Btrfs: Optimize compressed writeback and reads

When reading compressed extents, try to put pages into the page cache
for any pages covered by the compressed extent that readpages didn't already
preload.

Add an async work queue to handle transformations at delayed allocation processing
time.  Right now this is just compression.  The workflow is:

1) Find offsets in the file marked for delayed allocation
2) Lock the pages
3) Lock the state bits
4) Call the async delalloc code

The async delalloc code clears the state lock bits and delalloc bits.  It is
important this happens before the range goes into the work queue because
otherwise it might deadlock with other work queue items that try to lock
those extent bits.

The file pages are compressed, and if the compression doesn't work the
pages are written back directly.

An ordered work queue is used to make sure the inodes are written in the same
order that pdflush or writepages sent them down.

This changes extent_write_cache_pages to let the writepage function
update the wbc nr_written count.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

11 files changed, 849 insertions, 207 deletions

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 354913177ba..284f21025bc 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -33,6 +33,7 @@
 #include <linux/writeback.h>
 #include <linux/bit_spinlock.h>
 #include <linux/version.h>
+#include <linux/pagevec.h>
 #include "ctree.h"
 #include "disk-io.h"
 #include "transaction.h"
@@ -145,9 +146,9 @@ static void end_compressed_bio_read(struct bio *bio, int err)
 	}
 
 	/* do io completion on the original bio */
-	if (cb->errors)
+	if (cb->errors) {
 		bio_io_error(cb->orig_bio);
-	else
+	} else
 		bio_endio(cb->orig_bio, 0);
 
 	/* finally free the cb struct */
@@ -333,6 +334,7 @@ int btrfs_submit_compressed_write(struct inode *inode, u64 start,
 		}
 		bytes_left -= PAGE_CACHE_SIZE;
 		first_byte += PAGE_CACHE_SIZE;
+		cond_resched();
 	}
 	bio_get(bio);
 
@@ -346,6 +348,130 @@ int btrfs_submit_compressed_write(struct inode *inode, u64 start,
 	return 0;
 }
 
+static noinline int add_ra_bio_pages(struct inode *inode,
+				     u64 compressed_end,
+				     struct compressed_bio *cb)
+{
+	unsigned long end_index;
+	unsigned long page_index;
+	u64 last_offset;
+	u64 isize = i_size_read(inode);
+	int ret;
+	struct page *page;
+	unsigned long nr_pages = 0;
+	struct extent_map *em;
+	struct address_space *mapping = inode->i_mapping;
+	struct pagevec pvec;
+	struct extent_map_tree *em_tree;
+	struct extent_io_tree *tree;
+	u64 end;
+	int misses = 0;
+
+	page = cb->orig_bio->bi_io_vec[cb->orig_bio->bi_vcnt - 1].bv_page;
+	last_offset = (page_offset(page) + PAGE_CACHE_SIZE);
+	em_tree = &BTRFS_I(inode)->extent_tree;
+	tree = &BTRFS_I(inode)->io_tree;
+
+	if (isize == 0)
+		return 0;
+
+	end_index = (i_size_read(inode) - 1) >> PAGE_CACHE_SHIFT;
+
+	pagevec_init(&pvec, 0);
+	while(last_offset < compressed_end) {
+		page_index = last_offset >> PAGE_CACHE_SHIFT;
+
+		if (page_index > end_index)
+			break;
+
+		rcu_read_lock();
+		page = radix_tree_lookup(&mapping->page_tree, page_index);
+		rcu_read_unlock();
+		if (page) {
+			misses++;
+			if (misses > 4)
+				break;
+			goto next;
+		}
+
+		page = alloc_page(mapping_gfp_mask(mapping) | GFP_NOFS);
+		if (!page)
+			break;
+
+		page->index = page_index;
+		/*
+		 * what we want to do here is call add_to_page_cache_lru,
+		 * but that isn't exported, so we reproduce it here
+		 */
+		if (add_to_page_cache(page, mapping,
+				      page->index, GFP_NOFS)) {
+			page_cache_release(page);
+			goto next;
+		}
+
+		/* open coding of lru_cache_add, also not exported */
+		page_cache_get(page);
+		if (!pagevec_add(&pvec, page))
+			__pagevec_lru_add(&pvec);
+
+		end = last_offset + PAGE_CACHE_SIZE - 1;
+		/*
+		 * at this point, we have a locked page in the page cache
+		 * for these bytes in the file.  But, we have to make
+		 * sure they map to this compressed extent on disk.
+		 */
+		set_page_extent_mapped(page);
+		lock_extent(tree, last_offset, end, GFP_NOFS);
+		spin_lock(&em_tree->lock);
+		em = lookup_extent_mapping(em_tree, last_offset,
+					   PAGE_CACHE_SIZE);
+		spin_unlock(&em_tree->lock);
+
+		if (!em || last_offset < em->start ||
+		    (last_offset + PAGE_CACHE_SIZE > extent_map_end(em)) ||
+		    (em->block_start >> 9) != cb->orig_bio->bi_sector) {
+			free_extent_map(em);
+			unlock_extent(tree, last_offset, end, GFP_NOFS);
+			unlock_page(page);
+			page_cache_release(page);
+			break;
+		}
+		free_extent_map(em);
+
+		if (page->index == end_index) {
+			char *userpage;
+			size_t zero_offset = isize & (PAGE_CACHE_SIZE - 1);
+
+			if (zero_offset) {
+				int zeros;
+				zeros = PAGE_CACHE_SIZE - zero_offset;
+				userpage = kmap_atomic(page, KM_USER0);
+				memset(userpage + zero_offset, 0, zeros);
+				flush_dcache_page(page);
+				kunmap_atomic(userpage, KM_USER0);
+			}
+		}
+
+		ret = bio_add_page(cb->orig_bio, page,
+				   PAGE_CACHE_SIZE, 0);
+
+		if (ret == PAGE_CACHE_SIZE) {
+			nr_pages++;
+			page_cache_release(page);
+		} else {
+			unlock_extent(tree, last_offset, end, GFP_NOFS);
+			unlock_page(page);
+			page_cache_release(page);
+			break;
+		}
+next:
+		last_offset += PAGE_CACHE_SIZE;
+	}
+	if (pagevec_count(&pvec))
+		__pagevec_lru_add(&pvec);
+	return 0;
+}
+
 /*
  * for a compressed read, the bio we get passed has all the inode pages
  * in it.  We don't actually do IO on those pages but allocate new ones
@@ -373,6 +499,7 @@ int btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
 	struct block_device *bdev;
 	struct bio *comp_bio;
 	u64 cur_disk_byte = (u64)bio->bi_sector << 9;
+	u64 em_len;
 	struct extent_map *em;
 	int ret;
 
