[PATCH] OCFS2: The Second Oracle Cluster Filesystem

The OCFS2 file system module.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
Signed-off-by: Kurt Hackel <kurt.hackel@oracle.com>

1 files changed, 983 insertions, 0 deletions

diff --git a/fs/ocfs2/localalloc.c b/fs/ocfs2/localalloc.c
new file mode 100644
index 00000000000..fe373a2101d
--- /dev/null
+++ b/fs/ocfs2/localalloc.c
@@ -0,0 +1,983 @@
+/* -*- mode: c; c-basic-offset: 8; -*-
+ * vim: noexpandtab sw=8 ts=8 sts=0:
+ *
+ * localalloc.c
+ *
+ * Node local data allocation
+ *
+ * Copyright (C) 2002, 2004 Oracle.  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; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will 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 to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+
+#include <linux/fs.h>
+#include <linux/types.h>
+#include <linux/slab.h>
+#include <linux/highmem.h>
+#include <linux/bitops.h>
+
+#define MLOG_MASK_PREFIX ML_DISK_ALLOC
+#include <cluster/masklog.h>
+
+#include "ocfs2.h"
+
+#include "alloc.h"
+#include "dlmglue.h"
+#include "inode.h"
+#include "journal.h"
+#include "localalloc.h"
+#include "suballoc.h"
+#include "super.h"
+#include "sysfile.h"
+
+#include "buffer_head_io.h"
+
+#define OCFS2_LOCAL_ALLOC(dinode)	(&((dinode)->id2.i_lab))
+
+static inline int ocfs2_local_alloc_window_bits(struct ocfs2_super *osb);
+
+static u32 ocfs2_local_alloc_count_bits(struct ocfs2_dinode *alloc);
+
+static int ocfs2_local_alloc_find_clear_bits(struct ocfs2_super *osb,
+					     struct ocfs2_dinode *alloc,
+					     u32 numbits);
+
+static void ocfs2_clear_local_alloc(struct ocfs2_dinode *alloc);
+
+static int ocfs2_sync_local_to_main(struct ocfs2_super *osb,
+				    struct ocfs2_journal_handle *handle,
+				    struct ocfs2_dinode *alloc,
+				    struct inode *main_bm_inode,
+				    struct buffer_head *main_bm_bh);
+
+static int ocfs2_local_alloc_reserve_for_window(struct ocfs2_super *osb,
+						struct ocfs2_journal_handle *handle,
+						struct ocfs2_alloc_context **ac,
+						struct inode **bitmap_inode,
+						struct buffer_head **bitmap_bh);
+
+static int ocfs2_local_alloc_new_window(struct ocfs2_super *osb,
+					struct ocfs2_journal_handle *handle,
+					struct ocfs2_alloc_context *ac);
+
+static int ocfs2_local_alloc_slide_window(struct ocfs2_super *osb,
+					  struct inode *local_alloc_inode);
+
+/*
+ * Determine how large our local alloc window should be, in bits.
+ *
+ * These values (and the behavior in ocfs2_alloc_should_use_local) have
+ * been chosen so that most allocations, including new block groups go
+ * through local alloc.
+ */
+static inline int ocfs2_local_alloc_window_bits(struct ocfs2_super *osb)
+{
+	BUG_ON(osb->s_clustersize_bits < 12);
+
+	return 2048 >> (osb->s_clustersize_bits - 12);
+}
+
+/*
+ * Tell us whether a given allocation should use the local alloc
+ * file. Otherwise, it has to go to the main bitmap.
