Re: [PATCH] mkfs: fix filesystem and log size units

[Carlos Maiolino <cem@kernel.org>]

On Thu, Jun 18, 2026 at 08:11:11PM +0530, Manognya Singuru wrote:
> The actual thresholds enforced by mkfs are in MiB and GiB but the
> error messages and documentation report the limits as MB and GB.
> 
> Update the filesystem and log size threshold messages, comments,
> and man page to use MiB and GiB.
> 
> Signed-off-by: Manognya Singuru <msinguru@redhat.com>

Looks fine by me.

Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>

> ---
>  man/man8/mkfs.xfs.8.in |  6 +++---
>  mkfs/xfs_mkfs.c        | 14 +++++++-------
>  2 files changed, 10 insertions(+), 10 deletions(-)
> 
> diff --git a/man/man8/mkfs.xfs.8.in b/man/man8/mkfs.xfs.8.in
> index fbafc5c7..c4dee4fe 100644
> --- a/man/man8/mkfs.xfs.8.in
> +++ b/man/man8/mkfs.xfs.8.in
> @@ -463,7 +463,7 @@ is required if
>  is given. Otherwise, it is only needed if the filesystem should occupy
>  less space than the size of the special file.
>  
> -The data section must be at least 300MB in size.
> +The data section must be at least 300MiB in size.
>  .TP
>  .BI sunit= value
>  This is used to specify the stripe unit for a RAID device or a
> @@ -805,8 +805,8 @@ described above. The overriding minimum value for size is 512 blocks.
>  With some combinations of filesystem block size, inode size,
>  and directory block size, the minimum log size is larger than 512 blocks.
>  
> -The log must be at least 64MB in size.
> -The log cannot be more than 2GB in size.
> +The log must be at least 64MiB in size.
> +The log cannot be more than 2GiB in size.
>  .TP
>  .BI version= value
>  This specifies the version of the log. The current default is 2,
> diff --git a/mkfs/xfs_mkfs.c b/mkfs/xfs_mkfs.c
> index dd8a48c3..cbc703cc 100644
> --- a/mkfs/xfs_mkfs.c
> +++ b/mkfs/xfs_mkfs.c
> @@ -25,10 +25,10 @@
>  #define MEGABLOCKS(count, blog)	((uint64_t)(count) << (20 - (blog)))
>  
>  /*
> - * Realistically, the log should never be smaller than 64MB.  Studies by the
> + * Realistically, the log should never be smaller than 64MiB.  Studies by the
>   * kernel maintainer in early 2022 have shown a dramatic reduction in long tail
>   * latency of the xlog grant head waitqueue when running a heavy metadata
> - * update workload when the log size is at least 64MB.
> + * update workload when the log size is at least 64MiB.
>   */
>  #define XFS_MIN_REALISTIC_LOG_BLOCKS(blog)	(MEGABLOCKS(64, (blog)))
>  
> @@ -3435,19 +3435,19 @@ validate_supported(
>  		return;
>  
>  	/*
> -	 * We don't support filesystems smaller than 300MB anymore.  Tiny
> +	 * We don't support filesystems smaller than 300MiB anymore.  Tiny
>  	 * filesystems have never been XFS' design target.  This limit has been
>  	 * carefully calculated to prevent formatting with a log smaller than
>  	 * the "realistic" size.
>  	 *
> -	 * If the realistic log size is 64MB, there are four AGs, and the log
> +	 * If the realistic log size is 64MiB, there are four AGs, and the log
>  	 * AG should be at least 1/8 free after formatting, this gives us:
>  	 *
> -	 * 64MB * (8 / 7) * 4 = 293MB
> +	 * 64MiB * (8 / 7) * 4 = 293MiB
>  	 */
>  	if (mp->m_sb.sb_dblocks < MEGABLOCKS(300, mp->m_sb.sb_blocklog)) {
>  		fprintf(stderr,
> - _("Filesystem must be larger than 300MB.\n"));
> + _("Filesystem must be larger than 300MiB.\n"));
>  		usage();
>  	}
>  
> @@ -3458,7 +3458,7 @@ validate_supported(
>  	if (mp->m_sb.sb_logblocks <
>  			XFS_MIN_REALISTIC_LOG_BLOCKS(mp->m_sb.sb_blocklog)) {
>  		fprintf(stderr,
> - _("Log size must be at least 64MB.\n"));
> + _("Log size must be at least 64MiB.\n"));
>  		usage();
>  	}
>  
> -- 
> 2.54.0
> 
>