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Date:	Wed, 23 Jan 2008 04:12:16 -0500
From:	Abhishek Rai <abhishekrai@...gle.com>
To:	akpm@...ux-foundation.org
Cc:	linux-kernel@...r.kernel.org, linux-ext4@...r.kernel.org,
	rohitseth@...gle.com
Subject: Re: [CALL FOR TESTING] Make Ext3 fsck way faster [2.6.24-rc6 -mm patch]

Thanks a lot for the feedback Andrew.

I've addressed your comments, details follow. I've also retested this change and implemented a minor optimization after which sequential read with metaclustering is slightly better than normal.

On Jan 14, 2008 7:34 PM, Andrew Morton <akpm@...ux-foundation.org> wrote:
> On Mon, 14 Jan 2008 08:39:01 -0500
> Abhishek Rai <abhishekrai@...gle.com> wrote:
> 
> > This is the patch for 2.6.24-rc6 -mm tree, please let me know if anyone would like a patch against another recent kernel. Ingo Molnar has already posted a patch for 2.6.24-rc7.
> >
> 
> Please always retain and maintain the full changelog with each version of a
> patch.  The changelog in your earlier "Clustering indirect blocks in Ext3"
> patch was good.  I retained that (after renaming it to "ext3: indirect
> block clustering" rather than this dopey name) and then, err, dropped the
> patch ;)
> 
> Please cc linux-ext4 on ext2/3/4-related work.

OK

> Please update Documentation/filesystems/ext3.txt when adding new mount
> options.

Added.

> Here's a quick low-levelish nitpickingish implementation review.  I haven't
> thought about the design-level things yet.
> 
> This code will need careful checking regarding the journalling side of
> things - to verify that if the machine crashes at any stage, recovery will
> produce a consistent and secure fs.  It is all-nigh impossible to spot bugs
> in this area via the usual kernel bug reporting process and it is very hard
> to effectively runtime test recovery even in a development situation.
> Careful review unusually important here.

> 
> hm, so ext3_count_free() hits prime time.
> 
> ext3_count_free() should be converted to use the standard hweight8().
> Really it should be converted to hweight_long() or hweight32() or something
> - it is presently probably inefficient.
> 
> This function appears to be called frequently and it calls the slow-looking
> ext3_count_free() under spinlock.  This might have scalability problems on
> the right machine running the right workload.
> 
> Can we address that before we hit it?

Thanks for pointing this out. ext3_count_free() now uses hweight*() functions.

> Far too large to inline.  Please just remove all inlines from the patch.
> The compiler will sort it out.

Removed 'inline' keyword from all newly added functions except one (allow_mc_alloc()) which will most definitely get inlined.

> > +static ext3_grpblk_t
> > +bitmap_find_prev_zero_bit(char *map, ext3_grpblk_t start, ext3_grpblk_t lowest)
> > +{
> > +     ext3_grpblk_t k, blk;
> > +
> > +     k = start & ~7;
> > +     while (lowest <= k) {
> > +             if (map[k/8] != '\255' &&
> > +                     (blk = ext3_find_next_zero_bit(map, k + 8, k))
> > +                      < (k + 8))
> > +                             return blk;
> > +
> > +             k -= 8;
> > +     }
> > +     return -1;
> > +}
> 
> Please rename `k' to something meaningful.
> 
> The logic in here looks odd.  If (map[k/8] != 0xff) then the
> ext3_find_next_zero_bit() cannot fail.  So why do we test for it in this
> fashion?
> 
> Perhaps some commnetary is needed here.

Rewrote this function to search for a zero bit in strictly decreasing order of block numbers. The above code was doing the search in staircase pattern which was resulting in some unwanted fragmentation. The new code also improves sequential read performance slightly. Please take a look now.

> > +static ext3_grpblk_t
> > +bitmap_search_prev_usable_block(ext3_grpblk_t start, struct buffer_head *bh,
> > +                                     ext3_grpblk_t lowest)
> > +{
> > +     ext3_grpblk_t next;
> > +     struct journal_head *jh = bh2jh(bh);
> > +
> > +     /*
> > +      * The bitmap search --- search backward alternately through the actual
> > +      * bitmap and the last-committed copy until we find a bit free in
> > +      * both
> > +      */
> > +     while (start >= lowest) {
> 
> Little style nit: in bitmap_find_prev_zero_bit() you used (lowest < k)
> which is a little surprising but I assumeed that you were following the (a
> < b < c) layout.  But here you're not doing that.

As mentioned above, this code is gone now, new code doesn't have this inconsistency.

> Whoa.  The first ever use of cpu_relax in a filesystem (apart from sysfs,
> but that's hardy endorsement).
> 
> What are you trying to do here?  Why was this needed?

Agreed, it was not very useful / was an overkill, so nuked it.

> 
> > +             }
> > +             if (allocated < indirect_blks)
> > +                     blk = bitmap_search_prev_usable_block(blk, bitmap_bh,
> > +                                                             mc_start);
> > +     }
> > +     return allocated;
> > +}
> > +
> > +/*
> > + * check_allocated_blocks:
> > + *   Helper function for ext3_new_blocks. Checks newly allocated block
> > + *   numbers.
> > + */
> > +int check_allocated_blocks(ext3_fsblk_t blk, unsigned long num,
> > +                             struct super_block *sb, int group_no,
> > +                             struct ext3_group_desc *gdp,
> > +                             struct buffer_head *bitmap_bh)
> > +{
> > +     struct ext3_super_block *es = EXT3_SB(sb)->s_es;
> > +     struct ext3_sb_info *sbi = EXT3_SB(sb);
> > +     ext3_fsblk_t grp_blk = blk - ext3_group_first_block_no(sb, group_no);
> > +
> > +     if (in_range(le32_to_cpu(gdp->bg_block_bitmap), blk, num) ||
> > +             in_range(le32_to_cpu(gdp->bg_inode_bitmap), blk, num) ||
> > +             in_range(blk, le32_to_cpu(gdp->bg_inode_table),
> > +                             EXT3_SB(sb)->s_itb_per_group) ||
> > +             in_range(blk + num - 1, le32_to_cpu(gdp->bg_inode_table),
> > +                             EXT3_SB(sb)->s_itb_per_group)) {
> > +             ext3_error(sb, "ext3_new_blocks",
> > +                             "Allocating block in system zone - "
> > +                             "blocks from "E3FSBLK", length %lu",
> > +                             blk, num);
> > +             return 1;
> > +     }
> > +
> > +#ifdef CONFIG_JBD_DEBUG
> > +     {
> > +             struct buffer_head *debug_bh;
> > +
> > +             /* Record bitmap buffer state in the newly allocated block */
> > +             debug_bh = sb_find_get_block(sb, blk);
> > +             if (debug_bh) {
> > +                     BUFFER_TRACE(debug_bh, "state when allocated");
> > +                     BUFFER_TRACE2(debug_bh, bitmap_bh, "bitmap state");
> > +                     brelse(debug_bh);
> > +             }
> > +     }
> > +     jbd_lock_bh_state(bitmap_bh);
> > +     spin_lock(sb_bgl_lock(sbi, group_no));
> > +     if (buffer_jbd(bitmap_bh) && bh2jh(bitmap_bh)->b_committed_data) {
> > +             int i;
> > +
> > +             for (i = 0; i < num; i++) {
> > +                     if (ext3_test_bit(grp_blk+i,
> > +                                     bh2jh(bitmap_bh)->b_committed_data))
> > +                             printk(KERN_ERR "%s: block was unexpectedly set"
> > +                                     " in b_committed_data\n", __FUNCTION__);
> > +             }
> > +     }
> > +     ext3_debug("found bit %d\n", grp_blk);
> > +     spin_unlock(sb_bgl_lock(sbi, group_no));
> > +     jbd_unlock_bh_state(bitmap_bh);
> > +#endif
> 
> Has the CONFIG_JBD_DEBUG=y code been tested?

This piece of code was simply a reshuffle of existing code. In particular, the new check_allocated_blocks() function contains only what the old ext3_new_blocks() used to have for checking newly allocated blocks. So I'd think we don't need explicit testing of these cases as such. But if you think I should test it, please let me know and I'll be glad to do so.

> > +             /* Should this be called before ext3_journal_dirty_metadata? */
> 
> If you're concerned here I'd suggest that you formulate a question for the
> ext3/4 maintainers to think about.

Thanks for the suggestion, I've emailed linux-ext4.

> > + *   waier can unblock.
> 
> typo.

Fixed

> > + */
> > +static void ext3_ind_read_end_bio(struct bio *bio, int err)
> > +{
> > +     struct ext3_ind_read_info *read_info = bio->bi_private;
> > +     struct buffer_head *bh;
> > +     int uptodate = !err && test_bit(BIO_UPTODATE, &bio->bi_flags);
> 
> It's pretty regrettable that ext3 now starts using bios directly.  All of
> jbd and ext3 has thus far avoided this additional coupling.
> 
> Why was this necessary?
...
> 
> Again, I really don't see why we needed to dive into the BIO layer for
> this.  Why not use submit_bh() and friends for all of this?
> 
> Also, why is it necessary to do block sorting at the filesystem level?  The
> block layer does that.
> 

There are two main factors which are responsible for the way this patch was using bios.
(1) I initially started with what seemed like the most obvious choice to me, which is also what you suggested: issue read to each indirect block individually using submit_bh(). However, in my experiments I observed that coalescing of requests was sometimes suboptimal. I tried to investigate this behavior but gave up and started directly invoking bio layer to ensure maximum coalescing.
(2) The second problem I had was that bio layer would sometimes not behave correctly when invoked with a physically-discontiguous range of blocks, even though the interface suggests that this should work without any problems. Someone told me that it's "common understanding" that submit_bio() should only be used for a physically contiguous range. So I had to break the discontiguous requests into smaller contiguous requests which would each be sorted to be contiguous before invoking submit_bio.

I was not aware that Ext3 developers have put in a lot of effort to avoid directly accessing the bio layer. But now that you pointed this out, I went back and retried using submit_bh() for each buffer and turns out it's working fine now. So probably there was something amiss in my blktrace-based analysis previously which led me to believe that the IO stream going to disk is fragmented. The new patch uses submit_bh() here which makes it smaller by almost 300 lines of code.

> 
> This is far too large to be inlined.

Removed 'inline'.

> > +     max_read = min_t(unsigned long, remaining_ind_blks_in_dind,
> > +                      remaining_ind_blks_before_eof);
> 
> Can use plain old min() here.

Done

> > +     BUG_ON(max_read < 1);
> 
> Please prefer to use the (much) friendlier ext3_error() over the
> user-hostile BUG.  Where it makes sense.
> 
> This is especially the case where the assertion could be triggered by
> corrupted disk contents - doing a BUG() in response to that is a coding
> bug.

Done

> > +static void ind_info_swap(void *a, void *b, int size)
> > +{
> > +     struct ind_block_info *info_a = (struct ind_block_info *)a;
> > +     struct ind_block_info *info_b = (struct ind_block_info *)b;
> > +     struct ind_block_info tmp;
> > +
> > +     tmp = *info_a;
> > +     *info_a = *info_b;
> > +     *info_b = tmp;
> > +}
> 
> Unneeded (and undesirable) casts of void*.

