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Date: Mon, 11 Mar 2013 13:28:18 -0700
From: Tejun Heo <tj@...nel.org>
To: David Teigland <teigland@...hat.com>
Cc: linux-kernel@...r.kernel.org
Subject: Re: [PATCH 67/77] dlm: convert to idr_alloc()
Hello, David.
On Mon, Mar 11, 2013 at 03:29:55PM -0400, David Teigland wrote:
> On Wed, Feb 06, 2013 at 11:40:39AM -0800, Tejun Heo wrote:
> > static int create_lkb(struct dlm_ls *ls, struct dlm_lkb **lkb_ret)
> > {
> > struct dlm_lkb *lkb;
> > - int rv, id;
> > + int rv;
> >
> > lkb = dlm_allocate_lkb(ls);
> > if (!lkb)
> > @@ -1199,19 +1199,13 @@ static int create_lkb(struct dlm_ls *ls, struct dlm_lkb **lkb_ret)
> > mutex_init(&lkb->lkb_cb_mutex);
> > INIT_WORK(&lkb->lkb_cb_work, dlm_callback_work);
> >
> > - retry:
> > - rv = idr_pre_get(&ls->ls_lkbidr, GFP_NOFS);
> > - if (!rv)
> > - return -ENOMEM;
> > -
> > + idr_preload(GFP_NOFS);
> > spin_lock(&ls->ls_lkbidr_spin);
> > - rv = idr_get_new_above(&ls->ls_lkbidr, lkb, 1, &id);
> > - if (!rv)
> > - lkb->lkb_id = id;
> > + rv = idr_alloc(&ls->ls_lkbidr, lkb, 1, 0, GFP_NOWAIT);
>
> Hi Tejun,
> I'm seeing a number of new failure/warning messages within this idr_alloc.
> I've not seen idr_alloc itself return an error yet. Is this an expected
> failure where the warnings should be suppressed?
Ah, right, in preloaded section, the allocation is expected to fail
before falling back to the preload buffer and I forgot to add
__GFP_NOWARN to the first try. Something like the following should
make it go away. Can you please test it?
Thanks a lot!
diff --git a/lib/idr.c b/lib/idr.c
index 00739aa..e410e5d 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -106,8 +106,14 @@ static struct idr_layer *idr_layer_alloc(gfp_t gfp_mask, struct idr *layer_idr)
if (layer_idr)
return get_from_free_list(layer_idr);
- /* try to allocate directly from kmem_cache */
- new = kmem_cache_zalloc(idr_layer_cache, gfp_mask);
+ /*
+ * Try to allocate directly from kmem_cache. We want to try this
+ * before preload buffer; otherwise, non-preloading idr_alloc()
+ * users will end up taking advantage of preloading ones. As the
+ * following is allowed to fail for preloaded cases, suppress
+ * warning this time.
+ */
+ new = kmem_cache_zalloc(idr_layer_cache, gfp_mask | __GFP_NOWARN);
if (new)
return new;
@@ -115,18 +121,24 @@ static struct idr_layer *idr_layer_alloc(gfp_t gfp_mask, struct idr *layer_idr)
* Try to fetch one from the per-cpu preload buffer if in process
* context. See idr_preload() for details.
*/
- if (in_interrupt())
- return NULL;
-
- preempt_disable();
- new = __this_cpu_read(idr_preload_head);
- if (new) {
- __this_cpu_write(idr_preload_head, new->ary[0]);
- __this_cpu_dec(idr_preload_cnt);
- new->ary[0] = NULL;
+ if (!in_interrupt()) {
+ preempt_disable();
+ new = __this_cpu_read(idr_preload_head);
+ if (new) {
+ __this_cpu_write(idr_preload_head, new->ary[0]);
+ __this_cpu_dec(idr_preload_cnt);
+ new->ary[0] = NULL;
+ }
+ preempt_enable();
+ if (new)
+ return new;
}
- preempt_enable();
- return new;
+
+ /*
+ * Both failed. Try kmem_cache again w/o adding __GFP_NOWARN so
+ * that memory allocation failure warning is printed as intended.
+ */
+ return kmem_cache_zalloc(idr_layer_cache, gfp_mask);
}
static void idr_layer_rcu_free(struct rcu_head *head)
--
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