Re: [PATCH] mkfs: Round down log device size if aligned value is larger than device size

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Sun, Mar 17, 2019 at 02:49:43PM +0530, Chandan Rajendra wrote:
> When using a disk of size 798903808 bytes as the log device and when
> having a log stripe unit size of 32768, align_log_size() rounds up log
> device size to 195048 4k blocks i.e. 798916608. This value is larger
> than the device size. Hence the last call to write(2) inside
> libxfs_device_zero() would end up returning an error.
> 
> To fix this bug, we now round down the log device size if the newly
> computed size is larger than the actual log device size.
> 
> Signed-off-by: Chandan Rajendra <chandan@linux.ibm.com>
> ---
>  mkfs/xfs_mkfs.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/mkfs/xfs_mkfs.c b/mkfs/xfs_mkfs.c
> index d1387ddf..bd05d071 100644
> --- a/mkfs/xfs_mkfs.c
> +++ b/mkfs/xfs_mkfs.c
> @@ -2938,7 +2938,8 @@ _("log size %lld is not a multiple of the log stripe unit %d\n"),
>  
>  	/* If the log is too large, round down instead of round up */
>  	if ((tmp_logblocks > XFS_MAX_LOG_BLOCKS) ||
> -	    ((tmp_logblocks << cfg->blocklog) > XFS_MAX_LOG_BYTES)) {
> +		((tmp_logblocks << cfg->blocklog) > XFS_MAX_LOG_BYTES) ||
> +		(tmp_logblocks > cfg->logblocks)) {

I kinda wish you had turned all that into:

if (tmp_logblocks > XFS_MAX_LOG_BLOCKS ||
    tmp_logblocks > cfg->logblocks ||
    (tmp_logblocks << cfg->blocklog) > XFS_MAX_LOG_BYTES) {
	/* foo bar baz */
}

But otherwise the idea seems ok to me...

--D

>  		tmp_logblocks = (cfg->logblocks / sunit) * sunit;
>  	}
>  	cfg->logblocks = tmp_logblocks;
> -- 
> 2.19.1
>