[Cluster-devel] [GFS2 PATCH v3 01/14] GFS2: Update master statfs buffer with sd_statfs_spin locked

[Steven Whitehouse <swhiteho@redhat.com>]

Hi,

Looks good to me:
Acked-by: Steven Whitehouse <swhiteho@redhat.com>

Steve.

On 22/10/15 20:30, Bob Peterson wrote:
> Before this patch, function update_statfs called gfs2_statfs_change_out
> to update the master statfs buffer without the sd_statfs_spin held.
> In theory, another process could call gfs2_statfs_sync, which takes
> the sd_statfs_spin lock and re-reads m_sc from the buffer. So there's
> a theoretical timing window in which one process could write the
> master statfs buffer, then another comes along and re-reads it, wiping
> out the changes.
>
> Signed-off-by: Bob Peterson <rpeterso@redhat.com>
> ---
>   fs/gfs2/super.c | 5 ++---
>   1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c
> index 894fb01..a691725 100644
> --- a/fs/gfs2/super.c
> +++ b/fs/gfs2/super.c
> @@ -556,6 +556,7 @@ void update_statfs(struct gfs2_sbd *sdp, struct buffer_head *m_bh,
>   	struct gfs2_statfs_change_host *l_sc = &sdp->sd_statfs_local;
>   
>   	gfs2_trans_add_meta(l_ip->i_gl, l_bh);
> +	gfs2_trans_add_meta(m_ip->i_gl, m_bh);
>   
>   	spin_lock(&sdp->sd_statfs_spin);
>   	m_sc->sc_total += l_sc->sc_total;
> @@ -564,10 +565,8 @@ void update_statfs(struct gfs2_sbd *sdp, struct buffer_head *m_bh,
>   	memset(l_sc, 0, sizeof(struct gfs2_statfs_change));
>   	memset(l_bh->b_data + sizeof(struct gfs2_dinode),
>   	       0, sizeof(struct gfs2_statfs_change));
> -	spin_unlock(&sdp->sd_statfs_spin);
> -
> -	gfs2_trans_add_meta(m_ip->i_gl, m_bh);
>   	gfs2_statfs_change_out(m_sc, m_bh->b_data + sizeof(struct gfs2_dinode));
> +	spin_unlock(&sdp->sd_statfs_spin);
>   }
>   
>   int gfs2_statfs_sync(struct super_block *sb, int type)