ext2 reservations

Val's cross-port of the ext3 reservations code into ext2.

[mbligh@mbligh.org: Small type error for printk
[akpm@linux-foundation.org: fix types, sync with ext3]
[mbligh@mbligh.org: Bring ext2 reservations code in line with latest ext3]
[akpm@linux-foundation.org: kill noisy printk]
[akpm@linux-foundation.org: remember to dirty the gdp's block]
[akpm@linux-foundation.org: cross-port the missed 5dea5176e5c32ef9f0d1a41d28427b3bf6881b3a]
[akpm@linux-foundation.org: cross-port e6022603b9aa7d61d20b392e69edcdbbc1789969]
[akpm@linux-foundation.org: Port the omitted 08fb306fe63d98eb86e3b16f4cc21816fa47f18e]
[akpm@linux-foundation.org: Backport the missed 20acaa18d0c002fec180956f87adeb3f11f635a6]
[akpm@linux-foundation.org: fixes]
[cmm@us.ibm.com: fix reservation extension]
[bunk@stusta.de: make ext2_get_blocks() static]
[hugh@veritas.com: fix hang]
[hugh@veritas.com: ext2_new_blocks should reset the reservation window size]
[hugh@veritas.com: ext2 balloc: fix off-by-one against rsv_end]
[hugh@veritas.com: grp_goal 0 is a genuine goal (unlike -1), so ext2_try_to_allocate_with_rsv should treat it as such]
[hugh@veritas.com: rbtree usage cleanup]
[pbadari@us.ibm.com: Fix for ext2 reservation]
[bunk@kernel.org: remove fs/ext2/balloc.c:reserve_blocks()]
[hugh@veritas.com: ext2 balloc: use io_error label]
Cc: "Martin J. Bligh" <mbligh@mbligh.org>
Cc: Valerie Henson <val_henson@linux.intel.com>
Cc: Mingming Cao <cmm@us.ibm.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Badari Pulavarty <pbadari@us.ibm.com>
Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1072 insertions, 233 deletions

diff --git a/fs/ext2/balloc.c b/fs/ext2/balloc.c
index ffaa6d8..18a42de 100644
--- a/fs/ext2/balloc.c
+++ b/fs/ext2/balloc.c
@@ -133,41 +133,6 @@ error_out:
 	return NULL;
 }
 
-/*
- * Set sb->s_dirt here because the superblock was "logically" altered.  We
- * need to recalculate its free blocks count and flush it out.
- */
-static int reserve_blocks(struct super_block *sb, int count)
-{
-	struct ext2_sb_info *sbi = EXT2_SB(sb);
-	struct ext2_super_block *es = sbi->s_es;
-	unsigned free_blocks;
-	unsigned root_blocks;
-
-	free_blocks = percpu_counter_read_positive(&sbi->s_freeblocks_counter);
-	root_blocks = le32_to_cpu(es->s_r_blocks_count);
-
-	if (free_blocks < count)
-		count = free_blocks;
-
-	if (free_blocks < root_blocks + count && !capable(CAP_SYS_RESOURCE) &&
-	    sbi->s_resuid != current->fsuid &&
-	    (sbi->s_resgid == 0 || !in_group_p (sbi->s_resgid))) {
-		/*
-		 * We are too close to reserve and we are not privileged.
-		 * Can we allocate anything at all?
-		 */
-		if (free_blocks > root_blocks)
-			count = free_blocks - root_blocks;
-		else
-			return 0;
-	}
-
-	percpu_counter_sub(&sbi->s_freeblocks_counter, count);
-	sb->s_dirt = 1;
-	return count;
-}
-
 static void release_blocks(struct super_block *sb, int count)
 {
 	if (count) {
@@ -178,25 +143,7 @@ static void release_blocks(struct super_block *sb, int count)
 	}
 }
 
-static int group_reserve_blocks(struct ext2_sb_info *sbi, int group_no,
-	struct ext2_group_desc *desc, struct buffer_head *bh, int count)
-{
-	unsigned free_blocks;
-
-	if (!desc->bg_free_blocks_count)
-		return 0;
-
-	spin_lock(sb_bgl_lock(sbi, group_no));
-	free_blocks = le16_to_cpu(desc->bg_free_blocks_count);
-	if (free_blocks < count)
-		count = free_blocks;
-	desc->bg_free_blocks_count = cpu_to_le16(free_blocks - count);
-	spin_unlock(sb_bgl_lock(sbi, group_no));
-	mark_buffer_dirty(bh);
-	return count;
-}
-
-static void group_release_blocks(struct super_block *sb, int group_no,
+static void group_adjust_blocks(struct super_block *sb, int group_no,
 	struct ext2_group_desc *desc, struct buffer_head *bh, int count)
 {
 	if (count) {
@@ -212,7 +159,306 @@ static void group_release_blocks(struct super_block *sb, int group_no,
 	}
 }
 
-/* Free given blocks, update quota and i_blocks field */
+/*
+ * The reservation window structure operations
+ * --------------------------------------------
+ * Operations include:
+ * dump, find, add, remove, is_empty, find_next_reservable_window, etc.
+ *
+ * We use a red-black tree to represent per-filesystem reservation
+ * windows.
+ *
+ */
+
+/**
+ * __rsv_window_dump() -- Dump the filesystem block allocation reservation map
+ * @rb_root:		root of per-filesystem reservation rb tree
+ * @verbose:		verbose mode
+ * @fn:			function which wishes to dump the reservation map
+ *
+ * If verbose is turned on, it will print the whole block reservation
+ * windows(start, end). Otherwise, it will only print out the "bad" windows,
+ * those windows that overlap with their immediate neighbors.
+ */
+#if 1
+static void __rsv_window_dump(struct rb_root *root, int verbose,
+			      const char *fn)
+{
+	struct rb_node *n;
+	struct ext2_reserve_window_node *rsv, *prev;
+	int bad;
+
+restart:
+	n = rb_first(root);
+	bad = 0;
+	prev = NULL;
+
+	printk("Block Allocation Reservation Windows Map (%s):\n", fn);
+	while (n) {
+		rsv = rb_entry(n, struct ext2_reserve_window_node, rsv_node);
+		if (verbose)
+			printk("reservation window 0x%p "
+				"start: %lu, end: %lu\n",
+				rsv, rsv->rsv_start, rsv->rsv_end);
+		if (rsv->rsv_start && rsv->rsv_start >= rsv->rsv_end) {
+			printk("Bad reservation %p (start >= end)\n",
+			       rsv);
+			bad = 1;
+		}
+		if (prev && prev->rsv_end >= rsv->rsv_start) {
+			printk("Bad reservation %p (prev->end >= start)\n",
+			       rsv);
+			bad = 1;
+		}
+		if (bad) {
+			if (!verbose) {
+				printk("Restarting reservation walk in verbose mode\n");
+				verbose = 1;
+				goto restart;
+			}
+		}
+		n = rb_next(n);
+		prev = rsv;
+	}
+	printk("Window map complete.\n");
+	if (bad)
+		BUG();
+}
+#define rsv_window_dump(root, verbose) \
+	__rsv_window_dump((root), (verbose), __FUNCTION__)
+#else
+#define rsv_window_dump(root, verbose) do {} while (0)
+#endif
+
+/**
+ * goal_in_my_reservation()
+ * @rsv:		inode's reservation window
+ * @grp_goal:		given goal block relative to the allocation block group
+ * @group:		the current allocation block group
+ * @sb:			filesystem super block
+ *
+ * Test if the given goal block (group relative) is within the file's
+ * own block reservation window range.
+ *
+ * If the reservation window is outside the goal allocation group, return 0;
+ * grp_goal (given goal block) could be -1, which means no specific
+ * goal block. In this case, always return 1.
+ * If the goal block is within the reservation window, return 1;
+ * otherwise, return 0;
+ */
+static int
+goal_in_my_reservation(struct ext2_reserve_window *rsv, ext2_grpblk_t grp_goal,
+			unsigned int group, struct super_block * sb)
+{
+	ext2_fsblk_t group_first_block, group_last_block;
+
+	group_first_block = ext2_group_first_block_no(sb, group);
+	group_last_block = group_first_block + EXT2_BLOCKS_PER_GROUP(sb) - 1;
+
+	if ((rsv->_rsv_start > group_last_block) ||
+	    (rsv->_rsv_end < group_first_block))
+		return 0;
+	if ((grp_goal >= 0) && ((grp_goal + group_first_block < rsv->_rsv_start)
+		|| (grp_goal + group_first_block > rsv->_rsv_end)))
+		return 0;
+	return 1;
+}
+
+/**
+ * search_reserve_window()
+ * @rb_root:		root of reservation tree
+ * @goal:		target allocation block
+ *
+ * Find the reserved window which includes the goal, or the previous one
+ * if the goal is not in any window.
+ * Returns NULL if there are no windows or if all windows start after the goal.
+ */
+static struct ext2_reserve_window_node *
+search_reserve_window(struct rb_root *root, ext2_fsblk_t goal)
+{
+	struct rb_node *n = root->rb_node;
+	struct ext2_reserve_window_node *rsv;
+
+	if (!n)
+		return NULL;
+
+	do {
+		rsv = rb_entry(n, struct ext2_reserve_window_node, rsv_node);
+
+		if (goal < rsv->rsv_start)
+			n = n->rb_left;
+		else if (goal > rsv->rsv_end)
+			n = n->rb_right;
+		else
+			return rsv;
+	} while (n);
+	/*
+	 * We've fallen off the end of the tree: the goal wasn't inside
+	 * any particular node.  OK, the previous node must be to one
+	 * side of the interval containing the goal.  If it's the RHS,
+	 * we need to back up one.
+	 */
+	if (rsv->rsv_start > goal) {
+		n = rb_prev(&rsv->rsv_node);
+		rsv = rb_entry(n, struct ext2_reserve_window_node, rsv_node);
+	}
+	return rsv;
+}
+
+/*
+ * ext2_rsv_window_add() -- Insert a window to the block reservation rb tree.
+ * @sb:			super block
+ * @rsv:		reservation window to add
+ *
+ * Must be called with rsv_lock held.
+ */
+void ext2_rsv_window_add(struct super_block *sb,
+		    struct ext2_reserve_window_node *rsv)
+{
+	struct rb_root *root = &EXT2_SB(sb)->s_rsv_window_root;
+	struct rb_node *node = &rsv->rsv_node;
+	ext2_fsblk_t start = rsv->rsv_start;
+
+	struct rb_node ** p = &root->rb_node;
+	struct rb_node * parent = NULL;
+	struct ext2_reserve_window_node *this;
+
+	while (*p)
+	{
+		parent = *p;
+		this = rb_entry(parent, struct ext2_reserve_window_node, rsv_node);
+
+		if (start < this->rsv_start)
+			p = &(*p)->rb_left;
+		else if (start > this->rsv_end)
+			p = &(*p)->rb_right;
+		else {
+			rsv_window_dump(root, 1);
+			BUG();
+		}
+	}
+
+	rb_link_node(node, parent, p);
+	rb_insert_color(node, root);
+}
+
+/**
+ * rsv_window_remove() -- unlink a window from the reservation rb tree
+ * @sb:			super block
+ * @rsv:		reservation window to remove
+ *
+ * Mark the block reservation window as not allocated, and unlink it
+ * from the filesystem reservation window rb tree. Must be called with
+ * rsv_lock held.
+ */
+static void rsv_window_remove(struct super_block *sb,
+			      struct ext2_reserve_window_node *rsv)
+{
+	rsv->rsv_start = EXT2_RESERVE_WINDOW_NOT_ALLOCATED;
+	rsv->rsv_end = EXT2_RESERVE_WINDOW_NOT_ALLOCATED;
+	rsv->rsv_alloc_hit = 0;
+	rb_erase(&rsv->rsv_node, &EXT2_SB(sb)->s_rsv_window_root);
+}
+
+/*
+ * rsv_is_empty() -- Check if the reservation window is allocated.
+ * @rsv:		given reservation window to check
+ *
+ * returns 1 if the end block is EXT2_RESERVE_WINDOW_NOT_ALLOCATED.
+ */
+static inline int rsv_is_empty(struct ext2_reserve_window *rsv)
+{
+	/* a valid reservation end block could not be 0 */
+	return (rsv->_rsv_end == EXT2_RESERVE_WINDOW_NOT_ALLOCATED);
+}
+
+/**
+ * ext2_init_block_alloc_info()
+ * @inode:		file inode structure
+ *
+ * Allocate and initialize the  reservation window structure, and
+ * link the window to the ext2 inode structure at last
+ *
+ * The reservation window structure is only dynamically allocated
+ * and linked to ext2 inode the first time the open file
+ * needs a new block. So, before every ext2_new_block(s) call, for
+ * regular files, we should check whether the reservation window
+ * structure exists or not. In the latter case, this function is called.
+ * Fail to do so will result in block reservation being turned off for that
+ * open file.
+ *
+ * This function is called from ext2_get_blocks_handle(), also called
+ * when setting the reservation window size through ioctl before the file
+ * is open for write (needs block allocation).
+ *
+ * Needs truncate_mutex protection prior to calling this function.
+ */
+void ext2_init_block_alloc_info(struct inode *inode)
+{
+	struct ext2_inode_info *ei = EXT2_I(inode);
+	struct ext2_block_alloc_info *block_i = ei->i_block_alloc_info;
+	struct super_block *sb = inode->i_sb;
+
+	block_i = kmalloc(sizeof(*block_i), GFP_NOFS);
+	if (block_i) {
+		struct ext2_reserve_window_node *rsv = &block_i->rsv_window_node;
+
+		rsv->rsv_start = EXT2_RESERVE_WINDOW_NOT_ALLOCATED;
+		rsv->rsv_end = EXT2_RESERVE_WINDOW_NOT_ALLOCATED;
+
+	 	/*
+		 * if filesystem is mounted with NORESERVATION, the goal
+		 * reservation window size is set to zero to indicate
+		 * block reservation is off
+		 */
+		if (!test_opt(sb, RESERVATION))
+			rsv->rsv_goal_size = 0;
+		else
+			rsv->rsv_goal_size = EXT2_DEFAULT_RESERVE_BLOCKS;
+		rsv->rsv_alloc_hit = 0;
+		block_i->last_alloc_logical_block = 0;
+		block_i->last_alloc_physical_block = 0;
+	}
+	ei->i_block_alloc_info = block_i;
+}
+
+/**
+ * ext2_discard_reservation()
+ * @inode:		inode
+ *
+ * Discard(free) block reservation window on last file close, or truncate
+ * or at last iput().
+ *
+ * It is being called in three cases:
+ * 	ext2_release_file(): last writer closes the file
+ * 	ext2_clear_inode(): last iput(), when nobody links to this file.
+ * 	ext2_truncate(): when the block indirect map is about to change.
+ */
+void ext2_discard_reservation(struct inode *inode)
+{
+	struct ext2_inode_info *ei = EXT2_I(inode);
+	struct ext2_block_alloc_info *block_i = ei->i_block_alloc_info;
+	struct ext2_reserve_window_node *rsv;
+	spinlock_t *rsv_lock = &EXT2_SB(inode->i_sb)->s_rsv_window_lock;
+
+	if (!block_i)
+		return;
+
+	rsv = &block_i->rsv_window_node;
+	if (!rsv_is_empty(&rsv->rsv_window)) {
+		spin_lock(rsv_lock);
+		if (!rsv_is_empty(&rsv->rsv_window))
+			rsv_window_remove(inode->i_sb, rsv);
+		spin_unlock(rsv_lock);
+	}
+}
+
+/**
+ * ext2_free_blocks_sb() -- Free given blocks and update quota and i_blocks
+ * @inode:		inode
+ * @block:		start physcial block to free
+ * @count:		number of blocks to free
+ */
 void ext2_free_blocks (struct inode * inode, unsigned long block,
 		       unsigned long count)
 {
@@ -287,7 +533,7 @@ do_more:
 	if (sb->s_flags & MS_SYNCHRONOUS)
 		sync_dirty_buffer(bitmap_bh);
 
