ext4: factor out ext4_map_create_blocks() to allocate new blocks

Factor out a common helper ext4_map_create_blocks() from
ext4_map_blocks() to do a real blocks allocation, no logic changes.

[ Note: this first patch of a ten patch series named "v3: simplify the
  counting and management of delalloc reserved blocks".  The link to
  the v1 and v2 patch series are below. -- TYT ]
Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20240802115120.362902-1-yi.zhang@huaweicloud.com # v2 of patch series
Link: https://patch.msgid.link/20240601034149.2169771-1-yi.zhang@huaweicloud.com # v1 of the patch series

Link: https://patch.msgid.link/20240813123452.2824659-2-yi.zhang@huaweicloud.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/inode.c

@@ -482,6 +482,86 @@ static int ext4_map_query_blocks(handle_t *handle, struct inode *inode,
 	return retval;
 }
 
+static int ext4_map_create_blocks(handle_t *handle, struct inode *inode,
+				  struct ext4_map_blocks *map, int flags)
+{
+	struct extent_status es;
+	unsigned int status;
+	int err, retval = 0;
+
+	/*
+	 * Here we clear m_flags because after allocating an new extent,
+	 * it will be set again.
+	 */
+	map->m_flags &= ~EXT4_MAP_FLAGS;
+
+	/*
+	 * We need to check for EXT4 here because migrate could have
+	 * changed the inode type in between.
+	 */
+	if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) {
+		retval = ext4_ext_map_blocks(handle, inode, map, flags);
+	} else {
+		retval = ext4_ind_map_blocks(handle, inode, map, flags);
+
+		/*
+		 * We allocated new blocks which will result in i_data's
+		 * format changing. Force the migrate to fail by clearing
+		 * migrate flags.
+		 */
+		if (retval > 0 && map->m_flags & EXT4_MAP_NEW)
+			ext4_clear_inode_state(inode, EXT4_STATE_EXT_MIGRATE);
+	}
+	if (retval <= 0)
+		return retval;
+
+	if (unlikely(retval != map->m_len)) {
+		ext4_warning(inode->i_sb,
+			     "ES len assertion failed for inode %lu: "
+			     "retval %d != map->m_len %d",
+			     inode->i_ino, retval, map->m_len);
+		WARN_ON(1);
+	}
+
+	/*
+	 * We have to zeroout blocks before inserting them into extent
+	 * status tree. Otherwise someone could look them up there and
+	 * use them before they are really zeroed. We also have to
+	 * unmap metadata before zeroing as otherwise writeback can
+	 * overwrite zeros with stale data from block device.
+	 */
+	if (flags & EXT4_GET_BLOCKS_ZERO &&
+	    map->m_flags & EXT4_MAP_MAPPED && map->m_flags & EXT4_MAP_NEW) {
+		err = ext4_issue_zeroout(inode, map->m_lblk, map->m_pblk,
+					 map->m_len);
+		if (err)
+			return err;
+	}
+
+	/*
+	 * If the extent has been zeroed out, we don't need to update
+	 * extent status tree.
+	 */
+	if (flags & EXT4_GET_BLOCKS_PRE_IO &&
+	    ext4_es_lookup_extent(inode, map->m_lblk, NULL, &es)) {
+		if (ext4_es_is_written(&es))
+			return retval;
+	}
+
+	status = map->m_flags & EXT4_MAP_UNWRITTEN ?
+			EXTENT_STATUS_UNWRITTEN : EXTENT_STATUS_WRITTEN;
+	if (!(flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE) &&
+	    !(status & EXTENT_STATUS_WRITTEN) &&
+	    ext4_es_scan_range(inode, &ext4_es_is_delayed, map->m_lblk,
+			       map->m_lblk + map->m_len - 1))
+		status |= EXTENT_STATUS_DELAYED;
+
+	ext4_es_insert_extent(inode, map->m_lblk, map->m_len,
+			      map->m_pblk, status);
+
+	return retval;
+}
+
 /*
  * The ext4_map_blocks() function tries to look up the requested blocks,
  * and returns if the blocks are already mapped.
@@ -630,12 +710,6 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode,
 		if (!(flags & EXT4_GET_BLOCKS_CONVERT_UNWRITTEN))
 			return retval;
 
-	/*
-	 * Here we clear m_flags because after allocating an new extent,
-	 * it will be set again.
-	 */
-	map->m_flags &= ~EXT4_MAP_FLAGS;
-
 	/*
 	 * New blocks allocate and/or writing to unwritten extent
 	 * will possibly result in updating i_data, so we take
@@ -643,76 +717,7 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode,
 	 * with create == 1 flag.
 	 */
 	down_write(&EXT4_I(inode)->i_data_sem);
-
-	/*
-	 * We need to check for EXT4 here because migrate
-	 * could have changed the inode type in between
-	 */
-	if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) {
-		retval = ext4_ext_map_blocks(handle, inode, map, flags);
-	} else {
-		retval = ext4_ind_map_blocks(handle, inode, map, flags);
-
-		if (retval > 0 && map->m_flags & EXT4_MAP_NEW) {
-			/*
-			 * We allocated new blocks which will result in
-			 * i_data's format changing.  Force the migrate
-			 * to fail by clearing migrate flags
-			 */
-			ext4_clear_inode_state(inode, EXT4_STATE_EXT_MIGRATE);
-		}
-	}
-
-	if (retval > 0) {
-		unsigned int status;
-
-		if (unlikely(retval != map->m_len)) {
-			ext4_warning(inode->i_sb,
-				     "ES len assertion failed for inode "
-				     "%lu: retval %d != map->m_len %d",
-				     inode->i_ino, retval, map->m_len);
-			WARN_ON(1);
-		}
-
-		/*
-		 * We have to zeroout blocks before inserting them into extent
-		 * status tree. Otherwise someone could look them up there and
-		 * use them before they are really zeroed. We also have to
-		 * unmap metadata before zeroing as otherwise writeback can
-		 * overwrite zeros with stale data from block device.
-		 */
-		if (flags & EXT4_GET_BLOCKS_ZERO &&
-		    map->m_flags & EXT4_MAP_MAPPED &&
-		    map->m_flags & EXT4_MAP_NEW) {
-			ret = ext4_issue_zeroout(inode, map->m_lblk,
-						 map->m_pblk, map->m_len);
-			if (ret) {
-				retval = ret;
-				goto out_sem;
-			}
-		}
-
-		/*
-		 * If the extent has been zeroed out, we don't need to update
-		 * extent status tree.
-		 */
-		if ((flags & EXT4_GET_BLOCKS_PRE_IO) &&
-		    ext4_es_lookup_extent(inode, map->m_lblk, NULL, &es)) {
-			if (ext4_es_is_written(&es))
-				goto out_sem;
-		}
-		status = map->m_flags & EXT4_MAP_UNWRITTEN ?
-				EXTENT_STATUS_UNWRITTEN : EXTENT_STATUS_WRITTEN;
-		if (!(flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE) &&
-		    !(status & EXTENT_STATUS_WRITTEN) &&
-		    ext4_es_scan_range(inode, &ext4_es_is_delayed, map->m_lblk,
-				       map->m_lblk + map->m_len - 1))
-			status |= EXTENT_STATUS_DELAYED;
-		ext4_es_insert_extent(inode, map->m_lblk, map->m_len,
-				      map->m_pblk, status);
-	}
-
-out_sem:
+	retval = ext4_map_create_blocks(handle, inode, map, flags);
 	up_write((&EXT4_I(inode)->i_data_sem));
 	if (retval > 0 && map->m_flags & EXT4_MAP_MAPPED) {
 		ret = check_block_validity(inode, map);