From: Matthew Wilcox <willy@infradead.org>
To: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: linux-mm@kvack.org, Matthew Wilcox <mawilcox@microsoft.com>,
linux-kernel@vger.kernel.org,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: Re: [PATCH 3/4] mm: Add free()
Date: Fri, 23 Mar 2018 08:14:21 -0700 [thread overview]
Message-ID: <20180323151421.GC5624@bombadil.infradead.org> (raw)
In-Reply-To: <6fd1bba1-e60c-e5b3-58be-52e991cda74f@virtuozzo.com>
On Fri, Mar 23, 2018 at 04:33:24PM +0300, Kirill Tkhai wrote:
> > + page = virt_to_head_page(ptr);
> > + if (likely(PageSlab(page)))
> > + return kmem_cache_free(page->slab_cache, (void *)ptr);
>
> It seems slab_cache is not generic for all types of slabs. SLOB does not care about it:
Oof. I was sure I checked that. You're quite right that it doesn't ...
this should fix that problem:
diff --git a/mm/slob.c b/mm/slob.c
index 623e8a5c46ce..96339420c6fc 100644
--- a/mm/slob.c
+++ b/mm/slob.c
@@ -266,7 +266,7 @@ static void *slob_page_alloc(struct page *sp, size_t size, int align)
/*
* slob_alloc: entry point into the slob allocator.
*/
-static void *slob_alloc(size_t size, gfp_t gfp, int align, int node)
+static void *slob_alloc(size_t size, gfp_t gfp, int align, int node, void *c)
{
struct page *sp;
struct list_head *prev;
@@ -324,6 +324,7 @@ static void *slob_alloc(size_t size, gfp_t gfp, int align, int node)
sp->units = SLOB_UNITS(PAGE_SIZE);
sp->freelist = b;
INIT_LIST_HEAD(&sp->lru);
+ sp->slab_cache = c;
set_slob(b, SLOB_UNITS(PAGE_SIZE), b + SLOB_UNITS(PAGE_SIZE));
set_slob_page_free(sp, slob_list);
b = slob_page_alloc(sp, size, align);
@@ -440,7 +441,7 @@ __do_kmalloc_node(size_t size, gfp_t gfp, int node, unsigned long caller)
if (!size)
return ZERO_SIZE_PTR;
- m = slob_alloc(size + align, gfp, align, node);
+ m = slob_alloc(size + align, gfp, align, node, NULL);
if (!m)
return NULL;
@@ -544,7 +545,7 @@ static void *slob_alloc_node(struct kmem_cache *c, gfp_t flags, int node)
fs_reclaim_release(flags);
if (c->size < PAGE_SIZE) {
- b = slob_alloc(c->size, flags, c->align, node);
+ b = slob_alloc(c->size, flags, c->align, node, c);
trace_kmem_cache_alloc_node(_RET_IP_, b, c->object_size,
SLOB_UNITS(c->size) * SLOB_UNIT,
flags, node);
@@ -600,6 +601,8 @@ static void kmem_rcu_free(struct rcu_head *head)
void kmem_cache_free(struct kmem_cache *c, void *b)
{
+ if (!c)
+ return kfree(b);
kmemleak_free_recursive(b, c->flags);
if (unlikely(c->flags & SLAB_TYPESAFE_BY_RCU)) {
struct slob_rcu *slob_rcu;
> Also, using kmem_cache_free() for kmalloc()'ed memory will connect them hardly,
> and this may be difficult to maintain in the future.
I think the win from being able to delete all the little RCU callbacks
that just do a kmem_cache_free() is big enough to outweigh the
disadvantage of forcing slab allocators to support kmem_cache_free()
working on kmalloced memory.
> One more thing, there is
> some kasan checks on the main way of kfree(), and there is no guarantee they
> reflected in kmem_cache_free() identical.
Which function are you talking about here?
slub calls slab_free() for both kfree() and kmem_cache_free().
slab calls __cache_free() for both kfree() and kmem_cache_free().
Each of them do their kasan handling in the called function.
next prev parent reply other threads:[~2018-03-23 15:14 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-22 19:58 [PATCH 0/4] Add free() function Matthew Wilcox
2018-03-22 19:58 ` [PATCH 1/4] decompression: Rename malloc and free Matthew Wilcox
2018-03-22 19:58 ` [PATCH 2/4] Rename 'free' functions Matthew Wilcox
2018-03-22 19:58 ` [PATCH 3/4] mm: Add free() Matthew Wilcox
2018-03-23 8:04 ` Rasmus Villemoes
2018-03-23 14:34 ` Matthew Wilcox
2018-04-03 8:50 ` Pavel Machek
2018-04-03 11:41 ` Matthew Wilcox
2018-03-23 13:33 ` Kirill Tkhai
2018-03-23 15:14 ` Matthew Wilcox [this message]
2018-03-23 15:49 ` Kirill Tkhai
2018-03-23 16:15 ` Matthew Wilcox
2018-03-25 23:56 ` Matthew Wilcox
2018-03-24 7:38 ` kbuild test robot
2018-03-22 19:58 ` [PATCH 4/4] rcu: Switch to using free() instead of kfree() Matthew Wilcox
2018-03-24 7:07 ` kbuild test robot
2018-03-24 8:20 ` kbuild test robot
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