-	group_release_blocks(sb, block_group, desc, bh2, group_freed);
+	group_adjust_blocks(sb, block_group, desc, bh2, group_freed);
 	freed += group_freed;
 
 	if (overflow) {
@@ -301,16 +547,46 @@ error_return:
 	DQUOT_FREE_BLOCK(inode, freed);
 }
 
-static int grab_block(spinlock_t *lock, char *map, unsigned size, int goal)
+/**
+ * bitmap_search_next_usable_block()
+ * @start:		the starting block (group relative) of the search
+ * @bh:			bufferhead contains the block group bitmap
+ * @maxblocks:		the ending block (group relative) of the reservation
+ *
+ * The bitmap search --- search forward through the actual bitmap on disk until
+ * we find a bit free.
+ */
+static ext2_grpblk_t
+bitmap_search_next_usable_block(ext2_grpblk_t start, struct buffer_head *bh,
+					ext2_grpblk_t maxblocks)
 {
-	int k;
-	char *p, *r;
+	ext2_grpblk_t next;
 
-	if (!ext2_test_bit(goal, map))
-		goto got_it;
+	next = ext2_find_next_zero_bit(bh->b_data, maxblocks, start);
+	if (next >= maxblocks)
+		return -1;
+	return next;
+}
 
-repeat:
-	if (goal) {
+/**
+ * find_next_usable_block()
+ * @start:		the starting block (group relative) to find next
+ * 			allocatable block in bitmap.
+ * @bh:			bufferhead contains the block group bitmap
+ * @maxblocks:		the ending block (group relative) for the search
+ *
+ * Find an allocatable block in a bitmap.  We 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 ext2_grpblk_t
+find_next_usable_block(int start, struct buffer_head *bh, int maxblocks)
+{
+	ext2_grpblk_t here, next;
+	char *p, *r;
+
+	if (start > 0) {
 		/*
 		 * The goal was occupied; search forward for a free 
 		 * block within the next XX blocks.
@@ -319,244 +595,807 @@ repeat:
 		 * less than EXT2_BLOCKS_PER_GROUP. Aligning up to the
 		 * next 64-bit boundary is simple..
 		 */
-		k = (goal + 63) & ~63;
-		goal = ext2_find_next_zero_bit(map, k, goal);
-		if (goal < k)
-			goto got_it;
+		ext2_grpblk_t end_goal = (start + 63) & ~63;
+		if (end_goal > maxblocks)
+			end_goal = maxblocks;
+		here = ext2_find_next_zero_bit(bh->b_data, end_goal, start);
+		if (here < end_goal)
+			return here;
+		ext2_debug("Bit not found near goal\n");
+	}
+
+	here = start;
+	if (here < 0)
+		here = 0;
+
+	p = ((char *)bh->b_data) + (here >> 3);
+	r = memscan(p, 0, ((maxblocks + 7) >> 3) - (here >> 3));
+	next = (r - ((char *)bh->b_data)) << 3;
+
+	if (next < maxblocks && next >= here)
+		return next;
+
+	here = bitmap_search_next_usable_block(here, bh, maxblocks);
+	return here;
+}
+
+/*
+ * ext2_try_to_allocate()
+ * @sb:			superblock
+ * @handle:		handle to this transaction
+ * @group:		given allocation block group
+ * @bitmap_bh:		bufferhead holds the block bitmap
+ * @grp_goal:		given target block within the group
+ * @count:		target number of blocks to allocate
+ * @my_rsv:		reservation window
+ *
+ * Attempt to allocate blocks within a give range. Set the range of allocation
+ * first, then find the first free bit(s) from the bitmap (within the range),
+ * and at last, allocate the blocks by claiming the found free bit as allocated.
+ *
+ * To set the range of this allocation:
+ * 	if there is a reservation window, only try to allocate block(s)
+ * 	from the file's own reservation window;
+ * 	Otherwise, the allocation range starts from the give goal block,
+ * 	ends at the block group's last block.
+ *
+ * If we failed to allocate the desired block then we may end up crossing to a
+ * new bitmap.
+ */
+static int
+ext2_try_to_allocate(struct super_block *sb, int group,
+			struct buffer_head *bitmap_bh, ext2_grpblk_t grp_goal,
+			unsigned long *count,
+			struct ext2_reserve_window *my_rsv)
+{
+	ext2_fsblk_t group_first_block;
+       	ext2_grpblk_t start, end;
+	unsigned long num = 0;
+
+	/* we do allocation within the reservation window if we have a window */
+	if (my_rsv) {
+		group_first_block = ext2_group_first_block_no(sb, group);
+		if (my_rsv->_rsv_start >= group_first_block)
+			start = my_rsv->_rsv_start - group_first_block;
+		else
+			/* reservation window cross group boundary */
+			start = 0;
+		end = my_rsv->_rsv_end - group_first_block + 1;
+		if (end > EXT2_BLOCKS_PER_GROUP(sb))
+			/* reservation window crosses group boundary */
+			end = EXT2_BLOCKS_PER_GROUP(sb);
+		if ((start <= grp_goal) && (grp_goal < end))
+			start = grp_goal;
+		else
+			grp_goal = -1;
+	} else {
+		if (grp_goal > 0)
+			start = grp_goal;
+		else
+			start = 0;
+		end = EXT2_BLOCKS_PER_GROUP(sb);
+	}
+
+	BUG_ON(start > EXT2_BLOCKS_PER_GROUP(sb));
+
+repeat:
+	if (grp_goal < 0) {
+		grp_goal = find_next_usable_block(start, bitmap_bh, end);
+		if (grp_goal < 0)
+			goto fail_access;
+		if (!my_rsv) {
+			int i;
+
+			for (i = 0; i < 7 && grp_goal > start &&
+					!ext2_test_bit(grp_goal - 1,
+					     		bitmap_bh->b_data);
+			     		i++, grp_goal--)
+				;
+		}
+	}
+	start = grp_goal;
+
+	if (ext2_set_bit_atomic(sb_bgl_lock(EXT2_SB(sb), group), grp_goal,
+			       				bitmap_bh->b_data)) {
+		/*
+		 * The block was allocated by another thread, or it was
+		 * allocated and then freed by another thread
+		 */
+		start++;
+		grp_goal++;
+		if (start >= end)
+			goto fail_access;
+		goto repeat;
+	}
+	num++;
+	grp_goal++;
+	while (num < *count && grp_goal < end
+		&& !ext2_set_bit_atomic(sb_bgl_lock(EXT2_SB(sb), group),
+					grp_goal, bitmap_bh->b_data)) {
+		num++;
+		grp_goal++;
+	}
+	*count = num;
+	return grp_goal - num;
+fail_access:
+	*count = num;
+	return -1;
+}
+
+/**
+ * 	find_next_reservable_window():
+ *		find a reservable space within the given range.
+ *		It does not allocate the reservation window for now:
+ *		alloc_new_reservation() will do the work later.
+ *
+ * 	@search_head: the head of the searching list;
+ *		This is not necessarily the list head of the whole filesystem
+ *
+ *		We have both head and start_block to assist the search
+ *		for the reservable space. The list starts from head,
+ *		but we will shift to the place where start_block is,
+ *		then start from there, when looking for a reservable space.
+ *
+ * 	@size: the target new reservation window size
+ *
+ * 	@group_first_block: the first block we consider to start
+ *			the real search from
+ *
+ * 	@last_block:
+ *		the maximum block number that our goal reservable space
+ *		could start from. This is normally the last block in this
+ *		group. The search will end when we found the start of next
+ *		possible reservable space is out of this boundary.
+ *		This could handle the cross boundary reservation window
+ *		request.
+ *
+ * 	basically we search from the given range, rather than the whole
+ * 	reservation double linked list, (start_block, last_block)
+ * 	to find a free region that is of my size and has not
+ * 	been reserved.
+ *
+ */
+static int find_next_reservable_window(
+				struct ext2_reserve_window_node *search_head,
+				struct ext2_reserve_window_node *my_rsv,
+				struct super_block * sb,
+				ext2_fsblk_t start_block,
+				ext2_fsblk_t last_block)
+{
+	struct rb_node *next;
+	struct ext2_reserve_window_node *rsv, *prev;
+	ext2_fsblk_t cur;
+	int size = my_rsv->rsv_goal_size;
+
+	/* TODO: make the start of the reservation window byte-aligned */
+	/* cur = *start_block & ~7;*/
+	cur = start_block;
+	rsv = search_head;
+	if (!rsv)
+		return -1;
+
+	while (1) {
+		if (cur <= rsv->rsv_end)
+			cur = rsv->rsv_end + 1;
+
+		/* TODO?
+		 * in the case we could not find a reservable space
+		 * that is what is expected, during the re-search, we could
+		 * remember what's the largest reservable space we could have
+		 * and return that one.
+		 *
+		 * For now it will fail if we could not find the reservable
+		 * space with expected-size (or more)...
+		 */
+		if (cur > last_block)
+			return -1;		/* fail */
+
+		prev = rsv;
+		next = rb_next(&rsv->rsv_node);
+		rsv = rb_entry(next,struct ext2_reserve_window_node,rsv_node);
+
 		/*
-		 * Search in the remainder of the current group.
+		 * Reached the last reservation, we can just append to the
+		 * previous one.
 		 */
+		if (!next)
+			break;
+
+		if (cur + size <= rsv->rsv_start) {
+			/*
+			 * Found a reserveable space big enough.  We could
+			 * have a reservation across the group boundary here
+		 	 */
+			break;
+		}
 	}
+	/*
+	 * we come here either :
+	 * when we reach the end of the whole list,
+	 * and there is empty reservable space after last entry in the list.
+	 * append it to the end of the list.
+	 *
+	 * or we found one reservable space in the middle of the list,
+	 * return the reservation window that we could append to.
+	 * succeed.
+	 */
 
