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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: 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>
This commit is contained in:
Tejun Heo 2013-03-13 14:59:49 -07:00 committed by Linus Torvalds
parent 415586c9e6
commit 59bfbcf019
1 changed files with 25 additions and 13 deletions
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22
lib/idr.c
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@ -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) {
@ -126,7 +130,15 @@ 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)