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