fuse: truncate pending writes on O_TRUNC

Make sure cached writes are not reordered around open(..., O_TRUNC), with
the obvious wrong results.

Fixes: 4d99ff8f12eb ("fuse: Turn writeback cache on")
Cc: <stable@vger.kernel.org> # v3.15+
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

1 files changed, 7 insertions, 3 deletions

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 0f0225686aee..6edf949b9139 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -217,7 +217,7 @@ int fuse_open_common(struct inode *inode, struct file *file, bool isdir)
 {
         struct fuse_conn *fc = get_fuse_conn(inode);
         int err;
-        bool lock_inode = (file->f_flags & O_TRUNC) &&
+        bool is_wb_truncate = (file->f_flags & O_TRUNC) &&
                           fc->atomic_o_trunc &&
                           fc->writeback_cache;
 
@@ -225,16 +225,20 @@ int fuse_open_common(struct inode *inode, struct file *file, bool isdir)
         if (err)
                 return err;
 
-        if (lock_inode)
+        if (is_wb_truncate) {
                 inode_lock(inode);
+                fuse_set_nowrite(inode);
+        }
 
         err = fuse_do_open(fc, get_node_id(inode), file, isdir);
 
         if (!err)
                 fuse_finish_open(inode, file);
 
-        if (lock_inode)
+        if (is_wb_truncate) {
+                fuse_release_nowrite(inode);
                 inode_unlock(inode);
+        }
 
         return err;
 }