linux-ext4 - Re: [PATCH v3 2/3] ext4: rename EXT4_GET_BLOCKS_PRE

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Message-ID: <b4808ce1-7b4f-4fc5-bbfd-92871ad89ab9@huawei.com>
Date: Sat, 8 Nov 2025 09:49:16 +0800
From: Baokun Li <libaokun1@...wei.com>
To: Yang Erkun <yangerkun@...wei.com>
CC: <yi.zhang@...wei.com>, <yangerkun@...weicloud.com>,
	<linux-ext4@...r.kernel.org>, <tytso@....edu>, <adilger.kernel@...ger.ca>,
	<jack@...e.cz>, Baokun Li <libaokun1@...wei.com>
Subject: Re: [PATCH v3 2/3] ext4: rename EXT4_GET_BLOCKS_PRE_IO

On 2025-11-07 19:58, Yang Erkun wrote:
> 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@...wei.com>
> Reviewed-by: Jan Kara <jack@...e.cz>
> Signed-off-by: Yang Erkun <yangerkun@...wei.com>

Looks good. Feel free to add:

Reviewed-by: Baokun Li <libaokun1@...wei.com>

> ---
>  fs/ext4/ext4.h              | 21 +++++++++++++++------
>  fs/ext4/extents.c           | 16 ++++++++--------
>  include/trace/events/ext4.h |  2 +-
>  3 files changed, 24 insertions(+), 15 deletions(-)
>
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 57087da6c7be..6ee0bc072589 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -694,13 +694,22 @@ 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
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index ca5499e9412b..241b5f5d29ad 100644
> --- a/fs/ext4/extents.c
> +++ b/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);
>  		}
>  
> diff --git a/include/trace/events/ext4.h b/include/trace/events/ext4.h
> index a374e7ea7e57..ada2b9223df5 100644
> --- a/include/trace/events/ext4.h
> +++ b/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" },	\