+ */
+int ocfs2_alloc_should_use_local(struct ocfs2_super *osb, u64 bits)
+{
+	int la_bits = ocfs2_local_alloc_window_bits(osb);
+
+	if (osb->local_alloc_state != OCFS2_LA_ENABLED)
+		return 0;
+
+	/* la_bits should be at least twice the size (in clusters) of
+	 * a new block group. We want to be sure block group
+	 * allocations go through the local alloc, so allow an
+	 * allocation to take up to half the bitmap. */
+	if (bits > (la_bits / 2))
+		return 0;
+
+	return 1;
+}
+
+int ocfs2_load_local_alloc(struct ocfs2_super *osb)
+{
+	int status = 0;
+	struct ocfs2_dinode *alloc = NULL;
+	struct buffer_head *alloc_bh = NULL;
+	u32 num_used;
+	struct inode *inode = NULL;
+	struct ocfs2_local_alloc *la;
+
+	mlog_entry_void();
+
+	/* read the alloc off disk */
+	inode = ocfs2_get_system_file_inode(osb, LOCAL_ALLOC_SYSTEM_INODE,
+					    osb->slot_num);
+	if (!inode) {
+		status = -EINVAL;
+		mlog_errno(status);
+		goto bail;
+	}
+
+	status = ocfs2_read_block(osb, OCFS2_I(inode)->ip_blkno,
+				  &alloc_bh, 0, inode);
+	if (status < 0) {
+		mlog_errno(status);
+		goto bail;
+	}
+
+	alloc = (struct ocfs2_dinode *) alloc_bh->b_data;
+	la = OCFS2_LOCAL_ALLOC(alloc);
+
+	if (!(le32_to_cpu(alloc->i_flags) &
+	    (OCFS2_LOCAL_ALLOC_FL|OCFS2_BITMAP_FL))) {
+		mlog(ML_ERROR, "Invalid local alloc inode, %"MLFu64"\n",
+		     OCFS2_I(inode)->ip_blkno);
+		status = -EINVAL;
+		goto bail;
+	}
+
+	if ((la->la_size == 0) ||
+	    (le16_to_cpu(la->la_size) > ocfs2_local_alloc_size(inode->i_sb))) {
+		mlog(ML_ERROR, "Local alloc size is invalid (la_size = %u)\n",
+		     le16_to_cpu(la->la_size));
+		status = -EINVAL;
+		goto bail;
+	}
+
+	/* do a little verification. */
+	num_used = ocfs2_local_alloc_count_bits(alloc);
+
+	/* hopefully the local alloc has always been recovered before
+	 * we load it. */
+	if (num_used
+	    || alloc->id1.bitmap1.i_used
+	    || alloc->id1.bitmap1.i_total
+	    || la->la_bm_off)
+		mlog(ML_ERROR, "Local alloc hasn't been recovered!\n"
+		     "found = %u, set = %u, taken = %u, off = %u\n",
+		     num_used, le32_to_cpu(alloc->id1.bitmap1.i_used),
+		     le32_to_cpu(alloc->id1.bitmap1.i_total),
+		     OCFS2_LOCAL_ALLOC(alloc)->la_bm_off);
+
+	osb->local_alloc_bh = alloc_bh;
+	osb->local_alloc_state = OCFS2_LA_ENABLED;
+
+bail:
+	if (status < 0)
+		if (alloc_bh)
+			brelse(alloc_bh);
+	if (inode)
+		iput(inode);
+
+	mlog_exit(status);
+	return status;
+}
+
+/*
+ * return any unused bits to the bitmap and write out a clean
+ * local_alloc.
+ *
+ * local_alloc_bh is optional. If not passed, we will simply use the
+ * one off osb. If you do pass it however, be warned that it *will* be
+ * returned brelse'd and NULL'd out.*/
+void ocfs2_shutdown_local_alloc(struct ocfs2_super *osb)
+{
+	int status;
+	struct ocfs2_journal_handle *handle = NULL;
+	struct inode *local_alloc_inode = NULL;
+	struct buffer_head *bh = NULL;
+	struct buffer_head *main_bm_bh = NULL;
+	struct inode *main_bm_inode = NULL;
+	struct ocfs2_dinode *alloc_copy = NULL;
+	struct ocfs2_dinode *alloc = NULL;
+
+	mlog_entry_void();
+
+	if (osb->local_alloc_state == OCFS2_LA_UNUSED)
+		goto bail;
+
+	local_alloc_inode =
+		ocfs2_get_system_file_inode(osb,
+					    LOCAL_ALLOC_SYSTEM_INODE,
+					    osb->slot_num);
+	if (!local_alloc_inode) {
+		status = -ENOENT;
+		mlog_errno(status);
+		goto bail;
+	}
+
+	osb->local_alloc_state = OCFS2_LA_DISABLED;
+
+	handle = ocfs2_alloc_handle(osb);
+	if (!handle) {
+		status = -ENOMEM;
+		mlog_errno(status);
+		goto bail;