Fixed

> > +/*
> > + * ext3_read_indblocks_async --
> > + *      @sb:            super block
> > + *      @ind_blocks[]:  array of indirect block numbers on disk
> > + *      @count:         maximum number of indirect blocks to read
> > + *      @first_bh:      buffer_head for indirect block ind_blocks[0], may be
> > + *                      NULL
> > + *      @seq_prefetch:  if this is part of a sequential prefetch and buffers'
> > + *                      prefetch bit must be set.
> > + *      @blocks_done:   number of blocks considered for prefetching.
> > + *
> > + *      Issue a single bio request to read upto count buffers identified in
> > + *      ind_blocks[]. Fewer than count buffers may be read in some cases:
> > + *      - If a buffer is found to be uptodate and it's prefetch bit is set, we
> > + *      don't look at any more buffers as they will most likely be in the cache.
> > + *      - We skip buffers we cannot lock without blocking (except for first_bh
> > + *      if specified).
> > + *      - We skip buffers beyond a certain range on disk.
> > + *
> > + *      This function must issue read on first_bh if specified unless of course
> > + *      it's already uptodate.
> > + */
> 
> This comment is almost-but-not-quite in kerneldoc format.  Please review
> the /** comments in ext3 and convert newly-added commetns to match.

Fixed all comments in the patch.

> > +     count = min_t(unsigned long, count, EXT3_IND_READ_MAX);
> 
> Both count and EXT3_IND_READ_MAX are plain old int.  Forcing them to ulong
> for this comparison is a little odd.
> 
> Please check whether those two things have appropriate types - can they
> ever legitimately go negative?  I doubt it, in which case they should have
> unsigned types.
> 
> Please review all newly-added min_t's for these things.

Checked all newly added min and min_t's and changed some according to your suggestion.

> > +     *blocks_done = 0UL;
> > +
> > +     if (count == 1 && first_bh) {
> 
> This comparison could do with a comment explaining what's happening?

Added comment.

> > +                     brelse(bh);
> 
> brelse() is an old-fashioned thing which checks for a NULL arg.  Unless you
> really have a bh* which might legitimately be NULL, please prefer put_bh().
> 

Fixed.

> 
> I'm wondering about the interaction between this code and the
> buffer_boundary() logic.  I guess we should disable the buffer_boundary()
> handling when this code is in effect.  Have you reviewed and tested that
> aspect?

Thanks for pointing this out, I had totally missed this issue in my change. I've now made the call to set_buffer_boundary() in ext3_get_blocks_handle() subject to metacluster option being set.

> 
> > @@ -1692,6 +1699,13 @@ static int ext3_fill_super (struct super
> >       }
> >       sbi->s_frags_per_block = 1;
> >       sbi->s_blocks_per_group = le32_to_cpu(es->s_blocks_per_group);
> > +     if (test_opt(sb, METACLUSTER)) {
> > +             sbi->s_nonmc_blocks_per_group = sbi->s_blocks_per_group -
> > +                     sbi->s_blocks_per_group / 12;
> > +             sbi->s_nonmc_blocks_per_group &= ~7;
> > +     } else
> > +             sbi->s_nonmc_blocks_per_group = sbi->s_blocks_per_group;
> > +
> 
> hm, magic numbers.

Added comments explaining the magic numbers.

Thanks

Updated patch for linux-2.6.24-rc8 follows.


Signed-off-by: Abhishek Rai <abhishekrai@...gle.com>

diff -rupdN linux-2.6.24-rc8-clean/Documentation/filesystems/ext3.txt linux-2.6.24-rc8-ext3mc/Documentation/filesystems/ext3.txt
--- linux-2.6.24-rc8-clean/Documentation/filesystems/ext3.txt	2008-01-17 15:18:47.000000000 -0500
+++ linux-2.6.24-rc8-ext3mc/Documentation/filesystems/ext3.txt	2008-01-23 02:58:13.000000000 -0500
@@ -121,6 +121,8 @@ nobh			(a) cache disk block mapping info
 			"nobh" option tries to avoid associating buffer
 			heads (supported only for "writeback" mode).
 
+metacluster		Enable metaclustering for indirect block allocation.
+
 
 Specification
 =============
Binary files linux-2.6.24-rc8-clean/fs/ext3/.balloc.c.swp and linux-2.6.24-rc8-ext3mc/fs/ext3/.balloc.c.swp differ
Binary files linux-2.6.24-rc8-clean/fs/ext3/.bitmap.c.swp and linux-2.6.24-rc8-ext3mc/fs/ext3/.bitmap.c.swp differ
Binary files linux-2.6.24-rc8-clean/fs/ext3/.inode.c.swp and linux-2.6.24-rc8-ext3mc/fs/ext3/.inode.c.swp differ
diff -rupdN linux-2.6.24-rc8-clean/fs/ext3/balloc.c linux-2.6.24-rc8-ext3mc/fs/ext3/balloc.c
--- linux-2.6.24-rc8-clean/fs/ext3/balloc.c	2008-01-17 15:18:50.000000000 -0500
+++ linux-2.6.24-rc8-ext3mc/fs/ext3/balloc.c	2008-01-23 03:47:19.000000000 -0500
@@ -33,6 +33,29 @@
  * 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_fill_super).
+ *
+ * A note on ext3 metaclustering:
+ *
+ * 	Start of						End of
+ * 	block group						block group
+ * 	 ________________________________________________________________
+ * 	|	NON-MC REGION			|	MC REGION	 |
+ * 	|					|Overflow		 |
+ * 	|Data blocks and			|data		Indirect |
+ * 	|overflow indirect blocks		|blocks		blocks	 |
+ * 	|----------> 				|------->	<--------|
+ * 	|________________________________________________________________|
+ *
+ * 	Every block group has at its end a semi-reserved region called the
+ * 	metacluster mostly used for allocating indirect blocks. Under normal
+ * 	circumstances, the metacluster is used only for allocating indirect
+ * 	blocks which are allocated in decreasing order of block numbers.
+ * 	The non-Metacluster region is used for data block allocation which are
+ * 	allocated in increasing order of block numbers. However, when the MC
+ * 	runs out of space, indirect blocks can be allocated in the non-MC
+ * 	region along with the data blocks in the forward direction. Similarly,
+ * 	when non-MC runs out of space, new data blocks are allocated in MC but
+ * 	in the forward direction.
  */
 
 
@@ -108,6 +131,92 @@ read_block_bitmap(struct super_block *sb
 error_out:
 	return bh;
 }
+
+/*
+ * Count number of free blocks in a block group that don't lie in the
+ * metacluster region of the block group.
+ */
+static void
+ext3_init_grp_free_nonmc_blocks(struct super_block *sb,
+				struct buffer_head *bitmap_bh,
+				unsigned long block_group)
+{
+	struct ext3_sb_info *sbi = EXT3_SB(sb);
+	struct ext3_bg_info *bgi = &sbi->s_bginfo[block_group];
+
+	BUG_ON(!test_opt(sb, METACLUSTER));
+
+	spin_lock(sb_bgl_lock(sbi, block_group));
+	if (bgi->bgi_free_nonmc_blocks_count >= 0)
+		goto out;
+
+	bgi->bgi_free_nonmc_blocks_count =
+		ext3_count_free(bitmap_bh, sbi->s_nonmc_blocks_per_group/8);
+
+out:
+	spin_unlock(sb_bgl_lock(sbi, block_group));
+	if (bgi->bgi_free_nonmc_blocks_count > sbi->s_nonmc_blocks_per_group)
+		ext3_error(sb, "ext3_init_grp_free_nonmc_blocks",
+			"Number of free nonmc blocks (%d) exceeds max (%lu)",
+			bgi->bgi_free_nonmc_blocks_count,
+			sbi->s_nonmc_blocks_per_group);
+}
+
+/**
+ * ext3_update_nonmc_block_count - Update free nonmc blocks count for group.
+ * @group_no:	affected block group
+ * @start:		start of the [de]allocated range
+ * @count:		number of blocks [de]allocated
+ * @allocation:	1 if blocks were allocated, 0 otherwise.
+ */
+static void
+ext3_update_nonmc_block_count(struct super_block *sb, unsigned long block_group,
+				ext3_grpblk_t start, unsigned long count,
+				int allocation)
+{
+	struct ext3_sb_info *sbi = EXT3_SB(sb);
+	struct ext3_bg_info *bgi = &sbi->s_bginfo[block_group];
+	ext3_grpblk_t change;
+
+	BUG_ON(bgi->bgi_free_nonmc_blocks_count < 0);
+	BUG_ON(start >= sbi->s_nonmc_blocks_per_group);
+
+	change = min_t(ext3_grpblk_t, start + count,
+			sbi->s_nonmc_blocks_per_group) - start;
+
+	spin_lock(sb_bgl_lock(sbi, block_group));
+	if (allocation && bgi->bgi_free_nonmc_blocks_count < change)
+		ext3_error(sb, "ext3_update_nonmc_block_count",
+			"Allocated more nonmc blocks (%d) than are free (%d)",
+			change, bgi->bgi_free_nonmc_blocks_count);
+
+	bgi->bgi_free_nonmc_blocks_count += (allocation ? -change : change);
+
+	if (bgi->bgi_free_nonmc_blocks_count > sbi->s_nonmc_blocks_per_group)
+		ext3_error(sb, "ext3_update_nonmc_block_count",
+			"Number of free nonmc blocks (%d) exceeds max (%lu)",
+			bgi->bgi_free_nonmc_blocks_count,
+			sbi->s_nonmc_blocks_per_group);
+	spin_unlock(sb_bgl_lock(sbi, block_group));
+}
+
+/*
+ * Check if we can use metacluster region of a block group for data block
+ * allocation if needed. Ideally, we should allow this only if
+ * bgi_free_nonmc_blocks_count == 0, but sometimes there is a small number
+ * of blocks which don't get allocated in the first pass, no point
+ * breaking our file at the metacluster boundary because of that, so we
+ * relax the limit to 8.
+ */
+static inline int fail_datablk_alloc_from_mc(struct ext3_sb_info *sbi,
+					struct ext3_bg_info *bgi,
+					ext3_grpblk_t blk)
+{
+	return (blk >= 0 && blk >= sbi->s_nonmc_blocks_per_group &&
+		bgi->bgi_free_nonmc_blocks_count >= 8);
+}
+
+
 /*
  * The reservation window structure operations
  * --------------------------------------------
@@ -424,6 +533,7 @@ void ext3_free_blocks_sb(handle_t *handl
 	struct ext3_group_desc * desc;
 	struct ext3_super_block * es;
 	struct ext3_sb_info *sbi;
+	struct ext3_bg_info *bgi;
 	int err = 0, ret;
 	ext3_grpblk_t group_freed;
 
@@ -463,6 +573,13 @@ do_more:
 	if (!desc)
 		goto error_return;
 
+	if (test_opt(sb, METACLUSTER)) {
+		bgi = &sbi->s_bginfo[block_group];
+		if (bgi->bgi_free_nonmc_blocks_count < 0)
+			ext3_init_grp_free_nonmc_blocks(sb, bitmap_bh,
+							block_group);
+	}
+
 	if (in_range (le32_to_cpu(desc->bg_block_bitmap), block, count) ||
 	    in_range (le32_to_cpu(desc->bg_inode_bitmap), block, count) ||
 	    in_range (block, le32_to_cpu(desc->bg_inode_table),
@@ -582,6 +699,9 @@ do_more:
 	if (!err) err = ret;
 	*pdquot_freed_blocks += group_freed;
 
+	if (test_opt(sb, METACLUSTER) && bit < sbi->s_nonmc_blocks_per_group)
+		ext3_update_nonmc_block_count(sb, block_group, bit, count, 0);
+
 	if (overflow && !err) {
 		block += count;
 		count = overflow;
@@ -745,6 +865,73 @@ find_next_usable_block(ext3_grpblk_t sta
 	return here;
 }
 
