tree db54090eef99349d15b95fcd8c2620a2403d8db8
parent 8b09bee3083897e375bd0bf9d60f48daedfab3e0
author Trond Myklebust <Trond.Myklebust@netapp.com> 1175556592 -0400
committer Trond Myklebust <Trond.Myklebust@netapp.com> 1177996626 -0700

NFS: Fix a race when doing NFS write coalescing

Currently we do write coalescing in a very inefficient manner: one pass in
generic_writepages() in order to lock the pages for writing, then one pass
in nfs_flush_mapping() and/or nfs_sync_mapping_wait() in order to gather
the locked pages for coalescing into RPC requests of size "wsize".

In fact, it turns out there is actually a deadlock possible here since we
only start I/O on the second pass. If the user signals the process while
we're in nfs_sync_mapping_wait(), for instance, then we may exit before
starting I/O on all the requests that have been queued up.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>