+	}
+
+	main_bm_inode = ocfs2_get_system_file_inode(osb,
+						    GLOBAL_BITMAP_SYSTEM_INODE,
+						    OCFS2_INVALID_SLOT);
+	if (!main_bm_inode) {
+		status = -EINVAL;
+		mlog_errno(status);
+		goto bail;
+	}
+
+	ocfs2_handle_add_inode(handle, main_bm_inode);
+	status = ocfs2_meta_lock(main_bm_inode, handle, &main_bm_bh, 1);
+	if (status < 0) {
+		mlog_errno(status);
+		goto bail;
+	}
+
+	/* WINDOW_MOVE_CREDITS is a bit heavy... */
+	handle = ocfs2_start_trans(osb, handle, OCFS2_WINDOW_MOVE_CREDITS);
+	if (IS_ERR(handle)) {
+		mlog_errno(PTR_ERR(handle));
+		handle = NULL;
+		goto bail;
+	}
+
+	bh = osb->local_alloc_bh;
+	alloc = (struct ocfs2_dinode *) bh->b_data;
+
+	alloc_copy = kmalloc(bh->b_size, GFP_KERNEL);
+	if (!alloc_copy) {
+		status = -ENOMEM;
+		goto bail;
+	}
+	memcpy(alloc_copy, alloc, bh->b_size);
+
+	status = ocfs2_journal_access(handle, local_alloc_inode, bh,
+				      OCFS2_JOURNAL_ACCESS_WRITE);
+	if (status < 0) {
+		mlog_errno(status);
+		goto bail;
+	}
+
+	ocfs2_clear_local_alloc(alloc);
+
+	status = ocfs2_journal_dirty(handle, bh);
+	if (status < 0) {
+		mlog_errno(status);
+		goto bail;
+	}
+
+	brelse(bh);
+	osb->local_alloc_bh = NULL;
+	osb->local_alloc_state = OCFS2_LA_UNUSED;
+
+	status = ocfs2_sync_local_to_main(osb, handle, alloc_copy,
+					  main_bm_inode, main_bm_bh);
+	if (status < 0)
+		mlog_errno(status);
+
+bail:
+	if (handle)
+		ocfs2_commit_trans(handle);
+
+	if (main_bm_bh)
+		brelse(main_bm_bh);
+
+	if (main_bm_inode)
+		iput(main_bm_inode);
+
+	if (local_alloc_inode)
+		iput(local_alloc_inode);
+
+	if (alloc_copy)
+		kfree(alloc_copy);
+
+	mlog_exit_void();
+}
+
+/*
+ * We want to free the bitmap bits outside of any recovery context as
+ * we'll need a cluster lock to do so, but we must clear the local
+ * alloc before giving up the recovered nodes journal. To solve this,
+ * we kmalloc a copy of the local alloc before it's change for the
+ * caller to process with ocfs2_complete_local_alloc_recovery
+ */
+int ocfs2_begin_local_alloc_recovery(struct ocfs2_super *osb,
+				     int slot_num,
+				     struct ocfs2_dinode **alloc_copy)
+{
+	int status = 0;
+	struct buffer_head *alloc_bh = NULL;
+	struct inode *inode = NULL;
+	struct ocfs2_dinode *alloc;
+
+	mlog_entry("(slot_num = %d)\n", slot_num);
+
+	*alloc_copy = NULL;
+
+	inode = ocfs2_get_system_file_inode(osb,
+					    LOCAL_ALLOC_SYSTEM_INODE,
+					    slot_num);
+	if (!inode) {
+		status = -EINVAL;
+		mlog_errno(status);
+		goto bail;
+	}
+
+	down(&inode->i_sem);
+
+	status = ocfs2_read_block(osb, OCFS2_I(inode)->ip_blkno,
+				  &alloc_bh, 0, inode);
+	if (status < 0) {
+		mlog_errno(status);
+		goto bail;
+	}
+
+	*alloc_copy = kmalloc(alloc_bh->b_size, GFP_KERNEL);
+	if (!(*alloc_copy)) {
+		status = -ENOMEM;
+		goto bail;
+	}
+	memcpy((*alloc_copy), alloc_bh->b_data, alloc_bh->b_size);
+
+	alloc = (struct ocfs2_dinode *) alloc_bh->b_data;
+	ocfs2_clear_local_alloc(alloc);
+
+	status = ocfs2_write_block(osb, alloc_bh, inode);
+	if (status < 0)
+		mlog_errno(status);
+
+bail:
+	if ((status < 0) && (*alloc_copy)) {
+		kfree(*alloc_copy);
+		*alloc_copy = NULL;
+	}
+
+	if (alloc_bh)
+		brelse(alloc_bh);
+
+	if (inode) {
+		up(&inode->i_sem);
+		iput(inode);
+	}
+
+	mlog_exit(status);
+	return status;
+}
+
+/*
+ * Step 2: By now, we've completed the journal recovery, we've stamped
+ * a clean local alloc on disk and dropped the node out of the
+ * recovery map. Dlm locks will no longer stall, so lets clear out the
+ * main bitmap.
