Re: [pve-devel] [PATCH zfsonlinux v2 0/2] Update to ZFS 2.2.4

["Max Carrara" <m.carrara@proxmox.com>]

On Tue May 7, 2024 at 5:02 PM CEST, Stoiko Ivanov wrote:
> v1->v2:
> Patch 2/2 (adaptation of arc_summary/arcstat patch) modified:
> * right after sending the v1 I saw a report where pinning kernel 6.2 (thus
>   ZFS 2.1) leads to a similar traceback - which I seem to have overlooked
>   when packaging 2.2.0 ...
>   adapted the patch by booting a VM with kernel 6.2 and the current
>   userspace and running arc_summary /arcstat -a until no traceback was
>   displayed with a single-disk pool.

Testing
-------

* Built and installed ZFS with those two patches on my test VM
  - Note: Couldn't install zfs-initramfs and zfs-dracut due to some
    dependency issue
  - zfs-initramfs depends on initramfs-tools, but complained it wasn't
    available (even though the package is installed ...)
  - zfs-dracut did the same for dracut
  - initramfs-tools then conflicts with the virtual linux-initramfs-tool
  - Removing zfs-initramfs from the packages to be installed "fixed"
    this; all other packages then installed without any issue

* `arcstat -a` and `arc_summary` correctly displayed the new values
  while old kernel was still running

* Didn't encounter any exceptions

* VM also survived a reboot - same results for new kernel

* Didn't notice anything off overall while the VM was running - will
  holler if I find anything

Review
------

Looked specifically at patch 02; applied and diffed it on the upstream
ZFS sources checked out at tag `zfs-2.2.4`. What can I say, it's just
replacing calls to `obj.__getitem__()` with `obj.get('foo', 0)` - so,
pretty straightforward. (The original code could use a brush-up, but
that's beside the point.)

Summary
-------

All in all, LGTM - haven't really looked at patch 01 in detail, so I'll
add my R-b tag only to patch 02. Good work!


>
> original cover-letter for v1:
> This patchset updates ZFS to the recently released 2.2.4
>
> We had about half of the patches already in 2.2.3-2, due to the needed
> support for kernel 6.8.
>
> Compared to the last 2.2 point releases this one compares quite a few
> potential performance improvments:
> * for ZVOL workloads (relevant for qemu guests) multiple taskq were
>   introduced [1] - this change is active by default (can be put back to
>   the old behavior with explicitly setting `zvol_num_taskqs=1`
> * the interface for ZFS submitting operations to the kernel's block layer
>   was augmented to better deal with split-pages [2] - which should also
>   improve performance, and prevent unaligned writes which are rejected by
>   e.g. the SCSI subsystem. - The default remains with the current code
>   (`zfs_vdev_disk_classic=0` turns on the 'new' behavior...)
> * Speculative prefetching was improved [3], which introduced not kstats,
>   which are reported by`arc_summary` and `arcstat`, as before with the
>   MRU/MFU additions there was not guard for running the new user-space
>   with an old kernel resulting in Python exceptions of both tools.
>   I adapted the patch where Thomas fixed that back in the 2.1 release
>   times. - sending as separate patch for easier review - and I hope it's
>   ok that I dropped the S-o-b tag (as it's changed code) - glad to resend
>   it, if this should be adapted.
>
> Minimally tested on 2 VMs (the arcstat/arc_summary changes by running with
> an old kernel and new user-space)
>
>
> [0] https://github.com/openzfs/zfs/releases/tag/zfs-2.2.4
> [1] https://github.com/openzfs/zfs/pull/15992
> [2] https://github.com/openzfs/zfs/pull/15588
> [3] https://github.com/openzfs/zfs/pull/16022
>
> Stoiko Ivanov (2):
>   update zfs submodule to 2.2.4 and refresh patches
>   update arc_summary arcstat patch with new introduced values
>
>  ...md-unit-for-importing-specific-pools.patch |   4 +-
>  ...-move-manpage-arcstat-1-to-arcstat-8.patch |   2 +-
>  ...-guard-access-to-freshly-introduced-.patch | 438 ++++++++++++
>  ...-guard-access-to-l2arc-MFU-MRU-stats.patch | 113 ---
>  ...hten-bounds-for-noalloc-stat-availab.patch |   4 +-
>  ...rectly-handle-partition-16-and-later.patch |  52 --
>  ...-use-splice_copy_file_range-for-fall.patch | 135 ----
>  .../0014-linux-5.4-compat-page_size.patch     | 121 ----
>  .../patches/0015-abd-add-page-iterator.patch  | 334 ---------
>  ...-existing-functions-to-vdev_classic_.patch | 349 ---------
>  ...v_disk-reorganise-vdev_disk_io_start.patch | 111 ---
>  ...-read-write-IO-function-configurable.patch |  69 --
>  ...e-BIO-filling-machinery-to-avoid-spl.patch | 671 ------------------
>  ...dule-parameter-to-select-BIO-submiss.patch | 104 ---
>  ...se-bio_chain-to-submit-multiple-BIOs.patch | 363 ----------
>  ...on-t-use-compound-heads-on-Linux-4.5.patch |  96 ---
>  ...ault-to-classic-submission-for-2.2.x.patch |  90 ---
>  ...ion-caused-by-mmap-flushing-problems.patch | 104 ---
>  ...touch-vbio-after-its-handed-off-to-t.patch |  57 --
>  debian/patches/series                         |  16 +-
>  upstream                                      |   2 +-
>  21 files changed, 445 insertions(+), 2790 deletions(-)
>  create mode 100644 debian/patches/0009-arc-stat-summary-guard-access-to-freshly-introduced-.patch
>  delete mode 100644 debian/patches/0009-arc-stat-summary-guard-access-to-l2arc-MFU-MRU-stats.patch
>  delete mode 100644 debian/patches/0012-udev-correctly-handle-partition-16-and-later.patch
>  delete mode 100644 debian/patches/0013-Linux-6.8-compat-use-splice_copy_file_range-for-fall.patch
>  delete mode 100644 debian/patches/0014-linux-5.4-compat-page_size.patch
>  delete mode 100644 debian/patches/0015-abd-add-page-iterator.patch
>  delete mode 100644 debian/patches/0016-vdev_disk-rename-existing-functions-to-vdev_classic_.patch
>  delete mode 100644 debian/patches/0017-vdev_disk-reorganise-vdev_disk_io_start.patch
>  delete mode 100644 debian/patches/0018-vdev_disk-make-read-write-IO-function-configurable.patch
>  delete mode 100644 debian/patches/0019-vdev_disk-rewrite-BIO-filling-machinery-to-avoid-spl.patch
>  delete mode 100644 debian/patches/0020-vdev_disk-add-module-parameter-to-select-BIO-submiss.patch
>  delete mode 100644 debian/patches/0021-vdev_disk-use-bio_chain-to-submit-multiple-BIOs.patch
>  delete mode 100644 debian/patches/0022-abd_iter_page-don-t-use-compound-heads-on-Linux-4.5.patch
>  delete mode 100644 debian/patches/0023-vdev_disk-default-to-classic-submission-for-2.2.x.patch
>  delete mode 100644 debian/patches/0024-Fix-corruption-caused-by-mmap-flushing-problems.patch
>  delete mode 100644 debian/patches/0025-vdev_disk-don-t-touch-vbio-after-its-handed-off-to-t.patch



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