       |
+ *             |                                     5|
+ *             |            4 4 4 4 4 5 5            1|
+ *             |0           5 6 7 8 9 0 1            2|
+ *             ----------------------------------------
+ *                                |
+ *                                |
+ *                                V
+ *             ----------------------------------------
+ *             | Indirect Block                       |
+ *             |                         1 1 1 1 1   5|
+ *             |                         6 6 6 6 6   1|
+ *             |0                        3 4 5 6 7   2|
+ *             ----------------------------------------
+ *                                           |
+ *                                           |
+ *                                           V
+ *             ----------------------------------------
+ *             | Data block containing offset         |
+ *             |            101342453                 |
+ *             |                                      |
+ *             |                                      |
+ *             ----------------------------------------
+ *
+ */
+
+static void find_metapath(const struct gfs2_sbd *sdp, u64 block,
+			  struct metapath *mp, unsigned int height)
+{
+	unsigned int i;
+
+	for (i = height; i--;)
+		mp->mp_list[i] = do_div(block, sdp->sd_inptrs);
+
+}
+
+static inline unsigned int metapath_branch_start(const struct metapath *mp)
+{
+	if (mp->mp_list[0] == 0)
+		return 2;
+	return 1;
+}
+
+/**
+ * metapointer - Return pointer to start of metadata in a buffer
+ * @height: The metadata height (0 = dinode)
+ * @mp: The metapath
+ *
+ * Return a pointer to the block number of the next height of the metadata
+ * tree given a buffer containing the pointer to the current height of the
+ * metadata tree.
+ */
+
+static inline __be64 *metapointer(unsigned int height, const struct metapath *mp)
+{
+	struct buffer_head *bh = mp->mp_bh[height];
+	unsigned int head_size = (height > 0) ?
+		sizeof(struct gfs2_meta_header) : sizeof(struct gfs2_dinode);
+	return ((__be64 *)(bh->b_data + head_size)) + mp->mp_list[height];
+}
+
+static void gfs2_metapath_ra(struct gfs2_glock *gl,
+			     const struct buffer_head *bh, const __be64 *pos)
+{
+	struct buffer_head *rabh;
+	const __be64 *endp = (const __be64 *)(bh->b_data + bh->b_size);
+	const __be64 *t;
+
+	for (t = pos; t < endp; t++) {
+		if (!*t)
+			continue;
+
+		rabh = gfs2_getbuf(gl, be64_to_cpu(*t), CREATE);
+		if (trylock_buffer(rabh)) {
+			if (!buffer_uptodate(rabh)) {
+				rabh->b_end_io = end_buffer_read_sync;
+				submit_bh(READA | REQ_META, rabh);
+				continue;
+			}
+			unlock_buffer(rabh);
+		}
+		brelse(rabh);
+	}
+}
+
+/**
+ * lookup_metapath - Walk the metadata tree to a specific point
+ * @ip: The inode
+ * @mp: The metapath
+ *
+ * Assumes that the inode's buffer has already been looked up and
+ * hooked onto mp->mp_bh[0] and that the metapath has been initialised
+ * by find_metapath().
+ *
+ * If this function encounters part of the tree which has not been
+ * allocated, it returns the current height of the tree at the point
+ * at which it found the unallocated block. Blocks which are found are
+ * added to the mp->mp_bh[] list.
+ *
+ * Returns: error or height of metadata tree
+ */
+
+static int lookup_metapath(struct gfs2_inode *ip, struct metapath *mp)
+{
+	unsigned int end_of_metadata = ip->i_height - 1;
+	unsigned int x;
+	__be64 *ptr;
+	u64 dblock;
+	int ret;
+
+	for (x = 0; x < end_of_metadata; x++) {
+		ptr = metapointer(x, mp);
+		dblock = be64_to_cpu(*ptr);
+		if (!dblock)
+			return x + 1;
+
+		ret = gfs2_meta_indirect_buffer(ip, x+1, dblock, &mp->mp_bh[x+1]);
+		if (ret)
+			return ret;
+	}
+
+	return ip->i_height;
+}
+
+static inline void release_metapath(struct metapath *mp)
+{
+	int i;
+
+	for (i = 0; i < GFS2_MAX_META_HEIGHT; i++) {
+		if (mp->mp_bh[i] == NULL)
+			break;
+		brelse(mp->mp_bh[i]);
+	}
+}
+
+/**
+ * gfs2_extent_length - Returns length of an extent of blocks
+ * @start: Start of the buffer
+ * @len: Length of the buffer in bytes
+ * @ptr: Current position in the buffer
+ * @limit: Max extent length to return (0 = unlimited)
+ * @eob: Set to 1 if we hit "end of block"
+ *
+ * If the first block is zero (unallocated) it will return the number of
+ * unallocated blocks in the extent, otherwise it will return the number
+ * of contiguous blocks in the extent.
+ *
+ * Returns: The length of the extent (minimum of one block)
+ */
+
+static inline unsigned int gfs2_extent_length(void *start, unsigned int len, __be64 *ptr, size_t limit, int *eob)
+{
+	const __be64 *end = (start + len);
+	const __be64 *first = ptr;
+	u64 d = be64_to_cpu(*ptr);
+
+	*eob = 0;
+	do {
+		ptr++;
+		if (ptr >= end)
+			break;
+		if (limit && --limit == 0)
+			break;
+		if (d)
+			d++;
+	} while(be64_to_cpu(*ptr) == d);
+	if (ptr >= end)
+		*eob = 1;
+	return (ptr - first);
+}
+
+static inline void bmap_lock(struct gfs2_inode *ip, int create)
+{
+	if (create)
+		down_write(&ip->i_rw_mutex);
+	else
+		down_read(&ip->i_rw_mutex);
+}
+
+static inline void bmap_unlock(struct gfs2_inode *ip, int create)
+{
+	if (create)
+		up_write(&ip->i_rw_mutex);
+	else
+		up_read(&ip->i_rw_mutex);
+}
+
+static inline __be64 *gfs2_indirect_init(struct metapath *mp,
+					 struct gfs2_glock *gl, unsigned int i,
+					 unsigned offset, u64 bn)
+{
+	__be64 *ptr = (__be64 *)(mp->mp_bh[i - 1]->b_data +
+		       ((i > 1) ? sizeof(struct gfs2_meta_header) :
+				 sizeof(struct gfs2_dinode)));
+	BUG_ON(i < 1);
+	BUG_ON(mp->mp_bh[i] != NULL);
+	mp->mp_bh[i] = gfs2_meta_new(gl, bn);
+	gfs2_trans_add_meta(gl, mp->mp_bh[i]);
+	gfs2_metatype_set(mp->mp_bh[i], GFS2_METATYPE_IN, GFS2_FORMAT_IN);
+	gfs2_buffer_clear_tail(mp->mp_bh[i], sizeof(struct gfs2_meta_header));
+	ptr += offset;
+	*ptr = cpu_to_be64(bn);
+	return ptr;
+}
+
+enum alloc_state {
+	ALLOC_DATA = 0,
+	ALLOC_GROW_DEPTH = 1,
+	ALLOC_GROW_HEIGHT = 2,
+	/* ALLOC_UNSTUFF = 3,   TBD and rather complicated */
+};
+
+/**
+ * gfs2_bmap_alloc - Build a metadata tree of the requested height
+ * @inode: The GFS2 inode
+ * @lblock: The logical starting block of the extent
+ * @bh_map: This is used to return the mapping details
+ * @mp: The metapath
+ * @sheight: The starting height (i.e. whats already mapped)
+ * @height: The height to build to
+ * @maxlen: The max number of data blocks to alloc
+ *
+ * In this routine we may have to alloc:
+ *   i) Indirect blocks to grow the metadata tree height
+ *  ii) Indirect blocks to fill in lower part of the metadata tree
+ * iii) Data blocks
+ *
+ * The function is in two parts. The first part works out the total
+ * number of blocks which we need. The second part does the actual
+ * allocation asking for an extent at a time (if enough contiguous free
+ * blocks are available, there will only be one request per bmap call)
+ * and uses the state machine to initialise the blocks in order.
+ *
+ * Returns: errno on error
+ */
+
+static int gfs2_bmap_alloc(struct inode *inode, const sector_t lblock,
+			   struct buffer_head *bh_map, struct metapath *mp,
+			   const unsigned int sheight,
+			   const unsigned int height,
+			   const size_t maxlen)
+{
+	struct gfs2_inode *ip = GFS2_I(inode);
+	struct gfs2_sbd *sdp = GFS2_SB(inode);
+	struct super_block *sb = sdp->sd_vfs;
+	struct buffer_head *dibh = mp->mp_bh[0];
+	u64 bn, dblock = 0;
+	unsigned n, i, blks, alloced = 0, iblks = 0, branch_start = 0;
+	unsigned dblks = 0;
+	unsigned ptrs_per_blk;
+	const unsigned end_of_metadata = height - 1;
+	int ret;
+	int eob = 0;
+	enum alloc_state state;
+	__be64 *ptr;
+	__be64 zero_bn = 0;
+
+	BUG_ON(sheight < 1);
+	BUG_ON(dibh == NULL);
+
+	gfs2_trans_add_meta(ip->i_gl, dibh);
+
+	if (height == sheight) {
+		struct buffer_head *bh;
+		/* Bottom indirect block exists, find unalloced extent size */
+		ptr = metapointer(end_of_metadata, mp);
+		bh = mp->mp_bh[end_of_metadata];
+		dblks = gfs2_extent_length(bh->b_data, bh->b_size, ptr, maxlen,
+					   &eob);
+		BUG_ON(dblks < 1);
+		state = ALLOC_DATA;
+	} else {
+		/* Need to allocate indirect blocks */
+		ptrs_per_blk = height > 1 ? sdp->sd_inptrs : sdp->sd_diptrs;
+		dblks = min(maxlen, (size_t)(ptrs_per_blk -
+					     mp->mp_list[end_of_metadata]));
+		if (height == ip->i_height) {
+			/* Writing into existing tree, extend tree down */
+			iblks = height - sheight;
+			state = ALLOC_GROW_DEPTH;
+		} else {
+			/* Building up tree height */
+			state = ALLOC_GROW_HEIGHT;
+			iblks = height - ip->i_height;
+			branch_start = metapath_branch_start(mp);
+			iblks += (height - branch_start);
+		}
+	}
+
+	/* start of the second part of the function (state machine) */
+
+	blks = dblks + iblks;
+	i = sheight;
+	do {
+		int error;
+		n = blks - alloced;
+		error = gfs2_alloc_blocks(ip, &bn, &n, 0, NULL);
+		if (error)
