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Subject[PATCH v2] slab,slub: ignore __GFP_WAIT if we're booting or suspending
From: Pekka Enberg <penberg@cs.helsinki.fi>

As explained by Benjamin Herrenschmidt:

Oh and btw, your patch alone doesn't fix powerpc, because it's missing
a whole bunch of GFP_KERNEL's in the arch code... You would have to
grep the entire kernel for things that check slab_is_available() and
even then you'll be missing some.

For example, slab_is_available() didn't always exist, and so in the
early days on powerpc, we used a mem_init_done global that is set form
mem_init() (not perfect but works in practice). And we still have code
using that to do the test.

Therefore, ignore __GFP_WAIT in the slab allocators if we're booting or
suspending.

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Nick Piggin <npiggin@suse.de>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
---
v1 -> v2: fix up some missing cases pointed out by BenH

mm/slab.c | 19 ++++++++++++++++++-
mm/slub.c | 24 ++++++++++++++++++++++--
2 files changed, 40 insertions(+), 3 deletions(-)

diff --git a/mm/slab.c b/mm/slab.c
index f46b65d..5119c22 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -2812,6 +2812,15 @@ static int cache_grow(struct kmem_cache *cachep,

offset *= cachep->colour_off;

+ /*
+ * Lets not wait if we're booting up or suspending even if the user
+ * asks for it.
+ */
+ if (system_state != SYSTEM_RUNNING)
+ local_flags &= ~__GFP_WAIT;
+
+ might_sleep_if(local_flags & __GFP_WAIT);
+
if (local_flags & __GFP_WAIT)
local_irq_enable();

@@ -3073,7 +3082,6 @@ alloc_done:
static inline void cache_alloc_debugcheck_before(struct kmem_cache *cachep,
gfp_t flags)
{
- might_sleep_if(flags & __GFP_WAIT);
#if DEBUG
kmem_flagcheck(cachep, flags);
#endif
@@ -3238,6 +3246,15 @@ retry:

if (!obj) {
/*
+ * Lets not wait if we're booting up or suspending even if the user
+ * asks for it.
+ */
+ if (system_state != SYSTEM_RUNNING)
+ local_flags &= ~__GFP_WAIT;
+
+ might_sleep_if(local_flags & __GFP_WAIT);
+
+ /*
* This allocation will be performed within the constraints
* of the current cpuset / memory policy requirements.
* We may trigger various forms of reclaim on the allowed
diff --git a/mm/slub.c b/mm/slub.c
index 3964d3c..6387c19 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1548,6 +1548,20 @@ new_slab:
goto load_freelist;
}

+ /*
+ * Lets not wait if we're booting up or suspending even if the user
+ * asks for it.
+ */
+ if (system_state != SYSTEM_RUNNING)
+ gfpflags &= ~__GFP_WAIT;
+
+ /*
+ * Now that we really know whether or not we're going to sleep or not,
+ * lets do our debugging checks.
+ */
+ lockdep_trace_alloc(gfpflags);
+ might_sleep_if(gfpflags & __GFP_WAIT);
+
if (gfpflags & __GFP_WAIT)
local_irq_enable();

@@ -1595,8 +1609,7 @@ static __always_inline void *slab_alloc(struct kmem_cache *s,
unsigned long flags;
unsigned int objsize;

- lockdep_trace_alloc(gfpflags);
- might_sleep_if(gfpflags & __GFP_WAIT);
+ lockdep_trace_alloc(gfpflags & ~__GFP_WAIT);

if (should_failslab(s->objsize, gfpflags))
return NULL;
@@ -2607,6 +2620,13 @@ static noinline struct kmem_cache *dma_kmalloc_cache(int index, gfp_t flags)
if (s)
return s;

+ /*
+ * Lets not wait if we're booting up or suspending even if the user
+ * asks for it.
+ */
+ if (system_state != SYSTEM_RUNNING)
+ flags &= ~__GFP_WAIT;
+
/* Dynamically create dma cache */
if (flags & __GFP_WAIT)
down_write(&slub_lock);
--
1.6.0.4


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