[lustre-devel] Possible minor bug

[Patrick Farrell]

While doing some other work, I noticed something I believe is a potential problem in the server side quota code.

Specifically, in qmt_glimpse_lock:

While the resource lock (a spin lock) is held, it does

OBD_ALLOC_PTR(work);

Since allocations can sleep, doesn't this allocation need to be atomic?

So, following the current Lustre convention, it should be:
LIBCFS_ALLOC_ATOMIC(work, sizeof(struct
ldlm_glimpse_work));

I have seen no actual bugs from this, but I hit a hang while modifying the equivalent code in ofd_intent_policy for lock ahead, and I think the same hang is theoretically possible here.  My understanding is that, in general, doing allocations while holding a spin lock is not recommended.

I'm hoping for other input before I go further - Am I right that this is something which needs fixing?  If so, I'll open an LU and submit a patch.

Thanks,
- Patrick
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.lustre.org/pipermail/lustre-devel-lustre.org/attachments/20150527/f8295b6c/attachment.htm>