+/*
+ * Find previous zero bit in bitmap 'map' in the range [lowest, start]
+ * both inclusive.
+ */
+static ext3_grpblk_t
+bitmap_find_prev_zero_bit(char *map, ext3_grpblk_t start, ext3_grpblk_t lowest)
+{
+	ext3_grpblk_t blk;
+	unsigned int word, index, high_bit, low_bit, num_bits, last_set_bit;
+
+	blk = start;
+	index = (blk >> 3) & ~3U;
+	while (blk >= lowest) {
+		word = *((unsigned int *)&map[index]);
+		high_bit = blk & 31;
+		num_bits = 1 + min_t(unsigned int, high_bit, blk - lowest);
+
+		if (num_bits != 32 || word != ~0U) {
+			/*
+			 * Find last zero bit in word. Since we are using fls()
+			 * for this purpose, use complement of word. Also, if
+			 * num_bits != 32, only consider bits low_bit:num_bits
+			 * zeroing out the remaining bits.
+			 */
+			word = ~word;
+			if (num_bits != 32) {
+				low_bit = (high_bit + 1) - num_bits;
+				word &= (((1U << num_bits) - 1) << low_bit);
+			}
+			last_set_bit = fls(word);
+			if (last_set_bit)
+				return last_set_bit - 1 + (blk & ~31);
+		}
+
+		blk -= num_bits;
+		index -= 4;
+	}
+	return -1;
+}
+
+static ext3_grpblk_t
+bitmap_search_prev_usable_block(ext3_grpblk_t start, struct buffer_head *bh,
+					ext3_grpblk_t lowest)
+{
+	ext3_grpblk_t next;
+	struct journal_head *jh = bh2jh(bh);
+
+	/*
+	 * The bitmap search --- search backward alternately through the actual
+	 * bitmap and the last-committed copy until we find a bit free in
+	 * both
+	 */
+	while (start >= lowest) {
+		next = bitmap_find_prev_zero_bit(bh->b_data, start, lowest);
+		if (next < lowest)
+			return -1;
+		if (ext3_test_allocatable(next, bh))
+			return next;
+		jbd_lock_bh_state(bh);
+		if (jh->b_committed_data)
+			start = bitmap_find_prev_zero_bit(jh->b_committed_data,
+								next, lowest);
+		jbd_unlock_bh_state(bh);
+	}
+	return -1;
+}
+
 /**
  * claim_block()
  * @block:		the free block (group relative) to allocate
@@ -794,19 +981,27 @@ claim_block(spinlock_t *lock, ext3_grpbl
  *	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.  In that case we must release write access to the old one via
- * ext3_journal_release_buffer(), else we'll run out of credits.
  */
 static ext3_grpblk_t
 ext3_try_to_allocate(struct super_block *sb, handle_t *handle, int group,
 			struct buffer_head *bitmap_bh, ext3_grpblk_t grp_goal,
 			unsigned long *count, struct ext3_reserve_window *my_rsv)
 {
+	struct ext3_sb_info *sbi = EXT3_SB(sb);
+	struct ext3_group_desc *gdp;
+	struct ext3_bg_info *bgi = NULL;
+	struct buffer_head *gdp_bh;
 	ext3_fsblk_t group_first_block;
 	ext3_grpblk_t start, end;
 	unsigned long num = 0;
+	const int metaclustering = test_opt(sb, METACLUSTER);
+
+	if (metaclustering)
+		bgi = &sbi->s_bginfo[group];
+
+	gdp = ext3_get_group_desc(sb, group, &gdp_bh);
+	if (!gdp)
+		goto fail_access;
 
 	/* we do allocation within the reservation window if we have a window */
 	if (my_rsv) {
@@ -851,8 +1046,10 @@ repeat:
 	}
 	start = grp_goal;
 
-	if (!claim_block(sb_bgl_lock(EXT3_SB(sb), group),
-		grp_goal, bitmap_bh)) {
+	if (metaclustering && fail_datablk_alloc_from_mc(sbi, bgi, grp_goal))
+		goto fail_access;
+
+	if (!claim_block(sb_bgl_lock(sbi, group), grp_goal, bitmap_bh)) {
 		/*
 		 * The block was allocated by another thread, or it was
 		 * allocated and then freed by another thread
@@ -867,8 +1064,9 @@ repeat:
 	grp_goal++;
 	while (num < *count && grp_goal < end
 		&& ext3_test_allocatable(grp_goal, bitmap_bh)
-		&& claim_block(sb_bgl_lock(EXT3_SB(sb), group),
-				grp_goal, bitmap_bh)) {
+		&& (!metaclustering ||
+		    !fail_datablk_alloc_from_mc(sbi, bgi, grp_goal))
+		&& claim_block(sb_bgl_lock(sbi, group), grp_goal, bitmap_bh)) {
 		num++;
 		grp_goal++;
 	}
@@ -1099,7 +1297,9 @@ static int alloc_new_reservation(struct 
 
 	/*
 	 * find_next_reservable_window() simply finds a reservable window
-	 * inside the given range(start_block, group_end_block).
+	 * inside the given range(start_block, group_end_block). The
+	 * reservation window must have a reservable free bit inside it for our
+	 * callers to work correctly.
 	 *
 	 * To make sure the reservation window has a free bit inside it, we
 	 * need to check the bitmap after we found a reservable window.
@@ -1131,10 +1331,18 @@ retry:
 			my_rsv->rsv_start - group_first_block,
 			bitmap_bh, group_end_block - group_first_block + 1);
 
-	if (first_free_block < 0) {
+	if (first_free_block < 0 ||
+		(test_opt(sb, METACLUSTER)
+		 && fail_datablk_alloc_from_mc(EXT3_SB(sb),
+					&EXT3_SB(sb)->s_bginfo[group],
+					first_free_block))) {
 		/*
-		 * no free block left on the bitmap, no point
-		 * to reserve the space. return failed.
+		 * No free block left on the bitmap, no point to reserve space,
+		 * return failed. We also fail here if metaclustering is enabled
+		 * and the first free block in the window lies in the
+		 * metacluster while there are free non-mc blocks in the block
+		 * group, such a window or any window following it is not useful
+		 * to us.
 		 */
 		spin_lock(rsv_lock);
 		if (!rsv_is_empty(&my_rsv->rsv_window))
@@ -1237,25 +1445,17 @@ ext3_try_to_allocate_with_rsv(struct sup
 			unsigned int group, struct buffer_head *bitmap_bh,
 			ext3_grpblk_t grp_goal,
 			struct ext3_reserve_window_node * my_rsv,
-			unsigned long *count, int *errp)
+			unsigned long *count)
 {
+	struct ext3_bg_info *bgi;
 	ext3_fsblk_t group_first_block, group_last_block;
 	ext3_grpblk_t ret = 0;
-	int fatal;
 	unsigned long num = *count;
 
-	*errp = 0;
-
-	/*
-	 * 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(bitmap_bh, "get undo access for new block");
-	fatal = ext3_journal_get_undo_access(handle, bitmap_bh);
-	if (fatal) {
-		*errp = fatal;
-		return -1;
+	if (test_opt(sb, METACLUSTER)) {
+		bgi = &EXT3_SB(sb)->s_bginfo[group];
+		if (bgi->bgi_free_nonmc_blocks_count < 0)
+			ext3_init_grp_free_nonmc_blocks(sb, bitmap_bh, group);
 	}
 
 	/*
@@ -1331,19 +1531,6 @@ ext3_try_to_allocate_with_rsv(struct sup
 		num = *count;
 	}
 out:
-	if (ret >= 0) {
-		BUFFER_TRACE(bitmap_bh, "journal_dirty_metadata for "
-					"bitmap block");
-		fatal = ext3_journal_dirty_metadata(handle, bitmap_bh);
-		if (fatal) {
-			*errp = fatal;
-			return -1;
-		}
-		return ret;
-	}
-
-	BUFFER_TRACE(bitmap_bh, "journal_release_buffer");
-	ext3_journal_release_buffer(handle, bitmap_bh);
 	return ret;
 }
 
@@ -1389,22 +1576,138 @@ int ext3_should_retry_alloc(struct super
 	return journal_force_commit_nested(EXT3_SB(sb)->s_journal);
 }
 
