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Rob Norris
224393a321
In a4b21eadec we added the zap_micro_max_size tuneable to raise the size
at which "micro" (single-block) ZAPs are upgraded to "fat" (multi-block)
ZAPs. Before this, a microZAP was limited to 128KiB, which was the old
largest block size. The side effect of raising the max size past 128KiB
is that it be stored in a large block, requiring the large_blocks
feature.
Unfortunately, this means that a backup stream created without the
--large-block (-L) flag to zfs send would split the microZAP block into
smaller blocks and send those, as is normal behaviour for large blocks.
This would be received correctly, but since microZAPs are limited to the
first block in the object by definition, the entries in the later blocks
would be inaccessible. For directory ZAPs, this gives the appearance of
files being lost.
This commit adds a feature flag, large_microzap, that must be enabled
for microZAPs to grow beyond 128KiB, and which will be activated the
first time that occurs. This feature is later checked when generating
the stream and if active, the send operation will abort unless
--large-block has also been requested.
Changing the limit still requires zap_micro_max_size to be changed. The
state of this flag effectively sets the upper value for this tuneable,
that is, if the feature is disabled, the tuneable will be clamped to
128KiB.
A stream flag is also added to ensure that the receiver also activates
its own feature flag upon receiving the stream. This is not strictly
necessary to _use_ the received microZAP, since it doesn't care how
large its block is, but it is required to send the microZAP object on,
otherwise the original problem occurs again.
Because it's difficult to reliably distinguish a microZAP from a fatZAP
from outside the ZAP code, and because it seems unlikely that most
users are affected (a fairly niche tuneable combined with what should be
an uncommon use of send), and for the sake of expediency, this change
activates the feature the first time a microZAP grows to use a large
block, and is never deactivated after that. This can be improved in the
future.
This commit changes nothing for existing pools that already have large
microZAPs. The feature will not be retroactively applied, but will be
activated the next time a microZAP grows past the limit.
Don't use large_blocks feature for enable/disable tests. The
large_microzap depends on large_blocks, so it gets enabled as a
dependency, breaking the test. Instead use feature "longname", which has
the exact same feature characteristics.
Sponsored-by: Klara, Inc.
Sponsored-by: Wasabi Technology, Inc.
Reviewed-by: Allan Jude <allan@klarasystems.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Rob Norris <rob.norris@klarasystems.com>
Closes #16593
OpenZFS is an advanced file system and volume manager which was originally developed for Solaris and is now maintained by the OpenZFS community. This repository contains the code for running OpenZFS on Linux and FreeBSD.
Official Resources
- Documentation - for using and developing this repo
- ZoL Site - Linux release info & links
- Mailing lists
- OpenZFS site - for conference videos and info on other platforms (illumos, OSX, Windows, etc)
Installation
Full documentation for installing OpenZFS on your favorite operating system can be found at the Getting Started Page.
Contribute & Develop
We have a separate document with contribution guidelines.
We have a Code of Conduct.
Release
OpenZFS is released under a CDDL license.
For more details see the NOTICE, LICENSE and COPYRIGHT files; UCRL-CODE-235197
Supported Kernels
- The
METAfile contains the officially recognized supported Linux kernel versions. - Supported FreeBSD versions are any supported branches and releases starting from 13.0-RELEASE.