patch-2.4.15 linux/fs/ext3/balloc.c

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diff -u --recursive --new-file v2.4.14/linux/fs/ext3/balloc.c linux/fs/ext3/balloc.c
@@ -0,0 +1,995 @@
+/*
+ *  linux/fs/ext3/balloc.c
+ *
+ * Copyright (C) 1992, 1993, 1994, 1995
+ * Remy Card (card@masi.ibp.fr)
+ * Laboratoire MASI - Institut Blaise Pascal
+ * Universite Pierre et Marie Curie (Paris VI)
+ *
+ *  Enhanced block allocation by Stephen Tweedie (sct@redhat.com), 1993
+ *  Big-endian to little-endian byte-swapping/bitmaps by
+ *        David S. Miller (davem@caip.rutgers.edu), 1995
+ */
+
+#include <linux/config.h>
+#include <linux/sched.h>
+#include <linux/fs.h>
+#include <linux/jbd.h>
+#include <linux/ext3_fs.h>
+#include <linux/ext3_jbd.h>
+#include <linux/locks.h>
+#include <linux/quotaops.h>
+
+/*
+ * balloc.c contains the blocks allocation and deallocation routines
+ */
+
+/*
+ * The free blocks are managed by bitmaps.  A file system contains several
+ * blocks groups.  Each group contains 1 bitmap block for blocks, 1 bitmap
+ * block for inodes, N blocks for the inode table and data blocks.
+ *
+ * The file system contains group descriptors which are located after the
+ * super block.  Each descriptor contains the number of the bitmap block and
+ * the free blocks count in the block.  The descriptors are loaded in memory
+ * when a file system is mounted (see ext3_read_super).
+ */
+
+
+#define in_range(b, first, len)	((b) >= (first) && (b) <= (first) + (len) - 1)
+
+struct ext3_group_desc * ext3_get_group_desc(struct super_block * sb,
+					     unsigned int block_group,
+					     struct buffer_head ** bh)
+{
+	unsigned long group_desc;
+	unsigned long desc;
+	struct ext3_group_desc * gdp;
+
+	if (block_group >= sb->u.ext3_sb.s_groups_count) {
+		ext3_error (sb, "ext3_get_group_desc",
+			    "block_group >= groups_count - "
+			    "block_group = %d, groups_count = %lu",
+			    block_group, sb->u.ext3_sb.s_groups_count);
+
+		return NULL;
+	}
+	
+	group_desc = block_group / EXT3_DESC_PER_BLOCK(sb);
+	desc = block_group % EXT3_DESC_PER_BLOCK(sb);
+	if (!sb->u.ext3_sb.s_group_desc[group_desc]) {
+		ext3_error (sb, "ext3_get_group_desc",
+			    "Group descriptor not loaded - "
+			    "block_group = %d, group_desc = %lu, desc = %lu",
+			     block_group, group_desc, desc);
+		return NULL;
+	}
+	
+	gdp = (struct ext3_group_desc *) 
+	      sb->u.ext3_sb.s_group_desc[group_desc]->b_data;
+	if (bh)
+		*bh = sb->u.ext3_sb.s_group_desc[group_desc];
+	return gdp + desc;
+}
+
+/*
+ * Read the bitmap for a given block_group, reading into the specified 
+ * slot in the superblock's bitmap cache.
+ *
+ * Return >=0 on success or a -ve error code.
+ */
+
+static int read_block_bitmap (struct super_block * sb,
+			       unsigned int block_group,
+			       unsigned long bitmap_nr)
+{
+	struct ext3_group_desc * gdp;
+	struct buffer_head * bh = NULL;
+	int retval = -EIO;
+	
+	gdp = ext3_get_group_desc (sb, block_group, NULL);
+	if (!gdp)
+		goto error_out;
+	retval = 0;
+	bh = bread (sb->s_dev,
+			le32_to_cpu(gdp->bg_block_bitmap), sb->s_blocksize);
+	if (!bh) {
+		ext3_error (sb, "read_block_bitmap",
+			    "Cannot read block bitmap - "
+			    "block_group = %d, block_bitmap = %lu",
+			    block_group, (unsigned long) gdp->bg_block_bitmap);
+		retval = -EIO;
+	}
+	/*
+	 * On IO error, just leave a zero in the superblock's block pointer for
+	 * this group.  The IO will be retried next time.
+	 */
+error_out:
+	sb->u.ext3_sb.s_block_bitmap_number[bitmap_nr] = block_group;
+	sb->u.ext3_sb.s_block_bitmap[bitmap_nr] = bh;
+	return retval;
+}
+
+/*
+ * load_block_bitmap loads the block bitmap for a blocks group
+ *
+ * It maintains a cache for the last bitmaps loaded.  This cache is managed
+ * with a LRU algorithm.
+ *
+ * Notes:
+ * 1/ There is one cache per mounted file system.
+ * 2/ If the file system contains less than EXT3_MAX_GROUP_LOADED groups,
+ *    this function reads the bitmap without maintaining a LRU cache.
+ * 
+ * Return the slot used to store the bitmap, or a -ve error code.