+			return error;
+		alloced += n;
+		if (state != ALLOC_DATA || gfs2_is_jdata(ip))
+			gfs2_trans_add_unrevoke(sdp, bn, n);
+		switch (state) {
+		/* Growing height of tree */
+		case ALLOC_GROW_HEIGHT:
+			if (i == 1) {
+				ptr = (__be64 *)(dibh->b_data +
+						 sizeof(struct gfs2_dinode));
+				zero_bn = *ptr;
+			}
+			for (; i - 1 < height - ip->i_height && n > 0; i++, n--)
+				gfs2_indirect_init(mp, ip->i_gl, i, 0, bn++);
+			if (i - 1 == height - ip->i_height) {
+				i--;
+				gfs2_buffer_copy_tail(mp->mp_bh[i],
+						sizeof(struct gfs2_meta_header),
+						dibh, sizeof(struct gfs2_dinode));
+				gfs2_buffer_clear_tail(dibh,
+						sizeof(struct gfs2_dinode) +
+						sizeof(__be64));
+				ptr = (__be64 *)(mp->mp_bh[i]->b_data +
+					sizeof(struct gfs2_meta_header));
+				*ptr = zero_bn;
+				state = ALLOC_GROW_DEPTH;
+				for(i = branch_start; i < height; i++) {
+					if (mp->mp_bh[i] == NULL)
+						break;
+					brelse(mp->mp_bh[i]);
+					mp->mp_bh[i] = NULL;
+				}
+				i = branch_start;
+			}
+			if (n == 0)
+				break;
+		/* Branching from existing tree */
+		case ALLOC_GROW_DEPTH:
+			if (i > 1 && i < height)
+				gfs2_trans_add_meta(ip->i_gl, mp->mp_bh[i-1]);
+			for (; i < height && n > 0; i++, n--)
+				gfs2_indirect_init(mp, ip->i_gl, i,
+						   mp->mp_list[i-1], bn++);
+			if (i == height)
+				state = ALLOC_DATA;
+			if (n == 0)
+				break;
+		/* Tree complete, adding data blocks */
+		case ALLOC_DATA:
+			BUG_ON(n > dblks);
+			BUG_ON(mp->mp_bh[end_of_metadata] == NULL);
+			gfs2_trans_add_meta(ip->i_gl, mp->mp_bh[end_of_metadata]);
+			dblks = n;
+			ptr = metapointer(end_of_metadata, mp);
+			dblock = bn;
+			while (n-- > 0)
+				*ptr++ = cpu_to_be64(bn++);
+			if (buffer_zeronew(bh_map)) {
+				ret = sb_issue_zeroout(sb, dblock, dblks,
+						       GFP_NOFS);
+				if (ret) {
+					fs_err(sdp,
+					       "Failed to zero data buffers\n");
+					clear_buffer_zeronew(bh_map);
+				}
+			}
+			break;
+		}
+	} while ((state != ALLOC_DATA) || !dblock);
+
+	ip->i_height = height;
+	gfs2_add_inode_blocks(&ip->i_inode, alloced);
+	gfs2_dinode_out(ip, mp->mp_bh[0]->b_data);
+	map_bh(bh_map, inode->i_sb, dblock);
+	bh_map->b_size = dblks << inode->i_blkbits;
+	set_buffer_new(bh_map);
+	return 0;
+}
+
+/**
+ * gfs2_block_map - Map a block from an inode to a disk block
+ * @inode: The inode
+ * @lblock: The logical block number
+ * @bh_map: The bh to be mapped
+ * @create: True if its ok to alloc blocks to satify the request
+ *
+ * Sets buffer_mapped() if successful, sets buffer_boundary() if a
+ * read of metadata will be required before the next block can be
+ * mapped. Sets buffer_new() if new blocks were allocated.
+ *
+ * Returns: errno
+ */
+
+int gfs2_block_map(struct inode *inode, sector_t lblock,
+		   struct buffer_head *bh_map, int create)
+{
+	struct gfs2_inode *ip = GFS2_I(inode);
+	struct gfs2_sbd *sdp = GFS2_SB(inode);
+	unsigned int bsize = sdp->sd_sb.sb_bsize;
+	const size_t maxlen = bh_map->b_size >> inode->i_blkbits;
+	const u64 *arr = sdp->sd_heightsize;
+	__be64 *ptr;
+	u64 size;
+	struct metapath mp;
+	int ret;
+	int eob;
+	unsigned int len;
+	struct buffer_head *bh;
+	u8 height;
+
+	BUG_ON(maxlen == 0);
+
+	memset(mp.mp_bh, 0, sizeof(mp.mp_bh));
+	bmap_lock(ip, create);
+	clear_buffer_mapped(bh_map);
+	clear_buffer_new(bh_map);
+	clear_buffer_boundary(bh_map);
+	trace_gfs2_bmap(ip, bh_map, lblock, create, 1);
+	if (gfs2_is_dir(ip)) {
+		bsize = sdp->sd_jbsize;
+		arr = sdp->sd_jheightsize;
+	}
+
+	ret = gfs2_meta_inode_buffer(ip, &mp.mp_bh[0]);
+	if (ret)
+		goto out;
+
+	height = ip->i_height;
+	size = (lblock + 1) * bsize;
+	while (size > arr[height])
+		height++;
+	find_metapath(sdp, lblock, &mp, height);
+	ret = 1;
+	if (height > ip->i_height || gfs2_is_stuffed(ip))
+		goto do_alloc;
+	ret = lookup_metapath(ip, &mp);
+	if (ret < 0)
+		goto out;
+	if (ret != ip->i_height)
+		goto do_alloc;
+	ptr = metapointer(ip->i_height - 1, &mp);
+	if (*ptr == 0)
+		goto do_alloc;
+	map_bh(bh_map, inode->i_sb, be64_to_cpu(*ptr));
+	bh = mp.mp_bh[ip->i_height - 1];
+	len = gfs2_extent_length(bh->b_data, bh->b_size, ptr, maxlen, &eob);
+	bh_map->b_size = (len << inode->i_blkbits);
+	if (eob)
+		set_buffer_boundary(bh_map);
+	ret = 0;
+out:
+	release_metapath(&mp);
+	trace_gfs2_bmap(ip, bh_map, lblock, create, ret);
+	bmap_unlock(ip, create);
+	return ret;
+
+do_alloc:
+	/* All allocations are done here, firstly check create flag */
