Re: [PATCH 00/17] fs, btrfs refcount conversions

[Qu Wenruo]

At 03/03/2017 04:55 PM, Elena Reshetova wrote:
> Now when new refcount_t type and API are finally merged
> (see include/linux/refcount.h), the following
> patches convert various refcounters in the btrfs filesystem from atomic_t
> to refcount_t. By doing this we prevent intentional or accidental
> underflows or overflows that can led to use-after-free vulnerabilities.
>
> The below patches are fully independent and can be cherry-picked separately.
> Since we convert all kernel subsystems in the same fashion, resulting
> in about 300 patches, we have to group them for sending at least in some
> fashion to be manageable. Please excuse the long cc list.
>
> These patches have been tested with xfstests by running btrfs-related tests.
> btrfs debug was enabled, warns on refcount errors, too. No output related to
> refcount errors produced. However, the following errors were during the run:
>  * tests btrfs/078, btrfs/114, btrfs/115, no errors anywhere in dmesg, but
>  process hangs. They all seem to be around qgroup, sometimes error visible
>  such as qgroup scan failed -4 before it blocks, but not always.

-EINTR? That's strange.

Any blocked process backtrace?

>  * test btrfs/104 dmesg has additional error output:
>  BTRFS warning (device vdc): qgroup 258 reserved space underflow, have: 0,
>  to free: 4096

Known one, and fixes already sent to mail list while not merged yet:
https://patchwork.kernel.org/patch/9592765/

Thanks,
Qu

>  I tried looking at the code on what causes the failure, but could not figure
>  it out. It doesn't seem to be related to any refcount changes at least IMO.
>
> The above test failures are hard for me to understand and interpreted, but
> they don't seem to relate to refcount conversions.
>
> Elena Reshetova (17):
>   fs, btrfs: convert btrfs_bio.refs from atomic_t to refcount_t
>   fs, btrfs: convert btrfs_transaction.use_count from atomic_t to
>     refcount_t
>   fs, btrfs: convert extent_map.refs from atomic_t to refcount_t
>   fs, btrfs: convert btrfs_ordered_extent.refs from atomic_t to
>     refcount_t
>   fs, btrfs: convert btrfs_caching_control.count from atomic_t to
>     refcount_t
>   fs, btrfs: convert btrfs_delayed_ref_node.refs from atomic_t to
>     refcount_t
>   fs, btrfs: convert btrfs_delayed_node.refs from atomic_t to refcount_t
>   fs, btrfs: convert btrfs_delayed_item.refs from atomic_t to refcount_t
>   fs, btrfs: convert btrfs_root.refs from atomic_t to refcount_t
>   fs, btrfs: convert extent_state.refs from atomic_t to refcount_t
>   fs, btrfs: convert compressed_bio.pending_bios from atomic_t to
>     refcount_t
>   fs, btrfs: convert scrub_recover.refs from atomic_t to refcount_t
>   fs, btrfs: convert scrub_page.refs from atomic_t to refcount_t
>   fs, btrfs: convert scrub_block.refs from atomic_t to refcount_t
>   fs, btrfs: convert scrub_parity.refs from atomic_t to refcount_t
>   fs, btrfs: convert scrub_ctx.refs from atomic_t to refcount_t
>   fs, btrfs: convert btrfs_raid_bio.refs from atomic_t to refcount_t
>
>  fs/btrfs/backref.c           |  2 +-
>  fs/btrfs/compression.c       | 18 ++++++++---------
>  fs/btrfs/ctree.h             |  5 +++--
>  fs/btrfs/delayed-inode.c     | 46 ++++++++++++++++++++++----------------------
>  fs/btrfs/delayed-inode.h     |  5 +++--
>  fs/btrfs/delayed-ref.c       |  8 ++++----
>  fs/btrfs/delayed-ref.h       |  8 +++++---
>  fs/btrfs/disk-io.c           |  6 +++---
>  fs/btrfs/disk-io.h           |  4 ++--
>  fs/btrfs/extent-tree.c       | 20 +++++++++----------
>  fs/btrfs/extent_io.c         | 18 ++++++++---------
>  fs/btrfs/extent_io.h         |  3 ++-
>  fs/btrfs/extent_map.c        | 10 +++++-----
>  fs/btrfs/extent_map.h        |  3 ++-
>  fs/btrfs/ordered-data.c      | 20 +++++++++----------
>  fs/btrfs/ordered-data.h      |  2 +-
>  fs/btrfs/raid56.c            | 19 +++++++++---------
>  fs/btrfs/scrub.c             | 42 ++++++++++++++++++++--------------------
>  fs/btrfs/transaction.c       | 20 +++++++++----------
>  fs/btrfs/transaction.h       |  3 ++-
>  fs/btrfs/tree-log.c          |  2 +-
>  fs/btrfs/volumes.c           | 10 +++++-----
>  fs/btrfs/volumes.h           |  2 +-
>  include/trace/events/btrfs.h |  4 ++--
>  24 files changed, 143 insertions(+), 137 deletions(-)