[PATCH 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.

--- v2: moved the committed argument into the nfsd4_copy structure

Signed-off-by: Olga Kornievskaia <kolga@xxxxxxxxxx>
---
 fs/nfsd/nfs4proc.c | 14 +++++++++++++-
 fs/nfsd/xdr4.h     |  1 +
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index f4ce93d7f26e..dc7ac4b39eff 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -1375,7 +1375,8 @@ static const struct nfsd4_callback_ops nfsd4_cb_offload_ops = {
 
 static void nfsd4_init_copy_res(struct nfsd4_copy *copy, bool sync)
 {
-	copy->cp_res.wr_stable_how = NFS_UNSTABLE;
+	copy->cp_res.wr_stable_how =
+		copy->committed ? NFS_FILE_SYNC : NFS_UNSTABLE;
 	copy->cp_synchronous = sync;
 	gen_boot_verifier(&copy->cp_res.wr_verifier, copy->cp_clp->net);
 }
@@ -1386,6 +1387,7 @@ static ssize_t _nfsd_copy_file_range(struct nfsd4_copy *copy)
 	u64 bytes_total = copy->cp_count;
 	u64 src_pos = copy->cp_src_pos;
 	u64 dst_pos = copy->cp_dst_pos;
+	__be32 status;
 
 	/* See RFC 7862 p.67: */
 	if (bytes_total == 0)
@@ -1403,6 +1405,16 @@ 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)
+			copy->committed = true;
+	}
 	return bytes_copied;
 }
 
diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h
index a7c425254fee..3e4052e3bd50 100644
--- a/fs/nfsd/xdr4.h
+++ b/fs/nfsd/xdr4.h
@@ -567,6 +567,7 @@ struct nfsd4_copy {
 	struct vfsmount		*ss_mnt;
 	struct nfs_fh		c_fh;
 	nfs4_stateid		stateid;
+	bool			committed;
 };
 
 struct nfsd4_seek {
-- 
2.27.0