[Devel] [PATCH hci-8.1 0/3] dm-qcow2: keep images of a read-only table unmodified

[Konstantin Khorenko]

Three things found while reviewing the series, none of them for it.
Please fix them separately.

- A v3 image with header_length < 104 is not rejected. The only check
  is header_length < sizeof(struct QCowHeader), and only when the
  compression bit is set. qemu fails such an image with "qcow2 header
  too short". For us the extension parser then starts inside the
  header.

- For a v2 image hdr->header_length is never set, so it stays 0 from
  kzalloc() and the extensions are parsed from offset 0 of the header
  instead of 72. qemu sets header_length = 72 for v2.

- The table mode is still tested against FMODE_WRITE in
  qcow2_check_convert_hdr(), qcow2_attach_file(),
  qcow2_truncate_preallocations(), qcow2_postsuspend() and
  qcow2_preresume(), while the series switched to BLK_OPEN_WRITE. Same
  value today, but dm_table_get_mode() returns blk_mode_t. The is_ro
  in qcow2_check_convert_hdr() has only a commented-out user and can go.


Please file appropriate tasks and fix them separately.

--
Best regards,

Konstantin Khorenko,
Virtuozzo Linux Kernel Team