-	p = map + (goal >> 3);
-	r = memscan(p, 0, (size - goal + 7) >> 3);
-	k = (r - map) << 3;
-	if (k < size) {
-		/* 
-		 * We have succeeded in finding a free byte in the block
-		 * bitmap.  Now search backwards to find the start of this
-		 * group of free blocks - won't take more than 7 iterations.
+	if ((prev != my_rsv) && (!rsv_is_empty(&my_rsv->rsv_window)))
+		rsv_window_remove(sb, my_rsv);
+
+	/*
+	 * Let's book the whole avaliable window for now.  We will check the
+	 * disk bitmap later and then, if there are free blocks then we adjust
+	 * the window size if it's larger than requested.
+	 * Otherwise, we will remove this node from the tree next time
+	 * call find_next_reservable_window.
+	 */
+	my_rsv->rsv_start = cur;
+	my_rsv->rsv_end = cur + size - 1;
+	my_rsv->rsv_alloc_hit = 0;
+
+	if (prev != my_rsv)
+		ext2_rsv_window_add(sb, my_rsv);
+
+	return 0;
+}
+
+/**
+ * 	alloc_new_reservation()--allocate a new reservation window
+ *
+ *		To make a new reservation, we search part of the filesystem
+ *		reservation list (the list that inside the group). We try to
+ *		allocate a new reservation window near the allocation goal,
+ *		or the beginning of the group, if there is no goal.
+ *
+ *		We first find a reservable space after the goal, then from
+ *		there, we check the bitmap for the first free block after
+ *		it. If there is no free block until the end of group, then the
+ *		whole group is full, we failed. Otherwise, check if the free
+ *		block is inside the expected reservable space, if so, we
+ *		succeed.
+ *		If the first free block is outside the reservable space, then
+ *		start from the first free block, we search for next available
+ *		space, and go on.
+ *
+ *	on succeed, a new reservation will be found and inserted into the list
+ *	It contains at least one free block, and it does not overlap with other
+ *	reservation windows.
+ *
+ *	failed: we failed to find a reservation window in this group
+ *
+ *	@rsv: the reservation
+ *
+ *	@grp_goal: The goal (group-relative).  It is where the search for a
+ *		free reservable space should start from.
+ *		if we have a goal(goal >0 ), then start from there,
+ *		no goal(goal = -1), we start from the first block
+ *		of the group.
+ *
+ *	@sb: the super block
+ *	@group: the group we are trying to allocate in
+ *	@bitmap_bh: the block group block bitmap
+ *
+ */
+static int alloc_new_reservation(struct ext2_reserve_window_node *my_rsv,
+		ext2_grpblk_t grp_goal, struct super_block *sb,
+		unsigned int group, struct buffer_head *bitmap_bh)
+{
+	struct ext2_reserve_window_node *search_head;
+	ext2_fsblk_t group_first_block, group_end_block, start_block;
+	ext2_grpblk_t first_free_block;
+	struct rb_root *fs_rsv_root = &EXT2_SB(sb)->s_rsv_window_root;
+	unsigned long size;
+	int ret;
+	spinlock_t *rsv_lock = &EXT2_SB(sb)->s_rsv_window_lock;
+
+	group_first_block = ext2_group_first_block_no(sb, group);
+	group_end_block = group_first_block + (EXT2_BLOCKS_PER_GROUP(sb) - 1);
+
+	if (grp_goal < 0)
+		start_block = group_first_block;
+	else
+		start_block = grp_goal + group_first_block;
+
+	size = my_rsv->rsv_goal_size;
+
+	if (!rsv_is_empty(&my_rsv->rsv_window)) {
+		/*
+		 * if the old reservation is cross group boundary
+		 * and if the goal is inside the old reservation window,
+		 * we will come here when we just failed to allocate from
+		 * the first part of the window. We still have another part
+		 * that belongs to the next group. In this case, there is no
+		 * point to discard our window and try to allocate a new one
+		 * in this group(which will fail). we should
+		 * keep the reservation window, just simply move on.
+		 *
+		 * Maybe we could shift the start block of the reservation
+		 * window to the first block of next group.
 		 */
-		for (goal = k; goal && !ext2_test_bit (goal - 1, map); goal--)
-			;
-		goto got_it;
+
+		if ((my_rsv->rsv_start <= group_end_block) &&
+				(my_rsv->rsv_end > group_end_block) &&
+				(start_block >= my_rsv->rsv_start))
+			return -1;
+
+		if ((my_rsv->rsv_alloc_hit >
+		     (my_rsv->rsv_end - my_rsv->rsv_start + 1) / 2)) {
+			/*
+			 * if the previously allocation hit ratio is
+			 * greater than 1/2, then we double the size of
+			 * the reservation window the next time,
+			 * otherwise we keep the same size window
+			 */
+			size = size * 2;
+			if (size > EXT2_MAX_RESERVE_BLOCKS)
+				size = EXT2_MAX_RESERVE_BLOCKS;
+			my_rsv->rsv_goal_size= size;
+		}
 	}
 
