On Thu, Oct 04, 2007 at 02:04:25PM -0400, Wendy Cheng wrote:
> Red Hat bugzilla 295641... Wendy
>
>
>
> Fix a race condition where multiple glock demote requests are sent to
> a node back-to-back. This patch does a check inside handle_callback()
> to see whether a demote request is in progress. If true, it sets a flag
> to make sure run_queue() will loop again to handle the new request,
> instead of erroneously setting gl_demote_state to a different state.
>
> Signed-off-by: S. Wendy Cheng <[EMAIL PROTECTED]>
>
> glock.c | 13 ++++++++++++-
> incore.h | 2 ++
> 2 files changed, 14 insertions(+), 1 deletion(-)
>
> --- e48-brew/fs/gfs2/incore.h 2007-09-20 17:29:00.000000000 -0500
> +++ e48/fs/gfs2/incore.h 2007-10-02 16:45:38.000000000 -0500
> @@ -171,6 +171,7 @@ enum {
> GLF_DEMOTE = 3,
> GLF_PENDING_DEMOTE = 4,
> GLF_DIRTY = 5,
> + GLF_DEMOTE_IN_PROGRESS = 6,
> };
>
> struct gfs2_glock {
> @@ -190,6 +191,7 @@ struct gfs2_glock {
> struct list_head gl_holders;
> struct list_head gl_waiters1; /* HIF_MUTEX */
> struct list_head gl_waiters3; /* HIF_PROMOTE */
> + int gl_waiters2; /* GIF_DEMOTE */
>
> const struct gfs2_glock_operations *gl_ops;
>
> --- e48-brew/fs/gfs2/glock.c 2007-09-18 11:26:53.000000000 -0500
> +++ e48/fs/gfs2/glock.c 2007-10-02 18:19:12.000000000 -0500
> @@ -567,6 +567,7 @@ static int rq_demote(struct gfs2_glock *
> return 0;
> }
> set_bit(GLF_LOCK, &gl->gl_flags);
> + set_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags);
> if (gl->gl_demote_state == LM_ST_UNLOCKED ||
> gl->gl_state != LM_ST_EXCLUSIVE) {
> spin_unlock(&gl->gl_spin);
> @@ -575,6 +576,8 @@ static int rq_demote(struct gfs2_glock *
> spin_unlock(&gl->gl_spin);
> gfs2_glock_xmote_th(gl, NULL);
> }
> +
> + clear_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags);
> spin_lock(&gl->gl_spin);
>
May want to move the clear_bit inside the spin_lock so you don't end up having
the same race where we clear the bit while inside handle_callback.
Josef
