SLUB: Fix early boot GFP_DMA allocations

Recent change to use slab allocations earlier exposed a bug where
SLUB can call schedule_work and try to call sysfs before it is
safe to do so.

Reported-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Tested-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>

diff --git a/mm/slub.c b/mm/slub.c
index 30354bf..dcbfda0 100644 (file)
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2610,6 +2610,7 @@ static noinline struct kmem_cache *dma_kmalloc_cache(int index, gfp_t flags)
        struct kmem_cache *s;
        char *text;
        size_t realsize;
+       unsigned long slabflags;
 
        s = kmalloc_caches_dma[index];
        if (s)
@@ -2631,9 +2632,18 @@ static noinline struct kmem_cache *dma_kmalloc_cache(int index, gfp_t flags)
                         (unsigned int)realsize);
        s = kmalloc(kmem_size, flags & ~SLUB_DMA);
 
+       /*
+        * Must defer sysfs creation to a workqueue because we don't know
+        * what context we are called from. Before sysfs comes up, we don't
+        * need to do anything because our sysfs initcall will start by
+        * adding all existing slabs to sysfs.
+        */
+       slabflags = SLAB_CACHE_DMA;
+       if (slab_state >= SYSFS)
+               slabflags |= __SYSFS_ADD_DEFERRED;
+
        if (!s || !text || !kmem_cache_open(s, flags, text,
-                       realsize, ARCH_KMALLOC_MINALIGN,
-                       SLAB_CACHE_DMA|__SYSFS_ADD_DEFERRED, NULL)) {
+                       realsize, ARCH_KMALLOC_MINALIGN, slabflags, NULL)) {
                kfree(s);
                kfree(text);
                goto unlock_out;
@@ -2642,7 +2652,8 @@ static noinline struct kmem_cache *dma_kmalloc_cache(int index, gfp_t flags)
        list_add(&s->list, &slab_caches);
        kmalloc_caches_dma[index] = s;
 
-       schedule_work(&sysfs_add_work);
+       if (slab_state >= SYSFS)
+               schedule_work(&sysfs_add_work);
 
 unlock_out:
        up_write(&slub_lock);