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    SubjectRe: [PATCH SLAB 1/2 v3] duplicate the cache name in SLUB's saved_alias list, SLAB, and SLOB
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    On Fri, 2012-07-06 at 08:56 -0500, Christoph Lameter wrote:
    > I thought I posted this a couple of days ago. Would this not fix things
    > without having to change all the allocators?

    I was pointed by Glauber to the slab common code patches. I need some
    more time to read the patches. Now I think the slab/slot changes in this
    v3 are not needed, and can be ignored.

    But for the SLUB's saved_alias list issue, I don't think the following
    patch helps. Details below: (Maybe I am wrong, as I'm reading the patch
    based on the 3.5-rc6 code ...)

    >
    >
    > 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 <cl@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++;
    > /*

    ......
    up_write(&slub_lock);
    return s;
    }

    Here, the function returns without name string n be kfreed.

    But we couldn't kfree n here, because in sysfs_slab_alias(), if
    (slab_state < SYS_FS), the name need to be kept valid until
    slab_sysfs_init() is finished adding the entry into sysfs.

    > @@ -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
    >




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