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Subject[PATCH] concurrent block allocation for ext3
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Date

Hi!

Here is the small patch which implements concurrent block allocation
for ext3. It removes lock_super() in ext3_new_block() and ext3_free_blocks().
Modifications of counters in superblock and group descriptors are protected
by spinlock. Tested on SMP for several hours.


--- linux/fs/ext3/balloc.c Thu Feb 20 16:19:06 2003
+++ balloc.c Mon Mar 10 16:00:49 2003
@@ -118,7 +118,6 @@
printk ("ext3_free_blocks: nonexistent device");
return;
}
- lock_super (sb);
es = EXT3_SB(sb)->s_es;
if (block < le32_to_cpu(es->s_first_data_block) ||
block + count < block ||
@@ -214,11 +213,13 @@
block + i);
BUFFER_TRACE(bitmap_bh, "bit already cleared");
} else {
+ spin_lock(&EXT3_SB(sb)->s_alloc_lock);
dquot_freed_blocks++;
gdp->bg_free_blocks_count =
cpu_to_le16(le16_to_cpu(gdp->bg_free_blocks_count)+1);
es->s_free_blocks_count =
cpu_to_le32(le32_to_cpu(es->s_free_blocks_count)+1);
+ spin_unlock(&EXT3_SB(sb)->s_alloc_lock);
}
/* @@@ This prevents newly-allocated data from being
* freed and then reallocated within the same
@@ -267,7 +268,6 @@
error_return:
brelse(bitmap_bh);
ext3_std_error(sb, err);
- unlock_super(sb);
if (dquot_freed_blocks)
DQUOT_FREE_BLOCK(inode, dquot_freed_blocks);
return;
@@ -408,7 +408,6 @@
return 0;
}

- lock_super(sb);
es = EXT3_SB(sb)->s_es;
if (le32_to_cpu(es->s_free_blocks_count) <=
le32_to_cpu(es->s_r_blocks_count) &&
@@ -461,6 +460,7 @@

ext3_debug("Bit not found in block group %d.\n", group_no);

+repeat:
/*
* Now search the rest of the groups. We assume that
* i and gdp correctly point to the last group visited.
@@ -538,9 +538,9 @@

/* The superblock lock should guard against anybody else beating
* us to this point! */
- J_ASSERT_BH(bitmap_bh, !ext3_test_bit(ret_block, bitmap_bh->b_data));
BUFFER_TRACE(bitmap_bh, "setting bitmap bit");
- ext3_set_bit(ret_block, bitmap_bh->b_data);
+ if (ext3_set_bit(ret_block, bitmap_bh->b_data))
+ goto repeat;
performed_allocation = 1;

#ifdef CONFIG_JBD_DEBUG
@@ -586,11 +586,13 @@
ext3_debug("allocating block %d. Goal hits %d of %d.\n",
ret_block, goal_hits, goal_attempts);

+ spin_lock(&EXT3_SB(sb)->s_alloc_lock);
gdp->bg_free_blocks_count =
cpu_to_le16(le16_to_cpu(gdp->bg_free_blocks_count) - 1);
es->s_free_blocks_count =
cpu_to_le32(le32_to_cpu(es->s_free_blocks_count) - 1);
-
+ spin_unlock(&EXT3_SB(sb)->s_alloc_lock);
+
BUFFER_TRACE(gdp_bh, "journal_dirty_metadata for group descriptor");
err = ext3_journal_dirty_metadata(handle, gdp_bh);
if (!fatal)
@@ -606,7 +608,6 @@
if (fatal)
goto out;

- unlock_super(sb);
*errp = 0;
brelse(bitmap_bh);
return ret_block;
@@ -618,7 +619,6 @@
*errp = fatal;
ext3_std_error(sb, fatal);
}
- unlock_super(sb);
/*
* Undo the block allocation
*/
-
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