+/*
+ * Helper function for ext3_new_blocks. Allocates indirect blocks from the
+ * metacluster region only and stores their numbers in new_blocks[].
+ */
+int ext3_alloc_indirect_blocks(struct super_block *sb,
+			struct buffer_head *bitmap_bh,
+			struct ext3_group_desc *gdp,
+			int group_no, unsigned long indirect_blks,
+			ext3_fsblk_t new_blocks[])
+{
+	struct ext3_bg_info *bgi = &EXT3_SB(sb)->s_bginfo[group_no];
+	ext3_grpblk_t blk = EXT3_BLOCKS_PER_GROUP(sb) - 1;
+	ext3_grpblk_t mc_start = EXT3_SB(sb)->s_nonmc_blocks_per_group;
+	ext3_fsblk_t group_first_block;
+	int allocated = 0;
+
+	BUG_ON(!test_opt(sb, METACLUSTER));
+
+	/* This check is racy but that wouldn't harm us. */
+	if (bgi->bgi_free_nonmc_blocks_count >=
+		le16_to_cpu(gdp->bg_free_blocks_count))
+		return 0;
+
+	group_first_block = ext3_group_first_block_no(sb, group_no);
+	while (allocated < indirect_blks && blk >= mc_start) {
+		if (!ext3_test_allocatable(blk, bitmap_bh)) {
+			blk = bitmap_search_prev_usable_block(blk, bitmap_bh,
+								mc_start);
+			continue;
+		}
+		if (claim_block(sb_bgl_lock(EXT3_SB(sb), group_no), blk,
+				bitmap_bh))
+			new_blocks[allocated++] = group_first_block + blk;
+		if (allocated < indirect_blks)
+			blk = bitmap_search_prev_usable_block(blk, bitmap_bh,
+								mc_start);
+	}
+	return allocated;
+}
+
+/*
+ * Helper function for ext3_new_blocks. Checks newly allocated block numbers.
+ */
+int check_allocated_blocks(ext3_fsblk_t blk, unsigned long num,
+				struct super_block *sb, int group_no,
+				struct ext3_group_desc *gdp,
+				struct buffer_head *bitmap_bh)
+{
+	struct ext3_super_block *es = EXT3_SB(sb)->s_es;
+	struct ext3_sb_info *sbi = EXT3_SB(sb);
+	ext3_fsblk_t grp_blk = blk - ext3_group_first_block_no(sb, group_no);
+
+	if (in_range(le32_to_cpu(gdp->bg_block_bitmap), blk, num) ||
+		in_range(le32_to_cpu(gdp->bg_inode_bitmap), blk, num) ||
+		in_range(blk, le32_to_cpu(gdp->bg_inode_table),
+				EXT3_SB(sb)->s_itb_per_group) ||
+		in_range(blk + num - 1, le32_to_cpu(gdp->bg_inode_table),
+				EXT3_SB(sb)->s_itb_per_group))
+		ext3_error(sb, "ext3_new_blocks",
+				"Allocating block in system zone - "
+				"blocks from "E3FSBLK", length %lu",
+				blk, num);
+
+#ifdef CONFIG_JBD_DEBUG
+	{
+		struct buffer_head *debug_bh;
+
+		/* Record bitmap buffer state in the newly allocated block */
+		debug_bh = sb_find_get_block(sb, blk);
+		if (debug_bh) {
+			BUFFER_TRACE(debug_bh, "state when allocated");
+			BUFFER_TRACE2(debug_bh, bitmap_bh, "bitmap state");
+			brelse(debug_bh);
+		}
+	}
+	jbd_lock_bh_state(bitmap_bh);
+	spin_lock(sb_bgl_lock(sbi, group_no));
+	if (buffer_jbd(bitmap_bh) && bh2jh(bitmap_bh)->b_committed_data) {
+		int i;
+
+		for (i = 0; i < num; i++) {
+			if (ext3_test_bit(grp_blk+i,
+					bh2jh(bitmap_bh)->b_committed_data))
+				printk(KERN_ERR "%s: block was unexpectedly set"
+					" in b_committed_data\n", __FUNCTION__);
+		}
+	}
+	ext3_debug("found bit %d\n", grp_blk);
+	spin_unlock(sb_bgl_lock(sbi, group_no));
+	jbd_unlock_bh_state(bitmap_bh);
+#endif
+
+	if (blk + num - 1 >= le32_to_cpu(es->s_blocks_count)) {
+		ext3_error(sb, "ext3_new_blocks",
+				"block("E3FSBLK") >= blocks count(%d) - "
+				"block_group = %d, es == %p ", blk,
+				le32_to_cpu(es->s_blocks_count), group_no, es);
+		return 1;
+	}
+
+	return 0;
+}
+
 /**
- * ext3_new_blocks() -- core block(s) allocation function
- * @handle:		handle to this transaction
+ * ext3_new_blocks - allocate indirect blocks and direct blocks.
+ * @handle:	handle to this transaction
  * @inode:		file inode
  * @goal:		given target block(filesystem wide)
- * @count:		target number of blocks to allocate
- * @errp:		error code
+ * @indirect_blks:	number of indirect blocks to allocate
+ * @blks:		number of direct blocks to allocate
+ * @new_blocks:		this will store the block numbers of indirect blocks
+ *		and direct blocks upon return.
  *
- * ext3_new_blocks uses a goal block to assist allocation.  It tries to
- * allocate block(s) from the block group contains the goal block first. If that
- * fails, it will try to allocate block(s) from other block groups without
- * any specific goal block.
+ * returns the number of direct blocks allocated. Fewer than requested
+ * number of direct blocks may be allocated but all requested indirect
+ * blocks must be allocated in order to return success.
+ *
+ * Without metaclustering, ext3_new_block allocates all blocks using a
+ * goal block to assist allocation.  It tries to allocate block(s) from
+ * the block group contains the goal block first. If that fails, it will
+ * try to allocate block(s) from other block groups without any specific
+ * goal block.
+ *
+ * With metaclustering, the only difference is that indirect block
+ * allocation is first attempted in the metacluster region of the same
+ * block group failing which they are allocated along with direct blocks.
  *
+ * This function also updates quota and i_blocks field.
  */
-ext3_fsblk_t ext3_new_blocks(handle_t *handle, struct inode *inode,
-			ext3_fsblk_t goal, unsigned long *count, int *errp)
+int ext3_new_blocks(handle_t *handle, struct inode *inode,
+			ext3_fsblk_t goal, int indirect_blks, int blks,
+			ext3_fsblk_t new_blocks[4], int *errp)
 {
 	struct buffer_head *bitmap_bh = NULL;
 	struct buffer_head *gdp_bh;
@@ -1413,10 +1716,16 @@ ext3_fsblk_t ext3_new_blocks(handle_t *h
 	ext3_grpblk_t grp_target_blk;	/* blockgroup relative goal block */
 	ext3_grpblk_t grp_alloc_blk;	/* blockgroup-relative allocated block*/
 	ext3_fsblk_t ret_block;		/* filesyetem-wide allocated block */
+	ext3_fsblk_t group_first_block; /* first block in the group */
 	int bgi;			/* blockgroup iteration index */
 	int fatal = 0, err;
 	int performed_allocation = 0;
 	ext3_grpblk_t free_blocks;	/* number of free blocks in a group */
+	unsigned long ngroups;
+	unsigned long grp_mc_alloc;/* blocks allocated from mc in a group */
+	unsigned long grp_alloc;   /* blocks allocated outside mc in a group */
+	int indirect_blks_done = 0;/* total ind blocks allocated so far */
+	int blks_done = 0;	   /* total direct blocks allocated */
 	struct super_block *sb;
 	struct ext3_group_desc *gdp;
 	struct ext3_super_block *es;
@@ -1424,23 +1733,23 @@ ext3_fsblk_t ext3_new_blocks(handle_t *h
 	struct ext3_reserve_window_node *my_rsv = NULL;
 	struct ext3_block_alloc_info *block_i;
 	unsigned short windowsz = 0;
+	int i;
 #ifdef EXT3FS_DEBUG
 	static int goal_hits, goal_attempts;
 #endif
-	unsigned long ngroups;
-	unsigned long num = *count;
 
 	*errp = -ENOSPC;
 	sb = inode->i_sb;
 	if (!sb) {
-		printk("ext3_new_block: nonexistent device");
+		printk(KERN_INFO "ext3_new_blocks: nonexistent device");
+		*errp = -ENODEV;
 		return 0;
 	}
 
 	/*
 	 * Check quota for allocation of this block.
 	 */
-	if (DQUOT_ALLOC_BLOCK(inode, num)) {
+	if (DQUOT_ALLOC_BLOCK(inode, indirect_blks + blks)) {
 		*errp = -EDQUOT;
 		return 0;
 	}
@@ -1474,73 +1783,194 @@ ext3_fsblk_t ext3_new_blocks(handle_t *h
 	group_no = (goal - le32_to_cpu(es->s_first_data_block)) /
 			EXT3_BLOCKS_PER_GROUP(sb);
 	goal_group = group_no;
-retry_alloc:
-	gdp = ext3_get_group_desc(sb, group_no, &gdp_bh);
-	if (!gdp)
-		goto io_error;
-
-	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)) %
-				EXT3_BLOCKS_PER_GROUP(sb));
-		bitmap_bh = read_block_bitmap(sb, group_no);
-		if (!bitmap_bh)
-			goto io_error;
-		grp_alloc_blk = ext3_try_to_allocate_with_rsv(sb, handle,
-					group_no, bitmap_bh, grp_target_blk,
-					my_rsv,	&num, &fatal);
-		if (fatal)
-			goto out;
-		if (grp_alloc_blk >= 0)
-			goto allocated;
-	}
 
+retry_alloc:
+	grp_target_blk = ((goal - le32_to_cpu(es->s_first_data_block)) %
+			EXT3_BLOCKS_PER_GROUP(sb));
 	ngroups = EXT3_SB(sb)->s_groups_count;
 	smp_rmb();
 
 	/*
-	 * Now search the rest of the groups.  We assume that
-	 * i and gdp correctly point to the last group visited.
+	 * Iterate over successive block groups for allocating (any) indirect
+	 * blocks and direct blocks until at least one direct block has been
+	 * allocated. If metaclustering is enabled, we try allocating indirect
+	 * blocks first in the metacluster region and then in the general
+	 * region and if that fails too, we repeat the same algorithm in the
+	 * next block group and so on. This not only keeps the indirect blocks
+	 * together in the metacluster, but also keeps them in close proximity
+	 * to their corresponding direct blocks.
+	 *
+	 * The search begins and ends at the goal group, though the second time
+	 * we are at the goal group we try allocating without a goal.
 	 */
-	for (bgi = 0; bgi < ngroups; bgi++) {
-		group_no++;
+	bgi = 0;
+	while (bgi < ngroups + 1) {
+		grp_mc_alloc = 0;
+
 		if (group_no >= ngroups)
 			group_no = 0;
+
 		gdp = ext3_get_group_desc(sb, group_no, &gdp_bh);
 		if (!gdp)
 			goto io_error;
+
 		free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);
-		/*
-		 * skip this group if the number of
-		 * free blocks is less than half of the reservation
-		 * window size.
-		 */
-		if (free_blocks <= (windowsz/2))
-			continue;
+		if (group_no == goal_group) {
+			if (my_rsv && (free_blocks < windowsz)
+				&& (rsv_is_empty(&my_rsv->rsv_window)))
+				my_rsv = NULL;
+			if (free_blocks == 0)
+				goto next;
+		} else if (free_blocks <= windowsz/2)
+			goto next;
 
-		brelse(bitmap_bh);
 		bitmap_bh = read_block_bitmap(sb, group_no);
 		if (!bitmap_bh)
 			goto io_error;
+
 		/*
-		 * try to allocate block(s) from this group, without a goal(-1).
+		 * 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(bitmap_bh, "get undo access for new block");
+		fatal = ext3_journal_get_undo_access(handle, bitmap_bh);
+		if (fatal)
+			goto out;
+
+		/*
+		 * If metaclustering is enabled, first try to allocate indirect
+		 * blocks in the metacluster.
+		 */
+		if (test_opt(sb, METACLUSTER) &&
+			indirect_blks_done < indirect_blks)
+			grp_mc_alloc = ext3_alloc_indirect_blocks(sb,
+					bitmap_bh, gdp, group_no,
+					indirect_blks - indirect_blks_done,
+					new_blocks + indirect_blks_done);
+
+		/* Allocate data blocks and any leftover indirect blocks. */
+		grp_alloc = indirect_blks + blks
+				- (indirect_blks_done + grp_mc_alloc);
 		grp_alloc_blk = ext3_try_to_allocate_with_rsv(sb, handle,
-					group_no, bitmap_bh, -1, my_rsv,
-					&num, &fatal);
+					group_no, bitmap_bh, grp_target_blk,
+					my_rsv, &grp_alloc);
+		if (grp_alloc_blk < 0)
+			grp_alloc = 0;
+
+		/*
+		 * If we couldn't allocate anything, there is nothing more to
+		 * do with this block group, so move over to the next. But
+		 * before that We must release write access to the old one via
+		 * ext3_journal_release_buffer(), else we'll run out of credits.
+		 */
+		if (grp_mc_alloc == 0 && grp_alloc == 0) {
+			BUFFER_TRACE(bitmap_bh, "journal_release_buffer");
+			ext3_journal_release_buffer(handle, bitmap_bh);
+			goto next;
+		}
+
+		BUFFER_TRACE(bitmap_bh, "journal_dirty_metadata for "
+					"bitmap block");
+		fatal = ext3_journal_dirty_metadata(handle, bitmap_bh);
 		if (fatal)
 			goto out;
-		if (grp_alloc_blk >= 0)
+
+		ext3_debug("using block group %d(%d)\n",
+				group_no, gdp->bg_free_blocks_count);
+
+		BUFFER_TRACE(gdp_bh, "get_write_access");
+		fatal = ext3_journal_get_write_access(handle, gdp_bh);
+		if (fatal)
+			goto out;
+
+		/* Should this be called before ext3_journal_dirty_metadata? */
+		for (i = 0; i < grp_mc_alloc; i++) {
+			if (check_allocated_blocks(
+				new_blocks[indirect_blks_done + i], 1, sb,
+				group_no, gdp, bitmap_bh))
+				goto out;
+		}
+		if (grp_alloc > 0) {
+			ret_block = ext3_group_first_block_no(sb, group_no) +
+				grp_alloc_blk;
+			if (check_allocated_blocks(ret_block, grp_alloc, sb,
+						group_no, gdp, bitmap_bh))
+				goto out;
+		}
+
+		indirect_blks_done += grp_mc_alloc;
+		performed_allocation = 1;
+
+		/* The caller will add the new buffer to the journal. */
+		if (grp_alloc > 0)
+			ext3_debug("allocating block %lu. "
+					"Goal hits %d of %d.\n",
+					ret_block, goal_hits, goal_attempts);
+
+		spin_lock(sb_bgl_lock(sbi, group_no));
+		gdp->bg_free_blocks_count =
+			cpu_to_le16(le16_to_cpu(gdp->bg_free_blocks_count) -
+					(grp_mc_alloc + grp_alloc));
+		spin_unlock(sb_bgl_lock(sbi, group_no));
+		percpu_counter_sub(&sbi->s_freeblocks_counter,
+				(grp_mc_alloc + grp_alloc));
+
+		BUFFER_TRACE(gdp_bh, "journal_dirty_metadata for "
+				"group descriptor");
+		err = ext3_journal_dirty_metadata(handle, gdp_bh);
+		if (!fatal)
+			fatal = err;
+
+		sb->s_dirt = 1;
+		if (fatal)
+			goto out;
+
+		brelse(bitmap_bh);
+		bitmap_bh = NULL;
+
+		if (grp_alloc == 0)
+			goto next;
+
+		/* Update block group non-mc block count since we used some. */
+		if (test_opt(sb, METACLUSTER) &&
+			grp_alloc_blk < sbi->s_nonmc_blocks_per_group)
+			ext3_update_nonmc_block_count(sb, group_no,
+				grp_alloc_blk, grp_alloc, 1);
+
+		/*
+		 * Assign all the non-mc blocks that we allocated from this
+		 * block group.
+		 */
+		group_first_block = ext3_group_first_block_no(sb, group_no);
+		while (grp_alloc > 0 && indirect_blks_done < indirect_blks) {
+			new_blocks[indirect_blks_done++] =
+				group_first_block + grp_alloc_blk;
+			grp_alloc_blk++;
+			grp_alloc--;
+		}
+
+		if (grp_alloc > 0) {
+			blks_done = grp_alloc;
+			new_blocks[indirect_blks_done] =
+				group_first_block + grp_alloc_blk;
 			goto allocated;
+		}
+
+		/*
+		 * If we allocated something but not the minimum required,
+		 * it's OK to retry in this group as it might have more free
+		 * blocks.
+		 */
+		continue;
+
+next:
+		bgi++;
+		group_no++;
+		grp_target_blk = -1;
 	}
+
 	/*
 	 * We may end up a bogus ealier ENOSPC error due to
 	 * filesystem is "full" of reservations, but
@@ -1559,96 +1989,11 @@ retry_alloc:
 	goto out;
 
