Skip to content
Browse files

KMC_KVMEM disrupts kv_alloc() memory alignment expectations

On kernels with KASAN enabled the following failure can be observed as
soon as the zfs module is loaded:

  PANIC at spl-kmem-cache.c:228:kv_alloc()

The problem is kmalloc() has never guaranteed aligned allocations; this
requirement resulted in zfsonlinux/spl@8b45dda which removed all
kmalloc() usage in kv_alloc().

Until a GFP_ALIGNED flag (or equivalent functionality) is provided by
the kernel this commit partially reverts 6695588 and 6d948c3 to
prevent k(v)malloc() allocations in kv_alloc().

Reviewed-by: Kjeld Schouten <>
Reviewed-by: Michael Niewöhner <>
Reviewed-by: Brian Behlendorf <>
Signed-off-by: loli10K <>
Closes #9813
  • Loading branch information
loli10K authored and behlendorf committed Jan 14, 2020
1 parent 68a192e commit 7e2da7786ec089d1b9f9010677dc8e8a65dc01a1
Showing with 2 additions and 20 deletions.
  1. +2 −20 module/os/linux/spl/spl-kmem-cache.c
@@ -202,26 +202,8 @@ kv_alloc(spl_kmem_cache_t *skc, int size, int flags)
if (skc->skc_flags & KMC_KMEM) {
ptr = (void *)__get_free_pages(lflags, get_order(size));
} else if (skc->skc_flags & KMC_KVMEM) {
ptr = spl_kvmalloc(size, lflags);
} else {
* GFP_KERNEL allocations can safely use kvmalloc which may
* improve performance by avoiding a) high latency caused by
* vmalloc's on-access allocation, b) performance loss due to
* MMU memory address mapping and c) vmalloc locking overhead.
* This has the side-effect that the slab statistics will
* incorrectly report this as a vmem allocation, but that is
* purely cosmetic.
* For non-GFP_KERNEL allocations we stick to __vmalloc.
if ((lflags & GFP_KERNEL) == GFP_KERNEL) {
ptr = spl_kvmalloc(size, lflags);
} else {
ptr = __vmalloc(size, lflags | __GFP_HIGHMEM,
ptr = __vmalloc(size, lflags | __GFP_HIGHMEM, PAGE_KERNEL);

/* Resulting allocated memory will be page aligned */
@@ -249,7 +231,7 @@ kv_free(spl_kmem_cache_t *skc, void *ptr, int size)
free_pages((unsigned long)ptr, get_order(size));
} else {
spl_kmem_free_impl(ptr, size);

0 comments on commit 7e2da77

Please sign in to comment.
You can’t perform that action at this time.