+	if (!create) {
+		BUG_ON(gfs2_is_stuffed(ip));
+		ret = 0;
+		goto out;
+	}
+
+	/* At this point ret is the tree depth of already allocated blocks */
+	ret = gfs2_bmap_alloc(inode, lblock, bh_map, &mp, ret, height, maxlen);
+	goto out;
+}
+
+/*
+ * Deprecated: do not use in new code
+ */
+int gfs2_extent_map(struct inode *inode, u64 lblock, int *new, u64 *dblock, unsigned *extlen)
+{
+	struct buffer_head bh = { .b_state = 0, .b_blocknr = 0 };
+	int ret;
+	int create = *new;
+
+	BUG_ON(!extlen);
+	BUG_ON(!dblock);
+	BUG_ON(!new);
+
+	bh.b_size = 1 << (inode->i_blkbits + (create ? 0 : 5));
+	ret = gfs2_block_map(inode, lblock, &bh, create);
+	*extlen = bh.b_size >> inode->i_blkbits;
+	*dblock = bh.b_blocknr;
+	if (buffer_new(&bh))
+		*new = 1;
+	else
+		*new = 0;
+	return ret;
+}
+
+/**
+ * do_strip - Look for a layer a particular layer of the file and strip it off
+ * @ip: the inode
+ * @dibh: the dinode buffer
+ * @bh: A buffer of pointers
+ * @top: The first pointer in the buffer
+ * @bottom: One more than the last pointer
+ * @height: the height this buffer is at
+ * @sm: a pointer to a struct strip_mine
+ *
+ * Returns: errno
+ */
+
+static int do_strip(struct gfs2_inode *ip, struct buffer_head *dibh,
+		    struct buffer_head *bh, __be64 *top, __be64 *bottom,
+		    unsigned int height, struct strip_mine *sm)
+{
+	struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
+	struct gfs2_rgrp_list rlist;
+	u64 bn, bstart;
+	u32 blen, btotal;
+	__be64 *p;
+	unsigned int rg_blocks = 0;
+	int metadata;
+	unsigned int revokes = 0;
+	int x;
+	int error;
+
+	error = gfs2_rindex_update(sdp);
+	if (error)
+		return error;
+
+	if (!*top)
+		sm->sm_first = 0;
+
+	if (height != sm->sm_height)
+		return 0;
+
+	if (sm->sm_first) {
+		top++;
+		sm->sm_first = 0;
+	}
+
+	metadata = (height != ip->i_height - 1);
+	if (metadata)
+		revokes = (height) ? sdp->sd_inptrs : sdp->sd_diptrs;
+	else if (ip->i_depth)
+		revokes = sdp->sd_inptrs;
+
+	memset(&rlist, 0, sizeof(struct gfs2_rgrp_list));
+	bstart = 0;
+	blen = 0;
+
+	for (p = top; p < bottom; p++) {
+		if (!*p)
+			continue;
+
+		bn = be64_to_cpu(*p);
+
+		if (bstart + blen == bn)
+			blen++;
+		else {
+			if (bstart)
+				gfs2_rlist_add(ip, &rlist, bstart);
+
+			bstart = bn;
+			blen = 1;
+		}
+	}
+
+	if (bstart)
+		gfs2_rlist_add(ip, &rlist, bstart);
+	else
+		goto out; /* Nothing to do */
+
+	gfs2_rlist_alloc(&rlist, LM_ST_EXCLUSIVE);
+
+	for (x = 0; x < rlist.rl_rgrps; x++) {
+		struct gfs2_rgrpd *rgd;
+		rgd = rlist.rl_ghs[x].gh_gl->gl_object;
+		rg_blocks += rgd->rd_length;
+	}
+
+	error = gfs2_glock_nq_m(rlist.rl_rgrps, rlist.rl_ghs);
+	if (error)
+		goto out_rlist;
+
+	if (gfs2_rs_active(ip->i_res)) /* needs to be done with the rgrp glock held */
+		gfs2_rs_deltree(ip->i_res);
+
+	error = gfs2_trans_begin(sdp, rg_blocks + RES_DINODE +
+				 RES_INDIRECT + RES_STATFS + RES_QUOTA,
+				 revokes);
+	if (error)
+		goto out_rg_gunlock;
+
+	down_write(&ip->i_rw_mutex);
+
+	gfs2_trans_add_meta(ip->i_gl, dibh);
+	gfs2_trans_add_meta(ip->i_gl, bh);
+
+	bstart = 0;
+	blen = 0;
+	btotal = 0;
+
+	for (p = top; p < bottom; p++) {
+		if (!*p)
+			continue;
+
+		bn = be64_to_cpu(*p);
+
+		if (bstart + blen == bn)
+			blen++;
+		else {
+			if (bstart) {
+				__gfs2_free_blocks(ip, bstart, blen, metadata);
+				btotal += blen;
+			}
+
+			bstart = bn;
+			blen = 1;
+		}
+
+		*p = 0;
+		gfs2_add_inode_blocks(&ip->i_inode, -1);
+	}
+	if (bstart) {
+		__gfs2_free_blocks(ip, bstart, blen, metadata);
+		btotal += blen;
+	}
+
+	gfs2_statfs_change(sdp, 0, +btotal, 0);
+	gfs2_quota_change(ip, -(s64)btotal, ip->i_inode.i_uid,
+			  ip->i_inode.i_gid);
+
+	ip->i_inode.i_mtime = ip->i_inode.i_ctime = CURRENT_TIME;
+
+	gfs2_dinode_out(ip, dibh->b_data);
+
+	up_write(&ip->i_rw_mutex);
+
+	gfs2_trans_end(sdp);
+
+out_rg_gunlock:
+	gfs2_glock_dq_m(rlist.rl_rgrps, rlist.rl_ghs);
+out_rlist:
+	gfs2_rlist_free(&rlist);
+out:
+	return error;
+}
+
+/**
+ * recursive_scan - recursively scan through the end of a file
+ * @ip: the inode
+ * @dibh: the dinode buffer
+ * @mp: the path through the metadata to the point to start
+ * @height: the height the recursion is at
+ * @block: the indirect block to look at
+ * @first: 1 if this is the first block
+ * @sm: data opaque to this function to pass to @bc
+ *
+ * When this is first called @height and @block should be zero and
+ * @first should be 1.
