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>

3 files changed, 13 insertions, 3 deletions

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index b39a0468829b..be38b573495a 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -274,6 +274,15 @@ out_eof:
         return -EBADCOOKIE;
 }
 
+static bool
+nfs_readdir_inode_mapping_valid(struct nfs_inode *nfsi)
+{
+        if (nfsi->cache_validity & (NFS_INO_INVALID_ATTR|NFS_INO_INVALID_DATA))
+                return false;
+        smp_rmb();
+        return !test_bit(NFS_INO_INVALIDATING, &nfsi->flags);
+}
+
 static
 int nfs_readdir_search_for_cookie(struct nfs_cache_array *array, nfs_readdir_descriptor_t *desc)
 {
@@ -287,9 +296,8 @@ int nfs_readdir_search_for_cookie(struct nfs_cache_array *array, nfs_readdir_des
                         struct nfs_open_dir_context *ctx = desc->file->private_data;
 
                         new_pos = desc->current_index + i;
-                        if (ctx->attr_gencount != nfsi->attr_gencount
-                            || (nfsi->cache_validity & (NFS_INO_INVALID_ATTR|NFS_INO_INVALID_DATA))
-                            || test_bit(NFS_INO_INVALIDATING, &nfsi->flags)) {
+                        if (ctx->attr_gencount != nfsi->attr_gencount ||
+                            !nfs_readdir_inode_mapping_valid(nfsi)) {
                                 ctx->duped = 0;
                                 ctx->attr_gencount = nfsi->attr_gencount;
                         } else if (new_pos < desc->ctx->pos) {
diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index e5070aa5f175..02e185168602 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -1050,6 +1050,7 @@ int nfs_revalidate_mapping(struct inode *inode, struct address_space *mapping)
         }
 
         set_bit(NFS_INO_INVALIDATING, bitlock);
+        smp_wmb();
         nfsi->cache_validity &= ~NFS_INO_INVALID_DATA;
         spin_unlock(&inode->i_lock);
         trace_nfs_invalidate_mapping_enter(inode);
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: