Re: [PATCH 1/8] xfs: allow empty transactions while frozen

[Allison Henderson <allison.henderson@oracle.com>]

Looks fine
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>

On 06/21/2018 11:31 AM, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> In commit e89c041338ed6ef ("xfs: implement the GETFSMAP ioctl") we
> created the ability to obtain empty transactions.  These transactions
> have no log or block reservations and therefore can't modify anything.
> Since they're also NO_WRITECOUNT they can run while the fs is frozen,
> so we don't need to WARN_ON about that usage.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---
>   fs/xfs/xfs_trans.c |    7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)
> 
> 
> diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
> index e040af120b69..524f543c5b82 100644
> --- a/fs/xfs/xfs_trans.c
> +++ b/fs/xfs/xfs_trans.c
> @@ -258,7 +258,12 @@ xfs_trans_alloc(
>   	if (!(flags & XFS_TRANS_NO_WRITECOUNT))
>   		sb_start_intwrite(mp->m_super);
>   
> -	WARN_ON(mp->m_super->s_writers.frozen == SB_FREEZE_COMPLETE);
> +	/*
> +	 * Zero-reservation ("empty") transactions can't modify anything, so
> +	 * they're allowed to run while we're frozen.
> +	 */
> +	WARN_ON(resp->tr_logres > 0 &&
> +		mp->m_super->s_writers.frozen == SB_FREEZE_COMPLETE);
>   	atomic_inc(&mp->m_active_trans);
>   
>   	tp = kmem_zone_zalloc(xfs_trans_zone,
> 
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