linux-ext4 - Re: [PATCH v2 4/4] ext4: order mode should not take effect for DIO

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Message-ID: <m4alrnslmj753wmjmvzydo3w2vq66plzkjj3rff4k2fqfc53mx@mvtip26su7d7>
Date: Tue, 4 Nov 2025 16:07:16 +0100
From: Jan Kara <jack@...e.cz>
To: Yang Erkun <yangerkun@...wei.com>
Cc: linux-ext4@...r.kernel.org, tytso@....edu, adilger.kernel@...ger.ca, 
	jack@...e.cz, yi.zhang@...wei.com, libaokun1@...wei.com, 
	yangerkun@...weicloud.com
Subject: Re: [PATCH v2 4/4] ext4: order mode should not take effect for DIO

On Tue 04-11-25 21:17:50, Yang Erkun wrote:
> Since the size will be updated after the DIO completes, the data
> will not be shown to userspace before that.
> 
> Reviewed-by: Zhang Yi <yi.zhang@...wei.com>
> Signed-off-by: Yang Erkun <yangerkun@...wei.com>

Hum, is there some measurable performance benefit from this? If yes, it
would be good to mention it in the changelog. If not, then why bother?

								Honza

> ---
>  fs/ext4/ext4.h              | 2 ++
>  fs/ext4/inode.c             | 5 +++--
>  include/trace/events/ext4.h | 1 +
>  3 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 96d7d649ccb0..d0331697467d 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -715,6 +715,8 @@ enum {
>  #define EXT4_GET_BLOCKS_METADATA_NOFAIL		0x0020
>  	/* Don't normalize allocation size (used for fallocate) */
>  #define EXT4_GET_BLOCKS_NO_NORMALIZE		0x0040
> +	/* Get blocks from DIO */
> +#define EXT4_GET_BLOCKS_DIO			0x0080
>  	/* Convert written extents to unwritten */
>  #define EXT4_GET_BLOCKS_CONVERT_UNWRITTEN	0x0100
>  	/* Write zeros to newly created written extents */
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 3d8ada26d5cd..168dbcc9e921 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -818,6 +818,7 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode,
>  		if (map->m_flags & EXT4_MAP_NEW &&
>  		    !(map->m_flags & EXT4_MAP_UNWRITTEN) &&
>  		    !(flags & EXT4_GET_BLOCKS_ZERO) &&
> +		    !(flags & EXT4_GET_BLOCKS_DIO) &&
>  		    !ext4_is_quota_file(inode) &&
>  		    ext4_should_order_data(inode)) {
>  			loff_t start_byte =
> @@ -3729,9 +3730,9 @@ static int ext4_iomap_alloc(struct inode *inode, struct ext4_map_blocks *map,
>  	 * happening and thus expose allocated blocks to direct I/O reads.
>  	 */
>  	else if (((loff_t)map->m_lblk << blkbits) >= i_size_read(inode))
> -		m_flags = EXT4_GET_BLOCKS_CREATE;
> +		m_flags = EXT4_GET_BLOCKS_CREATE | EXT4_GET_BLOCKS_DIO;
>  	else if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
> -		m_flags = EXT4_GET_BLOCKS_IO_CREATE_EXT;
> +		m_flags = EXT4_GET_BLOCKS_IO_CREATE_EXT | EXT4_GET_BLOCKS_DIO;
>  
>  	if (flags & IOMAP_ATOMIC)
>  		ret = ext4_map_blocks_atomic_write(handle, inode, map, m_flags,
> diff --git a/include/trace/events/ext4.h b/include/trace/events/ext4.h
> index ada2b9223df5..de6d848f2e37 100644
> --- a/include/trace/events/ext4.h
> +++ b/include/trace/events/ext4.h
> @@ -43,6 +43,7 @@ struct partial_cluster;
>  	{ EXT4_GET_BLOCKS_CONVERT,		"CONVERT" },		\
>  	{ EXT4_GET_BLOCKS_METADATA_NOFAIL,	"METADATA_NOFAIL" },	\
>  	{ EXT4_GET_BLOCKS_NO_NORMALIZE,		"NO_NORMALIZE" },	\
> +	{ EXT4_GET_BLOCKS_DIO,			"DIO" },		\
>  	{ EXT4_GET_BLOCKS_CONVERT_UNWRITTEN,	"CONVERT_UNWRITTEN" },  \
>  	{ EXT4_GET_BLOCKS_ZERO,			"ZERO" },		\
>  	{ EXT4_GET_BLOCKS_IO_SUBMIT,		"IO_SUBMIT" },		\
> -- 
> 2.39.2
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR