----- Original Message -----
> This lockdep splat was being triggered on umount:
>
> [55715.973122] ===============================
> [55715.980169] [ INFO: suspicious RCU usage. ]
> [55715.981021] 4.3.0-11553-g8d3de01-dirty #15 Tainted: G W
> [55715.982353] -------------------------------
> [55715.983301] fs/gfs2/glock.c:1427 suspicious rcu_dereference_protected()
> usage!
>
> The code it refers to is the rht_for_each_entry_safe usage in
> glock_hash_walk. The condition that triggers the warning is
> lockdep_rht_bucket_is_held(tbl, hash) which is checked in the
> __rcu_dereference_protected macro.
>
> lockdep_rht_bucket_is_held returns false when rht_bucket_lock(tbl, hash)
> is not held, which suggests that glock_hash_walk should be holding the
> lock for each rhashtable bucket it looks at. Holding those locks clears
> up the warning.
>
> Signed-off-by: Andrew Price <anpr...@redhat.com>
> ---
> fs/gfs2/glock.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
> index 32e7471..7384cbb 100644
> --- a/fs/gfs2/glock.c
> +++ b/fs/gfs2/glock.c
> @@ -1424,11 +1424,13 @@ static void glock_hash_walk(glock_examiner examiner,
> const struct gfs2_sbd *sdp)
> rcu_read_lock();
> tbl = rht_dereference_rcu(gl_hash_table.tbl, &gl_hash_table);
> for (i = 0; i < tbl->size; i++) {
> + spin_lock(rht_bucket_lock(tbl, i));
> rht_for_each_entry_safe(gl, pos, next, tbl, i, gl_node) {
> if ((gl->gl_name.ln_sbd == sdp) &&
> lockref_get_not_dead(&gl->gl_lockref))
> examiner(gl);
> }
> + spin_unlock(rht_bucket_lock(tbl, i));
> }
> rcu_read_unlock();
> cond_resched();
> --
> 2.4.3
>
>
Hi Andy,
Thanks. I'll hold onto this until after the merge window is closed.
Regards,
Bob Peterson
Red Hat File Systems
