Git: 0522f6adedd2736cbca3c0e16ca51df668993eee Mon Sep 17 00:00:00 2001
From: Trond Myklebust <Trond.Myklebust@netapp.com>
Date: Wed, 26 May 2010 08:42:24 -0400
Subject: [PATCH] NFS: Fix another nfs_wb_page() deadlock
Patch-mainline: 2.6.35
References: bnc#612794

J.R. Okajima reports that the call to sync_inode() in nfs_wb_page() can
deadlock with other writeback flush calls. It boils down to the fact
that we cannot ever call writeback_single_inode() while holding a page
lock (even if we do set nr_to_write to zero) since another process may
already be waiting in the call to do_writepages(), and so will deny us
the I_SYNC lock.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Acked-by: NeilBrown <neilb@suse.de>

---
 fs/nfs/write.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- linux-2.6.34-openSUSE-11.3.orig/fs/nfs/write.c
+++ linux-2.6.34-openSUSE-11.3/fs/nfs/write.c
@@ -1582,14 +1582,17 @@ int nfs_wb_page(struct inode *inode, str
 	};
 	int ret;
 
-	while(PagePrivate(page)) {
+	for (;;) {
 		wait_on_page_writeback(page);
 		if (clear_page_dirty_for_io(page)) {
 			ret = nfs_writepage_locked(page, &wbc);
 			if (ret < 0)
 				goto out_error;
+			continue;
 		}
-		ret = sync_inode(inode, &wbc);
+		if (!PagePrivate(page))
+			break;
+		ret = nfs_commit_inode(inode, FLUSH_SYNC);
 		if (ret < 0)
 			goto out_error;
 	}