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>

1 files changed, 10 insertions, 3 deletions

diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index 283110e..2d5f670 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