[RFC PATCH v3 12/26] ext4: factor out bh handles to ext4_da_get_block_prep()

[Zhang Yi <yi.zhang@huaweicloud.com>]

From: Zhang Yi <yi.zhang@huawei.com>

Factor buffer_head related handles out from ext4_da_map_blocks() to
ext4_da_get_block_prep(), and make ext4_da_map_blocks() always return 0
if success, we can distinguish delalloc map through EXT4_MAP_DELAYED
flag.

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
---
 fs/ext4/inode.c | 75 ++++++++++++++++++++++++-------------------------
 1 file changed, 36 insertions(+), 39 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 9ac9bb548a4c..9f9b1fce8da8 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1690,48 +1690,37 @@ static int ext4_insert_delayed_blocks(struct inode *inode, ext4_lblk_t lblk,
  * time. This function looks up the requested blocks and sets the
  * buffer delay bit under the protection of i_data_sem.
  */
-static int ext4_da_map_blocks(struct inode *inode, sector_t iblock,
-			      struct ext4_map_blocks *map,
-			      struct buffer_head *bh)
+static int ext4_da_map_blocks(struct inode *inode, struct ext4_map_blocks *map)
 {
 	struct extent_status es;
 	int retval;
-	sector_t invalid_block = ~((sector_t) 0xffff);
 #ifdef ES_AGGRESSIVE_TEST
 	struct ext4_map_blocks orig_map;
 
 	memcpy(&orig_map, map, sizeof(*map));
 #endif
 
-	if (invalid_block < ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es))
-		invalid_block = ~0;
-
 	map->m_flags = 0;
 	ext_debug(inode, "max_blocks %u, logical block %lu\n", map->m_len,
 		  (unsigned long) map->m_lblk);
 
 	/* Lookup extent status tree firstly */
-	if (ext4_es_lookup_extent(inode, iblock, NULL, &es)) {
-		retval = es.es_len - (iblock - es.es_lblk);
-		if (retval > map->m_len)
-			retval = map->m_len;
-		map->m_len = retval;
-
-		if (ext4_es_is_hole(&es))
-			goto add_delayed;
+	if (ext4_es_lookup_extent(inode, map->m_lblk, NULL, &es)) {
+		retval = es.es_len - (map->m_lblk - es.es_lblk);
+		map->m_len = min_t(unsigned int, map->m_len, retval);
 
 		/*
 		 * Delayed extent could be allocated by fallocate.
 		 * So we need to check it.
 		 */
-		if (ext4_es_is_delayed(&es) && !ext4_es_is_unwritten(&es)) {
-			map_bh(bh, inode->i_sb, invalid_block);
-			set_buffer_new(bh);
-			set_buffer_delay(bh);
+		if (ext4_es_is_delonly(&es)) {
+			map->m_flags |= EXT4_MAP_DELAYED;
 			return 0;
 		}
+		if (ext4_es_is_hole(&es))
+			goto add_delayed;
 
-		map->m_pblk = ext4_es_pblock(&es) + iblock - es.es_lblk;
+		map->m_pblk = ext4_es_pblock(&es) + map->m_lblk - es.es_lblk;
 		if (ext4_es_is_written(&es))
 			map->m_flags |= EXT4_MAP_MAPPED;
 		else if (ext4_es_is_unwritten(&es))
@@ -1743,7 +1732,7 @@ static int ext4_da_map_blocks(struct inode *inode, sector_t iblock,
 		ext4_map_blocks_es_recheck(NULL, inode, map, &orig_map, 0);
 #endif
 		if (ext4_es_is_delayed(&es) || ext4_es_is_written(&es))
-			return retval;
+			return 0;
 
 		down_read(&EXT4_I(inode)->i_data_sem);
 		goto insert_extent;
@@ -1775,6 +1764,7 @@ static int ext4_da_map_blocks(struct inode *inode, sector_t iblock,
 			WARN_ON(1);
 		}
 insert_extent:
+		retval = 0;
 		status = map->m_flags & EXT4_MAP_UNWRITTEN ?
 				EXTENT_STATUS_UNWRITTEN : EXTENT_STATUS_WRITTEN;
 		if (status == EXTENT_STATUS_UNWRITTEN)
@@ -1788,14 +1778,10 @@ static int ext4_da_map_blocks(struct inode *inode, sector_t iblock,
 
 add_delayed:
 	down_write(&EXT4_I(inode)->i_data_sem);
+	map->m_flags |= EXT4_MAP_DELAYED;
 	retval = ext4_insert_delayed_blocks(inode, map->m_lblk, map->m_len);
 	up_write(&EXT4_I(inode)->i_data_sem);
-	if (retval)
-		return retval;
 
-	map_bh(bh, inode->i_sb, invalid_block);
-	set_buffer_new(bh);
-	set_buffer_delay(bh);
 	return retval;
 }
 
@@ -1815,11 +1801,15 @@ int ext4_da_get_block_prep(struct inode *inode, sector_t iblock,
 			   struct buffer_head *bh, int create)
 {
 	struct ext4_map_blocks map;
+	sector_t invalid_block = ~((sector_t) 0xffff);
 	int ret = 0;
 
 	BUG_ON(create == 0);
 	BUG_ON(bh->b_size != inode->i_sb->s_blocksize);
 
+	if (invalid_block < ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es))
+		invalid_block = ~0;
+
 	map.m_lblk = iblock;
 	map.m_len = 1;
 
@@ -1828,22 +1818,29 @@ int ext4_da_get_block_prep(struct inode *inode, sector_t iblock,
 	 * preallocated blocks are unmapped but should treated
 	 * the same as allocated blocks.
 	 */
-	ret = ext4_da_map_blocks(inode, iblock, &map, bh);
-	if (ret <= 0)
+	ret = ext4_da_map_blocks(inode, &map);
+	if (ret < 0)
 		return ret;
 
-	map_bh(bh, inode->i_sb, map.m_pblk);
-	ext4_update_bh_state(bh, map.m_flags);
-
-	if (buffer_unwritten(bh)) {
-		/* A delayed write to unwritten bh should be marked
-		 * new and mapped.  Mapped ensures that we don't do
-		 * get_block multiple times when we write to the same
-		 * offset and new ensures that we do proper zero out
-		 * for partial write.
-		 */
+	if (map.m_flags & EXT4_MAP_DELAYED) {
+		map_bh(bh, inode->i_sb, invalid_block);
 		set_buffer_new(bh);
-		set_buffer_mapped(bh);
+		set_buffer_delay(bh);
+	} else {
+		map_bh(bh, inode->i_sb, map.m_pblk);
+		ext4_update_bh_state(bh, map.m_flags);
+
+		if (buffer_unwritten(bh)) {
+			/*
+			 * A delayed write to unwritten bh should be marked
+			 * new and mapped.  Mapped ensures that we don't do
+			 * get_block multiple times when we write to the same
+			 * offset and new ensures that we do proper zero out
+			 * for partial write.
+			 */
+			set_buffer_new(bh);
+			set_buffer_mapped(bh);
+		}
 	}
 	return 0;
 }
-- 
2.39.2