On Tue, 2012-07-03 at 15:36 -0500, Christoph Lameter wrote:
> Looking through the emails it seems that there is an issue with alias
> strings.
To be more precise, there seems no big issue currently. I just wanted to
make following usage of kmem_cache_create (SLUB) possible:
name = some string kmalloced
kmem_cache_create(name, ...)
kfree(name);
And from my understanding of the code, the saved_alias list, which is
used to keep track of the alias entries during early boot (slab_state <
SYSFS), is a blocker. It needs the name string to be valid until
slab_sysfs_init() is finished.
> That can be solved by duping the name of the slab earlier in
> kmem_cache_create().
> Does this patch fix the issue?
I'm afraid not...
With the patch below, we still need to kfree the duplicated name in
slab_sysfs_init().
And I think it would be easier to understand if we duplicate the name
string when creating one entry for saved_alias list, and kfree it when
we remove one entry from saved_alias list.
I'm not sure whether you got the patch #1 of the two I sent previously.
If not, would you kindly spend some time reviewing it to see if I missed
anything? Link below for your convenience:
https://lkml.org/lkml/2012/6/27/83
Btw, as Ben suggested, I'm now working on duplicating the name string in
SLAB to make them consistent, so we don't need the #ifdef CONFIG_SLUB
any more. Will send it out for your review after it is finished.
> Subject: slub: Dup name earlier in kmem_cache_create
>
> Dup the name earlier in kmem_cache_create so that alias
> processing is done using the copy of the string and not
> the string itself.
>
> Signed-off-by: Christoph Lameter <c...@linux.com>
>
> ---
> mm/slub.c | 29 ++++++++++++++---------------
> 1 file changed, 14 insertions(+), 15 deletions(-)
>
> Index: linux-2.6/mm/slub.c
> ===================================================================
> --- linux-2.6.orig/mm/slub.c 2012-06-11 08:49:56.000000000 -0500
> +++ linux-2.6/mm/slub.c 2012-07-03 15:17:37.000000000 -0500
> @@ -3933,8 +3933,12 @@ struct kmem_cache *kmem_cache_create(con
> if (WARN_ON(!name))
> return NULL;
>
> + n = kstrdup(name, GFP_KERNEL);
> + if (!n)
> + goto out;
> +
> down_write(&slub_lock);
> - s = find_mergeable(size, align, flags, name, ctor);
> + s = find_mergeable(size, align, flags, n, ctor);
> if (s) {
> s->refcount++;
> /*
> @@ -3944,7 +3948,7 @@ struct kmem_cache *kmem_cache_create(con
> s->objsize = max(s->objsize, (int)size);
> s->inuse = max_t(int, s->inuse, ALIGN(size, sizeof(void *)));
>
> - if (sysfs_slab_alias(s, name)) {
> + if (sysfs_slab_alias(s, n)) {
> s->refcount--;
> goto err;
> }
> @@ -3952,31 +3956,26 @@ struct kmem_cache *kmem_cache_create(con
> return s;
> }
>
> - n = kstrdup(name, GFP_KERNEL);
> - if (!n)
> - goto err;
> -
> s = kmalloc(kmem_size, GFP_KERNEL);
> if (s) {
> if (kmem_cache_open(s, n,
> size, align, flags, ctor)) {
> list_add(&s->list, &slab_caches);
> up_write(&slub_lock);
> - if (sysfs_slab_add(s)) {
> - down_write(&slub_lock);
> - list_del(&s->list);
> - kfree(n);
> - kfree(s);
> - goto err;
> - }
> - return s;
> + if (!sysfs_slab_add(s))
> + return s;
> +
> + down_write(&slub_lock);
> + list_del(&s->list);
> }
> kfree(s);
> }
> - kfree(n);
> +
> err:
> + kfree(n);
> up_write(&slub_lock);
>
> +out:
> if (flags & SLAB_PANIC)
> panic("Cannot create slabcache %s\n", name);
> else
>
_______________________________________________
Linuxppc-dev mailing list
Linuxppc-dev@lists.ozlabs.org
https://lists.ozlabs.org/listinfo/linuxppc-dev