+ *
+ * Returns: errno
+ */
+
+static int recursive_scan(struct gfs2_inode *ip, struct buffer_head *dibh,
+			  struct metapath *mp, unsigned int height,
+			  u64 block, int first, struct strip_mine *sm)
+{
+	struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
+	struct buffer_head *bh = NULL;
+	__be64 *top, *bottom;
+	u64 bn;
+	int error;
+	int mh_size = sizeof(struct gfs2_meta_header);
+
+	if (!height) {
+		error = gfs2_meta_inode_buffer(ip, &bh);
+		if (error)
+			return error;
+		dibh = bh;
+
+		top = (__be64 *)(bh->b_data + sizeof(struct gfs2_dinode)) + mp->mp_list[0];
+		bottom = (__be64 *)(bh->b_data + sizeof(struct gfs2_dinode)) + sdp->sd_diptrs;
+	} else {
+		error = gfs2_meta_indirect_buffer(ip, height, block, &bh);
+		if (error)
+			return error;
+
+		top = (__be64 *)(bh->b_data + mh_size) +
+				  (first ? mp->mp_list[height] : 0);
+
+		bottom = (__be64 *)(bh->b_data + mh_size) + sdp->sd_inptrs;
+	}
+
+	error = do_strip(ip, dibh, bh, top, bottom, height, sm);
+	if (error)
+		goto out;
+
+	if (height < ip->i_height - 1) {
+
+		gfs2_metapath_ra(ip->i_gl, bh, top);
+
+		for (; top < bottom; top++, first = 0) {
+			if (!*top)
+				continue;
+
+			bn = be64_to_cpu(*top);
+
+			error = recursive_scan(ip, dibh, mp, height + 1, bn,
+					       first, sm);
+			if (error)
+				break;
+		}
+	}
+out:
+	brelse(bh);
+	return error;
+}
+
+
+/**
+ * gfs2_block_truncate_page - Deal with zeroing out data for truncate
+ *
+ * This is partly borrowed from ext3.
+ */
+static int gfs2_block_truncate_page(struct address_space *mapping, loff_t from)
+{
+	struct inode *inode = mapping->host;
+	struct gfs2_inode *ip = GFS2_I(inode);
+	unsigned long index = from >> PAGE_CACHE_SHIFT;
+	unsigned offset = from & (PAGE_CACHE_SIZE-1);
+	unsigned blocksize, iblock, length, pos;
+	struct buffer_head *bh;
+	struct page *page;
+	int err;
+
+	page = find_or_create_page(mapping, index, GFP_NOFS);
+	if (!page)
+		return 0;
+
+	blocksize = inode->i_sb->s_blocksize;
+	length = blocksize - (offset & (blocksize - 1));
+	iblock = index << (PAGE_CACHE_SHIFT - inode->i_sb->s_blocksize_bits);
+
+	if (!page_has_buffers(page))
+		create_empty_buffers(page, blocksize, 0);
+
+	/* Find the buffer that contains "offset" */
+	bh = page_buffers(page);
+	pos = blocksize;
+	while (offset >= pos) {
+		bh = bh->b_this_page;
+		iblock++;
+		pos += blocksize;
+	}
+
+	err = 0;
+
+	if (!buffer_mapped(bh)) {
+		gfs2_block_map(inode, iblock, bh, 0);
+		/* unmapped? It's a hole - nothing to do */
+		if (!buffer_mapped(bh))
+			goto unlock;
+	}
+
+	/* Ok, it's mapped. Make sure it's up-to-date */
+	if (PageUptodate(page))
+		set_buffer_uptodate(bh);
+
+	if (!buffer_uptodate(bh)) {
+		err = -EIO;
+		ll_rw_block(READ, 1, &bh);
+		wait_on_buffer(bh);
+		/* Uhhuh. Read error. Complain and punt. */
+		if (!buffer_uptodate(bh))
+			goto unlock;
+		err = 0;
+	}
+
+	if (!gfs2_is_writeback(ip))
+		gfs2_trans_add_data(ip->i_gl, bh);
+
+	zero_user(page, offset, length);
+	mark_buffer_dirty(bh);
+unlock:
+	unlock_page(page);
+	page_cache_release(page);
+	return err;
+}
+
+#define GFS2_JTRUNC_REVOKES 8192
+
+/**
+ * gfs2_journaled_truncate - Wrapper for truncate_pagecache for jdata files
+ * @inode: The inode being truncated
+ * @oldsize: The original (larger) size
+ * @newsize: The new smaller size
+ *
+ * With jdata files, we have to journal a revoke for each block which is
+ * truncated. As a result, we need to split this into separate transactions
+ * if the number of pages being truncated gets too large.
