NFS based on file size issue sync copy or fallback to generic copy offload

For small file sizes, it make sense to issue a synchronous copy (and
save an RPC callback operation). Also, for the inter copy offload,
copy len must be larger than the cost of doing a mount between the
destination and source server (14RPCs are sent during 4.x mount).

Signed-off-by: Olga Kornievskaia <[email protected]>

Author: olgakorn1

fs/nfs/nfs42.h

@@ -16,7 +16,7 @@
 #ifdef CONFIG_NFS_V4_2
 int nfs42_proc_allocate(struct file *, loff_t, loff_t);
 ssize_t nfs42_proc_copy(struct file *, loff_t, struct file *, loff_t, size_t,
-			struct nl4_server *, nfs4_stateid *);
+			struct nl4_server *, nfs4_stateid *, bool);
 int nfs42_proc_deallocate(struct file *, loff_t, loff_t);
 loff_t nfs42_proc_llseek(struct file *, loff_t, int);
 int nfs42_proc_layoutstats_generic(struct nfs_server *,

fs/nfs/nfs42proc.c

@@ -357,7 +357,7 @@ static ssize_t _nfs42_proc_copy(struct file *src,
 ssize_t nfs42_proc_copy(struct file *src, loff_t pos_src,
 			struct file *dst, loff_t pos_dst, size_t count,
 			struct nl4_server *nss,
-			nfs4_stateid *cnr_stateid)
+			nfs4_stateid *cnr_stateid, bool sync)
 {
 	struct nfs_server *server = NFS_SERVER(file_inode(dst));
 	struct nfs_lock_context *src_lock;
@@ -368,7 +368,7 @@ ssize_t nfs42_proc_copy(struct file *src, loff_t pos_src,
 		.dst_fh		= NFS_FH(file_inode(dst)),
 		.dst_pos	= pos_dst,
 		.count		= count,
-		.sync		= false,
+		.sync		= sync,
 	};
 	struct nfs42_copy_res res;
 	struct nfs4_exception src_exception = {

fs/nfs/nfs4file.c

@@ -138,6 +138,7 @@ static ssize_t __nfs4_copy_file_range(struct file *file_in, loff_t pos_in,
 	struct nl4_server *nss = NULL;
 	nfs4_stateid *cnrs = NULL;
 	ssize_t ret;
+	bool sync = false;
 
 	/* Only offload copy if superblock is the same */
 	if (file_inode(file_in)->i_sb != file_inode(file_out)->i_sb)
@@ -146,8 +147,21 @@ static ssize_t __nfs4_copy_file_range(struct file *file_in, loff_t pos_in,
 		return -EOPNOTSUPP;
 	if (file_inode(file_in) == file_inode(file_out))
 		return -EOPNOTSUPP;
+	/* if the copy size if smaller than 2 RPC payloads, make it
+	 * synchronous
+	 */
+	if (count <= 2 * NFS_SERVER(file_inode(file_in))->rsize)
+		sync = true;
 retry:
 	if (!nfs42_files_from_same_server(file_in, file_out)) {
+		/* for inter copy, if copy size if smaller than 12 RPC
+		 * payloads, fallback to traditional copy. There are
+		 * 14 RPCs during an NFSv4.x mount between source/dest
+		 * servers.
+		 */
+		if (sync ||
+			count <= 14 * NFS_SERVER(file_inode(file_in))->rsize)
+			return -EOPNOTSUPP;
 		cn_resp = kzalloc(sizeof(struct nfs42_copy_notify_res),
 				GFP_NOFS);
 		if (unlikely(cn_resp == NULL))
@@ -162,7 +176,7 @@ static ssize_t __nfs4_copy_file_range(struct file *file_in, loff_t pos_in,
 		cnrs = &cn_resp->cnr_stateid;
 	}
 	ret = nfs42_proc_copy(file_in, pos_in, file_out, pos_out, count,
-				nss, cnrs);
+				nss, cnrs, sync);
 out:
 	kfree(cn_resp);
 	if (ret == -EAGAIN)