+ */
+int ocfs2_complete_local_alloc_recovery(struct ocfs2_super *osb,
+					struct ocfs2_dinode *alloc)
+{
+	int status;
+	struct ocfs2_journal_handle *handle = NULL;
+	struct buffer_head *main_bm_bh = NULL;
+	struct inode *main_bm_inode = NULL;
+
+	mlog_entry_void();
+
+	handle = ocfs2_alloc_handle(osb);
+	if (!handle) {
+		status = -ENOMEM;
+		mlog_errno(status);
+		goto bail;
+	}
+
+	main_bm_inode = ocfs2_get_system_file_inode(osb,
+						    GLOBAL_BITMAP_SYSTEM_INODE,
+						    OCFS2_INVALID_SLOT);
+	if (!main_bm_inode) {
+		status = -EINVAL;
+		mlog_errno(status);
+		goto bail;
+	}
+
+	ocfs2_handle_add_inode(handle, main_bm_inode);
+	status = ocfs2_meta_lock(main_bm_inode, handle, &main_bm_bh, 1);
+	if (status < 0) {
+		mlog_errno(status);
+		goto bail;
+	}
+
+	handle = ocfs2_start_trans(osb, handle, OCFS2_WINDOW_MOVE_CREDITS);
+	if (IS_ERR(handle)) {
+		status = PTR_ERR(handle);
+		handle = NULL;
+		mlog_errno(status);
+		goto bail;
+	}
+
+	/* we want the bitmap change to be recorded on disk asap */
+	ocfs2_handle_set_sync(handle, 1);
+
+	status = ocfs2_sync_local_to_main(osb, handle, alloc,
+					  main_bm_inode, main_bm_bh);
+	if (status < 0)
+		mlog_errno(status);
+
+bail:
+	if (handle)
+		ocfs2_commit_trans(handle);
+
+	if (main_bm_bh)
+		brelse(main_bm_bh);
+
+	if (main_bm_inode)
+		iput(main_bm_inode);
+
+	mlog_exit(status);
+	return status;
+}
+
+/*
+ * make sure we've got at least bitswanted contiguous bits in the
+ * local alloc. You lose them when you drop i_sem.
+ *
+ * We will add ourselves to the transaction passed in, but may start
+ * our own in order to shift windows.
+ */
+int ocfs2_reserve_local_alloc_bits(struct ocfs2_super *osb,
+				   struct ocfs2_journal_handle *passed_handle,
+				   u32 bits_wanted,
+				   struct ocfs2_alloc_context *ac)
+{
+	int status;
+	struct ocfs2_dinode *alloc;
+	struct inode *local_alloc_inode;
+	unsigned int free_bits;
+
+	mlog_entry_void();
+
+	BUG_ON(!passed_handle);
+	BUG_ON(!ac);
+	BUG_ON(passed_handle->flags & OCFS2_HANDLE_STARTED);
+
+	local_alloc_inode =
+		ocfs2_get_system_file_inode(osb,
+					    LOCAL_ALLOC_SYSTEM_INODE,
+					    osb->slot_num);
+	if (!local_alloc_inode) {
+		status = -ENOENT;
+		mlog_errno(status);
+		goto bail;
+	}
+	ocfs2_handle_add_inode(passed_handle, local_alloc_inode);
+
+	if (osb->local_alloc_state != OCFS2_LA_ENABLED) {
+		status = -ENOSPC;
+		goto bail;
+	}
+
+	if (bits_wanted > ocfs2_local_alloc_window_bits(osb)) {
+		mlog(0, "Asking for more than my max window size!\n");
+		status = -ENOSPC;
+		goto bail;
+	}
+
+	alloc = (struct ocfs2_dinode *) osb->local_alloc_bh->b_data;
+