 allocated:
-
-	ext3_debug("using block group %d(%d)\n",
-			group_no, gdp->bg_free_blocks_count);
-
-	BUFFER_TRACE(gdp_bh, "get_write_access");
-	fatal = ext3_journal_get_write_access(handle, gdp_bh);
-	if (fatal)
-		goto out;
-
-	ret_block = grp_alloc_blk + ext3_group_first_block_no(sb, group_no);
-
-	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),
-		      EXT3_SB(sb)->s_itb_per_group) ||
-	    in_range(ret_block + num - 1, le32_to_cpu(gdp->bg_inode_table),
-		      EXT3_SB(sb)->s_itb_per_group))
-		ext3_error(sb, "ext3_new_block",
-			    "Allocating block in system zone - "
-			    "blocks from "E3FSBLK", length %lu",
-			     ret_block, num);
-
-	performed_allocation = 1;
-
-#ifdef CONFIG_JBD_DEBUG
-	{
-		struct buffer_head *debug_bh;
-
-		/* Record bitmap buffer state in the newly allocated block */
-		debug_bh = sb_find_get_block(sb, ret_block);
-		if (debug_bh) {
-			BUFFER_TRACE(debug_bh, "state when allocated");
-			BUFFER_TRACE2(debug_bh, bitmap_bh, "bitmap state");
-			brelse(debug_bh);
-		}
-	}
-	jbd_lock_bh_state(bitmap_bh);
-	spin_lock(sb_bgl_lock(sbi, group_no));
-	if (buffer_jbd(bitmap_bh) && bh2jh(bitmap_bh)->b_committed_data) {
-		int i;
-
-		for (i = 0; i < num; i++) {
-			if (ext3_test_bit(grp_alloc_blk+i,
-					bh2jh(bitmap_bh)->b_committed_data)) {
-				printk("%s: block was unexpectedly set in "
-					"b_committed_data\n", __FUNCTION__);
-			}
-		}
-	}
-	ext3_debug("found bit %d\n", grp_alloc_blk);
-	spin_unlock(sb_bgl_lock(sbi, group_no));
-	jbd_unlock_bh_state(bitmap_bh);
-#endif
-
-	if (ret_block + num - 1 >= le32_to_cpu(es->s_blocks_count)) {
-		ext3_error(sb, "ext3_new_block",
-			    "block("E3FSBLK") >= blocks count(%d) - "
-			    "block_group = %d, es == %p ", ret_block,
-			le32_to_cpu(es->s_blocks_count), group_no, 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 %lu. Goal hits %d of %d.\n",
-			ret_block, goal_hits, goal_attempts);
-
-	spin_lock(sb_bgl_lock(sbi, group_no));
-	gdp->bg_free_blocks_count =
-			cpu_to_le16(le16_to_cpu(gdp->bg_free_blocks_count)-num);
-	spin_unlock(sb_bgl_lock(sbi, group_no));
-	percpu_counter_sub(&sbi->s_freeblocks_counter, num);
-
-	BUFFER_TRACE(gdp_bh, "journal_dirty_metadata for group descriptor");
-	err = ext3_journal_dirty_metadata(handle, gdp_bh);
-	if (!fatal)
-		fatal = err;
-
-	sb->s_dirt = 1;
-	if (fatal)
-		goto out;
-
 	*errp = 0;
-	brelse(bitmap_bh);
-	DQUOT_FREE_BLOCK(inode, *count-num);
-	*count = num;
-	return ret_block;
+	DQUOT_FREE_BLOCK(inode,
+			indirect_blks + blks - indirect_blks_done - blks_done);
+
+	return blks_done;
 
 io_error:
 	*errp = -EIO;
@@ -1661,7 +2006,13 @@ out:
 	 * Undo the block allocation
 	 */
 	if (!performed_allocation)
-		DQUOT_FREE_BLOCK(inode, *count);
+		DQUOT_FREE_BLOCK(inode, indirect_blks + blks);
+	/*
+	 * Free any indirect blocks we allocated already. If the transaction
+	 * has been aborted this is essentially a no-op.
+	 */
+	for (i = 0; i < indirect_blks_done; i++)
+		ext3_free_blocks(handle, inode, new_blocks[i], 1);
 	brelse(bitmap_bh);
 	return 0;
 }
@@ -1669,9 +2020,13 @@ out:
 ext3_fsblk_t ext3_new_block(handle_t *handle, struct inode *inode,
 			ext3_fsblk_t goal, int *errp)
 {
-	unsigned long count = 1;
+	ext3_fsblk_t new_blocks[4];
 
-	return ext3_new_blocks(handle, inode, goal, &count, errp);
+	ext3_new_blocks(handle, inode, goal, 0, 1, new_blocks, errp);
+	if (*errp)
+		return 0;
+
+	return new_blocks[0];
 }
 
 /**
diff -rupdN linux-2.6.24-rc8-clean/fs/ext3/bitmap.c linux-2.6.24-rc8-ext3mc/fs/ext3/bitmap.c
--- linux-2.6.24-rc8-clean/fs/ext3/bitmap.c	2008-01-17 15:18:50.000000000 -0500
+++ linux-2.6.24-rc8-ext3mc/fs/ext3/bitmap.c	2008-01-23 03:48:10.000000000 -0500
@@ -11,22 +11,14 @@
 #include <linux/jbd.h>
 #include <linux/ext3_fs.h>
 
-#ifdef EXT3FS_DEBUG
-
-static const int nibblemap[] = {4, 3, 3, 2, 3, 2, 2, 1, 3, 2, 2, 1, 2, 1, 1, 0};
-
 unsigned long ext3_count_free (struct buffer_head * map, unsigned int numchars)
 {
 	unsigned int i;
 	unsigned long sum = 0;
 
-	if (!map)
-		return (0);
-	for (i = 0; i < numchars; i++)
-		sum += nibblemap[map->b_data[i] & 0xf] +
-			nibblemap[(map->b_data[i] >> 4) & 0xf];
-	return (sum);
+	for (i = 0; i < (numchars & ~0x3); i += 4)
+		sum += hweight32(~(*((unsigned int *)&map->b_data[i])));
+	for (; i < numchars; i++)
+		sum += hweight8(~((unsigned char)map->b_data[i]));
+	return sum;
 }
-
-#endif  /*  EXT3FS_DEBUG  */
-
diff -rupdN linux-2.6.24-rc8-clean/fs/ext3/inode.c linux-2.6.24-rc8-ext3mc/fs/ext3/inode.c
--- linux-2.6.24-rc8-clean/fs/ext3/inode.c	2008-01-17 15:18:50.000000000 -0500
+++ linux-2.6.24-rc8-ext3mc/fs/ext3/inode.c	2008-01-23 03:49:24.000000000 -0500
@@ -39,7 +39,29 @@
 #include "xattr.h"
 #include "acl.h"
 
+typedef struct {
+	__le32	*p;
+	__le32	key;
+	struct buffer_head *bh;
+} Indirect;
+
+struct ext3_ind_read_info {
+	int                     count;
+	int                     seq_prefetch;
+	long                    size;
+	struct buffer_head      *bh[0];
+};
+
+# define EXT3_IND_READ_INFO_SIZE(_c)        \
+	(sizeof(struct ext3_ind_read_info) + \
+	 sizeof(struct buffer_head *) * (_c))
+
+# define EXT3_IND_READ_MAX     	(32)
+
 static int ext3_writepage_trans_blocks(struct inode *inode);
+static Indirect *ext3_read_indblocks(struct inode *inode, int iblock,
+				     int depth, int offsets[4],
+				     Indirect chain[4], int *err);
 
 /*
  * Test whether an inode is a fast symlink.
@@ -233,12 +255,6 @@ no_delete:
 	clear_inode(inode);	/* We must guarantee clearing of inode... */
 }
 
-typedef struct {
-	__le32	*p;
-	__le32	key;
-	struct buffer_head *bh;
-} Indirect;
-
 static inline void add_chain(Indirect *p, struct buffer_head *bh, __le32 *v)
 {
 	p->key = *(p->p = v);
@@ -352,18 +368,21 @@ static int ext3_block_to_path(struct ino
  *	the whole chain, all way to the data (returns %NULL, *err == 0).
  */
 static Indirect *ext3_get_branch(struct inode *inode, int depth, int *offsets,
-				 Indirect chain[4], int *err)
+				 Indirect chain[4], int ind_readahead, int *err)
 {
 	struct super_block *sb = inode->i_sb;
 	Indirect *p = chain;
 	struct buffer_head *bh;
+	int index;
 
 	*err = 0;
 	/* i_data is not going away, no lock needed */
 	add_chain (chain, NULL, EXT3_I(inode)->i_data + *offsets);
 	if (!p->key)
 		goto no_block;
-	while (--depth) {
+	for (index = 0; index < depth - 1; index++) {
+		if (ind_readahead && depth > 2 && index == depth - 2)
+			break;
 		bh = sb_bread(sb, le32_to_cpu(p->key));
 		if (!bh)
 			goto failure;
@@ -396,7 +415,11 @@ no_block:
  *	It is used when heuristic for sequential allocation fails.
  *	Rules are:
  *	  + if there is a block to the left of our position - allocate near it.
- *	  + if pointer will live in indirect block - allocate near that block.
+ *	  + If METACLUSTER options is not specified, allocate the data
+ *	  block close to the metadata block. Otherwise, if pointer will live in
+ *	  indirect block, we cannot allocate near the indirect block since
+ *	  indirect blocks are allocated in the metacluster, just put in the same
+ *	  cylinder group as the inode.
  *	  + if pointer will live in inode - allocate in the same
  *	    cylinder group.
  *
@@ -421,9 +444,11 @@ static ext3_fsblk_t ext3_find_near(struc
 			return le32_to_cpu(*p);
 	}
 
