Messages in this thread | | | Date | Thu, 9 Aug 2007 23:15:42 -0700 | From | Andrew Morton <> | Subject | Re: [RFC 3/3] SGI Altix cross partition memory (XPMEM) |
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On Thu, 9 Aug 2007 20:14:35 -0500 Dean Nelson <dcn@sgi.com> wrote:
> This patch provides cross partition access to user memory (XPMEM) when > running multiple partitions on a single SGI Altix. >
- Please don't send multiple patches all with the same title.
- Feed the diff through checkpatch.pl, ponder the result.
- Avoid needless casts to and from void* (eg, vm_private_data)
- The test for PF_DUMPCORE in xpmem_fault_handler() is mysterious and merits a comment.
- xpmem_fault_handler() is scary.
- xpmem_fault_handler() appears to have imposed a kernel-wide rule that when taking multiple mmap_sems, one should take the lowest-addressed one first? If so, that probably wants a mention in that locking comment in filemap.c
- xpmem_fault_handler() does atomic_dec(&seg_tg->mm->mm_users). What happens if that was the last reference?
- Has it all been tested with lockdep enabled? Jugding from all the use of SPIN_LOCK_UNLOCKED, it has not.
Oh, ia64 doesn't implement lockdep. For this code, that is deeply regrettable.
- This code all predates the nopage->fault conversion and won't work in current kernels.
- xpmem_attach() does smp_processor_id() in preemptible code. Lucky that ia64 doesn't do preempt?
- Stuff like this:
+ ap_tg = xpmem_tg_ref_by_apid(apid); + if (IS_ERR(ap_tg)) + return PTR_ERR(ap_tg); + + ap = xpmem_ap_ref_by_apid(ap_tg, apid); + if (IS_ERR(ap)) { + xpmem_tg_deref(ap_tg); + return PTR_ERR(ap); + }
is fragile. It is easy to introduce leaks and locking errors as the code evolves. The code has a lot of these deeply-embedded `return' statments preceded by duplicated unwinding. Kenrel code generally prefers to do the `goto out' thing.
- "XPMEM_FLAG_VALIDPTEs"? Someone's pinky got tired at the end ;)
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