+	if (le32_to_cpu(alloc->id1.bitmap1.i_used) !=
+	    ocfs2_local_alloc_count_bits(alloc)) {
+		ocfs2_error(osb->sb, "local alloc inode %"MLFu64" says it has "
+			    "%u free bits, but a count shows %u",
+			    le64_to_cpu(alloc->i_blkno),
+			    le32_to_cpu(alloc->id1.bitmap1.i_used),
+			    ocfs2_local_alloc_count_bits(alloc));
+		status = -EIO;
+		goto bail;
+	}
+
+	free_bits = le32_to_cpu(alloc->id1.bitmap1.i_total) -
+		le32_to_cpu(alloc->id1.bitmap1.i_used);
+	if (bits_wanted > free_bits) {
+		/* uhoh, window change time. */
+		status =
+			ocfs2_local_alloc_slide_window(osb, local_alloc_inode);
+		if (status < 0) {
+			if (status != -ENOSPC)
+				mlog_errno(status);
+			goto bail;
+		}
+	}
+
+	ac->ac_inode = igrab(local_alloc_inode);
+	get_bh(osb->local_alloc_bh);
+	ac->ac_bh = osb->local_alloc_bh;
+	ac->ac_which = OCFS2_AC_USE_LOCAL;
+	status = 0;
+bail:
+	if (local_alloc_inode)
+		iput(local_alloc_inode);
+
+	mlog_exit(status);
+	return status;
+}
+
+int ocfs2_claim_local_alloc_bits(struct ocfs2_super *osb,
+				 struct ocfs2_journal_handle *handle,
+				 struct ocfs2_alloc_context *ac,
+				 u32 min_bits,
+				 u32 *bit_off,
+				 u32 *num_bits)
+{
+	int status, start;
+	struct inode *local_alloc_inode;
+	u32 bits_wanted;
+	void *bitmap;
+	struct ocfs2_dinode *alloc;
+	struct ocfs2_local_alloc *la;
+
+	mlog_entry_void();
+	BUG_ON(ac->ac_which != OCFS2_AC_USE_LOCAL);
+
+	bits_wanted = ac->ac_bits_wanted - ac->ac_bits_given;
+	local_alloc_inode = ac->ac_inode;
+	alloc = (struct ocfs2_dinode *) osb->local_alloc_bh->b_data;
+	la = OCFS2_LOCAL_ALLOC(alloc);
+
+	start = ocfs2_local_alloc_find_clear_bits(osb, alloc, bits_wanted);
+	if (start == -1) {
+		/* TODO: Shouldn't we just BUG here? */
+		status = -ENOSPC;
+		mlog_errno(status);
+		goto bail;
+	}
+
+	bitmap = la->la_bitmap;
+	*bit_off = le32_to_cpu(la->la_bm_off) + start;
+	/* local alloc is always contiguous by nature -- we never
+	 * delete bits from it! */
+	*num_bits = bits_wanted;
+
+	status = ocfs2_journal_access(handle, local_alloc_inode,
+				      osb->local_alloc_bh,
+				      OCFS2_JOURNAL_ACCESS_WRITE);
+	if (status < 0) {
+		mlog_errno(status);
+		goto bail;
+	}
+
+	while(bits_wanted--)
+		ocfs2_set_bit(start++, bitmap);
+
+	alloc->id1.bitmap1.i_used = cpu_to_le32(*num_bits +
+				le32_to_cpu(alloc->id1.bitmap1.i_used));
+
+	status = ocfs2_journal_dirty(handle, osb->local_alloc_bh);
+	if (status < 0) {
+		mlog_errno(status);
+		goto bail;
+	}
+
+	status = 0;
+bail:
+	mlog_exit(status);
+	return status;
+}
+
+static u32 ocfs2_local_alloc_count_bits(struct ocfs2_dinode *alloc)
+{
+	int i;
+	u8 *buffer;
+	u32 count = 0;
