Index: sys/kern/vfs_vnops.c
===================================================================
--- sys/kern/vfs_vnops.c
+++ sys/kern/vfs_vnops.c
@@ -3268,9 +3268,9 @@
 		    outvp->v_mount->mnt_stat.f_iosize);
 	if (blksize < 4096)
 		blksize = 4096;
-	else if (blksize > 1024 * 1024)
-		blksize = 1024 * 1024;
-	dat = malloc(blksize, M_TEMP, M_WAITOK);
+	else if (blksize > maxphys)
+		blksize = maxphys;
+	dat = malloc(maxphys, M_TEMP, M_WAITOK);
 
 	/*
 	 * If VOP_IOCTL(FIOSEEKHOLE) works for invp, use it and FIOSEEKDATA
@@ -3377,14 +3377,21 @@
 			error = 0;
 		}
 
-		xfer = blksize;
-		if (cantseek) {
+		/*
+		 * We only need to copy in chunks of size _PC_MIN_HOLE_SIZE if
+		 * FIOSEEKDATA or FIOSEEKHOLE return an error and we are going
+		 * to fall back on the "all bytes 0" method.
+		 */
+		if (__predict_false(cantseek)) {
+			xfer = blksize;
 			/*
 			 * Set first xfer to end at a block boundary, so that
 			 * holes are more likely detected in the loop below via
 			 * the for all bytes 0 method.
 			 */
 			xfer -= (*inoffp % blksize);
+		} else {
+			xfer = blksize = maxphys;
 		}
 		/* Loop copying the data block. */
 		while (copylen > 0 && error == 0 && !eof && interrupted == 0) {