Re: [PATCH v2] xfs: Output warning message when discard option was enabled even though the device does not support discard

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

On Mon, Sep 18, 2017 at 10:57:38PM +0900, Kenjiro Nakayama wrote:
> In order to using discard function, it is necessary that not only xfs
> is mounted with discard option, but also the discard function is
> supported by the device. Current code doesn't output any message when
> users mount with discard option on unsupported device, so it is
> difficult to notice that it was not enabled actually.
> 
> This patch adds the warning message to notice that discard option is
> not enabled due to unsupported device when the filesystem is mounted.
> 
> Changes in v2 (Suggested by Brian Foster):
>   - Move the unsupported device check into xfs_fs_fill_super().
>   - Clear the discard flag when device is unsupported.
> 
> Signed-off-by: Kenjiro Nakayama <nakayamakenjiro@gmail.com>

Looks ok, will test...
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

> ---
>  fs/xfs/xfs_super.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> index c996f4ae4a5f..584cf2d573ba 100644
> --- a/fs/xfs/xfs_super.c
> +++ b/fs/xfs/xfs_super.c
> @@ -1654,6 +1654,16 @@ xfs_fs_fill_super(
>  		"DAX and reflink have not been tested together!");
>  	}
>  
> +	if (mp->m_flags & XFS_MOUNT_DISCARD) {
> +		struct request_queue *q = bdev_get_queue(sb->s_bdev);
> +
> +		if (!blk_queue_discard(q)) {
> +			xfs_warn(mp, "mounting with \"discard\" option, but "
> +					"the device does not support discard");
> +			mp->m_flags &= ~XFS_MOUNT_DISCARD;
> +		}
> +	}
> +
>  	if (xfs_sb_version_hasrmapbt(&mp->m_sb)) {
>  		if (mp->m_sb.sb_rblocks) {
>  			xfs_alert(mp,
> -- 
> 2.13.5
> 
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