Re: [REVIEW] Move memory allocations for log tracing out of the critical path

[Christoph Hellwig <hch@xxxxxxxxxxxxx>]

On Tue, Aug 12, 2008 at 03:27:40PM +1000, Lachlan McIlroy wrote:
> Memory allocations for log->l_grant_trace and iclog->ic_trace are done
> on demand when the first event is logged.  In xlog_state_get_iclog_space()
> we call xlog_trace_iclog() under a spinlock and allocating memory here can
> cause us to sleep with a spinlock held and deadlock the system.
>
> For the log grant tracing we use KM_NOSLEEP but that means we can lose
> trace entries.  Since there is no locking to serialize the log grant
> tracing we could race and have multiple allocations and leak memory.
>
> So move the allocations to where we initialize the log/iclog structures.
> Use KM_NOFS to avoid recursing into the filesystem and drop log->l_trace
> since it's not even used.

Looks good to me.