+ */
+static int __load_block_bitmap (struct super_block * sb,
+			        unsigned int block_group)
+{
+	int i, j, retval = 0;
+	unsigned long block_bitmap_number;
+	struct buffer_head * block_bitmap;
+
+	if (block_group >= sb->u.ext3_sb.s_groups_count)
+		ext3_panic (sb, "load_block_bitmap",
+			    "block_group >= groups_count - "
+			    "block_group = %d, groups_count = %lu",
+			    block_group, sb->u.ext3_sb.s_groups_count);
+
+	if (sb->u.ext3_sb.s_groups_count <= EXT3_MAX_GROUP_LOADED) {
+		if (sb->u.ext3_sb.s_block_bitmap[block_group]) {
+			if (sb->u.ext3_sb.s_block_bitmap_number[block_group] ==
+			    block_group)
+				return block_group;
+			ext3_error (sb, "__load_block_bitmap",
+				    "block_group != block_bitmap_number");
+		}
+		retval = read_block_bitmap (sb, block_group, block_group);
+		if (retval < 0)
+			return retval;
+		return block_group;
+	}
+
+	for (i = 0; i < sb->u.ext3_sb.s_loaded_block_bitmaps &&
+		    sb->u.ext3_sb.s_block_bitmap_number[i] != block_group; i++)
+		;
+	if (i < sb->u.ext3_sb.s_loaded_block_bitmaps &&
+  	    sb->u.ext3_sb.s_block_bitmap_number[i] == block_group) {
+		block_bitmap_number = sb->u.ext3_sb.s_block_bitmap_number[i];
+		block_bitmap = sb->u.ext3_sb.s_block_bitmap[i];
+		for (j = i; j > 0; j--) {
+			sb->u.ext3_sb.s_block_bitmap_number[j] =
+				sb->u.ext3_sb.s_block_bitmap_number[j - 1];
+			sb->u.ext3_sb.s_block_bitmap[j] =
+				sb->u.ext3_sb.s_block_bitmap[j - 1];
+		}
+		sb->u.ext3_sb.s_block_bitmap_number[0] = block_bitmap_number;
+		sb->u.ext3_sb.s_block_bitmap[0] = block_bitmap;
+
+		/*
+		 * There's still one special case here --- if block_bitmap == 0
+		 * then our last attempt to read the bitmap failed and we have
+		 * just ended up caching that failure.  Try again to read it.
+		 */
+		if (!block_bitmap)
+			retval = read_block_bitmap (sb, block_group, 0);
+	} else {
+		if (sb->u.ext3_sb.s_loaded_block_bitmaps<EXT3_MAX_GROUP_LOADED)
+			sb->u.ext3_sb.s_loaded_block_bitmaps++;
+		else
+			brelse (sb->u.ext3_sb.s_block_bitmap
+					[EXT3_MAX_GROUP_LOADED - 1]);
+		for (j = sb->u.ext3_sb.s_loaded_block_bitmaps - 1;
+					j > 0;  j--) {
+			sb->u.ext3_sb.s_block_bitmap_number[j] =
+				sb->u.ext3_sb.s_block_bitmap_number[j - 1];
+			sb->u.ext3_sb.s_block_bitmap[j] =
+				sb->u.ext3_sb.s_block_bitmap[j - 1];
+		}
+		retval = read_block_bitmap (sb, block_group, 0);
+	}
+	return retval;
+}
+
+/*
+ * Load the block bitmap for a given block group.  First of all do a couple
+ * of fast lookups for common cases and then pass the request onto the guts
+ * of the bitmap loader.
+ *
+ * Return the slot number of the group in the superblock bitmap cache's on
+ * success, or a -ve error code.
+ *
+ * There is still one inconsistency here --- if the number of groups in this
+ * filesystems is <= EXT3_MAX_GROUP_LOADED, then we have no way of 
+ * differentiating between a group for which we have never performed a bitmap
+ * IO request, and a group for which the last bitmap read request failed.
+ */
+static inline int load_block_bitmap (struct super_block * sb,
+				     unsigned int block_group)
+{
+	int slot;
+	
+	/*
+	 * Do the lookup for the slot.  First of all, check if we're asking
+	 * for the same slot as last time, and did we succeed that last time?
+	 */
+	if (sb->u.ext3_sb.s_loaded_block_bitmaps > 0 &&
+	    sb->u.ext3_sb.s_block_bitmap_number[0] == block_group &&
+	    sb->u.ext3_sb.s_block_bitmap[0]) {
+		return 0;
+	}
+	/*
+	 * Or can we do a fast lookup based on a loaded group on a filesystem
+	 * small enough to be mapped directly into the superblock?
+	 */
+	else if (sb->u.ext3_sb.s_groups_count <= EXT3_MAX_GROUP_LOADED && 
+		 sb->u.ext3_sb.s_block_bitmap_number[block_group]==block_group
+			&& sb->u.ext3_sb.s_block_bitmap[block_group]) {
+		slot = block_group;
+	}
+	/*
+	 * If not, then do a full lookup for this block group.
+	 */
+	else {
+		slot = __load_block_bitmap (sb, block_group);
+	}
+
+	/*
+	 * <0 means we just got an error
+	 */
+	if (slot < 0)
+		return slot;
+	
+	/*
+	 * If it's a valid slot, we may still have cached a previous IO error,
+	 * in which case the bh in the superblock cache will be zero.
+	 */
+	if (!sb->u.ext3_sb.s_block_bitmap[slot])
+		return -EIO;
+	
+	/*
+	 * Must have been read in OK to get this far.
+	 */
+	return slot;
+}
+
+/* Free given blocks, update quota and i_blocks field */
+void ext3_free_blocks (handle_t *handle, struct inode * inode,
+			unsigned long block, unsigned long count)
+{
+	struct buffer_head *bitmap_bh;
+	struct buffer_head *gd_bh;
+	unsigned long block_group;
+	unsigned long bit;
+	unsigned long i;
+	int bitmap_nr;
+	unsigned long overflow;
+	struct super_block * sb;
+	struct ext3_group_desc * gdp;
+	struct ext3_super_block * es;
+	int err = 0, ret;
+	int dquot_freed_blocks = 0;
+
+	sb = inode->i_sb;
+	if (!sb) {
+		printk ("ext3_free_blocks: nonexistent device");
+		return;
+	}
+	lock_super (sb);
+	es = sb->u.ext3_sb.s_es;
+	if (block < le32_to_cpu(es->s_first_data_block) || 
+	    (block + count) > le32_to_cpu(es->s_blocks_count)) {
+		ext3_error (sb, "ext3_free_blocks",
+			    "Freeing blocks not in datazone - "
+			    "block = %lu, count = %lu", block, count);
+		goto error_return;
+	}
+
+	ext3_debug ("freeing block %lu\n", block);
+
+do_more:
+	overflow = 0;
+	block_group = (block - le32_to_cpu(es->s_first_data_block)) /
+		      EXT3_BLOCKS_PER_GROUP(sb);
+	bit = (block - le32_to_cpu(es->s_first_data_block)) %
+		      EXT3_BLOCKS_PER_GROUP(sb);
+	/*
+	 * Check to see if we are freeing blocks across a group
+	 * boundary.
+	 */
+	if (bit + count > EXT3_BLOCKS_PER_GROUP(sb)) {
+		overflow = bit + count - EXT3_BLOCKS_PER_GROUP(sb);
+		count -= overflow;
+	}
+	bitmap_nr = load_block_bitmap (sb, block_group);
+	if (bitmap_nr < 0)
+		goto error_return;
+	
+	bitmap_bh = sb->u.ext3_sb.s_block_bitmap[bitmap_nr];
+	gdp = ext3_get_group_desc (sb, block_group, &gd_bh);
+	if (!gdp)
+		goto error_return;
+
+	if (in_range (le32_to_cpu(gdp->bg_block_bitmap), block, count) ||
+	    in_range (le32_to_cpu(gdp->bg_inode_bitmap), block, count) ||
+	    in_range (block, le32_to_cpu(gdp->bg_inode_table),
+		      sb->u.ext3_sb.s_itb_per_group) ||
+	    in_range (block + count - 1, le32_to_cpu(gdp->bg_inode_table),
+		      sb->u.ext3_sb.s_itb_per_group))
+		ext3_error (sb, "ext3_free_blocks",
+			    "Freeing blocks in system zones - "
+			    "Block = %lu, count = %lu",
+			    block, count);
+
+	/*
+	 * We are about to start releasing blocks in the bitmap,
+	 * so we need undo access.
+	 */
+	/* @@@ check errors */
+	BUFFER_TRACE(bitmap_bh, "getting undo access");
+	err = ext3_journal_get_undo_access(handle, bitmap_bh);
+	if (err)
+		goto error_return;
+	
+	/*
+	 * We are about to modify some metadata.  Call the journal APIs
+	 * to unshare ->b_data if a currently-committing transaction is
+	 * using it
+	 */
+	BUFFER_TRACE(gd_bh, "get_write_access");
+	err = ext3_journal_get_write_access(handle, gd_bh);	
+	if (err)
+		goto error_return;
+
+	BUFFER_TRACE(sb->u.ext3_sb.s_sbh, "get_write_access");
+	err = ext3_journal_get_write_access(handle, sb->u.ext3_sb.s_sbh);
+	if (err)
+		goto error_return;
+
+	for (i = 0; i < count; i++) {
+		/*
+		 * An HJ special.  This is expensive...
+		 */
+#ifdef CONFIG_JBD_DEBUG
+		{
+			struct buffer_head *debug_bh;
+			debug_bh = get_hash_table(sb->s_dev, block + i,
+							sb->s_blocksize);
+			if (debug_bh) {
+				BUFFER_TRACE(debug_bh, "Deleted!");
+				if (!bh2jh(bitmap_bh)->b_committed_data)
+					BUFFER_TRACE(debug_bh,
+						"No commited data in bitmap");
+				BUFFER_TRACE2(debug_bh, bitmap_bh, "bitmap");
+				__brelse(debug_bh);
+			}
+		}
+#endif
+		BUFFER_TRACE(bitmap_bh, "clear bit");
+		if (!ext3_clear_bit (bit + i, bitmap_bh->b_data)) {
+			ext3_error (sb, __FUNCTION__,
+				      "bit already cleared for block %lu", 
+				      block + i);
+			BUFFER_TRACE(bitmap_bh, "bit already cleared");
+		} else {
+			dquot_freed_blocks++;
+			gdp->bg_free_blocks_count =
+			  cpu_to_le16(le16_to_cpu(gdp->bg_free_blocks_count)+1);
+			es->s_free_blocks_count =
+			  cpu_to_le32(le32_to_cpu(es->s_free_blocks_count)+1);
+		}
+		/* @@@ This prevents newly-allocated data from being
+		 * freed and then reallocated within the same
+		 * transaction. 
+		 * 
+		 * Ideally we would want to allow that to happen, but to
+		 * do so requires making journal_forget() capable of
+		 * revoking the queued write of a data block, which
+		 * implies blocking on the journal lock.  *forget()
+		 * cannot block due to truncate races.
+		 *
+		 * Eventually we can fix this by making journal_forget()
+		 * return a status indicating whether or not it was able
+		 * to revoke the buffer.  On successful revoke, it is
+		 * safe not to set the allocation bit in the committed
+		 * bitmap, because we know that there is no outstanding
+		 * activity on the buffer any more and so it is safe to
+		 * reallocate it.  
+		 */
+		BUFFER_TRACE(bitmap_bh, "clear in b_committed_data");
+		J_ASSERT_BH(bitmap_bh,
+				bh2jh(bitmap_bh)->b_committed_data != NULL);
+		ext3_set_bit(bit + i, bh2jh(bitmap_bh)->b_committed_data);
+	}
+
+	/* We dirtied the bitmap block */
+	BUFFER_TRACE(bitmap_bh, "dirtied bitmap block");
+	err = ext3_journal_dirty_metadata(handle, bitmap_bh);
+
+	/* And the group descriptor block */
+	BUFFER_TRACE(gd_bh, "dirtied group descriptor block");
+	ret = ext3_journal_dirty_metadata(handle, gd_bh);
+	if (!err) err = ret;
+
+	/* And the superblock */
+	BUFFER_TRACE(sb->u.ext3_sb.s_sbh, "dirtied superblock");
+	ret = ext3_journal_dirty_metadata(handle, sb->u.ext3_sb.s_sbh);
+	if (!err) err = ret;
+
+	if (overflow && !err) {
+		block += count;
+		count = overflow;
+		goto do_more;
+	}
+	sb->s_dirt = 1;
+error_return:
+	ext3_std_error(sb, err);
+	unlock_super(sb);
+	if (dquot_freed_blocks)
+		DQUOT_FREE_BLOCK(inode, dquot_freed_blocks);
+	return;
+}
+
+/* For ext3 allocations, we must not reuse any blocks which are
+ * allocated in the bitmap buffer's "last committed data" copy.  This
+ * prevents deletes from freeing up the page for reuse until we have
+ * committed the delete transaction.
+ *
+ * If we didn't do this, then deleting something and reallocating it as
+ * data would allow the old block to be overwritten before the
+ * transaction committed (because we force data to disk before commit).
+ * This would lead to corruption if we crashed between overwriting the
+ * data and committing the delete. 
+ *
+ * @@@ We may want to make this allocation behaviour conditional on
+ * data-writes at some point, and disable it for metadata allocations or
+ * sync-data inodes.
+ */
+static int ext3_test_allocatable(int nr, struct buffer_head *bh)
+{
+	if (ext3_test_bit(nr, bh->b_data))
+		return 0;
+	if (!buffer_jbd(bh) || !bh2jh(bh)->b_committed_data)
+		return 1;
+	return !ext3_test_bit(nr, bh2jh(bh)->b_committed_data);
+}
+
+/*
+ * Find an allocatable block in a bitmap.  We honour both the bitmap and
+ * its last-committed copy (if that exists), and perform the "most
+ * appropriate allocation" algorithm of looking for a free block near
+ * the initial goal; then for a free byte somewhere in the bitmap; then
+ * for any free bit in the bitmap.
+ */
+static int find_next_usable_block(int start,
+			struct buffer_head *bh, int maxblocks)
+{
+	int here, next;
+	char *p, *r;
+	
+	if (start > 0) {
+		/*
+		 * The goal was occupied; search forward for a free 
+		 * block within the next XX blocks.
+		 *
+		 * end_goal is more or less random, but it has to be
+		 * less than EXT3_BLOCKS_PER_GROUP. Aligning up to the
+		 * next 64-bit boundary is simple..
