From ce91f6ee5b3bbbad8caff61b1c46d845c8db19bf Mon Sep 17 00:00:00 2001
From: Michal Hocko <mhocko@suse.com>
Date: Thu, 7 Jun 2018 17:09:40 -0700
Subject: [PATCH] mm: kvmalloc does not fallback to vmalloc for incompatible
gfp flags
kvmalloc warned about incompatible gfp_mask to catch abusers (mostly
GFP_NOFS) with an intention that this will motivate authors of the code
to fix those. Linus argues that this just motivates people to do even
more hacks like
if (gfp == GFP_KERNEL)
kvmalloc
else
kmalloc
I haven't seen this happening much (Linus pointed to bucket_lock special
cases an atomic allocation but my git foo hasn't found much more) but it
is true that we can grow those in future. Therefore Linus suggested to
simply not fallback to vmalloc for incompatible gfp flags and rather
stick with the kmalloc path.
Link: http://lkml.kernel.org/r/20180601115329.27807-1-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Tom Herbert <tom@quantonium.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
lib/bucket_locks.c | 5 +----
mm/util.c | 6 ++++--
2 files changed, 5 insertions(+), 6 deletions(-)
diff --git a/lib/bucket_locks.c b/lib/bucket_locks.c
index 266a97c5708ba..ade3ce6c4af6a 100644
--- a/lib/bucket_locks.c
+++ b/lib/bucket_locks.c
@@ -30,10 +30,7 @@ int alloc_bucket_spinlocks(spinlock_t **locks, unsigned int *locks_mask,
}
if (sizeof(spinlock_t) != 0) {
- if (gfpflags_allow_blocking(gfp))
- tlocks = kvmalloc(size * sizeof(spinlock_t), gfp);
- else
- tlocks = kmalloc_array(size, sizeof(spinlock_t), gfp);
+ tlocks = kvmalloc_array(size, sizeof(spinlock_t), gfp);
if (!tlocks)
return -ENOMEM;
for (i = 0; i < size; i++)
diff --git a/mm/util.c b/mm/util.c
index c2d0a7cdb1898..3351659200e65 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -391,7 +391,8 @@ EXPORT_SYMBOL(vm_mmap);
* __GFP_RETRY_MAYFAIL is supported, and it should be used only if kmalloc is
* preferable to the vmalloc fallback, due to visible performance drawbacks.
*
- * Any use of gfp flags outside of GFP_KERNEL should be consulted with mm people.
+ * Please note that any use of gfp flags outside of GFP_KERNEL is careful to not
+ * fall back to vmalloc.
*/
void *kvmalloc_node(size_t size, gfp_t flags, int node)
{
@@ -402,7 +403,8 @@ void *kvmalloc_node(size_t size, gfp_t flags, int node)
* vmalloc uses GFP_KERNEL for some internal allocations (e.g page tables)
* so the given set of flags has to be compatible.
*/
- WARN_ON_ONCE((flags & GFP_KERNEL) != GFP_KERNEL);
+ if ((flags & GFP_KERNEL) != GFP_KERNEL)
+ return kmalloc_node(size, flags, node);
/*
* We want to attempt a large physically contiguous block first because
--
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