[PATCH 13/16] fuse: fuse_flush() should wait on writeback

[Maxim Patlasov <MPatlasov@parallels.com>]

The aim of .flush fop is to hint file-system that flushing its state or caches
or any other important data to reliable storage would be desirable now.
fuse_flush() passes this hint by sending FUSE_FLUSH request to userspace.
However, dirty pages and pages under writeback may be not visible to userspace
yet if we won't ensure it explicitly.

Signed-off-by: Maxim Patlasov <MPatlasov@parallels.com>
---
 fs/fuse/file.c |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index f48f796..86ef60f 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -19,6 +19,7 @@
 #include <linux/falloc.h>
 
 static const struct file_operations fuse_direct_io_file_operations;
+static void fuse_sync_writes(struct inode *inode);
 
 static int fuse_send_open(struct fuse_conn *fc, u64 nodeid, struct file *file,
 			  int opcode, struct fuse_open_out *outargp)
@@ -400,6 +401,14 @@ static int fuse_flush(struct file *file, fl_owner_t id)
 	if (fc->no_flush)
 		return 0;
 
+	err = filemap_write_and_wait(file->f_mapping);
+	if (err)
+		return err;
+
+	mutex_lock(&inode->i_mutex);
+	fuse_sync_writes(inode);
+	mutex_unlock(&inode->i_mutex);
+
 	req = fuse_get_req_nofail_nopages(fc, file);
 	memset(&inarg, 0, sizeof(inarg));
 	inarg.fh = ff->fh;