[RFC v2 1/1] NFSD add vfs_fsync after async copy is done

[Olga Kornievskaia <olga.kornievskaia@xxxxxxxxx>]

From: Olga Kornievskaia <kolga@xxxxxxxxxx>

Currently, the server does all copies as NFS_UNSTABLE. For synchronous
copies linux client will append a COMMIT to the COPY compound but for
async copies it does not (because COMMIT needs to be done after all
bytes are copied and not as a reply to the COPY operation).

However, in order to save the client doing a COMMIT as a separate
rpc, the server can reply back with NFS_FILE_SYNC copy. This patch
proposed to add vfs_fsync() call at the end of the async copy.

Signed-off-by: Olga Kornievskaia <kolga@xxxxxxxxxx>
---
 fs/nfsd/nfs4proc.c | 23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index 66dea2f1eed8..f63a2cb14a5e 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -1536,19 +1536,21 @@ static const struct nfsd4_callback_ops nfsd4_cb_offload_ops = {
 	.done = nfsd4_cb_offload_done
 };
 
-static void nfsd4_init_copy_res(struct nfsd4_copy *copy, bool sync)
+static void nfsd4_init_copy_res(struct nfsd4_copy *copy, bool sync,
+				bool committed)
 {
-	copy->cp_res.wr_stable_how = NFS_UNSTABLE;
+	copy->cp_res.wr_stable_how = committed ? NFS_FILE_SYNC : NFS_UNSTABLE;
 	copy->cp_synchronous = sync;
 	gen_boot_verifier(&copy->cp_res.wr_verifier, copy->cp_clp->net);
 }
 
-static ssize_t _nfsd_copy_file_range(struct nfsd4_copy *copy)
+static ssize_t _nfsd_copy_file_range(struct nfsd4_copy *copy, bool *committed)
 {
 	ssize_t bytes_copied = 0;
 	size_t bytes_total = copy->cp_count;
 	u64 src_pos = copy->cp_src_pos;
 	u64 dst_pos = copy->cp_dst_pos;
+	__be32 status;
 
 	do {
 		if (kthread_should_stop())
@@ -1563,6 +1565,16 @@ static ssize_t _nfsd_copy_file_range(struct nfsd4_copy *copy)
 		src_pos += bytes_copied;
 		dst_pos += bytes_copied;
 	} while (bytes_total > 0 && !copy->cp_synchronous);
+	/* for a non-zero asynchronous copy do a commit of data */
+	if (!copy->cp_synchronous && copy->cp_res.wr_bytes_written > 0) {
+		down_write(&copy->nf_dst->nf_rwsem);
+		status = vfs_fsync_range(copy->nf_dst->nf_file,
+					 copy->cp_dst_pos,
+					 copy->cp_res.wr_bytes_written, 0);
+		up_write(&copy->nf_dst->nf_rwsem);
+		if (!status)
+			*committed = true;
+	}
 	return bytes_copied;
 }
 
@@ -1570,15 +1582,16 @@ static __be32 nfsd4_do_copy(struct nfsd4_copy *copy, bool sync)
 {
 	__be32 status;
 	ssize_t bytes;
+	bool committed = false;
 
-	bytes = _nfsd_copy_file_range(copy);
+	bytes = _nfsd_copy_file_range(copy, &committed);
 	/* for async copy, we ignore the error, client can always retry
 	 * to get the error
 	 */
 	if (bytes < 0 && !copy->cp_res.wr_bytes_written)
 		status = nfserrno(bytes);
 	else {
-		nfsd4_init_copy_res(copy, sync);
+		nfsd4_init_copy_res(copy, sync, committed);
 		status = nfs_ok;
 	}
 
-- 
2.27.0