Re: [PATCH v4 16/23] ext4: disable online defrag when inode using iomap buffered I/O path

[Ojaswin Mujoo]

On Mon, May 11, 2026 at 03:23:36PM +0800, Zhang Yi wrote:
> From: Zhang Yi <yi.zhang@xxxxxxxxxx>
> 
> Online defragmentation does not currently support inodes using the
> iomap buffered I/O path. The existing implementation relies on
> buffer_head for sub-folio block management and data=ordered mode for
> data consistency, both of which are incompatible with the iomap path.
> 
> Signed-off-by: Zhang Yi <yi.zhang@xxxxxxxxxx>

Looks good, feel free to add:
Reviewed-by: Ojaswin Mujoo <ojaswin@xxxxxxxxxxxxx>

Regards,
Ojaswin

> ---
>  fs/ext4/move_extent.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
> index 3329b7ad5dbd..f707a1096544 100644
> --- a/fs/ext4/move_extent.c
> +++ b/fs/ext4/move_extent.c
> @@ -476,6 +476,17 @@ static int mext_check_validity(struct inode *orig_inode,
>  		return -EOPNOTSUPP;
>  	}
>  
> +	/*
> +	 * TODO: support online defrag for inodes that using the buffered
> +	 * I/O iomap path.
> +	 */
> +	if (ext4_inode_buffered_iomap(orig_inode) ||
> +	    ext4_inode_buffered_iomap(donor_inode)) {
> +		ext4_msg(sb, KERN_ERR,
> +			 "Online defrag not supported for inode with iomap buffered IO path");
> +		return -EOPNOTSUPP;
> +	}
> +
>  	if (donor_inode->i_mode & (S_ISUID|S_ISGID)) {
>  		ext4_debug("ext4 move extent: suid or sgid is set to donor file [ino:orig %llu, donor %llu]\n",
>  			   orig_inode->i_ino, donor_inode->i_ino);
> -- 
> 2.52.0
>