+		 */
+		int end_goal = (start + 63) & ~63;
+		here = ext3_find_next_zero_bit(bh->b_data, end_goal, start);
+		if (here < end_goal && ext3_test_allocatable(here, bh))
+			return here;
+		
+		ext3_debug ("Bit not found near goal\n");
+		
+	}
+	
+	here = start;
+	if (here < 0)
+		here = 0;
+	
+	/*
+	 * There has been no free block found in the near vicinity of
+	 * the goal: do a search forward through the block groups,
+	 * searching in each group first for an entire free byte in the
+	 * bitmap and then for any free bit.
+	 * 
+	 * Search first in the remainder of the current group 
+	 */
+	p = ((char *) bh->b_data) + (here >> 3);
+	r = memscan(p, 0, (maxblocks - here + 7) >> 3);
+	next = (r - ((char *) bh->b_data)) << 3;
+	
+	if (next < maxblocks && ext3_test_allocatable(next, bh))
+		return next;
+	
+	/* The bitmap search --- search forward alternately
+	 * through the actual bitmap and the last-committed copy
+	 * until we find a bit free in both. */
+
+	while (here < maxblocks) {
+		next  = ext3_find_next_zero_bit ((unsigned long *) bh->b_data, 
+						 maxblocks, here);
+		if (next >= maxblocks)
+			return -1;
+		if (ext3_test_allocatable(next, bh))
+			return next;
+
+		J_ASSERT_BH(bh, bh2jh(bh)->b_committed_data);
+		here = ext3_find_next_zero_bit
+			((unsigned long *) bh2jh(bh)->b_committed_data, 
+			 maxblocks, next);
+	}
+	return -1;
+}
+
+/*
+ * ext3_new_block uses a goal block to assist allocation.  If the goal is
+ * free, or there is a free block within 32 blocks of the goal, that block
+ * is allocated.  Otherwise a forward search is made for a free block; within 
+ * each block group the search first looks for an entire free byte in the block
+ * bitmap, and then for any free bit if that fails.
+ * This function also updates quota and i_blocks field.
+ */
+int ext3_new_block (handle_t *handle, struct inode * inode,
+		unsigned long goal, u32 * prealloc_count,
+		u32 * prealloc_block, int * errp)
+{
+	struct buffer_head * bh, *bhtmp;
+	struct buffer_head * bh2;
+#if 0
+	char * p, * r;
+#endif
+	int i, j, k, tmp, alloctmp;
+	int bitmap_nr;
+	int fatal = 0, err;
+	struct super_block * sb;
+	struct ext3_group_desc * gdp;
+	struct ext3_super_block * es;
+#ifdef EXT3FS_DEBUG
+	static int goal_hits = 0, goal_attempts = 0;
+#endif
+	*errp = -ENOSPC;
+	sb = inode->i_sb;
+	if (!sb) {
+		printk ("ext3_new_block: nonexistent device");
+		return 0;
+	}
+
+	/*
+	 * Check quota for allocation of this block.
+	 */
+	if (DQUOT_ALLOC_BLOCK(inode, 1)) {
+		*errp = -EDQUOT;
+		return 0;
+	}
+
+	lock_super (sb);
+	es = sb->u.ext3_sb.s_es;
+	if (le32_to_cpu(es->s_free_blocks_count) <=
+			le32_to_cpu(es->s_r_blocks_count) &&
+	    ((sb->u.ext3_sb.s_resuid != current->fsuid) &&
+	     (sb->u.ext3_sb.s_resgid == 0 ||
+	      !in_group_p (sb->u.ext3_sb.s_resgid)) && 
+	     !capable(CAP_SYS_RESOURCE)))
+		goto out;
+
+	ext3_debug ("goal=%lu.\n", goal);
+
+	/*
+	 * First, test whether the goal block is free.
+	 */
+	if (goal < le32_to_cpu(es->s_first_data_block) ||
+	    goal >= le32_to_cpu(es->s_blocks_count))
+		goal = le32_to_cpu(es->s_first_data_block);
+	i = (goal - le32_to_cpu(es->s_first_data_block)) /
+			EXT3_BLOCKS_PER_GROUP(sb);
+	gdp = ext3_get_group_desc (sb, i, &bh2);
+	if (!gdp)
+		goto io_error;
+
+	if (le16_to_cpu(gdp->bg_free_blocks_count) > 0) {
+		j = ((goal - le32_to_cpu(es->s_first_data_block)) %
+				EXT3_BLOCKS_PER_GROUP(sb));
+#ifdef EXT3FS_DEBUG
+		if (j)
+			goal_attempts++;
+#endif
+		bitmap_nr = load_block_bitmap (sb, i);
+		if (bitmap_nr < 0)
+			goto io_error;
+		
+		bh = sb->u.ext3_sb.s_block_bitmap[bitmap_nr];
+
+		ext3_debug ("goal is at %d:%d.\n", i, j);
+
+		if (ext3_test_allocatable(j, bh)) {
+#ifdef EXT3FS_DEBUG
+			goal_hits++;
+			ext3_debug ("goal bit allocated.\n");
+#endif
+			goto got_block;
+		}
+
+		j = find_next_usable_block(j, bh, EXT3_BLOCKS_PER_GROUP(sb));
+		if (j >= 0)
+			goto search_back;
+	}
+
+	ext3_debug ("Bit not found in block group %d.\n", i);
+
+	/*
+	 * Now search the rest of the groups.  We assume that 
+	 * i and gdp correctly point to the last group visited.
