Re: [PATCH] fs: fcntl_setlease defies lease_init assumptions

[Manfred Spraul <manfred@colorfullife.com>]

Pekka J Enberg wrote:

> I think you mean
>
> static inline struct kmem_cache *slab_get_cache(const void *obj)
> {
>        struct kmem_cache **p = (void *)((unsigned long) obj & ~(PAGE_SIZE-1));
>        return *p;
> }
>
>  
Of course.

> On Tue, 9 May 2006, Manfred Spraul wrote:
>  
>
> > The result would be a few small restrictions: all objects must start in the
> > first page of a slab (there are no exceptions on my 2.6.16 system), and
> > PAGE_SIZE'd caches are very expensive. Replacing the names_cache with
> > get_free_page is trivial. That leaves the pgd cache.
> >    
>
> Your plan makes sense for slabs that have slab management structures 
> embedded within.
No - it would only make sense if it could be used for all slabs. 
Otherwise: How should kfree figure out if it's called for a slab with 
embedded pointers or not?

> We already have enough free space there for one pointer 
> due to 
>
>    colour_off += cachep->slab_size;
>
> in the alloc_slabmgmt() function, I think. Are you planning to kill 
> external slab management allocation completely by switching to 
> get_free_pages() for those cases? I'd much rather make the switch to page 
> allocator under the hood so kmalloc(PAGE_SIZE*n) would still work because 
> it's much nicer API.
>  
How many kmalloc(PAGE_SIZE*n) users are there?

--
   Manfred
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