-	k = ext2_find_next_zero_bit ((u32 *)map, size, goal);
-	if (k < size) {
-		goal = k;
-		goto got_it;
+	spin_lock(rsv_lock);
+	/*
+	 * shift the search start to the window near the goal block
+	 */
+	search_head = search_reserve_window(fs_rsv_root, start_block);
+
+	/*
+	 * find_next_reservable_window() simply finds a reservable window
+	 * inside the given range(start_block, group_end_block).
+	 *
+	 * To make sure the reservation window has a free bit inside it, we
+	 * need to check the bitmap after we found a reservable window.
+	 */
+retry:
+	ret = find_next_reservable_window(search_head, my_rsv, sb,
+						start_block, group_end_block);
+
+	if (ret == -1) {
+		if (!rsv_is_empty(&my_rsv->rsv_window))
+			rsv_window_remove(sb, my_rsv);
+		spin_unlock(rsv_lock);
+		return -1;
 	}
-	return -1;
-got_it:
-	if (ext2_set_bit_atomic(lock, goal, (void *) map)) 
-		goto repeat;	
-	return goal;
+
+	/*
+	 * On success, find_next_reservable_window() returns the
+	 * reservation window where there is a reservable space after it.
+	 * Before we reserve this reservable space, we need
+	 * to make sure there is at least a free block inside this region.
+	 *
+	 * Search the first free bit on the block bitmap.  Search starts from
+	 * the start block of the reservable space we just found.
+	 */
+	spin_unlock(rsv_lock);
+	first_free_block = bitmap_search_next_usable_block(
+			my_rsv->rsv_start - group_first_block,
+			bitmap_bh, group_end_block - group_first_block + 1);
+
+	if (first_free_block < 0) {
+		/*
+		 * no free block left on the bitmap, no point
+		 * to reserve the space. return failed.
+		 */
+		spin_lock(rsv_lock);
+		if (!rsv_is_empty(&my_rsv->rsv_window))
+			rsv_window_remove(sb, my_rsv);
+		spin_unlock(rsv_lock);
+		return -1;		/* failed */
+	}
+
+	start_block = first_free_block + group_first_block;
+	/*
+	 * check if the first free block is within the
+	 * free space we just reserved
+	 */
+	if (start_block >= my_rsv->rsv_start && start_block <= my_rsv->rsv_end)
+		return 0;		/* success */
+	/*
+	 * if the first free bit we found is out of the reservable space
+	 * continue search for next reservable space,
+	 * start from where the free block is,
+	 * we also shift the list head to where we stopped last time
+	 */
+	search_head = my_rsv;
+	spin_lock(rsv_lock);
+	goto retry;
+}
+
+/**
+ * try_to_extend_reservation()
+ * @my_rsv:		given reservation window
+ * @sb:			super block
+ * @size:		the delta to extend
+ *
+ * Attempt to expand the reservation window large enough to have
+ * required number of free blocks
+ *
+ * Since ext2_try_to_allocate() will always allocate blocks within
+ * the reservation window range, if the window size is too small,
+ * multiple blocks allocation has to stop at the end of the reservation
+ * window. To make this more efficient, given the total number of
+ * blocks needed and the current size of the window, we try to
+ * expand the reservation window size if necessary on a best-effort
+ * basis before ext2_new_blocks() tries to allocate blocks.
+ */
+static void try_to_extend_reservation(struct ext2_reserve_window_node *my_rsv,
+			struct super_block *sb, int size)
+{
+	struct ext2_reserve_window_node *next_rsv;
+	struct rb_node *next;
+	spinlock_t *rsv_lock = &EXT2_SB(sb)->s_rsv_window_lock;
+
+	if (!spin_trylock(rsv_lock))
+		return;
+
+	next = rb_next(&my_rsv->rsv_node);
+
+	if (!next)
+		my_rsv->rsv_end += size;
+	else {
+		next_rsv = rb_entry(next, struct ext2_reserve_window_node, rsv_node);
+
+		if ((next_rsv->rsv_start - my_rsv->rsv_end - 1) >= size)
+			my_rsv->rsv_end += size;
+		else
+			my_rsv->rsv_end = next_rsv->rsv_start - 1;
+	}
+	spin_unlock(rsv_lock);
+}
+
+/**
+ * ext2_try_to_allocate_with_rsv()
+ * @sb:			superblock
+ * @group:		given allocation block group
+ * @bitmap_bh:		bufferhead holds the block bitmap
+ * @grp_goal:		given target block within the group
+ * @count:		target number of blocks to allocate
+ * @my_rsv:		reservation window
+ *
+ * This is the main function used to allocate a new block and its reservation
+ * window.
+ *
+ * Each time when a new block allocation is need, first try to allocate from
+ * its own reservation.  If it does not have a reservation window, instead of
+ * looking for a free bit on bitmap first, then look up the reservation list to
+ * see if it is inside somebody else's reservation window, we try to allocate a
+ * reservation window for it starting from the goal first. Then do the block
+ * allocation within the reservation window.
+ *
+ * This will avoid keeping on searching the reservation list again and
+ * again when somebody is looking for a free block (without
+ * reservation), and there are lots of free blocks, but they are all
+ * being reserved.
+ *
+ * We use a red-black tree for the per-filesystem reservation list.
+ */
+static ext2_grpblk_t
+ext2_try_to_allocate_with_rsv(struct super_block *sb, unsigned int group,
+			struct buffer_head *bitmap_bh, ext2_grpblk_t grp_goal,
+			struct ext2_reserve_window_node * my_rsv,
+			unsigned long *count)
+{
+	ext2_fsblk_t group_first_block, group_last_block;
+	ext2_grpblk_t ret = 0;
+	unsigned long num = *count;
+
+	/*
+	 * we don't deal with reservation when
+	 * filesystem is mounted without reservation
+	 * or the file is not a regular file
+	 * or last attempt to allocate a block with reservation turned on failed
+	 */
+	if (my_rsv == NULL) {
+		return ext2_try_to_allocate(sb, group, bitmap_bh,
+						grp_goal, count, NULL);
+	}
+	/*
+	 * grp_goal is a group relative block number (if there is a goal)
+	 * 0 <= grp_goal < EXT2_BLOCKS_PER_GROUP(sb)
+	 * first block is a filesystem wide block number
+	 * first block is the block number of the first block in this group
+	 */
+	group_first_block = ext2_group_first_block_no(sb, group);
+	group_last_block = group_first_block + (EXT2_BLOCKS_PER_GROUP(sb) - 1);
+
+	/*
+	 * Basically we will allocate a new block from inode's reservation
+	 * window.
+	 *
+	 * We need to allocate a new reservation window, if:
+	 * a) inode does not have a reservation window; or
+	 * b) last attempt to allocate a block from existing reservation
+	 *    failed; or
+	 * c) we come here with a goal and with a reservation window
+	 *
+	 * We do not need to allocate a new reservation window if we come here
+	 * at the beginning with a goal and the goal is inside the window, or
+	 * we don't have a goal but already have a reservation window.
+	 * then we could go to allocate from the reservation window directly.
+	 */
+	while (1) {
+		if (rsv_is_empty(&my_rsv->rsv_window) || (ret < 0) ||
+			!goal_in_my_reservation(&my_rsv->rsv_window,
+						grp_goal, group, sb)) {
+			if (my_rsv->rsv_goal_size < *count)
+				my_rsv->rsv_goal_size = *count;
+			ret = alloc_new_reservation(my_rsv, grp_goal, sb,
+							group, bitmap_bh);
+			if (ret < 0)
+				break;			/* failed */
+
+			if (!goal_in_my_reservation(&my_rsv->rsv_window,
+							grp_goal, group, sb))
+				grp_goal = -1;
+		} else if (grp_goal >= 0) {
+			int curr = my_rsv->rsv_end -
+					(grp_goal + group_first_block) + 1;
+
+			if (curr < *count)
+				try_to_extend_reservation(my_rsv, sb,
+							*count - curr);
+		}
+
+		if ((my_rsv->rsv_start > group_last_block) ||
+				(my_rsv->rsv_end < group_first_block)) {
+			rsv_window_dump(&EXT2_SB(sb)->s_rsv_window_root, 1);
+			BUG();
+		}
+		ret = ext2_try_to_allocate(sb, group, bitmap_bh, grp_goal,
+					   &num, &my_rsv->rsv_window);
+		if (ret >= 0) {
+			my_rsv->rsv_alloc_hit += num;
+			*count = num;
+			break;				/* succeed */
+		}
+		num = *count;
+	}
+	return ret;
+}
+
+/**
+ * ext2_has_free_blocks()
+ * @sbi:		in-core super block structure.
+ *
+ * Check if filesystem has at least 1 free block available for allocation.
+ */
+static int ext2_has_free_blocks(struct ext2_sb_info *sbi)
+{
+	ext2_fsblk_t free_blocks, root_blocks;
+
+	free_blocks = percpu_counter_read_positive(&sbi->s_freeblocks_counter);
+	root_blocks = le32_to_cpu(sbi->s_es->s_r_blocks_count);
+	if (free_blocks < root_blocks + 1 && !capable(CAP_SYS_RESOURCE) &&
+		sbi->s_resuid != current->fsuid &&
+		(sbi->s_resgid == 0 || !in_group_p (sbi->s_resgid))) {
+		return 0;
+	}
+	return 1;
 }
 