+ */
+
+static int gfs2_journaled_truncate(struct inode *inode, u64 oldsize, u64 newsize)
+{
+	struct gfs2_sbd *sdp = GFS2_SB(inode);
+	u64 max_chunk = GFS2_JTRUNC_REVOKES * sdp->sd_vfs->s_blocksize;
+	u64 chunk;
+	int error;
+
+	while (oldsize != newsize) {
+		chunk = oldsize - newsize;
+		if (chunk > max_chunk)
+			chunk = max_chunk;
+		truncate_pagecache(inode, oldsize - chunk);
+		oldsize -= chunk;
+		gfs2_trans_end(sdp);
+		error = gfs2_trans_begin(sdp, RES_DINODE, GFS2_JTRUNC_REVOKES);
+		if (error)
+			return error;
+	}
+
+	return 0;
+}
+
+static int trunc_start(struct inode *inode, u64 oldsize, u64 newsize)
+{
+	struct gfs2_inode *ip = GFS2_I(inode);
+	struct gfs2_sbd *sdp = GFS2_SB(inode);
+	struct address_space *mapping = inode->i_mapping;
+	struct buffer_head *dibh;
+	int journaled = gfs2_is_jdata(ip);
+	int error;
+
+	if (journaled)
+		error = gfs2_trans_begin(sdp, RES_DINODE + RES_JDATA, GFS2_JTRUNC_REVOKES);
+	else
+		error = gfs2_trans_begin(sdp, RES_DINODE, 0);
+	if (error)
+		return error;
+
+	error = gfs2_meta_inode_buffer(ip, &dibh);
+	if (error)
+		goto out;
+
+	gfs2_trans_add_meta(ip->i_gl, dibh);
+
+	if (gfs2_is_stuffed(ip)) {
+		gfs2_buffer_clear_tail(dibh, sizeof(struct gfs2_dinode) + newsize);
+	} else {
+		if (newsize & (u64)(sdp->sd_sb.sb_bsize - 1)) {
+			error = gfs2_block_truncate_page(mapping, newsize);
+			if (error)
+				goto out_brelse;
+		}
+		ip->i_diskflags |= GFS2_DIF_TRUNC_IN_PROG;
+	}
+
+	i_size_write(inode, newsize);
+	ip->i_inode.i_mtime = ip->i_inode.i_ctime = CURRENT_TIME;
+	gfs2_dinode_out(ip, dibh->b_data);
+
+	if (journaled)
+		error = gfs2_journaled_truncate(inode, oldsize, newsize);
+	else
+		truncate_pagecache(inode, newsize);
+
+	if (error) {
+		brelse(dibh);
+		return error;
+	}
+
+out_brelse:
+	brelse(dibh);
+out:
+	gfs2_trans_end(sdp);
+	return error;
+}
+
+static int trunc_dealloc(struct gfs2_inode *ip, u64 size)
+{
+	struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
+	unsigned int height = ip->i_height;
+	u64 lblock;
+	struct metapath mp;
+	int error;
+
+	if (!size)
+		lblock = 0;
+	else
+		lblock = (size - 1) >> sdp->sd_sb.sb_bsize_shift;
+
+	find_metapath(sdp, lblock, &mp, ip->i_height);
+	error = gfs2_rindex_update(sdp);
+	if (error)
+		return error;
+
+	error = gfs2_quota_hold(ip, NO_UID_QUOTA_CHANGE, NO_GID_QUOTA_CHANGE);
+	if (error)
+		return error;
+
+	while (height--) {
+		struct strip_mine sm;
+		sm.sm_first = !!size;
+		sm.sm_height = height;
+
+		error = recursive_scan(ip, NULL, &mp, 0, 0, 1, &sm);
+		if (error)
+			break;
+	}
+
+	gfs2_quota_unhold(ip);
+
+	return error;
+}
+
+static int trunc_end(struct gfs2_inode *ip)
+{
+	struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
+	struct buffer_head *dibh;
+	int error;
+
+	error = gfs2_trans_begin(sdp, RES_DINODE, 0);
+	if (error)
+		return error;
+
+	down_write(&ip->i_rw_mutex);
+
+	error = gfs2_meta_inode_buffer(ip, &dibh);
+	if (error)
+		goto out;
+
+	if (!i_size_read(&ip->i_inode)) {
+		ip->i_height = 0;
+		ip->i_goal = ip->i_no_addr;
+		gfs2_buffer_clear_tail(dibh, sizeof(struct gfs2_dinode));
+		gfs2_ordered_del_inode(ip);
+	}
+	ip->i_inode.i_mtime = ip->i_inode.i_ctime = CURRENT_TIME;
+	ip->i_diskflags &= ~GFS2_DIF_TRUNC_IN_PROG;
+
+	gfs2_trans_add_meta(ip->i_gl, dibh);
+	gfs2_dinode_out(ip, dibh->b_data);
+	brelse(dibh);
+
+out:
+	up_write(&ip->i_rw_mutex);
+	gfs2_trans_end(sdp);
+	return error;
+}
+
+/**
+ * do_shrink - make a file smaller
+ * @inode: the inode
+ * @oldsize: the current inode size
+ * @newsize: the size to make the file
+ *
+ * Called with an exclusive lock on @inode. The @size must
+ * be equal to or smaller than the current inode size.