+	struct ocfs2_local_alloc *la = OCFS2_LOCAL_ALLOC(alloc);
+
+	mlog_entry_void();
+
+	buffer = la->la_bitmap;
+	for (i = 0; i < le16_to_cpu(la->la_size); i++)
+		count += hweight8(buffer[i]);
+
+	mlog_exit(count);
+	return count;
+}
+
+static int ocfs2_local_alloc_find_clear_bits(struct ocfs2_super *osb,
+					     struct ocfs2_dinode *alloc,
+					     u32 numbits)
+{
+	int numfound, bitoff, left, startoff, lastzero;
+	void *bitmap = NULL;
+
+	mlog_entry("(numbits wanted = %u)\n", numbits);
+
+	if (!alloc->id1.bitmap1.i_total) {
+		mlog(0, "No bits in my window!\n");
+		bitoff = -1;
+		goto bail;
+	}
+
+	bitmap = OCFS2_LOCAL_ALLOC(alloc)->la_bitmap;
+
+	numfound = bitoff = startoff = 0;
+	lastzero = -1;
+	left = le32_to_cpu(alloc->id1.bitmap1.i_total);
+	while ((bitoff = ocfs2_find_next_zero_bit(bitmap, left, startoff)) != -1) {
+		if (bitoff == left) {
+			/* mlog(0, "bitoff (%d) == left", bitoff); */
+			break;
+		}
+		/* mlog(0, "Found a zero: bitoff = %d, startoff = %d, "
+		   "numfound = %d\n", bitoff, startoff, numfound);*/
+
+		/* Ok, we found a zero bit... is it contig. or do we
+		 * start over?*/
+		if (bitoff == startoff) {
+			/* we found a zero */
+			numfound++;
+			startoff++;
+		} else {
+			/* got a zero after some ones */
+			numfound = 1;
+			startoff = bitoff+1;
+		}
+		/* we got everything we needed */
+		if (numfound == numbits) {
+			/* mlog(0, "Found it all!\n"); */
+			break;
+		}
+	}
+
+	mlog(0, "Exiting loop, bitoff = %d, numfound = %d\n", bitoff,
+	     numfound);
+
+	if (numfound == numbits)
+		bitoff = startoff - numfound;
+	else
+		bitoff = -1;
+
+bail:
+	mlog_exit(bitoff);
+	return bitoff;
+}
+
+static void ocfs2_clear_local_alloc(struct ocfs2_dinode *alloc)
+{
+	struct ocfs2_local_alloc *la = OCFS2_LOCAL_ALLOC(alloc);
+	int i;
+	mlog_entry_void();
+
+	alloc->id1.bitmap1.i_total = 0;
+	alloc->id1.bitmap1.i_used = 0;
+	la->la_bm_off = 0;
+	for(i = 0; i < le16_to_cpu(la->la_size); i++)
+		la->la_bitmap[i] = 0;
+
+	mlog_exit_void();
+}
+
+#if 0
+/* turn this on and uncomment below to aid debugging window shifts. */
+static void ocfs2_verify_zero_bits(unsigned long *bitmap,
+				   unsigned int start,
+				   unsigned int count)
+{
+	unsigned int tmp = count;
+	while(tmp--) {
+		if (ocfs2_test_bit(start + tmp, bitmap)) {
+			printk("ocfs2_verify_zero_bits: start = %u, count = "
+			       "%u\n", start, count);
+			printk("ocfs2_verify_zero_bits: bit %u is set!",
+			       start + tmp);
+			BUG();
+		}
+	}
+}
+#endif
+
+/*
+ * sync the local alloc to main bitmap.
+ *
+ * assumes you've already locked the main bitmap -- the bitmap inode
+ * passed is used for caching.