-	/* No such thing, so let's try location of indirect block */
-	if (ind->bh)
-		return ind->bh->b_blocknr;
+	if (!test_opt(inode->i_sb, METACLUSTER)) {
+		/* No such thing, so let's try location of indirect block */
+		if (ind->bh)
+			return ind->bh->b_blocknr;
+	}
 
 	/*
 	 * It is going to be referred to from the inode itself? OK, just put it
@@ -475,8 +500,7 @@ static ext3_fsblk_t ext3_find_goal(struc
  *	@blks: number of data blocks to be mapped.
  *	@blocks_to_boundary:  the offset in the indirect block
  *
- *	return the total number of blocks to be allocate, including the
- *	direct and indirect blocks.
+ *	return the total number of direct blocks to be allocated.
  */
 static int ext3_blks_to_allocate(Indirect *branch, int k, unsigned long blks,
 		int blocks_to_boundary)
@@ -505,75 +529,18 @@ static int ext3_blks_to_allocate(Indirec
 }
 
 /**
- *	ext3_alloc_blocks: multiple allocate blocks needed for a branch
- *	@indirect_blks: the number of blocks need to allocate for indirect
- *			blocks
- *
- *	@new_blocks: on return it will store the new block numbers for
- *	the indirect blocks(if needed) and the first direct block,
- *	@blks:	on return it will store the total number of allocated
- *		direct blocks
- */
-static int ext3_alloc_blocks(handle_t *handle, struct inode *inode,
-			ext3_fsblk_t goal, int indirect_blks, int blks,
-			ext3_fsblk_t new_blocks[4], int *err)
-{
-	int target, i;
-	unsigned long count = 0;
-	int index = 0;
-	ext3_fsblk_t current_block = 0;
-	int ret = 0;
-
-	/*
-	 * Here we try to allocate the requested multiple blocks at once,
-	 * on a best-effort basis.
-	 * To build a branch, we should allocate blocks for
-	 * the indirect blocks(if not allocated yet), and at least
-	 * the first direct block of this branch.  That's the
-	 * minimum number of blocks need to allocate(required)
-	 */
-	target = blks + indirect_blks;
-
-	while (1) {
-		count = target;
-		/* allocating blocks for indirect blocks and direct blocks */
-		current_block = ext3_new_blocks(handle,inode,goal,&count,err);
-		if (*err)
-			goto failed_out;
-
-		target -= count;
-		/* allocate blocks for indirect blocks */
-		while (index < indirect_blks && count) {
-			new_blocks[index++] = current_block++;
-			count--;
-		}
-
-		if (count > 0)
-			break;
-	}
-
-	/* save the new block number for the first direct block */
-	new_blocks[index] = current_block;
-
-	/* total number of blocks allocated for direct blocks */
-	ret = count;
-	*err = 0;
-	return ret;
-failed_out:
-	for (i = 0; i <index; i++)
-		ext3_free_blocks(handle, inode, new_blocks[i], 1);
-	return ret;
-}
-
-/**
  *	ext3_alloc_branch - allocate and set up a chain of blocks.
  *	@inode: owner
  *	@indirect_blks: number of allocated indirect blocks
  *	@blks: number of allocated direct blocks
+ *	@goal: goal for allocation
  *	@offsets: offsets (in the blocks) to store the pointers to next.
  *	@branch: place to store the chain in.
  *
- *	This function allocates blocks, zeroes out all but the last one,
+ *	returns error and number of direct blocks allocated via *blks
+ *
+ *	This function allocates indirect_blks + *blks, zeroes out all
+ *	indirect blocks,
  *	links them into chain and (if we are synchronous) writes them to disk.
  *	In other words, it prepares a branch that can be spliced onto the
  *	inode. It stores the information about that chain in the branch[], in
@@ -602,7 +569,7 @@ static int ext3_alloc_branch(handle_t *h
 	ext3_fsblk_t new_blocks[4];
 	ext3_fsblk_t current_block;
 
-	num = ext3_alloc_blocks(handle, inode, goal, indirect_blks,
+	num = ext3_new_blocks(handle, inode, goal, indirect_blks,
 				*blks, new_blocks, &err);
 	if (err)
 		return err;
@@ -799,17 +766,21 @@ int ext3_get_blocks_handle(handle_t *han
 	int blocks_to_boundary = 0;
 	int depth;
 	struct ext3_inode_info *ei = EXT3_I(inode);
-	int count = 0;
+	int count = 0, ind_readahead;
 	ext3_fsblk_t first_block = 0;
 
-
 	J_ASSERT(handle != NULL || create == 0);
 	depth = ext3_block_to_path(inode,iblock,offsets,&blocks_to_boundary);
 
 	if (depth == 0)
 		goto out;
 
-	partial = ext3_get_branch(inode, depth, offsets, chain, &err);
+	ind_readahead = !create && depth > 2;
+	partial = ext3_get_branch(inode, depth, offsets, chain,
+				  ind_readahead, &err);
+	if (!partial && ind_readahead)
+		partial = ext3_read_indblocks(inode, iblock, depth,
+					      offsets, chain, &err);
 
 	/* Simplest case - block found, no allocation needed */
 	if (!partial) {
@@ -844,7 +815,7 @@ int ext3_get_blocks_handle(handle_t *han
 	}
 
 	/* Next simple case - plain lookup or failed read of indirect block */
-	if (!create || err == -EIO)
+	if (!create || (err && err != -EAGAIN))
 		goto cleanup;
 
 	mutex_lock(&ei->truncate_mutex);
@@ -866,7 +837,8 @@ int ext3_get_blocks_handle(handle_t *han
 			brelse(partial->bh);
 			partial--;
 		}
-		partial = ext3_get_branch(inode, depth, offsets, chain, &err);
+		partial = ext3_get_branch(inode, depth, offsets, chain, 0,
+					&err);
 		if (!partial) {
 			count++;
 			mutex_unlock(&ei->truncate_mutex);
@@ -925,7 +897,11 @@ int ext3_get_blocks_handle(handle_t *han
 	set_buffer_new(bh_result);
 got_it:
 	map_bh(bh_result, inode->i_sb, le32_to_cpu(chain[depth-1].key));
-	if (count > blocks_to_boundary)
+	/*
+	 * If metaclustering is enabled, we assume that indirect blocks are in
+	 * the metacluster so we don't need to set buffer_boundary() here.
+	 */
+	if (!test_opt(inode->i_sb, METACLUSTER) && count > blocks_to_boundary)
 		set_buffer_boundary(bh_result);
 	err = count;
 	/* Clean up and exit */
@@ -1974,7 +1950,7 @@ static Indirect *ext3_find_shared(struct
 	/* Make k index the deepest non-null offest + 1 */
 	for (k = depth; k > 1 && !offsets[k-1]; k--)
 		;
-	partial = ext3_get_branch(inode, k, offsets, chain, &err);
+	partial = ext3_get_branch(inode, k, offsets, chain, 0, &err);
 	/* Writer: pointers */
 	if (!partial)
 		partial = chain + k-1;
@@ -3297,3 +3273,388 @@ int ext3_change_inode_journal_flag(struc
 
