Allan Jude fc34dfba8e Fix L2ARC reads when compressed ARC disabled
When reading compressed blocks from the L2ARC, with
compressed ARC disabled, arc_hdr_size() returns
LSIZE rather than PSIZE, but the actual read is PSIZE.
This causes l2arc_read_done() to compare the checksum
against the wrong size, resulting in checksum failure.

This manifests as an increase in the kstat l2_cksum_bad
and the read being retried from the main pool, making the
L2ARC ineffective.

Add new L2ARC tests with Compressed ARC enabled/disabled

Blocks are handled differently depending on the state of the
zfs_compressed_arc_enabled tunable.

If a block is compressed on-disk, and compressed_arc is enabled:
- the block is read from disk
- It is NOT decompressed
- It is added to the ARC in its compressed form
- l2arc_write_buffers() may write it to the L2ARC (as is)
- l2arc_read_done() compares the checksum to the BP (compressed)

However, if compressed_arc is disabled:
- the block is read from disk
- It is decompressed
- It is added to the ARC (uncompressed)
- l2arc_write_buffers() will use l2arc_apply_transforms() to
  recompress the block, before writing it to the L2ARC
- l2arc_read_done() compares the checksum to the BP (compressed)
- l2arc_read_done() will use l2arc_untransform() to uncompress it

This test writes out a test file to a pool consisting of one disk
and one cache device, then randomly reads from it. Since the arc_max
in the tests is low, this will feed the L2ARC, and result in reads
from the L2ARC.

We compare the value of the kstat l2_cksum_bad before and after
to determine if any blocks failed to survive the trip through the
L2ARC.

Sponsored-by: The FreeBSD Foundation
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Allan Jude <allanjude@freebsd.org>
Closes #10693
2020-08-13 23:31:20 -07:00
2020-08-13 14:59:24 -07:00
2020-07-31 21:10:52 -07:00
2020-07-14 17:33:44 -07:00
2020-04-14 11:36:28 -07:00
2019-04-30 10:58:45 -07:00
2020-06-09 21:24:09 -07:00
2018-05-29 16:00:33 -07:00
2020-04-09 09:16:46 -07:00
2018-09-18 12:03:47 -07:00
2018-05-29 16:00:33 -07:00
2020-06-03 19:46:31 -07:00
2020-03-16 10:46:03 -07:00

img

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.

codecov coverity

Official Resources

Installation

Full documentation for installing OpenZFS on your favorite Linux distribution can be found at the ZoL Site.

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 META file contains the officially recognized supported Linux kernel versions.
  • Supported FreeBSD versions are 12-STABLE and 13-CURRENT.
S
Description
No description provided
Readme 122 MiB
Languages
C 70.2%
Shell 19.9%
Assembly 5.1%
M4 1.9%
Python 1.6%
Other 1.3%