ext4: rename EXT4_GET_BLOCKS_PRE_IO

This flag has been generalized to split an unwritten extent when we do
dio or dioread_nolock writeback, or to avoid merge new extents which was
created by extents split. Update some related comments too.

Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Baokun Li <libaokun1@huawei.com>
Signed-off-by: Yang Erkun <yangerkun@huawei.com>
Message-ID: <20251112084538.1658232-2-yangerkun@huawei.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Author: Yang Erkun

fs/ext4/ext4.h

@@ -695,13 +695,22 @@ enum {
 	/* Caller is from the delayed allocation writeout path
 	 * finally doing the actual allocation of delayed blocks */
 #define EXT4_GET_BLOCKS_DELALLOC_RESERVE	0x0004
-	/* caller is from the direct IO path, request to creation of an
-	unwritten extents if not allocated, split the unwritten
-	extent if blocks has been preallocated already*/
-#define EXT4_GET_BLOCKS_PRE_IO			0x0008
-#define EXT4_GET_BLOCKS_CONVERT			0x0010
-#define EXT4_GET_BLOCKS_IO_CREATE_EXT		(EXT4_GET_BLOCKS_PRE_IO|\
+	/*
+	 * This means that we cannot merge newly allocated extents, and if we
+	 * found an unwritten extent, we need to split it.
+	 */
+#define EXT4_GET_BLOCKS_SPLIT_NOMERGE		0x0008
+	/*
+	 * Caller is from the dio or dioread_nolock buffered IO, reqest to
+	 * create an unwritten extent if it does not exist or split the
+	 * found unwritten extent. Also do not merge the newly created
+	 * unwritten extent, io end will convert unwritten to written,
+	 * and try to merge the written extent.
+	 */
+#define EXT4_GET_BLOCKS_IO_CREATE_EXT		(EXT4_GET_BLOCKS_SPLIT_NOMERGE|\
 					 EXT4_GET_BLOCKS_CREATE_UNWRIT_EXT)
+	/* Convert unwritten extent to initialized. */
+#define EXT4_GET_BLOCKS_CONVERT			0x0010
 	/* Eventual metadata allocation (due to growing extent tree)
 	 * should not fail, so try to use reserved blocks for that.*/
 #define EXT4_GET_BLOCKS_METADATA_NOFAIL		0x0020

fs/ext4/extents.c

@@ -333,7 +333,7 @@ ext4_force_split_extent_at(handle_t *handle, struct inode *inode,
 			   int nofail)
 {
 	int unwritten = ext4_ext_is_unwritten(path[path->p_depth].p_ext);
-	int flags = EXT4_EX_NOCACHE | EXT4_GET_BLOCKS_PRE_IO;
+	int flags = EXT4_EX_NOCACHE | EXT4_GET_BLOCKS_SPLIT_NOMERGE;
 
 	if (nofail)
 		flags |= EXT4_GET_BLOCKS_METADATA_NOFAIL | EXT4_EX_NOFAIL;
@@ -2002,7 +2002,7 @@ ext4_ext_insert_extent(handle_t *handle, struct inode *inode,
 	}
 
 	/* try to insert block into found extent and return */
-	if (ex && !(gb_flags & EXT4_GET_BLOCKS_PRE_IO)) {
+	if (ex && !(gb_flags & EXT4_GET_BLOCKS_SPLIT_NOMERGE)) {
 
 		/*
 		 * Try to see whether we should rather test the extent on
@@ -2181,7 +2181,7 @@ ext4_ext_insert_extent(handle_t *handle, struct inode *inode,
 
 merge:
 	/* try to merge extents */
-	if (!(gb_flags & EXT4_GET_BLOCKS_PRE_IO))
+	if (!(gb_flags & EXT4_GET_BLOCKS_SPLIT_NOMERGE))
 		ext4_ext_try_to_merge(handle, inode, path, nearex);
 
 	/* time to correct all indexes above */
@@ -3224,7 +3224,7 @@ static struct ext4_ext_path *ext4_split_extent_at(handle_t *handle,
 		else
 			ext4_ext_mark_initialized(ex);
 
