Messages in this thread | | | Subject | Re: SLUB defrag pull request? | From | Miklos Szeredi <> | Date | Wed, 22 Oct 2008 09:10:36 +0200 |
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On Tue, 21 Oct 2008, Christoph Lameter wrote: > The only way that a secure reference can be established is if the > slab page is locked. That requires a spinlock. The slab allocator > calls the get() functions while the slab lock guarantees object > existence. Then locks are dropped and reclaim actions can start with > the guarantee that the slab object will not suddenly vanish.
Yes, you've made up your mind, that you want to do it this way. But it's the _wrong_ way, this "want to get a secure reference for use later" leads to madness when applied to dentries or inodes. Try for a minute to think outside this template.
For example dcache_lock will protect against dentries moving to/from d_lru. So you can do this:
take dcache_lock check if d_lru is non-empty take sb->s_umount free dentry release sb->s_umount release dcache_lock
Yeah, locking will be more complicated in reality. Still, much less complicated than trying to do the same across two separate phases.
Why can't something like that work?
Miklos
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