[PATCH 2/2] ext4: track all extent status in extent status tree

[Theodore Ts'o <tytso@mit.edu>]

From: Zheng Liu <wenqing.lz@taobao.com>

By recording the phycisal block and status, extent status tree is able
to track the status of every extents.  When we call _map_blocks
functions to lookup an extent or create a new written/unwritten/delayed
extent, this extent will be inserted into extent status tree.  The hole
extent is inserted in ext4_ext_put_gap_in_cache().  If there is no any
extent, we will not insert a hole extent [0, ~0] into the extent status
tree in order to reduce the complextiy of code.

We don't load all extents from disk in alloc_inode() because it costs
too much memory, and if a file is opened and closed frequently it will
takes too much time to load all extent information.  So currently when
we create/lookup an extent, this extent will be inserted into extent
status tree.  Hence, the extent status tree may not comprehensively
contain all of the extents found in the file.

Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: Jan kara <jack@suse.cz>
---
 fs/ext4/extents_status.c | 18 ++++++++++++----
 fs/ext4/inode.c          | 53 ++++++++++++++++++++++++++++++------------------
 2 files changed, 47 insertions(+), 24 deletions(-)

diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
index df72e95..839a91d 100644
--- a/fs/ext4/extents_status.c
+++ b/fs/ext4/extents_status.c
@@ -267,15 +267,25 @@ ext4_lblk_t ext4_es_find_delayed_extent(struct inode *inode,
 	es1 = __es_tree_search(&tree->root, es->es_lblk);
 
 out:
-	if (es1) {
+	if (es1 && !ext4_es_is_delayed(es1)) {
+		while ((node = rb_next(&es1->rb_node)) != NULL) {
+			es1 = rb_entry(node, struct extent_status, rb_node);
+			if (ext4_es_is_delayed(es1))
+				break;
+		}
+	}
+
+	if (es1 && ext4_es_is_delayed(es1)) {
 		tree->cache_es = es1;
 		es->es_lblk = es1->es_lblk;
 		es->es_len = es1->es_len;
 		es->es_pblk = es1->es_pblk;
-		node = rb_next(&es1->rb_node);
-		if (node) {
+		while ((node = rb_next(&es1->rb_node)) != NULL) {
 			es1 = rb_entry(node, struct extent_status, rb_node);
-			ret = es1->es_lblk;
+			if (ext4_es_is_delayed(es1)) {
+				ret = es1->es_lblk;
+				break;
+			}
 		}
 	}
 
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index cd75f65..01875fe 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -524,20 +524,22 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode,
 		retval = ext4_ind_map_blocks(handle, inode, map, flags &
 					     EXT4_GET_BLOCKS_KEEP_SIZE);
 	}
+	if (retval > 0) {
+		int ret;
+		unsigned long long status;
+
+		status = map->m_flags & EXT4_MAP_UNWRITTEN ?
+				EXTENT_STATUS_UNWRITTEN : EXTENT_STATUS_WRITTEN;
+		ret = ext4_es_insert_extent(inode, map->m_lblk,
+					    map->m_len, map->m_pblk, status);
+		if (ret < 0)
+			retval = ret;
+	}
 	if (!(flags & EXT4_GET_BLOCKS_NO_LOCK))
 		up_read((&EXT4_I(inode)->i_data_sem));
 
 	if (retval > 0 && map->m_flags & EXT4_MAP_MAPPED) {
-		int ret;
-		if (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE) {
-			/* delayed alloc may be allocated by fallocate and
-			 * coverted to initialized by directIO.
-			 * we need to handle delayed extent here.
-			 */
-			down_write((&EXT4_I(inode)->i_data_sem));
-			goto delayed_mapped;
-		}
-		ret = check_block_validity(inode, map);
+		int ret = check_block_validity(inode, map);
 		if (ret != 0)
 			return ret;
 	}
@@ -606,18 +608,19 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode,
 			(flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE))
 			ext4_da_update_reserve_space(inode, retval, 1);
 	}
-	if (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE) {
+	if (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE)
 		ext4_clear_inode_state(inode, EXT4_STATE_DELALLOC_RESERVED);
 
-		if (retval > 0 && map->m_flags & EXT4_MAP_MAPPED) {
-			int ret;
-delayed_mapped:
-			/* delayed allocation blocks has been allocated */
-			ret = ext4_es_remove_extent(inode, map->m_lblk,
-						    map->m_len);
-			if (ret < 0)
-				retval = ret;
-		}
+	if (retval > 0) {
+		int ret;
+		unsigned long long status;
+
+		status = map->m_flags & EXT4_MAP_UNWRITTEN ?
+				EXTENT_STATUS_UNWRITTEN : EXTENT_STATUS_WRITTEN;
+		ret = ext4_es_insert_extent(inode, map->m_lblk, map->m_len,
+					    map->m_pblk, status);
+		if (ret < 0)
+			retval = ret;
 	}
 
 	up_write((&EXT4_I(inode)->i_data_sem));
@@ -1787,6 +1790,16 @@ static int ext4_da_map_blocks(struct inode *inode, sector_t iblock,
 		map_bh(bh, inode->i_sb, invalid_block);
 		set_buffer_new(bh);
 		set_buffer_delay(bh);
+	} else if (retval > 0) {
+		int ret;
+		unsigned long long status;
+
+		status = map->m_flags & EXT4_MAP_UNWRITTEN ?
+				EXTENT_STATUS_UNWRITTEN : EXTENT_STATUS_WRITTEN;
+		ret = ext4_es_insert_extent(inode, map->m_lblk, map->m_len,
+					    map->m_pblk, status);
+		if (ret != 0)
+			retval = ret;
 	}
 
 out_unlock:
-- 
1.7.12.rc0.22.gcdd159b