idr: idr_alloc() shouldn't trigger lowmem warning when preloaded
GFP_NOIO is often used for idr_alloc() inside preloaded section as the
allocation mask doesn't really matter. If the idr tree needs to be
expanded, idr_alloc() first tries to allocate using the specified
allocation mask and if it fails falls back to the preloaded buffer. This
order prevent non-preloading idr_alloc() users from taking advantage of
preloading ones by using preload buffer without filling it shifting the
burden of allocation to the preload users.
Unfortunately, this allowed/expected-to-fail kmem_cache allocation ends up
generating spurious slab lowmem warning before succeeding the request from
the preload buffer.
This patch makes idr_layer_alloc() add __GFP_NOWARN to the first
kmem_cache attempt and try kmem_cache again w/o __GFP_NOWARN after
allocation from preload_buffer fails so that lowmem warning is generated
if not suppressed by the original @gfp_mask.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: David Teigland <teigland@redhat.com>
Tested-by: David Teigland <teigland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/lib/idr.c b/lib/idr.c
index c6fb829..322e281 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -106,8 +106,14 @@
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 @@
* 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)