zfs_clone_range should return a more descriptive return value

module/os/freebsd/zfs/zfs_vnops_os.c

@@ -6290,7 +6290,7 @@ zfs_freebsd_copy_file_range(struct vop_copy_file_range_args *ap)
 
 	error = zfs_clone_range(VTOZ(invp), ap->a_inoffp, VTOZ(outvp),
 	    ap->a_outoffp, &len, ap->a_outcred);
-	if (error == EXDEV || error == EOPNOTSUPP)
+	if (error == EXDEV || error == EINVAL || error == EOPNOTSUPP)
 		goto bad_locked_fallback;
 	*ap->a_lenp = (size_t)len;
 out_locked:

module/os/linux/zfs/zpl_file_range.c

@@ -103,15 +103,15 @@ zpl_copy_file_range(struct file *src_file, loff_t src_off,
 	 * Since Linux 5.3 the filesystem driver is responsible for executing
 	 * an appropriate fallback, and a generic fallback function is provided.
 	 */
-	if (ret == -EOPNOTSUPP || ret == -EXDEV)
+	if (ret == -EOPNOTSUPP || ret == -EINVAL || ret == -EXDEV)
 		ret = generic_copy_file_range(src_file, src_off, dst_file,
 		    dst_off, len, flags);
 #else
 	/*
 	 * Before Linux 5.3 the filesystem has to return -EOPNOTSUPP to signal
 	 * to the kernel that it should fallback to a content copy.
 	 */
-	if (ret == -EXDEV)
+	if (ret == -EINVAL || ret == -EXDEV)
 		ret = -EOPNOTSUPP;
 #endif /* HAVE_VFS_GENERIC_COPY_FILE_RANGE */
 

module/zfs/brt.c

@@ -174,7 +174,7 @@
  *	                size_t len, unsigned int flags);
  *
  * Even though offsets and length represent bytes, they have to be
- * block-aligned or we will return the EXDEV error so the upper layer can
+ * block-aligned or we will return an error so the upper layer can
  * fallback to the generic mechanism that will just copy the data.
  * Using copy_file_range(2) will call OS-independent zfs_clone_range() function.
  * This function was implemented based on zfs_write(), but instead of writing
@@ -192,9 +192,9 @@
  * Some special cases to consider and how we address them:
  * - The block we want to clone may have been created within the same
  *   transaction group that we are trying to clone. Such block has no BP
- *   allocated yet, so cannot be immediately cloned. We return EXDEV.
+ *   allocated yet, so cannot be immediately cloned. We return EAGAIN.
  * - The block we want to clone may have been modified within the same
- *   transaction group. We return EXDEV.
+ *   transaction group. We return EAGAIN.
  * - A block may be cloned multiple times during one transaction group (that's
  *   why pending list is actually a tree and not an append-only list - this
  *   way we can figure out faster if this block is cloned for the first time

module/zfs/zfs_vnops.c

@@ -1028,6 +1028,10 @@ zfs_exit_two(zfsvfs_t *zfsvfs1, zfsvfs_t *zfsvfs2, const char *tag)
  *
  * On success, the function return the number of bytes copied in *lenp.
  * Note, it doesn't return how much bytes are left to be copied.
+ * On errors which are caused by any file system limitations or
+ * brt limitations `EINVAL` is returned. In the most cases a user
+ * requested bad parameters, it could be possible to clone the file but
+ * some parameters don't match the requirements.
  */
 int
 zfs_clone_range(znode_t *inzp, uint64_t *inoffp, znode_t *outzp,
@@ -1171,23 +1175,23 @@ zfs_clone_range(znode_t *inzp, uint64_t *inoffp, znode_t *outzp,
 	 * We cannot clone into files with different block size.
 	 */
 	if (inblksz != outzp->z_blksz && outzp->z_size > inblksz) {
-		error = SET_ERROR(EXDEV);
+		error = SET_ERROR(EINVAL);
 		goto unlock;
 	}
 
 	/*
 	 * Offsets and len must be at block boundries.
 	 */
 	if ((inoff % inblksz) != 0 || (outoff % inblksz) != 0) {
-		error = SET_ERROR(EXDEV);
+		error = SET_ERROR(EINVAL);
 		goto unlock;
 	}
 	/*
 	 * Length must be multipe of blksz, except for the end of the file.
 	 */
 	if ((len % inblksz) != 0 &&
 	    (len < inzp->z_size - inoff || len < outzp->z_size - outoff)) {
-		error = SET_ERROR(EXDEV);
+		error = SET_ERROR(EINVAL);
 		goto unlock;
 	}
 
@@ -1246,9 +1250,6 @@ zfs_clone_range(znode_t *inzp, uint64_t *inoffp, znode_t *outzp,
 			 * in the current transaction group. Return an error,
 			 * so the caller can fallback to just copying the data.
 			 */
-			if (error == EAGAIN) {
-				error = SET_ERROR(EXDEV);
-			}
 			break;
 		}
 		/*