 /*
- * ext2_new_block uses a goal block to assist allocation.  If the goal is
+ * ext2_new_blocks() -- core block(s) allocation function
+ * @inode:		file inode
+ * @goal:		given target block(filesystem wide)
+ * @count:		target number of blocks to allocate
+ * @errp:		error code
+ *
+ * ext2_new_blocks 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 ext2_new_block(struct inode *inode, unsigned long goal,
-			u32 *prealloc_count, u32 *prealloc_block, int *err)
+ext2_fsblk_t ext2_new_blocks(struct inode *inode, ext2_fsblk_t goal,
+		    unsigned long *count, int *errp)
 {
 	struct buffer_head *bitmap_bh = NULL;
-	struct buffer_head *gdp_bh;	/* bh2 */
-	struct ext2_group_desc *desc;
-	int group_no;			/* i */
-	int ret_block;			/* j */
-	int group_idx;			/* k */
-	int target_block;		/* tmp */
-	int block = 0;
-	struct super_block *sb = inode->i_sb;
-	struct ext2_sb_info *sbi = EXT2_SB(sb);
-	struct ext2_super_block *es = sbi->s_es;
-	unsigned group_size = EXT2_BLOCKS_PER_GROUP(sb);
-	unsigned prealloc_goal = es->s_prealloc_blocks;
-	unsigned group_alloc = 0, es_alloc, dq_alloc;
-	int nr_scanned_groups;
-
-	if (!prealloc_goal--)
-		prealloc_goal = EXT2_DEFAULT_PREALLOC_BLOCKS - 1;
-	if (!prealloc_count || *prealloc_count)
-		prealloc_goal = 0;
-
-	if (DQUOT_ALLOC_BLOCK(inode, 1)) {
-		*err = -EDQUOT;
-		goto out;
+	struct buffer_head *gdp_bh;
+	int group_no;
+	int goal_group;
+	ext2_grpblk_t grp_target_blk;	/* blockgroup relative goal block */
+	ext2_grpblk_t grp_alloc_blk;	/* blockgroup-relative allocated block*/
+	ext2_fsblk_t ret_block;		/* filesyetem-wide allocated block */
+	int bgi;			/* blockgroup iteration index */
+	int performed_allocation = 0;
+	ext2_grpblk_t free_blocks;	/* number of free blocks in a group */
+	struct super_block *sb;
+	struct ext2_group_desc *gdp;
+	struct ext2_super_block *es;
+	struct ext2_sb_info *sbi;
+	struct ext2_reserve_window_node *my_rsv = NULL;
+	struct ext2_block_alloc_info *block_i;
+	unsigned short windowsz = 0;
+	unsigned long ngroups;
+	unsigned long num = *count;
+
+	*errp = -ENOSPC;
+	sb = inode->i_sb;
+	if (!sb) {
+		printk("ext2_new_blocks: nonexistent device");
+		return 0;
 	}
 
-	while (prealloc_goal && DQUOT_PREALLOC_BLOCK(inode, prealloc_goal))
-		prealloc_goal--;
+	/*
+	 * Check quota for allocation of this block.
+	 */
+	if (DQUOT_ALLOC_BLOCK(inode, num)) {
+		*errp = -EDQUOT;
+		return 0;
+	}
 
-	dq_alloc = prealloc_goal + 1;
-	es_alloc = reserve_blocks(sb, dq_alloc);
-	if (!es_alloc) {
-		*err = -ENOSPC;
-		goto out_dquot;
+	sbi = EXT2_SB(sb);
+	es = EXT2_SB(sb)->s_es;
+	ext2_debug("goal=%lu.\n", goal);
+	/*
+	 * Allocate a block from reservation only when
+	 * filesystem is mounted with reservation(default,-o reservation), and
+	 * it's a regular file, and
+	 * the desired window size is greater than 0 (One could use ioctl
+	 * command EXT2_IOC_SETRSVSZ to set the window size to 0 to turn off
+	 * reservation on that particular file)
+	 */
+	block_i = EXT2_I(inode)->i_block_alloc_info;
+	if (block_i) {
+		windowsz = block_i->rsv_window_node.rsv_goal_size;
+		if (windowsz > 0)
+			my_rsv = &block_i->rsv_window_node;
 	}
 
-	ext2_debug ("goal=%lu.\n", goal);
+	if (!ext2_has_free_blocks(sbi)) {
+		*errp = -ENOSPC;
+		goto out;
+	}
 
+	/*
+	 * 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);
-	group_no = (goal - le32_to_cpu(es->s_first_data_block)) / group_size;
-	desc = ext2_get_group_desc (sb, group_no, &gdp_bh);
-	if (!desc) {
-		/*
-		 * gdp_bh may still be uninitialised.  But group_release_blocks
-		 * will not touch it because group_alloc is zero.
-		 */
+	group_no = (goal - le32_to_cpu(es->s_first_data_block)) /
+			EXT2_BLOCKS_PER_GROUP(sb);
+	goal_group = group_no;
+retry_alloc:
+	gdp = ext2_get_group_desc(sb, group_no, &gdp_bh);
+	if (!gdp)
 		goto io_error;
-	}
 
-	group_alloc = group_reserve_blocks(sbi, group_no, desc,
-					gdp_bh, es_alloc);
-	if (group_alloc) {
-		ret_block = ((goal - le32_to_cpu(es->s_first_data_block)) %
-					group_size);
-		brelse(bitmap_bh);
+	free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);
+	/*
+	 * if there is not enough free blocks to make a new resevation
+	 * turn off reservation for this allocation
+	 */
+	if (my_rsv && (free_blocks < windowsz)
+		&& (rsv_is_empty(&my_rsv->rsv_window)))
+		my_rsv = NULL;
+
+	if (free_blocks > 0) {
+		grp_target_blk = ((goal - le32_to_cpu(es->s_first_data_block)) %
+				EXT2_BLOCKS_PER_GROUP(sb));
 		bitmap_bh = read_block_bitmap(sb, group_no);
 		if (!bitmap_bh)
 			goto io_error;
-		
-		ext2_debug("goal is at %d:%d.\n", group_no, ret_block);
-
-		ret_block = grab_block(sb_bgl_lock(sbi, group_no),
-				bitmap_bh->b_data, group_size, ret_block);
-		if (ret_block >= 0)
-			goto got_block;
-		group_release_blocks(sb, group_no, desc, gdp_bh, group_alloc);
-		group_alloc = 0;
+		grp_alloc_blk = ext2_try_to_allocate_with_rsv(sb, group_no,
+					bitmap_bh, grp_target_blk,
+					my_rsv, &num);
+		if (grp_alloc_blk >= 0)
+			goto allocated;
 	}
 
-	ext2_debug ("Bit not found in block group %d.\n", group_no);
+	ngroups = EXT2_SB(sb)->s_groups_count;
+	smp_rmb();
 
 	/*
 	 * Now search the rest of the groups.  We assume that 
-	 * i and desc correctly point to the last group visited.
+	 * i and gdp correctly point to the last group visited.
 	 */
-	nr_scanned_groups = 0;
-retry:
-	for (group_idx = 0; !group_alloc &&
-			group_idx < sbi->s_groups_count; group_idx++) {
+	for (bgi = 0; bgi < ngroups; bgi++) {
 		group_no++;
-		if (group_no >= sbi->s_groups_count)
+		if (group_no >= ngroups)
 			group_no = 0;
-		desc = ext2_get_group_desc(sb, group_no, &gdp_bh);
-		if (!desc)
+		gdp = ext2_get_group_desc(sb, group_no, &gdp_bh);
+		if (!gdp)
 			goto io_error;
-		group_alloc = group_reserve_blocks(sbi, group_no, desc,
-						gdp_bh, es_alloc);
-	}
-	if (!group_alloc) {
-		*err = -ENOSPC;
-		goto out_release;
-	}
-	brelse(bitmap_bh);
-	bitmap_bh = read_block_bitmap(sb, group_no);
-	if (!bitmap_bh)
-		goto io_error;
 