@@ -393,6 +520,7 @@ int btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
 
 	cb->start = em->start;
 	compressed_len = em->block_len;
+	em_len = em->len;
 	free_extent_map(em);
 
 	cb->len = uncompressed_len;
@@ -411,6 +539,17 @@ int btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
 	}
 	cb->nr_pages = nr_pages;
 
+	add_ra_bio_pages(inode, cb->start + em_len, cb);
+
+	if (!btrfs_test_opt(root, NODATASUM) &&
+	    !btrfs_test_flag(inode, NODATASUM)) {
+		btrfs_lookup_bio_sums(root, inode, cb->orig_bio);
+	}
+
+	/* include any pages we added in add_ra-bio_pages */
+	uncompressed_len = bio->bi_vcnt * PAGE_CACHE_SIZE;
+	cb->len = uncompressed_len;
+
 	comp_bio = compressed_bio_alloc(bdev, cur_disk_byte, GFP_NOFS);
 	comp_bio->bi_private = cb;
 	comp_bio->bi_end_io = end_compressed_bio_read;
@@ -442,9 +581,10 @@ int btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
 			comp_bio = compressed_bio_alloc(bdev, cur_disk_byte,
 							GFP_NOFS);
 			atomic_inc(&cb->pending_bios);
-			bio->bi_private = cb;
-			bio->bi_end_io = end_compressed_bio_write;
-			bio_add_page(bio, page, PAGE_CACHE_SIZE, 0);
+			comp_bio->bi_private = cb;
+			comp_bio->bi_end_io = end_compressed_bio_read;
+
+			bio_add_page(comp_bio, page, PAGE_CACHE_SIZE, 0);
 		}
 		cur_disk_byte += PAGE_CACHE_SIZE;
 	}
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 689df070c8e..c83cc5b2ded 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -625,8 +625,8 @@ struct btrfs_fs_info {
 	struct btrfs_transaction *running_transaction;
 	wait_queue_head_t transaction_throttle;
 	wait_queue_head_t transaction_wait;
-	wait_queue_head_t async_submit_wait;
 
+	wait_queue_head_t async_submit_wait;
 	wait_queue_head_t tree_log_wait;
 
 	struct btrfs_super_block super_copy;
@@ -653,6 +653,7 @@ struct btrfs_fs_info {
 	atomic_t nr_async_submits;
 	atomic_t async_submit_draining;
 	atomic_t nr_async_bios;
+	atomic_t async_delalloc_pages;
 	atomic_t tree_log_writers;
 	atomic_t tree_log_commit;
 	unsigned long tree_log_batch;
@@ -677,6 +678,7 @@ struct btrfs_fs_info {
 	 * two
 	 */
 	struct btrfs_workers workers;
+	struct btrfs_workers delalloc_workers;
 	struct btrfs_workers endio_workers;
 	struct btrfs_workers endio_write_workers;
 	struct btrfs_workers submit_workers;
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index e0a28f705a6..8efc123d222 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -539,6 +539,13 @@ int btrfs_wq_submit_bio(struct btrfs_fs_info *fs_info, struct inode *inode,
 			   (atomic_read(&fs_info->nr_async_bios) < limit),
 			   HZ/10);
 	}
+
+	while(atomic_read(&fs_info->async_submit_draining) &&
+	      atomic_read(&fs_info->nr_async_submits)) {
+		wait_event(fs_info->async_submit_wait,
+			   (atomic_read(&fs_info->nr_async_submits) == 0));
+	}
+
 	return 0;
 }
 
