Fix partial uiomove size handling

- ensure loops process the same dbuf until all bytes are moved
- update loop variables using amount actually copied
- fix indentation

Signed-off-by: Codex <[email protected]>

Author: snajpa

module/zfs/dmu.c

@@ -1417,26 +1417,30 @@ dmu_read_uio_dnode(dnode_t *dn, zfs_uio_t *uio, uint64_t size)
 	err = dmu_buf_hold_array_by_dnode(dn, zfs_uio_offset(uio), size,
 	    TRUE, FTAG, &numbufs, &dbp, 0);
 	if (err)
-		return (err);
+	return (err);
 
-	for (i = 0; i < numbufs; i++) {
-		uint64_t tocpy;
-		int64_t bufoff;
-		dmu_buf_t *db = dbp[i];
+	for (i = 0; i < numbufs && size > 0; ) {
+	uint64_t tocpy;
+	int64_t bufoff;
+	dmu_buf_t *db = dbp[i];
 
-		ASSERT(size > 0);
+	bufoff = zfs_uio_offset(uio) - db->db_offset;
+	tocpy = MIN(db->db_size - bufoff, size);
 
-		bufoff = zfs_uio_offset(uio) - db->db_offset;
-		tocpy = MIN(db->db_size - bufoff, size);
+	ASSERT(db->db_data != NULL);
 
-		ASSERT(db->db_data != NULL);
-		err = zfs_uio_fault_move((char *)db->db_data + bufoff, tocpy,
-		    UIO_READ, uio);
+	uint64_t resid_before = uio->uio_resid;
+	err = zfs_uio_fault_move((char *)db->db_data + bufoff,
+	tocpy, UIO_READ, uio);
+	uint64_t moved = resid_before - uio->uio_resid;
 
-		if (err)
-			break;
+	size -= moved;
 
-		size -= tocpy;
+	if (err || moved == 0)
+	break;
+
+	if (bufoff + moved >= db->db_size)
+	i++;
 	}
 	dmu_buf_rele_array(dbp, numbufs, FTAG);
 
@@ -1536,41 +1540,44 @@ dmu_write_uio_dnode(dnode_t *dn, zfs_uio_t *uio, uint64_t size, dmu_tx_t *tx)
 	if (err)
 		return (err);
 
-	for (int i = 0; i < numbufs; i++) {
-		uint64_t tocpy;
-		int64_t bufoff;
-		dmu_buf_t *db = dbp[i];
+	for (int i = 0; i < numbufs && write_size > 0; ) {
+	uint64_t tocpy;
+	int64_t bufoff;
+	dmu_buf_t *db = dbp[i];
 
-		ASSERT(write_size > 0);
+	offset_t off = zfs_uio_offset(uio);
+	bufoff = off - db->db_offset;
+	tocpy = MIN(db->db_size - bufoff, write_size);
 
-		offset_t off = zfs_uio_offset(uio);
-		bufoff = off - db->db_offset;
-		tocpy = MIN(db->db_size - bufoff, write_size);
+	ASSERT(i == 0 || i == numbufs-1 || tocpy == db->db_size);
 
-		ASSERT(i == 0 || i == numbufs-1 || tocpy == db->db_size);
+	if (tocpy == db->db_size)
+	dmu_buf_will_fill(db, tx, B_TRUE);
+	else
+	dmu_buf_will_dirty(db, tx);
 
-		if (tocpy == db->db_size)
-			dmu_buf_will_fill(db, tx, B_TRUE);
-		else
-			dmu_buf_will_dirty(db, tx);
+	ASSERT(db->db_data != NULL);
+	uint64_t resid_before = uio->uio_resid;
+	err = zfs_uio_fault_move((char *)db->db_data + bufoff,
+	    tocpy, UIO_WRITE, uio);
+	uint64_t moved = resid_before - uio->uio_resid;
 
-		ASSERT(db->db_data != NULL);
-		err = zfs_uio_fault_move((char *)db->db_data + bufoff,
-		    tocpy, UIO_WRITE, uio);
+	if (tocpy == db->db_size && dmu_buf_fill_done(db, tx, err)) {
+	/* The fill was reverted.  Undo any uio progress. */
+	zfs_uio_advance(uio, off - zfs_uio_offset(uio));
+	}
 
-		if (tocpy == db->db_size && dmu_buf_fill_done(db, tx, err)) {
-			/* The fill was reverted.  Undo any uio progress. */
-			zfs_uio_advance(uio, off - zfs_uio_offset(uio));
-		}
+	if (err || moved == 0)
+	break;
 
-		if (err)
-			break;
+	write_size -= moved;
+	size -= moved;
 
-		write_size -= tocpy;
-		size -= tocpy;
+	if (bufoff + moved >= db->db_size)
+	i++;
 	}
 
-	IMPLY(err == 0, write_size == 0);
+		IMPLY(err == 0, write_size == 0);
 
 	dmu_buf_rele_array(dbp, numbufs, FTAG);