1 files changed, 16 insertions, 0 deletions
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index ff476e654b8f..8ca642fe9b21 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -513,6 +513,22 @@ __be32 nfsd4_clone_file_range(struct file *src, u64 src_pos, struct file *dst,
 			count));
 }
 
+ssize_t nfsd_copy_file_range(struct file *src, u64 src_pos, struct file *dst,
+			     u64 dst_pos, u64 count)
+{
+
+	/*
+	 * Limit copy to 4MB to prevent indefinitely blocking an nfsd
+	 * thread and client rpc slot.  The choice of 4MB is somewhat
+	 * arbitrary.  We might instead base this on r/wsize, or make it
+	 * tunable, or use a time instead of a byte limit, or implement
+	 * asynchronous copy.  In theory a client could also recognize a
+	 * limit like this and pipeline multiple COPY requests.
+	 */
+	count = min_t(u64, count, 1 << 22);
+	return vfs_copy_file_range(src, src_pos, dst, dst_pos, count, 0);
+}
+
 __be32 nfsd4_vfs_fallocate(struct svc_rqst *rqstp, struct svc_fh *fhp,
 			   struct file *file, loff_t offset, loff_t len,
 			   int flags)