tree 8334f03c598343bb93340f081fcde5ba659b440b
parent 392ddc32982a5c661dd90dd49a3cb37f1c68b782
author Jens Axboe <jens.axboe@oracle.com> 1228806682 +0100
committer Jens Axboe <jens.axboe@oracle.com> 1230535790 +0100

aio: make the lookup_ioctx() lockless

The mm->ioctx_list is currently protected by a reader-writer lock,
so we always grab that lock on the read side for doing ioctx
lookups. As the workload is extremely reader biased, turn this into
an rcu hlist so we can make lookup_ioctx() lockless. Get rid of
the rwlock and use a spinlock for providing update side exclusion.

There's usually only 1 entry on this list, so it doesn't make sense
to look into fancier data structures.

Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>