@@ -1437,6 +1444,7 @@ struct btrfs_root *open_ctree(struct super_block *sb,
 	INIT_LIST_HEAD(&fs_info->space_info);
 	btrfs_mapping_init(&fs_info->mapping_tree);
 	atomic_set(&fs_info->nr_async_submits, 0);
+	atomic_set(&fs_info->async_delalloc_pages, 0);
 	atomic_set(&fs_info->async_submit_draining, 0);
 	atomic_set(&fs_info->nr_async_bios, 0);
 	atomic_set(&fs_info->throttles, 0);
@@ -1550,6 +1558,9 @@ struct btrfs_root *open_ctree(struct super_block *sb,
 	btrfs_init_workers(&fs_info->workers, "worker",
 			   fs_info->thread_pool_size);
 
+	btrfs_init_workers(&fs_info->delalloc_workers, "delalloc",
+			   fs_info->thread_pool_size);
+
 	btrfs_init_workers(&fs_info->submit_workers, "submit",
 			   min_t(u64, fs_devices->num_devices,
 			   fs_info->thread_pool_size));
@@ -1560,15 +1571,12 @@ struct btrfs_root *open_ctree(struct super_block *sb,
 	 */
 	fs_info->submit_workers.idle_thresh = 64;
 
-	/* fs_info->workers is responsible for checksumming file data
-	 * blocks and metadata.  Using a larger idle thresh allows each
-	 * worker thread to operate on things in roughly the order they
-	 * were sent by the writeback daemons, improving overall locality
-	 * of the IO going down the pipe.
-	 */
-	fs_info->workers.idle_thresh = 8;
+	fs_info->workers.idle_thresh = 16;
 	fs_info->workers.ordered = 1;
 
+	fs_info->delalloc_workers.idle_thresh = 2;
+	fs_info->delalloc_workers.ordered = 1;
+
 	btrfs_init_workers(&fs_info->fixup_workers, "fixup", 1);
 	btrfs_init_workers(&fs_info->endio_workers, "endio",
 			   fs_info->thread_pool_size);
@@ -1584,6 +1592,7 @@ struct btrfs_root *open_ctree(struct super_block *sb,
 
 	btrfs_start_workers(&fs_info->workers, 1);
 	btrfs_start_workers(&fs_info->submit_workers, 1);
+	btrfs_start_workers(&fs_info->delalloc_workers, 1);
 	btrfs_start_workers(&fs_info->fixup_workers, 1);
 	btrfs_start_workers(&fs_info->endio_workers, fs_info->thread_pool_size);
 	btrfs_start_workers(&fs_info->endio_write_workers,
@@ -1732,6 +1741,7 @@ fail_tree_root:
 fail_sys_array:
 fail_sb_buffer:
 	btrfs_stop_workers(&fs_info->fixup_workers);
+	btrfs_stop_workers(&fs_info->delalloc_workers);
 	btrfs_stop_workers(&fs_info->workers);
 	btrfs_stop_workers(&fs_info->endio_workers);
 	btrfs_stop_workers(&fs_info->endio_write_workers);
@@ -1988,6 +1998,7 @@ int close_ctree(struct btrfs_root *root)
 	truncate_inode_pages(fs_info->btree_inode->i_mapping, 0);
 
 	btrfs_stop_workers(&fs_info->fixup_workers);
+	btrfs_stop_workers(&fs_info->delalloc_workers);
 	btrfs_stop_workers(&fs_info->workers);
 	btrfs_stop_workers(&fs_info->endio_workers);
 	btrfs_stop_workers(&fs_info->endio_write_workers);
@@ -2062,7 +2073,7 @@ void btrfs_btree_balance_dirty(struct btrfs_root *root, unsigned long nr)
 	struct extent_io_tree *tree;
 	u64 num_dirty;
 	u64 start = 0;
-	unsigned long thresh = 96 * 1024 * 1024;
+	unsigned long thresh = 32 * 1024 * 1024;
 	tree = &BTRFS_I(root->fs_info->btree_inode)->io_tree;
 
 	if (current_is_pdflush() || current->flags & PF_MEMALLOC)
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 8af39521eb7..ebd8275a193 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -768,7 +768,11 @@ static int __btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
 	l = path->nodes[0];
 