+ *
+ * Returns: errno
+ */
+
+static int do_shrink(struct inode *inode, u64 oldsize, u64 newsize)
+{
+	struct gfs2_inode *ip = GFS2_I(inode);
+	int error;
+
+	error = trunc_start(inode, oldsize, newsize);
+	if (error < 0)
+		return error;
+	if (gfs2_is_stuffed(ip))
+		return 0;
+
+	error = trunc_dealloc(ip, newsize);
+	if (error == 0)
+		error = trunc_end(ip);
+
+	return error;
+}
+
+void gfs2_trim_blocks(struct inode *inode)
+{
+	u64 size = inode->i_size;
+	int ret;
+
+	ret = do_shrink(inode, size, size);
+	WARN_ON(ret != 0);
+}
+
+/**
+ * do_grow - Touch and update inode size
+ * @inode: The inode
+ * @size: The new size
+ *
+ * This function updates the timestamps on the inode and
+ * may also increase the size of the inode. This function
+ * must not be called with @size any smaller than the current
+ * inode size.
+ *
+ * Although it is not strictly required to unstuff files here,
+ * earlier versions of GFS2 have a bug in the stuffed file reading
+ * code which will result in a buffer overrun if the size is larger
+ * than the max stuffed file size. In order to prevent this from
+ * occurring, such files are unstuffed, but in other cases we can
+ * just update the inode size directly.
+ *
+ * Returns: 0 on success, or -ve on error
+ */
+
+static int do_grow(struct inode *inode, u64 size)
+{
+	struct gfs2_inode *ip = GFS2_I(inode);
+	struct gfs2_sbd *sdp = GFS2_SB(inode);
+	struct gfs2_alloc_parms ap = { .target = 1, };
+	struct buffer_head *dibh;
+	int error;
+	int unstuff = 0;
+
+	if (gfs2_is_stuffed(ip) &&
+	    (size > (sdp->sd_sb.sb_bsize - sizeof(struct gfs2_dinode)))) {
+		error = gfs2_quota_lock_check(ip, &ap);
+		if (error)
+			return error;
+
+		error = gfs2_inplace_reserve(ip, &ap);
+		if (error)
+			goto do_grow_qunlock;
+		unstuff = 1;
+	}
+
+	error = gfs2_trans_begin(sdp, RES_DINODE + RES_STATFS + RES_RG_BIT +
+				 (sdp->sd_args.ar_quota == GFS2_QUOTA_OFF ?
+				  0 : RES_QUOTA), 0);
+	if (error)
+		goto do_grow_release;
+
+	if (unstuff) {
+		error = gfs2_unstuff_dinode(ip, NULL);
+		if (error)
+			goto do_end_trans;
+	}
+
+	error = gfs2_meta_inode_buffer(ip, &dibh);
+	if (error)
+		goto do_end_trans;
+
+	i_size_write(inode, size);
+	ip->i_inode.i_mtime = ip->i_inode.i_ctime = CURRENT_TIME;
+	gfs2_trans_add_meta(ip->i_gl, dibh);
+	gfs2_dinode_out(ip, dibh->b_data);
+	brelse(dibh);
+
+do_end_trans:
+	gfs2_trans_end(sdp);
+do_grow_release:
+	if (unstuff) {
+		gfs2_inplace_release(ip);
+do_grow_qunlock:
+		gfs2_quota_unlock(ip);
+	}
+	return error;
+}
+
+/**
+ * gfs2_setattr_size - make a file a given size
+ * @inode: the inode
+ * @newsize: the size to make the file
+ *
+ * The file size can grow, shrink, or stay the same size. This
+ * is called holding i_mutex and an exclusive glock on the inode
+ * in question.
+ *
+ * Returns: errno
+ */
+
+int gfs2_setattr_size(struct inode *inode, u64 newsize)
+{
+	struct gfs2_inode *ip = GFS2_I(inode);
+	int ret;
+	u64 oldsize;
+
+	BUG_ON(!S_ISREG(inode->i_mode));
+
+	ret = inode_newsize_ok(inode, newsize);
+	if (ret)
+		return ret;
+
+	ret = get_write_access(inode);
+	if (ret)
+		return ret;
+
+	inode_dio_wait(inode);
+
+	ret = gfs2_rs_alloc(ip);
+	if (ret)
+		goto out;
+
+	oldsize = inode->i_size;
+	if (newsize >= oldsize) {
+		ret = do_grow(inode, newsize);
+		goto out;
+	}
+
+	gfs2_rs_deltree(ip->i_res);
+	ret = do_shrink(inode, oldsize, newsize);
+out:
+	put_write_access(inode);
+	return ret;
+}
+
+int gfs2_truncatei_resume(struct gfs2_inode *ip)
+{
+	int error;
+	error = trunc_dealloc(ip, i_size_read(&ip->i_inode));
+	if (!error)
+		error = trunc_end(ip);
+	return error;
+}
+
+int gfs2_file_dealloc(struct gfs2_inode *ip)
+{
+	return trunc_dealloc(ip, 0);
+}
+
+/**
+ * gfs2_free_journal_extents - Free cached journal bmap info
+ * @jd: The journal
+ *
+ */
+
+void gfs2_free_journal_extents(struct gfs2_jdesc *jd)
+{
+	struct gfs2_journal_extent *jext;
+
+	while(!list_empty(&jd->extent_list)) {
+		jext = list_entry(jd->extent_list.next, struct gfs2_journal_extent, list);
+		list_del(&jext->list);
+		kfree(jext);
+	}
+}
+
+/**
+ * gfs2_add_jextent - Add or merge a new extent to extent cache
+ * @jd: The journal descriptor
+ * @lblock: The logical block at start of new extent
+ * @dblock: The physical block at start of new extent
+ * @blocks: Size of extent in fs blocks
+ *
+ * Returns: 0 on success or -ENOMEM
+ */
+
+static int gfs2_add_jextent(struct gfs2_jdesc *jd, u64 lblock, u64 dblock, u64 blocks)
+{
+	struct gfs2_journal_extent *jext;
+
+	if (!list_empty(&jd->extent_list)) {
+		jext = list_entry(jd->extent_list.prev, struct gfs2_journal_extent, list);
+		if ((jext->dblock + jext->blocks) == dblock) {
+			jext->blocks += blocks;
+			return 0;
+		}
+	}
+
+	jext = kzalloc(sizeof(struct gfs2_journal_extent), GFP_NOFS);
+	if (jext == NULL)
+		return -ENOMEM;
+	jext->dblock = dblock;
+	jext->lblock = lblock;
+	jext->blocks = blocks;
+	list_add_tail(&jext->list, &jd->extent_list);
+	jd->nr_extents++;
+	return 0;
+}
+
+/**
+ * gfs2_map_journal_extents - Cache journal bmap info
+ * @sdp: The super block
+ * @jd: The journal to map
+ *
+ * Create a reusable "extent" mapping from all logical
+ * blocks to all physical blocks for the given journal.  This will save
+ * us time when writing journal blocks.  Most journals will have only one
+ * extent that maps all their logical blocks.  That's because gfs2.mkfs
+ * arranges the journal blocks sequentially to maximize performance.