+ */
+static int ocfs2_sync_local_to_main(struct ocfs2_super *osb,
+				    struct ocfs2_journal_handle *handle,
+				    struct ocfs2_dinode *alloc,
+				    struct inode *main_bm_inode,
+				    struct buffer_head *main_bm_bh)
+{
+	int status = 0;
+	int bit_off, left, count, start;
+	u64 la_start_blk;
+	u64 blkno;
+	void *bitmap;
+	struct ocfs2_local_alloc *la = OCFS2_LOCAL_ALLOC(alloc);
+
+	mlog_entry("total = %u, COUNT = %u, used = %u\n",
+		   le32_to_cpu(alloc->id1.bitmap1.i_total),
+		   ocfs2_local_alloc_count_bits(alloc),
+		   le32_to_cpu(alloc->id1.bitmap1.i_used));
+
+	if (!alloc->id1.bitmap1.i_total) {
+		mlog(0, "nothing to sync!\n");
+		goto bail;
+	}
+
+	if (le32_to_cpu(alloc->id1.bitmap1.i_used) ==
+	    le32_to_cpu(alloc->id1.bitmap1.i_total)) {
+		mlog(0, "all bits were taken!\n");
+		goto bail;
+	}
+
+	la_start_blk = ocfs2_clusters_to_blocks(osb->sb,
+						le32_to_cpu(la->la_bm_off));
+	bitmap = la->la_bitmap;
+	start = count = bit_off = 0;
+	left = le32_to_cpu(alloc->id1.bitmap1.i_total);
+
+	while ((bit_off = ocfs2_find_next_zero_bit(bitmap, left, start))
+	       != -1) {
+		if ((bit_off < left) && (bit_off == start)) {
+			count++;
+			start++;
+			continue;
+		}
+		if (count) {
+			blkno = la_start_blk +
+				ocfs2_clusters_to_blocks(osb->sb,
+							 start - count);
+
+			mlog(0, "freeing %u bits starting at local "
+			     "alloc bit %u (la_start_blk = %"MLFu64", "
+			     "blkno = %"MLFu64")\n", count, start - count,
+			     la_start_blk, blkno);
+
+			status = ocfs2_free_clusters(handle, main_bm_inode,
+						     main_bm_bh, blkno, count);
+			if (status < 0) {
+				mlog_errno(status);
+				goto bail;
+			}
+		}
+		if (bit_off >= left)
+			break;
+		count = 1;
+		start = bit_off + 1;
+	}
+
+bail:
+	mlog_exit(status);
+	return status;
+}
+
+static int ocfs2_local_alloc_reserve_for_window(struct ocfs2_super *osb,
+						struct ocfs2_journal_handle *handle,
+						struct ocfs2_alloc_context **ac,
+						struct inode **bitmap_inode,
+						struct buffer_head **bitmap_bh)
+{
+	int status;
+
+	*ac = kcalloc(1, sizeof(struct ocfs2_alloc_context), GFP_KERNEL);
+	if (!(*ac)) {
+		status = -ENOMEM;
+		mlog_errno(status);
+		goto bail;
+	}
+
+	(*ac)->ac_handle = handle;
+	(*ac)->ac_bits_wanted = ocfs2_local_alloc_window_bits(osb);
+
+	status = ocfs2_reserve_cluster_bitmap_bits(osb, *ac);
+	if (status < 0) {
+		if (status != -ENOSPC)
+			mlog_errno(status);
+		goto bail;
+	}
+
+	*bitmap_inode = (*ac)->ac_inode;
+	igrab(*bitmap_inode);
+	*bitmap_bh = (*ac)->ac_bh;
+	get_bh(*bitmap_bh);
+	status = 0;
+bail:
+	if ((status < 0) && *ac) {
+		ocfs2_free_alloc_context(*ac);
+		*ac = NULL;
+	}
+
+	mlog_exit(status);
+	return status;
+}
+
+/*
+ * pass it the bitmap lock in lock_bh if you have it.
+ */
+static int ocfs2_local_alloc_new_window(struct ocfs2_super *osb,
+					struct ocfs2_journal_handle *handle,
+					struct ocfs2_alloc_context *ac)
+{
+	int status = 0;
+	u32 cluster_off, cluster_count;
+	struct ocfs2_dinode *alloc = NULL;
+	struct ocfs2_local_alloc *la;
+
+	mlog_entry_void();
+
+	alloc = (struct ocfs2_dinode *) osb->local_alloc_bh->b_data;
+	la = OCFS2_LOCAL_ALLOC(alloc);
+
+	if (alloc->id1.bitmap1.i_total)
+		mlog(0, "asking me to alloc a new window over a non-empty "
+		     "one\n");
+
+	mlog(0, "Allocating %u clusters for a new window.\n",
+	     ocfs2_local_alloc_window_bits(osb));
+	/* we used the generic suballoc reserve function, but we set
+	 * everything up nicely, so there's no reason why we can't use
+	 * the more specific cluster api to claim bits. */