+	 */
+	for (k = 0; k < sb->u.ext3_sb.s_groups_count; k++) {
+		i++;
+		if (i >= sb->u.ext3_sb.s_groups_count)
+			i = 0;
+		gdp = ext3_get_group_desc (sb, i, &bh2);
+		if (!gdp) {
+			*errp = -EIO;
+			goto out;
+		}
+		if (le16_to_cpu(gdp->bg_free_blocks_count) > 0) {
+			bitmap_nr = load_block_bitmap (sb, i);
+			if (bitmap_nr < 0)
+				goto io_error;
+	
+			bh = sb->u.ext3_sb.s_block_bitmap[bitmap_nr];
+			j = find_next_usable_block(-1, bh, 
+						   EXT3_BLOCKS_PER_GROUP(sb));
+			if (j >= 0) 
+				goto search_back;
+		}
+	}
+
+	/* No space left on the device */
+	unlock_super (sb);
+	return 0;
+
+search_back:
+	/* 
+	 * We have succeeded in finding a free byte in the block
+	 * bitmap.  Now search backwards up to 7 bits to find the
+	 * start of this group of free blocks.
+	 */
+	for (	k = 0;
+		k < 7 && j > 0 && ext3_test_allocatable(j - 1, bh);
+		k++, j--)
+		;
+	
+got_block:
+
+	ext3_debug ("using block group %d(%d)\n", i, gdp->bg_free_blocks_count);
+
+	/* Make sure we use undo access for the bitmap, because it is
+           critical that we do the frozen_data COW on bitmap buffers in
+           all cases even if the buffer is in BJ_Forget state in the
+           committing transaction.  */
+	BUFFER_TRACE(bh, "get undo access for marking new block");
+	fatal = ext3_journal_get_undo_access(handle, bh);
+	if (fatal) goto out;
+	
+	BUFFER_TRACE(bh2, "get_write_access");
+	fatal = ext3_journal_get_write_access(handle, bh2);
+	if (fatal) goto out;
+
+	BUFFER_TRACE(sb->u.ext3_sb.s_sbh, "get_write_access");
+	fatal = ext3_journal_get_write_access(handle, sb->u.ext3_sb.s_sbh);
+	if (fatal) goto out;
+
+	tmp = j + i * EXT3_BLOCKS_PER_GROUP(sb)
+				+ le32_to_cpu(es->s_first_data_block);
+
+	if (tmp == le32_to_cpu(gdp->bg_block_bitmap) ||
+	    tmp == le32_to_cpu(gdp->bg_inode_bitmap) ||
+	    in_range (tmp, le32_to_cpu(gdp->bg_inode_table),
+		      sb->u.ext3_sb.s_itb_per_group))
+		ext3_error (sb, "ext3_new_block",
+			    "Allocating block in system zone - "
+			    "block = %u", tmp);
+
+	/* The superblock lock should guard against anybody else beating
+	 * us to this point! */
+	J_ASSERT_BH(bh, !ext3_test_bit(j, bh->b_data));
+	BUFFER_TRACE(bh, "setting bitmap bit");
+	ext3_set_bit(j, bh->b_data);
+
+#ifdef CONFIG_JBD_DEBUG
+	{
+		struct buffer_head *debug_bh;
+
+		/* Record bitmap buffer state in the newly allocated block */
+		debug_bh = get_hash_table(sb->s_dev, tmp, sb->s_blocksize);
+		if (debug_bh) {
+			BUFFER_TRACE(debug_bh, "state when allocated");
+			BUFFER_TRACE2(debug_bh, bh, "bitmap state");
+			brelse(debug_bh);
+		}
+	}
+#endif
+	if (buffer_jbd(bh) && bh2jh(bh)->b_committed_data)
+		J_ASSERT_BH(bh, !ext3_test_bit(j, bh2jh(bh)->b_committed_data));
+	bhtmp = bh;
+	alloctmp = j;
+
+	ext3_debug ("found bit %d\n", j);
+
+	/*
+	 * Do block preallocation now if required.
+	 */
+#ifdef EXT3_PREALLOCATE
+	/*
+	 * akpm: this is not enabled for ext3.  Need to use
+	 * ext3_test_allocatable()
+	 */
+	/* Writer: ->i_prealloc* */
+	if (prealloc_count && !*prealloc_count) {
+		int	prealloc_goal;
+		unsigned long next_block = tmp + 1;
+
+		prealloc_goal = es->s_prealloc_blocks ?
