[PATCH v4 09/34] ext4: make ext4_da_map_blocks() buffer_head unaware

[Zhang Yi]

From: Zhang Yi <yi.zhang@xxxxxxxxxx>

After calling ext4_da_map_blocks(), a delalloc extent state could be
distinguished through EXT4_MAP_DELAYED flag in map. So factor out
buffer_head related handles in ext4_da_map_blocks(), make it
buffer_head unaware, make it become a common helper, it could be used
for iomap in the future.

Signed-off-by: Zhang Yi <yi.zhang@xxxxxxxxxx>
---
 fs/ext4/inode.c | 54 +++++++++++++++++++++++--------------------------
 1 file changed, 25 insertions(+), 29 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 08e2692b7286..1731c1d24362 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1749,33 +1749,26 @@ static int ext4_insert_delayed_blocks(struct inode *inode, ext4_lblk_t lblk,
  * This function is grabs code from the very beginning of
  * ext4_map_blocks, but assumes that the caller is from delayed write
  * time. This function looks up the requested blocks and sets the
- * buffer delay bit under the protection of i_data_sem.
+ * delalloc extent map under the protection of i_data_sem.
  */
-static int ext4_da_map_blocks(struct inode *inode, 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, map->m_lblk, NULL, &es)) {
-		retval = es.es_len - (map->m_lblk - es.es_lblk);
-		if (retval > map->m_len)
-			retval = map->m_len;
-		map->m_len = retval;
+		map->m_len = min_t(unsigned int, map->m_len,
+				   es.es_len - (map->m_lblk - es.es_lblk));
 
 		if (ext4_es_is_hole(&es))
 			goto add_delayed;
@@ -1785,10 +1778,8 @@ static int ext4_da_map_blocks(struct inode *inode, struct ext4_map_blocks *map,
 		 * 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;
 		}
 
@@ -1803,7 +1794,7 @@ static int ext4_da_map_blocks(struct inode *inode, struct ext4_map_blocks *map,
 #ifdef ES_AGGRESSIVE_TEST
 		ext4_map_blocks_es_recheck(NULL, inode, map, &orig_map, 0);
 #endif
-		return retval;
+		return 0;
 	}
 
 	/*
@@ -1817,7 +1808,7 @@ static int ext4_da_map_blocks(struct inode *inode, struct ext4_map_blocks *map,
 		retval = ext4_map_query_blocks(NULL, inode, map);
 	up_read(&EXT4_I(inode)->i_data_sem);
 	if (retval)
-		return retval;
+		return retval < 0 ? retval : 0;
 
 add_delayed:
 	down_write(&EXT4_I(inode)->i_data_sem);
@@ -1827,10 +1818,8 @@ static int ext4_da_map_blocks(struct inode *inode, struct ext4_map_blocks *map,
 	 * whitout holding i_rwsem and folio lock.
 	 */
 	if (ext4_es_lookup_extent(inode, map->m_lblk, NULL, &es)) {
-		retval = es.es_len - (map->m_lblk - es.es_lblk);
-		if (retval > map->m_len)
-			retval = map->m_len;
-		map->m_len = retval;
+		map->m_len = min_t(unsigned int, map->m_len,
+				   es.es_len - (map->m_lblk - es.es_lblk));
 
 		if (!ext4_es_is_hole(&es)) {
 			up_write(&EXT4_I(inode)->i_data_sem);
@@ -1840,18 +1829,14 @@ static int ext4_da_map_blocks(struct inode *inode, struct ext4_map_blocks *map,
 		retval = ext4_map_query_blocks(NULL, inode, map);
 		if (retval) {
 			up_write(&EXT4_I(inode)->i_data_sem);
-			return retval;
+			return retval < 0 ? retval : 0;
 		}
 	}
 
+	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;
 }
 
@@ -1871,11 +1856,15 @@ 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;
 
@@ -1884,10 +1873,17 @@ 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, &map, bh);
-	if (ret <= 0)
+	ret = ext4_da_map_blocks(inode, &map);
+	if (ret < 0)
 		return ret;
 
+	if (map.m_flags & EXT4_MAP_DELAYED) {
+		map_bh(bh, inode->i_sb, invalid_block);
+		set_buffer_new(bh);
+		set_buffer_delay(bh);
+		return 0;
+	}
+
 	map_bh(bh, inode->i_sb, map.m_pblk);
 	ext4_update_bh_state(bh, map.m_flags);
 
-- 
2.39.2