nfs: add memory barriers around NFS_INO_INVALID_DATA and NFS_INO_INVALIDATING

If the setting of NFS_INO_INVALIDATING gets reordered to before the
clearing of NFS_INO_INVALID_DATA, then another task may hit a race
window where both appear to be clear, even though the inode's pages are
still in need of invalidation. Fix this by adding the appropriate memory
barriers.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 5511a4247190..9a3b6a4cd6b9 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -915,6 +915,7 @@ static bool nfs_write_pageuptodate(struct page *page, struct inode *inode)
                 goto out;
         if (nfsi->cache_validity & (NFS_INO_INVALID_DATA|NFS_INO_REVAL_PAGECACHE))
                 return false;
+        smp_rmb();
         if (test_bit(NFS_INO_INVALIDATING, &nfsi->flags))
                 return false;
 out: