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Commit 59bfbcf0 authored by Tejun Heo's avatar Tejun Heo Committed by Linus Torvalds
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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: default avatarTejun Heo <tj@kernel.org>
Reported-by: default avatarDavid Teigland <teigland@redhat.com>
Tested-by: default avatarDavid Teigland <teigland@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 415586c9

lib/idr.c

+25 −13
Original line number Diff line number Diff line
@@ -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;
@@ -115,9 +121,7 @@ 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;



	if (!in_interrupt()) {

		preempt_disable();

		new = __this_cpu_read(idr_preload_head);

		if (new) {
@@ -126,9 +130,17 @@ static struct idr_layer *idr_layer_alloc(gfp_t gfp_mask, struct idr *layer_idr) 
			new->ary[0] = NULL;

		}

		preempt_enable();

		if (new)

			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)

{

	struct idr_layer *layer;