-	ret_block = grab_block(sb_bgl_lock(sbi, group_no), bitmap_bh->b_data,
-				group_size, 0);
-	if (ret_block < 0) {
+		free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);
 		/*
-		 * If a free block counter is corrupted we can loop inifintely.
-		 * Detect that here.
+		 * skip this group if the number of
+		 * free blocks is less than half of the reservation
+		 * window size.
 		 */
-		nr_scanned_groups++;
-		if (nr_scanned_groups > 2 * sbi->s_groups_count) {
-			ext2_error(sb, "ext2_new_block",
-				"corrupted free blocks counters");
+		if (free_blocks <= (windowsz/2))
+			continue;
+
+		brelse(bitmap_bh);
+		bitmap_bh = read_block_bitmap(sb, group_no);
+		if (!bitmap_bh)
 			goto io_error;
-		}
 		/*
-		 * Someone else grabbed the last free block in this blockgroup
-		 * before us.  Retry the scan.
+		 * try to allocate block(s) from this group, without a goal(-1).
 		 */
-		group_release_blocks(sb, group_no, desc, gdp_bh, group_alloc);
-		group_alloc = 0;
-		goto retry;
+		grp_alloc_blk = ext2_try_to_allocate_with_rsv(sb, group_no,
+					bitmap_bh, -1, my_rsv, &num);
+		if (grp_alloc_blk >= 0)
+			goto allocated;
+	}
+	/*
+	 * We may end up a bogus ealier ENOSPC error due to
+	 * filesystem is "full" of reservations, but
+	 * there maybe indeed free blocks avaliable on disk
+	 * In this case, we just forget about the reservations
+	 * just do block allocation as without reservations.
+	 */
+	if (my_rsv) {
+		my_rsv = NULL;
+		windowsz = 0;
+		group_no = goal_group;
+		goto retry_alloc;
 	}
+	/* No space left on the device */
+	*errp = -ENOSPC;
+	goto out;
+
+allocated:
 
-got_block:
 	ext2_debug("using block group %d(%d)\n",
-		group_no, desc->bg_free_blocks_count);
+			group_no, gdp->bg_free_blocks_count);
 
-	target_block = ret_block + group_no * group_size +
-			le32_to_cpu(es->s_first_data_block);
+	ret_block = grp_alloc_blk + ext2_group_first_block_no(sb, group_no);
 
-	if (target_block == le32_to_cpu(desc->bg_block_bitmap) ||
-	    target_block == le32_to_cpu(desc->bg_inode_bitmap) ||
-	    in_range(target_block, le32_to_cpu(desc->bg_inode_table),
-		      sbi->s_itb_per_group))
-		ext2_error (sb, "ext2_new_block",
+	if (in_range(le32_to_cpu(gdp->bg_block_bitmap), ret_block, num) ||
+	    in_range(le32_to_cpu(gdp->bg_inode_bitmap), ret_block, num) ||
+	    in_range(ret_block, le32_to_cpu(gdp->bg_inode_table),
+		      EXT2_SB(sb)->s_itb_per_group) ||
+	    in_range(ret_block + num - 1, le32_to_cpu(gdp->bg_inode_table),
+		      EXT2_SB(sb)->s_itb_per_group))
+		ext2_error(sb, "ext2_new_blocks",
 			    "Allocating block in system zone - "
-			    "block = %u", target_block);
+			    "blocks from "E2FSBLK", length %lu",
+			    ret_block, num);
 
-	if (target_block >= le32_to_cpu(es->s_blocks_count)) {
-		ext2_error (sb, "ext2_new_block",
-			    "block(%d) >= blocks count(%d) - "
+	performed_allocation = 1;
+
+	if (ret_block + num - 1 >= le32_to_cpu(es->s_blocks_count)) {
+		ext2_error(sb, "ext2_new_blocks",
+			    "block("E2FSBLK") >= blocks count(%d) - "
 			    "block_group = %d, es == %p ", ret_block,
 			le32_to_cpu(es->s_blocks_count), group_no, es);
-		goto io_error;
+		goto out;
 	}
-	block = target_block;
-
-	/* OK, we _had_ allocated something */
-	ext2_debug("found bit %d\n", ret_block);
-
-	dq_alloc--;
-	es_alloc--;
-	group_alloc--;
 
-	/*
-	 * Do block preallocation now if required.
-	 */
-	write_lock(&EXT2_I(inode)->i_meta_lock);
-	if (group_alloc && !*prealloc_count) {
-		unsigned n;
-
-		for (n = 0; n < group_alloc && ++ret_block < group_size; n++) {
-			if (ext2_set_bit_atomic(sb_bgl_lock(sbi, group_no),
-						ret_block,
-						(void*) bitmap_bh->b_data))
- 				break;
-		}
-		*prealloc_block = block + 1;
-		*prealloc_count = n;
-		es_alloc -= n;
-		dq_alloc -= n;
-		group_alloc -= n;
-	}
-	write_unlock(&EXT2_I(inode)->i_meta_lock);
+	group_adjust_blocks(sb, group_no, gdp, gdp_bh, -num);
+	percpu_counter_sub(&sbi->s_freeblocks_counter, num);
 
 	mark_buffer_dirty(bitmap_bh);
 	if (sb->s_flags & MS_SYNCHRONOUS)
 		sync_dirty_buffer(bitmap_bh);
 
-	ext2_debug ("allocating block %d. ", block);
+	*errp = 0;
+	brelse(bitmap_bh);
+	DQUOT_FREE_BLOCK(inode, *count-num);
+	*count = num;
+	return ret_block;
 
-	*err = 0;
-out_release:
-	group_release_blocks(sb, group_no, desc, gdp_bh, group_alloc);
-	release_blocks(sb, es_alloc);
-out_dquot:
-	DQUOT_FREE_BLOCK(inode, dq_alloc);
+io_error:
+	*errp = -EIO;
 out:
+	/*
+	 * Undo the block allocation
+	 */
+	if (!performed_allocation)
+		DQUOT_FREE_BLOCK(inode, *count);
 	brelse(bitmap_bh);
-	return block;
+	return 0;
+}
 
-io_error:
-	*err = -EIO;
-	goto out_release;
+ext2_fsblk_t ext2_new_block(struct inode *inode, unsigned long goal, int *errp)
+{
+	unsigned long count = 1;
+
+	return ext2_new_blocks(inode, goal, &count, errp);
 }
 
 #ifdef EXT2FS_DEBUG