NFS: Avoid a deadlock situation on write

When processes are allowed to attempt to lock a non-contiguous range of nfs
write requests, it is possible for generic_writepages to 'wrap round' the
address space, and call writepage() on a request that is already locked by
the same process.

We avoid the deadlock by checking if the page index is contiguous with the
list of nfs write requests that is already held in our
nfs_pageio_descriptor prior to attempting to lock a new request.

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

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/nfs_page.h b/include/linux/nfs_page.h
index 41afab6b5f09..bd193af80162 100644
--- a/include/linux/nfs_page.h
+++ b/include/linux/nfs_page.h
@@ -81,6 +81,7 @@ extern	void nfs_pageio_init(struct nfs_pageio_descriptor *desc,
 extern  int nfs_pageio_add_request(struct nfs_pageio_descriptor *,
                                    struct nfs_page *);
 extern  void nfs_pageio_complete(struct nfs_pageio_descriptor *desc);
+extern  void nfs_pageio_cond_complete(struct nfs_pageio_descriptor *, pgoff_t);
 extern  int nfs_wait_on_request(struct nfs_page *);
 extern  void nfs_unlock_request(struct nfs_page *req);
 extern  int nfs_set_page_writeback_locked(struct nfs_page *req);