+	status = ocfs2_claim_clusters(osb, handle, ac,
+				      ocfs2_local_alloc_window_bits(osb),
+				      &cluster_off, &cluster_count);
+	if (status < 0) {
+		if (status != -ENOSPC)
+			mlog_errno(status);
+		goto bail;
+	}
+
+	la->la_bm_off = cpu_to_le32(cluster_off);
+	alloc->id1.bitmap1.i_total = cpu_to_le32(cluster_count);
+	/* just in case... In the future when we find space ourselves,
+	 * we don't have to get all contiguous -- but we'll have to
+	 * set all previously used bits in bitmap and update
+	 * la_bits_set before setting the bits in the main bitmap. */
+	alloc->id1.bitmap1.i_used = 0;
+	memset(OCFS2_LOCAL_ALLOC(alloc)->la_bitmap, 0,
+	       le16_to_cpu(la->la_size));
+
+	mlog(0, "New window allocated:\n");
+	mlog(0, "window la_bm_off = %u\n",
+	     OCFS2_LOCAL_ALLOC(alloc)->la_bm_off);
+	mlog(0, "window bits = %u\n", le32_to_cpu(alloc->id1.bitmap1.i_total));
+
+bail:
+	mlog_exit(status);
+	return status;
+}
+
+/* Note that we do *NOT* lock the local alloc inode here as
+ * it's been locked already for us. */
+static int ocfs2_local_alloc_slide_window(struct ocfs2_super *osb,
+					  struct inode *local_alloc_inode)
+{
+	int status = 0;
+	struct buffer_head *main_bm_bh = NULL;
+	struct inode *main_bm_inode = NULL;
+	struct ocfs2_journal_handle *handle = NULL;
+	struct ocfs2_dinode *alloc;
+	struct ocfs2_dinode *alloc_copy = NULL;
+	struct ocfs2_alloc_context *ac = NULL;
+
+	mlog_entry_void();
+
+	handle = ocfs2_alloc_handle(osb);
+	if (!handle) {
+		status = -ENOMEM;
+		mlog_errno(status);
+		goto bail;
+	}
+
+	/* This will lock the main bitmap for us. */
+	status = ocfs2_local_alloc_reserve_for_window(osb,
+						      handle,
+						      &ac,
+						      &main_bm_inode,
+						      &main_bm_bh);
+	if (status < 0) {
+		if (status != -ENOSPC)
+			mlog_errno(status);
+		goto bail;
+	}
+
+	handle = ocfs2_start_trans(osb, handle, OCFS2_WINDOW_MOVE_CREDITS);
+	if (IS_ERR(handle)) {
+		status = PTR_ERR(handle);
+		handle = NULL;
+		mlog_errno(status);
+		goto bail;
+	}
+
+	alloc = (struct ocfs2_dinode *) osb->local_alloc_bh->b_data;
+
+	/* We want to clear the local alloc before doing anything
+	 * else, so that if we error later during this operation,
+	 * local alloc shutdown won't try to double free main bitmap
+	 * bits. Make a copy so the sync function knows which bits to
+	 * free. */
+	alloc_copy = kmalloc(osb->local_alloc_bh->b_size, GFP_KERNEL);
+	if (!alloc_copy) {
+		status = -ENOMEM;
+		mlog_errno(status);
+		goto bail;
+	}
+	memcpy(alloc_copy, alloc, osb->local_alloc_bh->b_size);
+
+	status = ocfs2_journal_access(handle, local_alloc_inode,
+				      osb->local_alloc_bh,
+				      OCFS2_JOURNAL_ACCESS_WRITE);
+	if (status < 0) {
+		mlog_errno(status);
+		goto bail;
+	}
+
+	ocfs2_clear_local_alloc(alloc);
+
+	status = ocfs2_journal_dirty(handle, osb->local_alloc_bh);
+	if (status < 0) {
+		mlog_errno(status);
+		goto bail;
+	}
+
+	status = ocfs2_sync_local_to_main(osb, handle, alloc_copy,
+					  main_bm_inode, main_bm_bh);
+	if (status < 0) {
+		mlog_errno(status);
+		goto bail;
+	}
+
+	status = ocfs2_local_alloc_new_window(osb, handle, ac);
+	if (status < 0) {
+		if (status != -ENOSPC)
+			mlog_errno(status);
+		goto bail;
+	}
+
+	atomic_inc(&osb->alloc_stats.moves);
+
+	status = 0;
+bail:
+	if (handle)
+		ocfs2_commit_trans(handle);
+
+	if (main_bm_bh)
+		brelse(main_bm_bh);
+
+	if (main_bm_inode)
+		iput(main_bm_inode);
+
+	if (alloc_copy)
+		kfree(alloc_copy);
+
+	if (ac)
+		ocfs2_free_alloc_context(ac);
+
+	mlog_exit(status);
+	return status;
+}
+