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/extent_io.c

@@ -1144,6 +1144,14 @@ int set_extent_delalloc(struct extent_io_tree *tree, u64 start, u64 end,
 			      NULL, cached_state, mask);
 }
 
+int set_extent_defrag(struct extent_io_tree *tree, u64 start, u64 end,
+		      struct extent_state **cached_state, gfp_t mask)
+{
+	return set_extent_bit(tree, start, end,
+			      EXTENT_DELALLOC | EXTENT_UPTODATE | EXTENT_DEFRAG,
+			      NULL, cached_state, mask);
+}
+
 int clear_extent_dirty(struct extent_io_tree *tree, u64 start, u64 end,
 		       gfp_t mask)
 {

fs/btrfs/extent_io.h

@@ -235,6 +235,8 @@ int convert_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
 		       int bits, int clear_bits, gfp_t mask);
 int set_extent_delalloc(struct extent_io_tree *tree, u64 start, u64 end,
 			struct extent_state **cached_state, gfp_t mask);
+int set_extent_defrag(struct extent_io_tree *tree, u64 start, u64 end,
+		      struct extent_state **cached_state, gfp_t mask);
 int find_first_extent_bit(struct extent_io_tree *tree, u64 start,
 			  u64 *start_ret, u64 *end_ret, int bits);
 struct extent_state *find_first_extent_bit_state(struct extent_io_tree *tree,

fs/btrfs/file.c

@@ -1203,8 +1203,8 @@ static noinline int prepare_pages(struct btrfs_root *root, struct file *file,
 
 		clear_extent_bit(&BTRFS_I(inode)->io_tree, start_pos,
 				  last_pos - 1, EXTENT_DIRTY | EXTENT_DELALLOC |
-				  EXTENT_DO_ACCOUNTING, 0, 0, &cached_state,
-				  GFP_NOFS);
+				  EXTENT_DO_ACCOUNTING | EXTENT_DEFRAG,
+				  0, 0, &cached_state, GFP_NOFS);
 		unlock_extent_cached(&BTRFS_I(inode)->io_tree,
 				     start_pos, last_pos - 1, &cached_state,
 				     GFP_NOFS);

fs/btrfs/inode.c

@@ -3549,7 +3549,8 @@ int btrfs_truncate_page(struct inode *inode, loff_t from, loff_t len,
 	}
 
 	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 @@ static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock,
 	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 @@ static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock,
 			 */
 			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 @@ static void btrfs_invalidatepage(struct page *page, unsigned long offset)
 		 */
 		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 @@ static void btrfs_invalidatepage(struct page *page, unsigned long offset)
 	}
 	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 @@ int btrfs_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
 	 * 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,

fs/btrfs/ioctl.c

@@ -1023,8 +1023,8 @@ static int cluster_pages_for_defrag(struct inode *inode,
 			 page_start, page_end - 1, 0, &cached_state);
 	clear_extent_bit(&BTRFS_I(inode)->io_tree, page_start,
 			  page_end - 1, EXTENT_DIRTY | EXTENT_DELALLOC |
-			  EXTENT_DO_ACCOUNTING, 0, 0, &cached_state,
-			  GFP_NOFS);
+			  EXTENT_DO_ACCOUNTING | EXTENT_DEFRAG, 0, 0,
+			  &cached_state, GFP_NOFS);
 
 	if (i_done != page_cnt) {
 		spin_lock(&BTRFS_I(inode)->lock);
@@ -1035,8 +1035,8 @@ static int cluster_pages_for_defrag(struct inode *inode,
 	}
 
 
-	btrfs_set_extent_delalloc(inode, page_start, page_end - 1,
-				  &cached_state);
+	set_extent_defrag(&BTRFS_I(inode)->io_tree, page_start, page_end - 1,
+			  &cached_state, GFP_NOFS);
 
 	unlock_extent_cached(&BTRFS_I(inode)->io_tree,
 			     page_start, page_end - 1, &cached_state,