 	btrfs_item_key_to_cpu(l, &key, path->slots[0]);
-	BUG_ON(key.objectid != bytenr);
+	if (key.objectid != bytenr) {
+		btrfs_print_leaf(root->fs_info->extent_root, path->nodes[0]);
+		printk("wanted %Lu found %Lu\n", bytenr, key.objectid);
+		BUG();
+	}
 	BUG_ON(key.type != BTRFS_EXTENT_ITEM_KEY);
 
 	item = btrfs_item_ptr(l, path->slots[0], struct btrfs_extent_item);
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 9b37ce6e516..bbe3bcfcf4a 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -47,6 +47,11 @@ struct extent_page_data {
 	struct bio *bio;
 	struct extent_io_tree *tree;
 	get_extent_t *get_extent;
+
+	/* tells writepage not to lock the state bits for this range
+	 * it still does the unlocking
+	 */
+	int extent_locked;
 };
 
 int __init extent_io_init(void)
@@ -1198,11 +1203,18 @@ static noinline int lock_delalloc_pages(struct inode *inode,
 			 * the caller is taking responsibility for
 			 * locked_page
 			 */
-			if (pages[i] != locked_page)
+			if (pages[i] != locked_page) {
 				lock_page(pages[i]);
+				if (pages[i]->mapping != inode->i_mapping) {
+					ret = -EAGAIN;
+					unlock_page(pages[i]);
+					page_cache_release(pages[i]);
+					goto done;
+				}
+			}
 			page_cache_release(pages[i]);
+			pages_locked++;
 		}
-		pages_locked += ret;
 		nrpages -= ret;
 		index += ret;
 		cond_resched();
@@ -1262,8 +1274,7 @@ again:
 	 * if we're looping.
 	 */
 	if (delalloc_end + 1 - delalloc_start > max_bytes && loops) {
-		delalloc_end = (delalloc_start + PAGE_CACHE_SIZE - 1) &
-			~((u64)PAGE_CACHE_SIZE - 1);
+		delalloc_end = delalloc_start + PAGE_CACHE_SIZE - 1;
 	}
 	/* step two, lock all the pages after the page that has start */
 	ret = lock_delalloc_pages(inode, locked_page,
@@ -1306,7 +1317,10 @@ out_failed:
 int extent_clear_unlock_delalloc(struct inode *inode,
 				struct extent_io_tree *tree,
 				u64 start, u64 end, struct page *locked_page,
-				int clear_dirty, int set_writeback,
+				int unlock_pages,
+				int clear_unlock,
+				int clear_delalloc, int clear_dirty,
+				int set_writeback,
 				int end_writeback)
 {
 	int ret;
@@ -1315,12 +1329,19 @@ int extent_clear_unlock_delalloc(struct inode *inode,
 	unsigned long end_index = end >> PAGE_CACHE_SHIFT;
 	unsigned long nr_pages = end_index - index + 1;
 	int i;
-	int clear_bits = EXTENT_LOCKED | EXTENT_DELALLOC;
+	int clear_bits = 0;
 
+	if (clear_unlock)
+		clear_bits |= EXTENT_LOCKED;
 	if (clear_dirty)
 		clear_bits |= EXTENT_DIRTY;
 
+	if (clear_delalloc)
+		clear_bits |= EXTENT_DELALLOC;
+
 	clear_extent_bit(tree, start, end, clear_bits, 1, 0, GFP_NOFS);
+	if (!(unlock_pages || clear_dirty || set_writeback || end_writeback))
+		return 0;
 
 	while(nr_pages > 0) {
 		ret = find_get_pages_contig(inode->i_mapping, index,
@@ -1336,7 +1357,8 @@ int extent_clear_unlock_delalloc(struct inode *inode,
 				set_page_writeback(pages[i]);
 			if (end_writeback)
 				end_page_writeback(pages[i]);
-			unlock_page(pages[i]);
+			if (unlock_pages)
+				unlock_page(pages[i]);
 			page_cache_release(pages[i]);
 		}
 		nr_pages -= ret;
@@ -1741,9 +1763,10 @@ static void end_bio_extent_readpage(struct bio *bio, int err)
 			}
 		}
 
-		if (uptodate)
+		if (uptodate) {
 			set_extent_uptodate(tree, start, end,
 					    GFP_ATOMIC);
+		}
 		unlock_extent(tree, start, end, GFP_ATOMIC);
 
 		if (whole_page) {
@@ -1925,6 +1948,7 @@ void set_page_extent_mapped(struct page *page)
 		set_page_private(page, EXTENT_PAGE_PRIVATE);
 	}
 }
+EXPORT_SYMBOL(set_page_extent_mapped);
 
 void set_page_extent_head(struct page *page, unsigned long len)
 {
@@ -2143,12 +2167,17 @@ static int __extent_writepage(struct page *page, struct writeback_control *wbc,
 	u64 delalloc_end;
 	int page_started;
 	int compressed;
+	unsigned long nr_written = 0;
 