 	return err;
 }
+
+/**
+ * ext3_get_max_read - Compute maximum indirect blocks that can be read.
+ * @inode: inode of file.
+ * @block: block number in file (starting from zero).
+ * @offset_in_dind_block: offset of the indirect block inside it's parent
+ * doubly-indirect block.
+ *
+ * The maximum no. of indirect blocks that can be read is subject to
+ * following constraints:
+ * - Don't read indirect blocks beyond the end of current doubly-indirect
+ *   block.
+ * - Don't read beyond eof.
+ */
+static unsigned long ext3_get_max_read(const struct inode *inode,
+					int block,
+					int offset_in_dind_block)
+{
+	struct super_block *sb = inode->i_sb;
+	unsigned long max_read;
+	unsigned long ptrs = EXT3_ADDR_PER_BLOCK(inode->i_sb);
+	unsigned long ptrs_bits = EXT3_ADDR_PER_BLOCK_BITS(inode->i_sb);
+	unsigned long blocks_in_file =
+		(inode->i_size + sb->s_blocksize - 1) >> sb->s_blocksize_bits;
+	unsigned long remaining_ind_blks_in_dind =
+		(ptrs >= offset_in_dind_block) ? (ptrs - offset_in_dind_block)
+					       : 0;
+	unsigned long remaining_ind_blks_before_eof =
+		((blocks_in_file - EXT3_NDIR_BLOCKS + ptrs - 1) >> ptrs_bits) -
+		((block - EXT3_NDIR_BLOCKS) >> ptrs_bits);
+
+	if (block >= blocks_in_file)
+		ext3_error(sb, "ext3_get_max_read",
+			"block(%d) should be < blocks_in_file(%lu)", block,
+			blocks_in_file);
+
+	max_read = min(remaining_ind_blks_in_dind,
+			remaining_ind_blks_before_eof);
+
+	if (max_read < 1)
+		ext3_error(sb, "ext3_get_max_read",
+			"max_read %lu should be >= 1", max_read);
+
+	return max_read;
+}
+
+/*
+ * Callback passed to submit_bh() by ext3_read_indblocks_async().
+ */
+static void ext3_end_ind_buffer_read(struct buffer_head *bh, int uptodate)
+{
+	if (uptodate) {
+		BUG_ON(buffer_uptodate(bh));
+		BUG_ON(ext3_buffer_prefetch(bh));
+		if (bh->b_private) {
+			ext3_set_buffer_prefetch(bh);
+			bh->b_private = NULL;
+		}
+	}
+}
+
+/**
+ * ext3_read_indblocks_async - Read given indirect blocks asynchronously.
+ * @sb:			super block
+ * @ind_blocks[]:	array of indirect block numbers on disk
+ * @count:		maximum number of indirect blocks to read
+ * @first_bh:		buffer_head for block ind_blocks[0], may be NULL.
+ * @seq_prefetch:	if this is part of a sequential prefetch and buffers'
+ *		 	prefetch bit must be set.
+ * @blocks_done:	number of blocks considered for prefetching.
+ *
+ * Issue submit_bh() requests to read upto count buffers identified in
+ * ind_blocks[]. Fewer than count buffers may be read in some cases:
+ * - If a buffer is found to be uptodate and it's prefetch bit is set, we
+ * don't look at any more buffers as they will most likely be in the cache.
+ * - We skip buffers we cannot lock without blocking (except for first_bh
+ * if specified).
+ * - We skip buffers beyond a certain range on disk.
+ *
+ * This function must issue read on first_bh if specified unless of course
+ * it's already uptodate.
+ */
+static int ext3_read_indblocks_async(struct super_block *sb,
+				     const __le32 ind_blocks[],
+				     unsigned long count,
+				     struct buffer_head *first_bh,
+				     int seq_prefetch,
+				     unsigned long *blocks_done)
+{
+	struct buffer_head *bh;
+	int blk;
+	ext3_fsblk_t io_start_blk = 0, curr;
+	int err = 0;
+
+	BUG_ON(count < 1);
+	/* Don't move this to ext3_get_max_read() since callers often need to
+	 * trim the count returned by that function. So this bound must only
+	 * be imposed at the last moment. */
+	count = min_t(unsigned long, count, EXT3_IND_READ_MAX);
+	*blocks_done = 0UL;
+
+	for (blk = 0; blk < count; blk++) {
+		curr = le32_to_cpu(ind_blocks[blk]);
+		if (!curr)
+			continue;
+
+		/*
+		 * Skip this block if it lies too far from blocks we have
+		 * already decided to read. "Too far" should typically indicate
+		 * lying on a different track on the disk. EXT3_IND_READ_MAX
+		 * seems reasonable for most disks.
+		 */
+		if (io_start_blk > 0 &&
+			(max(io_start_blk, curr) - min(io_start_blk, curr) >=
+				EXT3_IND_READ_MAX))
+			continue;
+
+		/* Lock the buffer without blocking, skipping any buffers
+		 * which would require us to block. first_bh when specified is
+		 * an exception as caller typically wants it to be read for
+		 * sure (e.g., ext3_read_indblocks_sync).
+		 */
+		if (blk == 0 && first_bh) {
+			bh = first_bh;
+			get_bh(bh);
+			lock_buffer(bh);
+		} else {
+			bh = sb_getblk(sb, curr);
+			if (unlikely(!bh)) {
+				err = -ENOMEM;
+				goto failure;
+			}
+			if (test_set_buffer_locked(bh)) {
+				put_bh(bh);
+				continue;
+			}
+		}
+
+		/* Check again with the buffer locked. */
+		if (buffer_uptodate(bh)) {
+			if (ext3_buffer_prefetch(bh)) {
+				unlock_buffer(bh);
+				put_bh(bh);
+				break;
+			}
+			unlock_buffer(bh);
+			put_bh(bh);
+			continue;
+		}
+
+		if (io_start_blk == 0)
+			io_start_blk = curr;
+
+		/* bh->b_private != NULL indicates a sequential prefetch. */
+		bh->b_end_io = ext3_end_ind_buffer_read;
+		bh->b_private = seq_prefetch ? bh : NULL;
+		submit_bh(READ, bh);
+		++(*blocks_done);
+	}
+	return 0;
+
+failure:
+	return err;
+}
+
+/**
+ * ext3_read_indblocks_sync - Read given indirect blocks synchronously.
+ * @sb:		super block
+ * @ind_blocks[]: array of indirect block numbers on disk
+ * @count:	maximum number of indirect blocks to read
+ * @first_bh:	buffer_head for indirect block ind_blocks[0], must be non-NULL.
+ * @seq_prefetch: set prefetch bit of buffers, used when this is part of a
+ *		  sequential prefetch.
+ * @blocks_done:number of blocks considered for prefetching.
+ *
+ * Synchronously read at most count indirect blocks listed in ind_blocks[].
+ * This function calls ext3_read_indblocks_async() to do all the hard work.
+ * It waits for read to complete on first_bh before returning.
+ */
+
+static int ext3_read_indblocks_sync(struct super_block *sb,
+				    const __le32 ind_blocks[],
+				    unsigned long count,
+				    struct buffer_head *first_bh,
+				    int seq_prefetch,
+				    unsigned long *blocks_done)
+{
+	int err;
+
+	BUG_ON(count < 1);
+	BUG_ON(!first_bh);
+
+	err = ext3_read_indblocks_async(sb, ind_blocks, count, first_bh,
+					seq_prefetch, blocks_done);
+	if (err)
+		return err;
+
+	wait_on_buffer(first_bh);
+	if (!buffer_uptodate(first_bh))
+		err = -EIO;
+
+	/* if seq_prefetch != 0, ext3_read_indblocks_async() sets prefetch bit
+	 * for all buffers, but the first buffer for sync IO is never a prefetch
+	 * buffer since it's needed presently so mark it so.
+	 */
+	if (seq_prefetch)
+		ext3_clear_buffer_prefetch(first_bh);
+
+	BUG_ON(ext3_buffer_prefetch(first_bh));
+
+	return err;
+}
+
+/**
+ * ext3_read_indblocks - Read and prefetch indirect blocks for inode.
+ * @inode:	inode of file
+ * @iblock:	block number inside file (starting from 0).
+ * @depth:	depth of path from inode to data block.
+ * @offsets:	array of offsets within blocks identified in 'chain'.
+ * @chain:	array of Indirect with info about all levels of blocks until
+ * 		the data block.
+ * @err:	error pointer.
+ *
+ * This function is called after reading all metablocks leading to 'iblock'
+ * except the (singly) indirect block. It reads the indirect block if not
+ * already in the cache and may also prefetch next few indirect blocks.
+ * It uses a combination of synchronous and asynchronous requests to
+ * accomplish this. We do prefetching even for random reads by reading ahead
+ * one indirect block since reads of size >=512KB have at least 12% chance of
+ * spanning two indirect blocks.
+ */
+
+static Indirect *ext3_read_indblocks(struct inode *inode, int iblock,
+				     int depth, int offsets[4],
+				     Indirect chain[4], int *err)
+{
+	struct super_block *sb = inode->i_sb;
+	struct buffer_head *first_bh, *prev_bh;
+	unsigned long max_read, blocks_done = 0;
+	__le32 *ind_blocks;
+
+	/* Must have doubly indirect block for prefetching indirect blocks. */
+	BUG_ON(depth <= 2);
+	BUG_ON(!chain[depth-2].key);
+
+	*err = 0;
+
+	/* Handle first block */
+	ind_blocks = chain[depth-2].p;
+	first_bh = sb_getblk(sb, le32_to_cpu(ind_blocks[0]));
+	if (unlikely(!first_bh)) {
+		printk(KERN_ERR "Failed to get block %u for sb %p\n",
+		       le32_to_cpu(ind_blocks[0]), sb);
+		goto failure;
+	}
+
+	BUG_ON(first_bh->b_size != sb->s_blocksize);
+
+	if (buffer_uptodate(first_bh)) {
+		/* Found the buffer in cache, either it was accessed recently or
+		 * it was prefetched while reading previous indirect block(s).
+		 * We need to figure out if we need to prefetch the following
+		 * indirect blocks.
+		 */
+		if (!ext3_buffer_prefetch(first_bh)) {
+			/* Either we've seen this indirect block before while
+			 * accessing another data block, or this is a random
+			 * read. In the former case, we must have done the
+			 * needful the first time we had a cache hit on this
+			 * indirect block, in the latter case we obviously
+			 * don't need to do any prefetching.
+			 */
+			goto done;
+		}
+
+		max_read = ext3_get_max_read(inode, iblock,
+					     offsets[depth-2]);
+
+		/* This indirect block is in the cache due to prefetching and
+		 * this is its first cache hit, clear the prefetch bit and
+		 * make sure the following blocks are also prefetched.
+		 */
+		ext3_clear_buffer_prefetch(first_bh);
+
+		if (max_read >= 2) {
+			/* ext3_read_indblocks_async() stops at the first
+			 * indirect block which has the prefetch bit set which
+			 * will most likely be the very next indirect block.
+			 */
+			ext3_read_indblocks_async(sb, &ind_blocks[1],
+						  max_read - 1,
+						  NULL, 1, &blocks_done);
+		}
+
+	} else {
+		/* Buffer is not in memory, we need to read it. If we are
+		 * reading sequentially from the previous indirect block, we
+		 * have just detected a sequential read and we must prefetch
+		 * some indirect blocks for future.
+		 */
+
+		max_read = ext3_get_max_read(inode, iblock,
+					     offsets[depth-2]);
+
+		if ((ind_blocks - (__le32 *)chain[depth-2].bh->b_data) >= 1) {
+			prev_bh = sb_getblk(sb, le32_to_cpu(ind_blocks[-1]));
+			if (buffer_uptodate(prev_bh) &&
+			    !ext3_buffer_prefetch(prev_bh)) {
+				/* Detected sequential read. */
+				put_bh(prev_bh);
+
+				/* Sync read indirect block, also read the next
+				 * few indirect blocks.
+				 */
+				*err = ext3_read_indblocks_sync(sb, ind_blocks,
+							 max_read, first_bh, 1,
+							 &blocks_done);
+
+				if (*err)
+					goto out;
+
+				/* In case the very next indirect block is
+				 * discontiguous by a non-trivial amount,
+				 * ext3_read_indblocks_sync() above won't
+				 * prefetch it (indicated by blocks_done < 2).
+				 * So to help sequential read, schedule an
+				 * async request for reading the next
+				 * contiguous indirect block range (which
+				 * in metaclustering case would be the next
+				 * metacluster, without metaclustering it
+				 * would be the next indirect block). This is
+				 * expected to benefit the non-metaclustering
+				 * case.
+				 */
+				if (max_read >= 2 && blocks_done < 2)
+					ext3_read_indblocks_async(sb,
+							&ind_blocks[1],
+							max_read - 1,
+							NULL, 1, &blocks_done);
+
+				goto done;
+			}
+			put_bh(prev_bh);
+		}
+
+		/* Either random read, or sequential detection failed above.
+		 * We always prefetch the next indirect block in this case
+		 * whenever possible.
+		 * This is because for random reads of size ~512KB, there is
+		 * >12% chance that a read will span two indirect blocks.
+		 */
+		*err = ext3_read_indblocks_sync(sb, ind_blocks,
+						(max_read >= 2) ? 2 : 1,
+						first_bh, 0, &blocks_done);
+		if (*err)
+			goto out;
+	}
+
+done:
+	/* Reader: pointers */
+	if (!verify_chain(chain, &chain[depth - 2])) {
+		put_bh(first_bh);
+		goto changed;
+	}
+	add_chain(&chain[depth - 1], first_bh,
+		  (__le32 *)first_bh->b_data + offsets[depth - 1]);
+	/* Reader: end */
+	if (!chain[depth - 1].key)
+		goto out;
+
+	BUG_ON(!buffer_uptodate(first_bh));
+	return NULL;
+
+changed:
+	*err = -EAGAIN;
+	goto out;
+failure:
+	*err = -EIO;
+out:
+	if (*err) {
+		ext3_debug("Error %d reading indirect blocks\n", *err);
+		return &chain[depth - 2];
+	} else
+		return &chain[depth - 1];
+}
diff -rupdN linux-2.6.24-rc8-clean/fs/ext3/super.c linux-2.6.24-rc8-ext3mc/fs/ext3/super.c
--- linux-2.6.24-rc8-clean/fs/ext3/super.c	2008-01-17 15:18:50.000000000 -0500
+++ linux-2.6.24-rc8-ext3mc/fs/ext3/super.c	2008-01-23 03:35:33.000000000 -0500
@@ -625,6 +625,9 @@ static int ext3_show_options(struct seq_
 	else if (test_opt(sb, DATA_FLAGS) == EXT3_MOUNT_WRITEBACK_DATA)
 		seq_puts(seq, ",data=writeback");
 
