commit 9e8a4a8b0b9484e8d14674fc62c9ad8ac9dbce5b
author Liu Bo <bo.li.liu@oracle.com> Wed Sep 05 19:10:51 2012 -0600
committer Chris Mason <chris.mason@fusionio.com> Mon Oct 01 15:19:15 2012 -0400
tree d1c2cc07c1d016b6d9e8352a41247e1da2778f28
parent 3d6b5c3b5c0b970ce8a9d3bac6854f5c0ce0295a

Btrfs: use flag EXTENT_DEFRAG for snapshot-aware defrag

We're going to use this flag EXTENT_DEFRAG to indicate which range
belongs to defragment so that we can implement snapshow-aware defrag:

We set the EXTENT_DEFRAG flag when dirtying the extents that need
defragmented, so later on writeback thread can differentiate between
normal writeback and writeback started by defragmentation.

Original-Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Liu Bo <bo.li.liu@oracle.com>

fs/btrfs/inode.c

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index d34eb32..9b21cf9 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -3549,7 +3549,8 @@
 	}
 
 	clear_extent_bit(&BTRFS_I(inode)->io_tree, page_start, page_end,
-			  EXTENT_DIRTY | EXTENT_DELALLOC | EXTENT_DO_ACCOUNTING,
+			  EXTENT_DIRTY | EXTENT_DELALLOC |
+			  EXTENT_DO_ACCOUNTING | EXTENT_DEFRAG,
 			  0, 0, &cached_state, GFP_NOFS);
 
 	ret = btrfs_set_extent_delalloc(inode, page_start, page_end,
@@ -6061,7 +6062,8 @@
 	if (lockstart < lockend) {
 		if (create && len < lockend - lockstart) {
 			clear_extent_bit(&BTRFS_I(inode)->io_tree, lockstart,
-					 lockstart + len - 1, unlock_bits, 1, 0,
+					 lockstart + len - 1,
+					 unlock_bits | EXTENT_DEFRAG, 1, 0,
 					 &cached_state, GFP_NOFS);
 			/*
 			 * Beside unlock, we also need to cleanup reserved space
@@ -6069,8 +6071,8 @@
 			 */
 			clear_extent_bit(&BTRFS_I(inode)->io_tree,
 					 lockstart + len, lockend,
-					 unlock_bits | EXTENT_DO_ACCOUNTING,
-					 1, 0, NULL, GFP_NOFS);
+					 unlock_bits | EXTENT_DO_ACCOUNTING |
+					 EXTENT_DEFRAG, 1, 0, NULL, GFP_NOFS);
 		} else {
 			clear_extent_bit(&BTRFS_I(inode)->io_tree, lockstart,
 					 lockend, unlock_bits, 1, 0,
@@ -6635,8 +6637,8 @@
 		 */
 		clear_extent_bit(tree, page_start, page_end,
 				 EXTENT_DIRTY | EXTENT_DELALLOC |
-				 EXTENT_LOCKED | EXTENT_DO_ACCOUNTING, 1, 0,
-				 &cached_state, GFP_NOFS);
+				 EXTENT_LOCKED | EXTENT_DO_ACCOUNTING |
+				 EXTENT_DEFRAG, 1, 0, &cached_state, GFP_NOFS);
 		/*
 		 * whoever cleared the private bit is responsible
 		 * for the finish_ordered_io
@@ -6652,7 +6654,8 @@
 	}
 	clear_extent_bit(tree, page_start, page_end,
 		 EXTENT_LOCKED | EXTENT_DIRTY | EXTENT_DELALLOC |
-		 EXTENT_DO_ACCOUNTING, 1, 1, &cached_state, GFP_NOFS);
+		 EXTENT_DO_ACCOUNTING | EXTENT_DEFRAG, 1, 1,
+		 &cached_state, GFP_NOFS);
 	__btrfs_releasepage(page, GFP_NOFS);
 
 	ClearPageChecked(page);
@@ -6749,7 +6752,8 @@
 	 * prepare_pages in the normal write path.
 	 */
 	clear_extent_bit(&BTRFS_I(inode)->io_tree, page_start, page_end,
-			  EXTENT_DIRTY | EXTENT_DELALLOC | EXTENT_DO_ACCOUNTING,
+			  EXTENT_DIRTY | EXTENT_DELALLOC |
+			  EXTENT_DO_ACCOUNTING | EXTENT_DEFRAG,
 			  0, 0, &cached_state, GFP_NOFS);
 
 	ret = btrfs_set_extent_delalloc(inode, page_start, page_end,