 	WARN_ON(!PageLocked(page));
 	pg_offset = i_size & (PAGE_CACHE_SIZE - 1);
 	if (page->index > end_index ||
 	   (page->index == end_index && !pg_offset)) {
-		page->mapping->a_ops->invalidatepage(page, 0);
+		if (epd->extent_locked) {
+			if (tree->ops && tree->ops->writepage_end_io_hook)
+				tree->ops->writepage_end_io_hook(page, start,
+							 page_end, NULL, 1);
+		}
 		unlock_page(page);
 		return 0;
 	}
@@ -2169,27 +2198,33 @@ static int __extent_writepage(struct page *page, struct writeback_control *wbc,
 	delalloc_start = start;
 	delalloc_end = 0;
 	page_started = 0;
-	while(delalloc_end < page_end) {
-		nr_delalloc = find_lock_delalloc_range(inode, tree,
+	if (!epd->extent_locked) {
+		while(delalloc_end < page_end) {
+			nr_delalloc = find_lock_delalloc_range(inode, tree,
 						       page,
 						       &delalloc_start,
 						       &delalloc_end,
 						       128 * 1024 * 1024);
-		if (nr_delalloc == 0) {
+			if (nr_delalloc == 0) {
+				delalloc_start = delalloc_end + 1;
+				continue;
+			}
+			tree->ops->fill_delalloc(inode, page, delalloc_start,
+						 delalloc_end, &page_started,
+						 &nr_written);
 			delalloc_start = delalloc_end + 1;
-			continue;
 		}
-		tree->ops->fill_delalloc(inode, page, delalloc_start,
-					 delalloc_end, &page_started);
-		delalloc_start = delalloc_end + 1;
-	}
 
-	/* did the fill delalloc function already unlock and start the IO? */
-	if (page_started) {
-		return 0;
+		/* did the fill delalloc function already unlock and start
+		 * the IO?
+		 */
+		if (page_started) {
+			ret = 0;
+			goto update_nr_written;
+		}
 	}
-
 	lock_extent(tree, start, page_end, GFP_NOFS);
+
 	unlock_start = start;
 
 	if (tree->ops && tree->ops->writepage_start_hook) {
@@ -2199,10 +2234,13 @@ static int __extent_writepage(struct page *page, struct writeback_control *wbc,
 			unlock_extent(tree, start, page_end, GFP_NOFS);
 			redirty_page_for_writepage(wbc, page);
 			unlock_page(page);
-			return 0;
+			ret = 0;
+			goto update_nr_written;
 		}
 	}
 
+	nr_written++;
+
 	end = page_end;
 	if (test_range_bit(tree, start, page_end, EXTENT_DELALLOC, 0)) {
 		printk("found delalloc bits after lock_extent\n");
@@ -2333,6 +2371,12 @@ done:
 	if (unlock_start <= page_end)
 		unlock_extent(tree, unlock_start, page_end, GFP_NOFS);
 	unlock_page(page);
+
+update_nr_written:
+	wbc->nr_to_write -= nr_written;
+	if (wbc->range_cyclic || (wbc->nr_to_write > 0 &&
+	    wbc->range_start == 0 && wbc->range_end == LLONG_MAX))
+		page->mapping->writeback_index = page->index + nr_written;
 	return 0;
 }
 
@@ -2431,7 +2475,7 @@ retry:
 				unlock_page(page);
 				ret = 0;
 			}
-			if (ret || (--(wbc->nr_to_write) <= 0))
+			if (ret || wbc->nr_to_write <= 0)
 				done = 1;
 			if (wbc->nonblocking && bdi_write_congested(bdi)) {
 				wbc->encountered_congestion = 1;
@@ -2452,6 +2496,8 @@ retry:
 	}
 	if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
 		mapping->writeback_index = index;
+		if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
+			range_whole = 1;
 
 	if (wbc->range_cont)
 		wbc->range_start = index << PAGE_CACHE_SHIFT;
@@ -2469,6 +2515,7 @@ int extent_write_full_page(struct extent_io_tree *tree, struct page *page,
 		.bio = NULL,
 		.tree = tree,
 		.get_extent = get_extent,
+		.extent_locked = 0,
 	};
 	struct writeback_control wbc_writepages = {
 		.bdi		= wbc->bdi,
@@ -2491,6 +2538,52 @@ int extent_write_full_page(struct extent_io_tree *tree, struct page *page,
 }
 EXPORT_SYMBOL(extent_write_full_page);
 
+int extent_write_locked_range(struct extent_io_tree *tree, struct inode *inode,
+			      u64 start, u64 end, get_extent_t *get_extent,
+			      int mode)
+{
+	int ret = 0;
+	struct address_space *mapping = inode->i_mapping;
+	struct page *page;
+	unsigned long nr_pages = (end - start + PAGE_CACHE_SIZE) >>
+		PAGE_CACHE_SHIFT;
+
+	struct extent_page_data epd = {
+		.bio = NULL,
+		.tree = tree,
+		.get_extent = get_extent,
+		.extent_locked = 1,
+	};
+	struct writeback_control wbc_writepages = {
+		.bdi		= inode->i_mapping->backing_dev_info,
+		.sync_mode	= mode,
+		.older_than_this = NULL,
+		.nr_to_write	= nr_pages * 2,
+		.range_start	= start,
+		.range_end	= end + 1,
+	};
+
+	while(start <= end) {
+		page = find_get_page(mapping, start >> PAGE_CACHE_SHIFT);
+		if (clear_page_dirty_for_io(page))
+			ret = __extent_writepage(page, &wbc_writepages, &epd);
+		else {
+			if (tree->ops && tree->ops->writepage_end_io_hook)
+				tree->ops->writepage_end_io_hook(page, start,
+						 start + PAGE_CACHE_SIZE - 1,
+						 NULL, 1);
+			unlock_page(page);
+		}
+		page_cache_release(page);
+		start += PAGE_CACHE_SIZE;
+	}
+
+	if (epd.bio)
+		submit_one_bio(WRITE, epd.bio, 0, 0);
+	return ret;
+}
+EXPORT_SYMBOL(extent_write_locked_range);
+
 
 int extent_writepages(struct extent_io_tree *tree,
 		      struct address_space *mapping,
@@ -2502,6 +2595,7 @@ int extent_writepages(struct extent_io_tree *tree,
 		.bio = NULL,
 		.tree = tree,
 		.get_extent = get_extent,
+		.extent_locked = 0,
 	};
 
 	ret = extent_write_cache_pages(tree, mapping, wbc,
diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index 283110ec4ee..2d5f67065b6 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -35,7 +35,8 @@ typedef	int (extent_submit_bio_hook_t)(struct inode *inode, int rw,
 				       unsigned long bio_flags);
 struct extent_io_ops {
 	int (*fill_delalloc)(struct inode *inode, struct page *locked_page,
-			     u64 start, u64 end, int *page_started);
+			     u64 start, u64 end, int *page_started,
+			     unsigned long *nr_written);
 	int (*writepage_start_hook)(struct page *page, u64 start, u64 end);
 	int (*writepage_io_hook)(struct page *page, u64 start, u64 end);
 	extent_submit_bio_hook_t *submit_bio_hook;
@@ -172,6 +173,9 @@ int extent_invalidatepage(struct extent_io_tree *tree,
 int extent_write_full_page(struct extent_io_tree *tree, struct page *page,
 			  get_extent_t *get_extent,
 			  struct writeback_control *wbc);
+int extent_write_locked_range(struct extent_io_tree *tree, struct inode *inode,
+			      u64 start, u64 end, get_extent_t *get_extent,
+			      int mode);
 int extent_writepages(struct extent_io_tree *tree,
 		      struct address_space *mapping,
 		      get_extent_t *get_extent,
@@ -256,6 +260,9 @@ int extent_range_uptodate(struct extent_io_tree *tree,
 int extent_clear_unlock_delalloc(struct inode *inode,
 				struct extent_io_tree *tree,
 				u64 start, u64 end, struct page *locked_page,
-				int clear_dirty, int set_writeback,
-				int clear_writeback);
+				int unlock_page,
+				int clear_unlock,
+				int clear_delalloc, int clear_dirty,
+				int set_writeback,
+				int end_writeback);
 #endif
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 0c8cc35a8b9..337221ecca2 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -368,6 +368,8 @@ int noinline btrfs_drop_extents(struct btrfs_trans_handle *trans,
 	u64 search_start = start;
 	u64 leaf_start;
 	u64 ram_bytes = 0;
+	u64 orig_parent = 0;
+	u64 disk_bytenr = 0;
 	u8 compression;
 	u8 encryption;
 	u16 other_encoding = 0;
@@ -500,17 +502,31 @@ next_slot:
 				keep = 1;
 		}
 
-		if (bookend && found_extent && locked_end < extent_end) {
-			ret = try_lock_extent(&BTRFS_I(inode)->io_tree,
-					locked_end, extent_end - 1, GFP_NOFS);
-			if (!ret) {
-				btrfs_release_path(root, path);
-				lock_extent(&BTRFS_I(inode)->io_tree,
-					locked_end, extent_end - 1, GFP_NOFS);
+		if (bookend && found_extent) {
+			if (locked_end < extent_end) {
+				ret = try_lock_extent(&BTRFS_I(inode)->io_tree,
+						locked_end, extent_end - 1,
+						GFP_NOFS);
+				if (!ret) {
+					btrfs_release_path(root, path);
+					lock_extent(&BTRFS_I(inode)->io_tree,
+						locked_end, extent_end - 1,
+						GFP_NOFS);
+					locked_end = extent_end;
+					continue;
+				}
 				locked_end = extent_end;
-				continue;
 			}
-			locked_end = extent_end;
+			orig_parent = path->nodes[0]->start;
+			disk_bytenr = le64_to_cpu(old.disk_bytenr);
+			if (disk_bytenr != 0) {
+				ret = btrfs_inc_extent_ref(trans, root,
+					   disk_bytenr,
+					   le64_to_cpu(old.disk_num_bytes),
+					   orig_parent, root->root_key.objectid,
+					   trans->transid, inode->i_ino);
+				BUG_ON(ret);
+			}
 		}
 