+ * So the extent would map the first block for the entire file length.
+ * However, gfs2_jadd can happen while file activity is happening, so
+ * those journals may not be sequential.  Less likely is the case where
+ * the users created their own journals by mounting the metafs and
+ * laying it out.  But it's still possible.  These journals might have
+ * several extents.
+ *
+ * Returns: 0 on success, or error on failure
+ */
+
+int gfs2_map_journal_extents(struct gfs2_sbd *sdp, struct gfs2_jdesc *jd)
+{
+	u64 lblock = 0;
+	u64 lblock_stop;
+	struct gfs2_inode *ip = GFS2_I(jd->jd_inode);
+	struct buffer_head bh;
+	unsigned int shift = sdp->sd_sb.sb_bsize_shift;
+	u64 size;
+	int rc;
+
+	lblock_stop = i_size_read(jd->jd_inode) >> shift;
+	size = (lblock_stop - lblock) << shift;
+	jd->nr_extents = 0;
+	WARN_ON(!list_empty(&jd->extent_list));
+
+	do {
+		bh.b_state = 0;
+		bh.b_blocknr = 0;
+		bh.b_size = size;
+		rc = gfs2_block_map(jd->jd_inode, lblock, &bh, 0);
+		if (rc || !buffer_mapped(&bh))
+			goto fail;
+		rc = gfs2_add_jextent(jd, lblock, bh.b_blocknr, bh.b_size >> shift);
+		if (rc)
+			goto fail;
+		size -= bh.b_size;
+		lblock += (bh.b_size >> ip->i_inode.i_blkbits);
+	} while(size > 0);
+
+	fs_info(sdp, "journal %d mapped with %u extents\n", jd->jd_jid,
+		jd->nr_extents);
+	return 0;
+
+fail:
+	fs_warn(sdp, "error %d mapping journal %u at offset %llu (extent %u)\n",
+		rc, jd->jd_jid,
+		(unsigned long long)(i_size_read(jd->jd_inode) - size),
+		jd->nr_extents);
+	fs_warn(sdp, "bmap=%d lblock=%llu block=%llu, state=0x%08lx, size=%llu\n",
+		rc, (unsigned long long)lblock, (unsigned long long)bh.b_blocknr,
+		bh.b_state, (unsigned long long)bh.b_size);
+	gfs2_free_journal_extents(jd);
+	return rc;
+}
+
+/**
+ * gfs2_write_alloc_required - figure out if a write will require an allocation
+ * @ip: the file being written to
+ * @offset: the offset to write to
+ * @len: the number of bytes being written
+ *
+ * Returns: 1 if an alloc is required, 0 otherwise
+ */
+
+int gfs2_write_alloc_required(struct gfs2_inode *ip, u64 offset,
+			      unsigned int len)
+{
+	struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
+	struct buffer_head bh;
+	unsigned int shift;
+	u64 lblock, lblock_stop, size;
+	u64 end_of_file;
+
+	if (!len)
+		return 0;
+
+	if (gfs2_is_stuffed(ip)) {
+		if (offset + len >
+		    sdp->sd_sb.sb_bsize - sizeof(struct gfs2_dinode))
+			return 1;
+		return 0;
+	}
+
+	shift = sdp->sd_sb.sb_bsize_shift;
+	BUG_ON(gfs2_is_dir(ip));
+	end_of_file = (i_size_read(&ip->i_inode) + sdp->sd_sb.sb_bsize - 1) >> shift;
+	lblock = offset >> shift;
+	lblock_stop = (offset + len + sdp->sd_sb.sb_bsize - 1) >> shift;
+	if (lblock_stop > end_of_file)
+		return 1;
+
+	size = (lblock_stop - lblock) << shift;
+	do {
+		bh.b_state = 0;
+		bh.b_size = size;
+		gfs2_block_map(&ip->i_inode, lblock, &bh, 0);
+		if (!buffer_mapped(&bh))
+			return 1;
+		size -= bh.b_size;
+		lblock += (bh.b_size >> ip->i_inode.i_blkbits);
+	} while(size > 0);
+
+	return 0;
+}
+