Messages in this thread | | | Date | Fri, 14 Dec 2012 14:49:27 +0000 | From | Al Viro <> | Subject | Re: [PATCH] mm: Downgrade mmap_sem before locking or populating on mmap |
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On Fri, Dec 14, 2012 at 03:14:50AM -0800, Andy Lutomirski wrote:
> > Wait a minute. get_user_pages() relies on ->mmap_sem being held. Unless > > I'm seriously misreading your patch it removes that protection. And yes, > > I'm aware of execve-related exception; it's in special circumstances - > > bprm->mm is guaranteed to be not shared (and we need to rearchitect that > > area anyway, but that's a separate story). > > Unless I completely screwed up the patch, ->mmap_sem is still held for > read (it's downgraded from write). It's just not held for write > anymore.
Huh? I'm talking about the call of get_user_pages() in aio_setup_ring(). With your patch it's done completely outside of ->mmap_sem, isn't it?
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