 		if (found_inline) {
@@ -537,8 +553,12 @@ next_slot:
 					inode_sub_bytes(inode, old_num -
 							new_num);
 				}
-				btrfs_set_file_extent_num_bytes(leaf, extent,
-								new_num);
+				if (!compression && !encryption) {
+					btrfs_set_file_extent_ram_bytes(leaf,
+							extent, new_num);
+				}
+				btrfs_set_file_extent_num_bytes(leaf,
+							extent, new_num);
 				btrfs_mark_buffer_dirty(leaf);
 			} else if (key.offset < inline_limit &&
 				   (end > extent_end) &&
@@ -582,11 +602,11 @@ next_slot:
 		}
 		/* create bookend, splitting the extent in two */
 		if (bookend && found_extent) {
-			u64 disk_bytenr;
 			struct btrfs_key ins;
 			ins.objectid = inode->i_ino;
 			ins.offset = end;
 			btrfs_set_key_type(&ins, BTRFS_EXTENT_DATA_KEY);
+
 			btrfs_release_path(root, path);
 			ret = btrfs_insert_empty_item(trans, root, path, &ins,
 						      sizeof(*extent));
@@ -623,14 +643,13 @@ next_slot:
 
 			btrfs_mark_buffer_dirty(path->nodes[0]);
 
-			disk_bytenr = le64_to_cpu(old.disk_bytenr);
 			if (disk_bytenr != 0) {
-				ret = btrfs_inc_extent_ref(trans, root,
-						disk_bytenr,
-						le64_to_cpu(old.disk_num_bytes),
-						leaf->start,
+				ret = btrfs_update_extent_ref(trans, root,
+						disk_bytenr, orig_parent,
+					        leaf->start,
 						root->root_key.objectid,
 						trans->transid, ins.objectid);
+
 				BUG_ON(ret);
 			}
 			btrfs_release_path(root, path);
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 3df0ffad976..e01c0d0310a 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -86,6 +86,10 @@ static unsigned char btrfs_type_by_mode[S_IFMT >> S_SHIFT] = {
 
 static void btrfs_truncate(struct inode *inode);
 static int btrfs_finish_ordered_io(struct inode *inode, u64 start, u64 end);
+static noinline int cow_file_range(struct inode *inode,
+				   struct page *locked_page,
+				   u64 start, u64 end, int *page_started,
+				   unsigned long *nr_written, int unlock);
 
 /*
  * a very lame attempt at stopping writes when the FS is 85% full.  There
@@ -262,35 +266,72 @@ static int cow_file_range_inline(struct btrfs_trans_handle *trans,
 	return 0;
 }
 
+struct async_extent {
+	u64 start;
+	u64 ram_size;
+	u64 compressed_size;
+	struct page **pages;
+	unsigned long nr_pages;
+	struct list_head list;
+};
+
+struct async_cow {
+	struct inode *inode;
+	struct btrfs_root *root;
+	struct page *locked_page;
+	u64 start;
+	u64 end;
+	struct list_head extents;
+	struct btrfs_work work;
+};
+
+static noinline int add_async_extent(struct async_cow *cow,
+				     u64 start, u64 ram_size,
+				     u64 compressed_size,
+				     struct page **pages,
+				     unsigned long nr_pages)
+{
+	struct async_extent *async_extent;
+
+	async_extent = kmalloc(sizeof(*async_extent), GFP_NOFS);
+	async_extent->start = start;
+	async_extent->ram_size = ram_size;
+	async_extent->compressed_size = compressed_size;
+	async_extent->pages = pages;
+	async_extent->nr_pages = nr_pages;
+	list_add_tail(&async_extent->list, &cow->extents);
+	return 0;
+}
+
 /*
- * when extent_io.c finds a delayed allocation range in the file,
- * the call backs end up in this code.  The basic idea is to
- * allocate extents on disk for the range, and create ordered data structs
- * in ram to track those extents.
+ * we create compressed extents in two phases.  The first
+ * phase compresses a range of pages that have already been
+ * locked (both pages and state bits are locked).
  *
- * locked_page is the page that writepage had locked already.  We use
- * it to make sure we don't do extra locks or unlocks.
+ * This is done inside an ordered work queue, and the compression
+ * is spread across many cpus.  The actual IO submission is step
+ * two, and the ordered work queue takes care of making sure that
+ * happens in the same order things were put onto the queue by
+ * writepages and friends.
  *
- * *page_started is set to one if we unlock locked_page and do everything
- * required to start IO on it.  It may be clean and already done with
- * IO when we return.
+ * If this code finds it can't get good compression, it puts an
+ * entry onto the work queue to write the uncompressed bytes.  This
+ * makes sure that both compressed inodes and uncompressed inodes
+ * are written in the same order that pdflush sent them down.
  */
-static int cow_file_range(struct inode *inode, struct page *locked_page,
-			  u64 start, u64 end, int *page_started)
+static noinline int compress_file_range(struct inode *inode,
+					struct page *locked_page,
+					u64 start, u64 end,
+					struct async_cow *async_cow,
+					int *num_added)
 {
 	struct btrfs_root *root = BTRFS_I(inode)->root;
 	struct btrfs_trans_handle *trans;
-	u64 alloc_hint = 0;
 	u64 num_bytes;
-	unsigned long ram_size;
 	u64 orig_start;
 	u64 disk_num_bytes;
-	u64 cur_alloc_size;
 	u64 blocksize = root->sectorsize;
 	u64 actual_end;
-	struct btrfs_key ins;
-	struct extent_map *em;
-	struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
 	int ret = 0;
 	struct page **pages = NULL;
 	unsigned long nr_pages;
@@ -298,22 +339,12 @@ static int cow_file_range(struct inode *inode, struct page *locked_page,
 	unsigned long total_compressed = 0;
 	unsigned long total_in = 0;
 	unsigned long max_compressed = 128 * 1024;
-	unsigned long max_uncompressed = 256 * 1024;
+	unsigned long max_uncompressed = 128 * 1024;
 	int i;
-	int ordered_type;
 	int will_compress;
 
