slab,slub: don't enable interrupts during early boot

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, mask out __GFP_WAIT, __GFP_IO, and __GFP_FS in the slab allocators
in early boot code to avoid enabling interrupts.

Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>

2 files changed, 34 insertions, 0 deletions

diff --git a/mm/slab.c b/mm/slab.c
index cd76964b53bc..453efcb1c980 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -304,6 +304,12 @@ struct kmem_list3 {
 };
 
 /*
+ * The slab allocator is initialized with interrupts disabled. Therefore, make
+ * sure early boot allocations don't accidentally enable interrupts.
+ */
+static gfp_t slab_gfp_mask __read_mostly = SLAB_GFP_BOOT_MASK;
+
+/*
  * Need this for bootstrapping a per node allocator.
  */
 #define NUM_INIT_LISTS (3 * MAX_NUMNODES)
@@ -1654,6 +1660,14 @@ void __init kmem_cache_init(void)
          */
 }
 
+void __init kmem_cache_init_late(void)
+{
+        /*
+         * Interrupts are enabled now so all GFP allocations are safe.
+         */
+        slab_gfp_mask = __GFP_BITS_MASK;
+}
+
 static int __init cpucache_init(void)
 {
         int cpu;
@@ -3354,6 +3368,8 @@ __cache_alloc_node(struct kmem_cache *cachep, gfp_t flags, int nodeid,
         unsigned long save_flags;
         void *ptr;
 
+        flags &= slab_gfp_mask;
+
         lockdep_trace_alloc(flags);
 
         if (slab_should_failslab(cachep, flags))
@@ -3434,6 +3450,8 @@ __cache_alloc(struct kmem_cache *cachep, gfp_t flags, void *caller)
         unsigned long save_flags;
         void *objp;
 
+        flags &= slab_gfp_mask;
+
         lockdep_trace_alloc(flags);
 
         if (slab_should_failslab(cachep, flags))
diff --git a/mm/slub.c b/mm/slub.c
index 3964d3ce4c15..30354bfeb43d 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -178,6 +178,12 @@ static enum {
         SYSFS           /* Sysfs up */
 } slab_state = DOWN;
 
+/*
+ * The slab allocator is initialized with interrupts disabled. Therefore, make
+ * sure early boot allocations don't accidentally enable interrupts.
+ */
+static gfp_t slab_gfp_mask __read_mostly = SLAB_GFP_BOOT_MASK;
+
 /* A list of all slab caches on the system */
 static DECLARE_RWSEM(slub_lock);
 static LIST_HEAD(slab_caches);
@@ -1595,6 +1601,8 @@ static __always_inline void *slab_alloc(struct kmem_cache *s,
         unsigned long flags;
         unsigned int objsize;
 
+        gfpflags &= slab_gfp_mask;
+
         lockdep_trace_alloc(gfpflags);
         might_sleep_if(gfpflags & __GFP_WAIT);
 
@@ -3104,6 +3112,14 @@ void __init kmem_cache_init(void)
                 nr_cpu_ids, nr_node_ids);
 }
 
+void __init kmem_cache_init_late(void)
+{
+        /*
+         * Interrupts are enabled now so all GFP allocations are safe.
+         */
+        slab_gfp_mask = __GFP_BITS_MASK;
+}
+
 /*
  * Find a mergeable slab cache
  */