+			es->s_prealloc_blocks : EXT3_DEFAULT_PREALLOC_BLOCKS;
+
+		*prealloc_block = next_block;
+		/* Writer: end */
+		for (k = 1;
+		     k < prealloc_goal && (j + k) < EXT3_BLOCKS_PER_GROUP(sb);
+		     k++, next_block++) {
+			if (DQUOT_PREALLOC_BLOCK(inode, 1))
+				break;
+			/* Writer: ->i_prealloc* */
+			if (*prealloc_block + *prealloc_count != next_block ||
+			    ext3_set_bit (j + k, bh->b_data)) {
+				/* Writer: end */
+				DQUOT_FREE_BLOCK(inode, 1);
+ 				break;
+			}
+			(*prealloc_count)++;
+			/* Writer: end */
+		}	
+		/*
+		 * As soon as we go for per-group spinlocks we'll need these
+		 * done inside the loop above.
+		 */
+		gdp->bg_free_blocks_count =
+			cpu_to_le16(le16_to_cpu(gdp->bg_free_blocks_count) -
+			       (k - 1));
+		es->s_free_blocks_count =
+			cpu_to_le32(le32_to_cpu(es->s_free_blocks_count) -
+			       (k - 1));
+		ext3_debug ("Preallocated a further %lu bits.\n",
+			       (k - 1));
+	}
+#endif
+
+	j = tmp;
+
+	BUFFER_TRACE(bh, "journal_dirty_metadata for bitmap block");
+	err = ext3_journal_dirty_metadata(handle, bh);
+	if (!fatal) fatal = err;
+	
+	if (j >= le32_to_cpu(es->s_blocks_count)) {
+		ext3_error (sb, "ext3_new_block",
+			    "block(%d) >= blocks count(%d) - "
+			    "block_group = %d, es == %p ",j,
+			le32_to_cpu(es->s_blocks_count), i, es);
+		goto out;
+	}
+
+	/*
+	 * It is up to the caller to add the new buffer to a journal
+	 * list of some description.  We don't know in advance whether
+	 * the caller wants to use it as metadata or data.
+	 */
+
+	ext3_debug ("allocating block %d. "
+		    "Goal hits %d of %d.\n", j, goal_hits, goal_attempts);
+
+	gdp->bg_free_blocks_count =
+			cpu_to_le16(le16_to_cpu(gdp->bg_free_blocks_count) - 1);
+	es->s_free_blocks_count =
+			cpu_to_le32(le32_to_cpu(es->s_free_blocks_count) - 1);
+
+	BUFFER_TRACE(bh2, "journal_dirty_metadata for group descriptor");
+	err = ext3_journal_dirty_metadata(handle, bh2);
+	if (!fatal) fatal = err;
+	
+	BUFFER_TRACE(bh, "journal_dirty_metadata for superblock");
+	err = ext3_journal_dirty_metadata(handle, sb->u.ext3_sb.s_sbh);
+	if (!fatal) fatal = err;
+
+	sb->s_dirt = 1;
+	if (fatal)
+		goto out;
+
+	unlock_super (sb);
+	*errp = 0;
+	return j;
+	
+io_error:
+	*errp = -EIO;
+out:
+	if (fatal) {
+		*errp = fatal;
+		ext3_std_error(sb, fatal);
+	}
+	unlock_super (sb);
+	return 0;
+	
+}
+
+unsigned long ext3_count_free_blocks (struct super_block * sb)
+{
+#ifdef EXT3FS_DEBUG
+	struct ext3_super_block * es;
+	unsigned long desc_count, bitmap_count, x;
+	int bitmap_nr;
+	struct ext3_group_desc * gdp;
+	int i;
+	
+	lock_super (sb);
+	es = sb->u.ext3_sb.s_es;
+	desc_count = 0;
+	bitmap_count = 0;
+	gdp = NULL;
+	for (i = 0; i < sb->u.ext3_sb.s_groups_count; i++) {
+		gdp = ext3_get_group_desc (sb, i, NULL);
+		if (!gdp)
+			continue;
+		desc_count += le16_to_cpu(gdp->bg_free_blocks_count);
+		bitmap_nr = load_block_bitmap (sb, i);
+		if (bitmap_nr < 0)
+			continue;
+		
+		x = ext3_count_free (sb->u.ext3_sb.s_block_bitmap[bitmap_nr],
+				     sb->s_blocksize);
+		printk ("group %d: stored = %d, counted = %lu\n",
+			i, le16_to_cpu(gdp->bg_free_blocks_count), x);
+		bitmap_count += x;
+	}
+	printk("ext3_count_free_blocks: stored = %lu, computed = %lu, %lu\n",
+	       le32_to_cpu(es->s_free_blocks_count), desc_count, bitmap_count);
+	unlock_super (sb);
+	return bitmap_count;
+#else
+	return le32_to_cpu(sb->u.ext3_sb.s_es->s_free_blocks_count);
+#endif
+}
+
+static inline int block_in_use (unsigned long block,
+				struct super_block * sb,
+				unsigned char * map)
+{
+	return ext3_test_bit ((block -
+		le32_to_cpu(sb->u.ext3_sb.s_es->s_first_data_block)) %
+			 EXT3_BLOCKS_PER_GROUP(sb), map);
+}
+
+static inline int test_root(int a, int b)
+{
+	if (a == 0)
+		return 1;
+	while (1) {
+		if (a == 1)
+			return 1;
+		if (a % b)
+			return 0;
+		a = a / b;
+	}
+}
+
+int ext3_group_sparse(int group)
+{
+	return (test_root(group, 3) || test_root(group, 5) ||
+		test_root(group, 7));
+}
+
+/**
+ *	ext3_bg_has_super - number of blocks used by the superblock in group
+ *	@sb: superblock for filesystem
+ *	@group: group number to check
+ *
+ *	Return the number of blocks used by the superblock (primary or backup)
+ *	in this group.  Currently this will be only 0 or 1.