-	trans = btrfs_join_transaction(root, 1);
-	BUG_ON(!trans);
-	btrfs_set_trans_block_group(trans, inode);
 	orig_start = start;
 
-	/*
-	 * compression made this loop a bit ugly, but the basic idea is to
-	 * compress some pages but keep the total size of the compressed
-	 * extent relatively small.  If compression is off, this goto target
-	 * is never used.
-	 */
 again:
 	will_compress = 0;
 	nr_pages = (end >> PAGE_CACHE_SHIFT) - (start >> PAGE_CACHE_SHIFT) + 1;
@@ -324,7 +355,13 @@ again:
 
 	/* we want to make sure that amount of ram required to uncompress
 	 * an extent is reasonable, so we limit the total size in ram
-	 * of a compressed extent to 256k
+	 * of a compressed extent to 128k.  This is a crucial number
+	 * because it also controls how easily we can spread reads across
+	 * cpus for decompression.
+	 *
+	 * We also want to make sure the amount of IO required to do
+	 * a random read is reasonably small, so we limit the size of
+	 * a compressed extent to 128k.
 	 */
 	total_compressed = min(total_compressed, max_uncompressed);
 	num_bytes = (end - start + blocksize) & ~(blocksize - 1);
@@ -333,18 +370,16 @@ again:
 	total_in = 0;
 	ret = 0;
 
-	/* we do compression for mount -o compress and when the
-	 * inode has not been flagged as nocompress
+	/*
+	 * we do compression for mount -o compress and when the
+	 * inode has not been flagged as nocompress.  This flag can
+	 * change at any time if we discover bad compression ratios.
 	 */
 	if (!btrfs_test_flag(inode, NOCOMPRESS) &&
 	    btrfs_test_opt(root, COMPRESS)) {
 		WARN_ON(pages);
 		pages = kzalloc(sizeof(struct page *) * nr_pages, GFP_NOFS);
 
-		/* we want to make sure the amount of IO required to satisfy
-		 * a random read is reasonably small, so we limit the size
-		 * of a compressed extent to 128k
-		 */
 		ret = btrfs_zlib_compress_pages(inode->i_mapping, start,
 						total_compressed, pages,
 						nr_pages, &nr_pages_ret,
@@ -371,26 +406,34 @@ again:
 		}
 	}
 	if (start == 0) {
+		trans = btrfs_join_transaction(root, 1);
+		BUG_ON(!trans);
+		btrfs_set_trans_block_group(trans, inode);
+
 		/* lets try to make an inline extent */
-		if (ret || total_in < (end - start + 1)) {
+		if (ret || total_in < (actual_end - start)) {
 			/* we didn't compress the entire range, try
-			 * to make an uncompressed inline extent.  This
-			 * is almost sure to fail, but maybe inline sizes
-			 * will get bigger later
+			 * to make an uncompressed inline extent.
 			 */
 			ret = cow_file_range_inline(trans, root, inode,
 						    start, end, 0, NULL);
 		} else {
+			/* try making a compressed inline extent */
 			ret = cow_file_range_inline(trans, root, inode,
 						    start, end,
 						    total_compressed, pages);
 		}
+		btrfs_end_transaction(trans, root);
 		if (