Re: [PATCH] fs: fcntl_setlease defies lease_init assumptions

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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?

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