+	if (test_opt(sb, METACLUSTER))
+		seq_puts(seq, ",metacluster");
+
 	ext3_show_quota_options(seq, sb);
 
 	return 0;
@@ -758,7 +761,7 @@ enum {
 	Opt_usrjquota, Opt_grpjquota, Opt_offusrjquota, Opt_offgrpjquota,
 	Opt_jqfmt_vfsold, Opt_jqfmt_vfsv0, Opt_quota, Opt_noquota,
 	Opt_ignore, Opt_barrier, Opt_err, Opt_resize, Opt_usrquota,
-	Opt_grpquota
+	Opt_grpquota, Opt_metacluster
 };
 
 static match_table_t tokens = {
@@ -808,6 +811,7 @@ static match_table_t tokens = {
 	{Opt_quota, "quota"},
 	{Opt_usrquota, "usrquota"},
 	{Opt_barrier, "barrier=%u"},
+	{Opt_metacluster, "metacluster"},
 	{Opt_err, NULL},
 	{Opt_resize, "resize"},
 };
@@ -1140,6 +1144,9 @@ clear_qf_name:
 		case Opt_bh:
 			clear_opt(sbi->s_mount_opt, NOBH);
 			break;
+		case Opt_metacluster:
+			set_opt(sbi->s_mount_opt, METACLUSTER);
+			break;
 		default:
 			printk (KERN_ERR
 				"EXT3-fs: Unrecognized mount option \"%s\" "
@@ -1674,6 +1681,20 @@ static int ext3_fill_super (struct super
 	}
 	sbi->s_frags_per_block = 1;
 	sbi->s_blocks_per_group = le32_to_cpu(es->s_blocks_per_group);
+	/*
+	 * We maintain a ratio of approximately 1:EXT3_NDIR_BLOCKS between
+	 * metacluster blocks and data blocks in a block group which ensures
+	 * that there is enough space in the metacluster region of the block
+	 * group to accommodate all indirect blocks corresponding to data
+	 * blocks in the block group for most cases.
+	 */
+	if (test_opt(sb, METACLUSTER)) {
+		sbi->s_nonmc_blocks_per_group = sbi->s_blocks_per_group -
+			sbi->s_blocks_per_group / (1 + EXT3_NDIR_BLOCKS);
+		sbi->s_nonmc_blocks_per_group &= ~7;    /* align to 8 */
+	} else
+		sbi->s_nonmc_blocks_per_group = sbi->s_blocks_per_group;
+
 	sbi->s_frags_per_group = le32_to_cpu(es->s_frags_per_group);
 	sbi->s_inodes_per_group = le32_to_cpu(es->s_inodes_per_group);
 	if (EXT3_INODE_SIZE(sb) == 0 || EXT3_INODES_PER_GROUP(sb) == 0)
@@ -1783,6 +1804,18 @@ static int ext3_fill_super (struct super
 	sbi->s_rsv_window_head.rsv_goal_size = 0;
 	ext3_rsv_window_add(sb, &sbi->s_rsv_window_head);
 
+	if (test_opt(sb, METACLUSTER)) {
+		sbi->s_bginfo = kmalloc(sbi->s_groups_count *
+					sizeof(*sbi->s_bginfo), GFP_KERNEL);
+		if (!sbi->s_bginfo) {
+			printk(KERN_ERR "EXT3-fs: not enough memory\n");
+			goto failed_mount3;
+		}
+		for (i = 0; i < sbi->s_groups_count; i++)
+			sbi->s_bginfo[i].bgi_free_nonmc_blocks_count = -1;
+	} else
+		sbi->s_bginfo = NULL;
+
 	/*
 	 * set up enough so that it can read an inode
 	 */
@@ -1808,16 +1841,16 @@ static int ext3_fill_super (struct super
 	if (!test_opt(sb, NOLOAD) &&
 	    EXT3_HAS_COMPAT_FEATURE(sb, EXT3_FEATURE_COMPAT_HAS_JOURNAL)) {
 		if (ext3_load_journal(sb, es, journal_devnum))
-			goto failed_mount3;
+			goto failed_mount4;
 	} else if (journal_inum) {
 		if (ext3_create_journal(sb, es, journal_inum))
-			goto failed_mount3;
+			goto failed_mount4;
 	} else {
 		if (!silent)
 			printk (KERN_ERR
 				"ext3: No journal on filesystem on %s\n",
 				sb->s_id);
-		goto failed_mount3;
+		goto failed_mount4;
 	}
 
 	/* We have now updated the journal if required, so we can
@@ -1840,7 +1873,7 @@ static int ext3_fill_super (struct super
 		    (sbi->s_journal, 0, 0, JFS_FEATURE_INCOMPAT_REVOKE)) {
 			printk(KERN_ERR "EXT3-fs: Journal does not support "
 			       "requested data journaling mode\n");
-			goto failed_mount4;
+			goto failed_mount5;
 		}
 	default:
 		break;
@@ -1863,13 +1896,13 @@ static int ext3_fill_super (struct super
 	if (!sb->s_root) {
 		printk(KERN_ERR "EXT3-fs: get root inode failed\n");
 		iput(root);
-		goto failed_mount4;
+		goto failed_mount5;
 	}
 	if (!S_ISDIR(root->i_mode) || !root->i_blocks || !root->i_size) {
 		dput(sb->s_root);
 		sb->s_root = NULL;
 		printk(KERN_ERR "EXT3-fs: corrupt root inode, run e2fsck\n");
-		goto failed_mount4;
+		goto failed_mount5;
 	}
 
 	ext3_setup_super (sb, es, sb->s_flags & MS_RDONLY);
@@ -1901,8 +1934,10 @@ cantfind_ext3:
 		       sb->s_id);
 	goto failed_mount;
 
-failed_mount4:
+failed_mount5:
 	journal_destroy(sbi->s_journal);
+failed_mount4:
+	kfree(sbi->s_bginfo);
 failed_mount3:
 	percpu_counter_destroy(&sbi->s_freeblocks_counter);
 	percpu_counter_destroy(&sbi->s_freeinodes_counter);
diff -rupdN linux-2.6.24-rc8-clean/include/linux/ext3_fs.h linux-2.6.24-rc8-ext3mc/include/linux/ext3_fs.h
--- linux-2.6.24-rc8-clean/include/linux/ext3_fs.h	2008-01-17 15:18:51.000000000 -0500
+++ linux-2.6.24-rc8-ext3mc/include/linux/ext3_fs.h	2008-01-23 02:58:13.000000000 -0500
@@ -380,6 +380,7 @@ struct ext3_inode {
 #define EXT3_MOUNT_QUOTA		0x80000 /* Some quota option set */
 #define EXT3_MOUNT_USRQUOTA		0x100000 /* "old" user quota */
 #define EXT3_MOUNT_GRPQUOTA		0x200000 /* "old" group quota */
+#define EXT3_MOUNT_METACLUSTER		0x400000 /* Indirect block clustering */
 
 /* Compatibility, for having both ext2_fs.h and ext3_fs.h included at once */
 #ifndef _LINUX_EXT2_FS_H
@@ -493,6 +494,7 @@ struct ext3_super_block {
 #ifdef __KERNEL__
 #include <linux/ext3_fs_i.h>
 #include <linux/ext3_fs_sb.h>
+#include <linux/buffer_head.h>
 static inline struct ext3_sb_info * EXT3_SB(struct super_block *sb)
 {
 	return sb->s_fs_info;
@@ -742,6 +744,11 @@ struct dir_private_info {
 	__u32		next_hash;
 };
 
+/* Special bh flag used by the metacluster readahead logic. */
+enum ext3_bh_state_bits {
+	EXT3_BH_PREFETCH = BH_JBD_Sentinel,
+};
+
 /* calculate the first block number of the group */
 static inline ext3_fsblk_t
 ext3_group_first_block_no(struct super_block *sb, unsigned long group_no)
@@ -750,6 +757,24 @@ ext3_group_first_block_no(struct super_b
 		le32_to_cpu(EXT3_SB(sb)->s_es->s_first_data_block);
 }
 
+static inline void
+ext3_set_buffer_prefetch(struct buffer_head *bh)
+{
+	set_bit(EXT3_BH_PREFETCH, &bh->b_state);
+}
+
+static inline void
+ext3_clear_buffer_prefetch(struct buffer_head *bh)
+{
+	clear_bit(EXT3_BH_PREFETCH, &bh->b_state);
+}
+
+static inline int
+ext3_buffer_prefetch(struct buffer_head *bh)
+{
+	return test_bit(EXT3_BH_PREFETCH, &bh->b_state);
+}
+
 /*
  * Special error return code only used by dx_probe() and its callers.
  */
@@ -772,8 +797,9 @@ extern int ext3_bg_has_super(struct supe
 extern unsigned long ext3_bg_num_gdb(struct super_block *sb, int group);
 extern ext3_fsblk_t ext3_new_block (handle_t *handle, struct inode *inode,
 			ext3_fsblk_t goal, int *errp);
-extern ext3_fsblk_t ext3_new_blocks (handle_t *handle, struct inode *inode,
-			ext3_fsblk_t goal, unsigned long *count, int *errp);
+extern int ext3_new_blocks(handle_t *handle, struct inode *inode,
+			ext3_fsblk_t goal, int indirect_blks, int blks,
+			ext3_fsblk_t new_blocks[], int *errp);
 extern void ext3_free_blocks (handle_t *handle, struct inode *inode,
 			ext3_fsblk_t block, unsigned long count);
 extern void ext3_free_blocks_sb (handle_t *handle, struct super_block *sb,
diff -rupdN linux-2.6.24-rc8-clean/include/linux/ext3_fs_sb.h linux-2.6.24-rc8-ext3mc/include/linux/ext3_fs_sb.h
--- linux-2.6.24-rc8-clean/include/linux/ext3_fs_sb.h	2008-01-17 15:18:51.000000000 -0500
+++ linux-2.6.24-rc8-ext3mc/include/linux/ext3_fs_sb.h	2008-01-23 02:58:13.000000000 -0500
@@ -24,6 +24,8 @@
 #endif
 #include <linux/rbtree.h>
 
+struct ext3_bg_info;
+
 /*
  * third extended-fs super-block data in memory
  */
@@ -33,6 +35,7 @@ struct ext3_sb_info {
 	unsigned long s_inodes_per_block;/* Number of inodes per block */
 	unsigned long s_frags_per_group;/* Number of fragments in a group */
 	unsigned long s_blocks_per_group;/* Number of blocks in a group */
+	unsigned long s_nonmc_blocks_per_group;/* Number of non-metacluster blocks in a group */
 	unsigned long s_inodes_per_group;/* Number of inodes in a group */
 	unsigned long s_itb_per_group;	/* Number of inode table blocks per group */
 	unsigned long s_gdb_count;	/* Number of group descriptor blocks */
@@ -67,6 +70,9 @@ struct ext3_sb_info {
 	struct rb_root s_rsv_window_root;
 	struct ext3_reserve_window_node s_rsv_window_head;
 
+	/* array of per-bg in-memory info */
+	struct ext3_bg_info *s_bginfo;
+
 	/* Journaling */
 	struct inode * s_journal_inode;
 	struct journal_s * s_journal;
@@ -83,4 +89,11 @@ struct ext3_sb_info {
 #endif
 };
 
+/*
+ * in-memory data associated with each block group.
+ */
+struct ext3_bg_info {
+	int bgi_free_nonmc_blocks_count;/* Number of free non-metacluster blocks in group */
+};
+
 #endif	/* _LINUX_EXT3_FS_SB */
diff -rupdN linux-2.6.24-rc8-clean/include/linux/jbd.h linux-2.6.24-rc8-ext3mc/include/linux/jbd.h
--- linux-2.6.24-rc8-clean/include/linux/jbd.h	2008-01-17 15:18:51.000000000 -0500
+++ linux-2.6.24-rc8-ext3mc/include/linux/jbd.h	2008-01-23 02:58:13.000000000 -0500
@@ -295,6 +295,7 @@ enum jbd_state_bits {
 	BH_State,		/* Pins most journal_head state */
 	BH_JournalHead,		/* Pins bh->b_private and jh->b_bh */
 	BH_Unshadow,		/* Dummy bit, for BJ_Shadow wakeup filtering */
+	BH_JBD_Sentinel,	/* Start bit for clients of jbd */
 };
 
 BUFFER_FNS(JBD, jbd)
-
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