+ */
+int ext3_bg_has_super(struct super_block *sb, int group)
+{
+	if (EXT3_HAS_RO_COMPAT_FEATURE(sb,EXT3_FEATURE_RO_COMPAT_SPARSE_SUPER)&&
+	    !ext3_group_sparse(group))
+		return 0;
+	return 1;
+}
+
+/**
+ *	ext3_bg_num_gdb - number of blocks used by the group table in group
+ *	@sb: superblock for filesystem
+ *	@group: group number to check
+ *
+ *	Return the number of blocks used by the group descriptor table
+ *	(primary or backup) in this group.  In the future there may be a
+ *	different number of descriptor blocks in each group.
+ */
+unsigned long ext3_bg_num_gdb(struct super_block *sb, int group)
+{
+	if (EXT3_HAS_RO_COMPAT_FEATURE(sb,EXT3_FEATURE_RO_COMPAT_SPARSE_SUPER)&&
+	    !ext3_group_sparse(group))
+		return 0;
+	return EXT3_SB(sb)->s_gdb_count;
+}
+
+#ifdef CONFIG_EXT3_CHECK
+/* Called at mount-time, super-block is locked */
+void ext3_check_blocks_bitmap (struct super_block * sb)
+{
+	struct buffer_head * bh;
+	struct ext3_super_block * es;
+	unsigned long desc_count, bitmap_count, x, j;
+	unsigned long desc_blocks;
+	int bitmap_nr;
+	struct ext3_group_desc * gdp;
+	int i;
+
+	es = sb->u.ext3_sb.s_es;
+	desc_count = 0;
+	bitmap_count = 0;
+	gdp = NULL;
+	for (i = 0; i < sb->u.ext3_sb.s_groups_count; i++) {
+		gdp = ext3_get_group_desc (sb, i, NULL);
+		if (!gdp)
+			continue;
+		desc_count += le16_to_cpu(gdp->bg_free_blocks_count);
+		bitmap_nr = load_block_bitmap (sb, i);
+		if (bitmap_nr < 0)
+			continue;
+
+		bh = EXT3_SB(sb)->s_block_bitmap[bitmap_nr];
+
+		if (ext3_bg_has_super(sb, i) && !ext3_test_bit(0, bh->b_data))
+			ext3_error(sb, __FUNCTION__,
+				   "Superblock in group %d is marked free", i);
+
+		desc_blocks = ext3_bg_num_gdb(sb, i);
+		for (j = 0; j < desc_blocks; j++)
+			if (!ext3_test_bit(j + 1, bh->b_data))
+				ext3_error(sb, __FUNCTION__,
+					   "Descriptor block #%ld in group "
+					   "%d is marked free", j, i);
+
+		if (!block_in_use (le32_to_cpu(gdp->bg_block_bitmap),
+						sb, bh->b_data))
+			ext3_error (sb, "ext3_check_blocks_bitmap",
+				    "Block bitmap for group %d is marked free",
+				    i);
+
+		if (!block_in_use (le32_to_cpu(gdp->bg_inode_bitmap),
+						sb, bh->b_data))
+			ext3_error (sb, "ext3_check_blocks_bitmap",
+				    "Inode bitmap for group %d is marked free",
+				    i);
+
+		for (j = 0; j < sb->u.ext3_sb.s_itb_per_group; j++)
+			if (!block_in_use (le32_to_cpu(gdp->bg_inode_table) + j,
+							sb, bh->b_data))
+				ext3_error (sb, "ext3_check_blocks_bitmap",
+					    "Block #%d of the inode table in "
+					    "group %d is marked free", j, i);
+
+		x = ext3_count_free (bh, sb->s_blocksize);
+		if (le16_to_cpu(gdp->bg_free_blocks_count) != x)
+			ext3_error (sb, "ext3_check_blocks_bitmap",
+				    "Wrong free blocks count for group %d, "
+				    "stored = %d, counted = %lu", i,
+				    le16_to_cpu(gdp->bg_free_blocks_count), x);
+		bitmap_count += x;
+	}
+	if (le32_to_cpu(es->s_free_blocks_count) != bitmap_count)
+		ext3_error (sb, "ext3_check_blocks_bitmap",
+			"Wrong free blocks count in super block, "
+			"stored = %lu, counted = %lu",
+			(unsigned long)le32_to_cpu(es->s_free_blocks_count),
+			bitmap_count);
+}
+#endif
FUNET's LINUX-ADM group, linux-adm@nic.funet.fi
TCL-scripts by Sam Shen (who was at: slshen@lbl.gov)