NFS: Prevent a deadlock in the new writeback code
We have to unlock the nfs_page before we call nfs_end_page_writeback
to avoid races with functions that expect the page to be unlocked
when PG_locked and PG_writeback are not set.
The problem is that nfs_unlock_request also releases the nfs_page,
causing a deadlock if the release of the nfs_open_context
triggers an iput() while the PG_writeback flag is still set...
The solution is to separate the unlocking and release of the nfs_page,
so that we can do the former before nfs_end_page_writeback and the
latter after.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: Fred Isaman <iisaman@netapp.com>
diff --git a/include/linux/nfs_page.h b/include/linux/nfs_page.h
index f9ee9eb..ef75042 100644
--- a/include/linux/nfs_page.h
+++ b/include/linux/nfs_page.h
@@ -96,6 +96,7 @@
struct nfs_page *req);
extern int nfs_wait_on_request(struct nfs_page *);
extern void nfs_unlock_request(struct nfs_page *req);
+extern void nfs_unlock_request_dont_release(struct nfs_page *req);
/*
* Lock the page of an asynchronous request without getting a new reference