-		if (!(flags & EXT4_GET_BLOCKS_PRE_IO))
+		if (!(flags & EXT4_GET_BLOCKS_SPLIT_NOMERGE))
 			ext4_ext_try_to_merge(handle, inode, path, ex);
 
 		err = ext4_ext_dirty(handle, inode, path + path->p_depth);
@@ -3368,7 +3368,7 @@ static struct ext4_ext_path *ext4_split_extent(handle_t *handle,
 
 	if (map->m_lblk + map->m_len < ee_block + ee_len) {
 		split_flag1 = split_flag & EXT4_EXT_MAY_ZEROOUT;
-		flags1 = flags | EXT4_GET_BLOCKS_PRE_IO;
+		flags1 = flags | EXT4_GET_BLOCKS_SPLIT_NOMERGE;
 		if (unwritten)
 			split_flag1 |= EXT4_EXT_MARK_UNWRIT1 |
 				       EXT4_EXT_MARK_UNWRIT2;
@@ -3739,7 +3739,7 @@ static struct ext4_ext_path *ext4_split_convert_extents(handle_t *handle,
 			      EXT4_EXT_MAY_ZEROOUT : 0;
 		split_flag |= (EXT4_EXT_MARK_UNWRIT2 | EXT4_EXT_DATA_VALID2);
 	}
-	flags |= EXT4_GET_BLOCKS_PRE_IO;
+	flags |= EXT4_GET_BLOCKS_SPLIT_NOMERGE;
 	return ext4_split_extent(handle, inode, path, map, split_flag, flags,
 				 allocated);
 }
@@ -3911,7 +3911,7 @@ ext4_ext_handle_unwritten_extents(handle_t *handle, struct inode *inode,
 						*allocated, newblock);
 
 	/* get_block() before submitting IO, split the extent */
-	if (flags & EXT4_GET_BLOCKS_PRE_IO) {
+	if (flags & EXT4_GET_BLOCKS_SPLIT_NOMERGE) {
 		path = ext4_split_convert_extents(handle, inode, map, path,
 				flags | EXT4_GET_BLOCKS_CONVERT, allocated);
 		if (IS_ERR(path))
@@ -5618,7 +5618,7 @@ static int ext4_insert_range(struct file *file, loff_t offset, loff_t len)
 			path = ext4_split_extent_at(handle, inode, path,
 					start_lblk, split_flag,
 					EXT4_EX_NOCACHE |
-					EXT4_GET_BLOCKS_PRE_IO |
+					EXT4_GET_BLOCKS_SPLIT_NOMERGE |
 					EXT4_GET_BLOCKS_METADATA_NOFAIL);
 		}
 

fs/ext4/inode.c

@@ -653,7 +653,7 @@ static int ext4_map_create_blocks(handle_t *handle, struct inode *inode,
 	 * If the extent has been zeroed out, we don't need to update
 	 * extent status tree.
 	 */
-	if (flags & EXT4_GET_BLOCKS_PRE_IO &&
+	if (flags & EXT4_GET_BLOCKS_SPLIT_NOMERGE &&
 	    ext4_es_lookup_extent(inode, map->m_lblk, NULL, &es, &map->m_seq)) {
 		if (ext4_es_is_written(&es))
 			return retval;

include/trace/events/ext4.h

@@ -39,7 +39,7 @@ struct partial_cluster;
 	{ EXT4_GET_BLOCKS_CREATE,		"CREATE" },		\
 	{ EXT4_GET_BLOCKS_UNWRIT_EXT,		"UNWRIT" },		\
 	{ EXT4_GET_BLOCKS_DELALLOC_RESERVE,	"DELALLOC" },		\
-	{ EXT4_GET_BLOCKS_PRE_IO,		"PRE_IO" },		\
+	{ EXT4_GET_BLOCKS_SPLIT_NOMERGE,	"SPLIT_NOMERGE" },	\
 	{ EXT4_GET_BLOCKS_CONVERT,		"CONVERT" },		\
 	{ EXT4_GET_BLOCKS_METADATA_NOFAIL,	"METADATA_NOFAIL" },	\
 	{ EXT4_GET_BLOCKS_NO_NORMALIZE,		"NO_NORMALIZE" },	\