Brian Atkinson b4e4cbeb20 Always validate checksums for Direct I/O reads
This fixes an oversight in the Direct I/O PR. There is nothing that
stops a process from manipulating the contents of a buffer for a
Direct I/O read while the I/O is in flight. This can lead checksum
verify failures. However, the disk contents are still correct, and this
would lead to false reporting of checksum validation failures.

To remedy this, all Direct I/O reads that have a checksum verification
failure are treated as suspicious. In the event a checksum validation
failure occurs for a Direct I/O read, then the I/O request will be
reissued though the ARC. This allows for actual validation to happen and
removes any possibility of the buffer being manipulated after the I/O
has been issued.

Just as with Direct I/O write checksum validation failures, Direct I/O
read checksum validation failures are reported though zpool status -d in
the DIO column. Also the zevent has been updated to have both:
1. dio_verify_wr -> Checksum verification failure for writes
2. dio_verify_rd -> Checksum verification failure for reads.
This allows for determining what I/O operation was the culprit for the
checksum verification failure. All DIO errors are reported only on the
top-level VDEV.

Even though FreeBSD can write protect pages (stable pages) it still has
the same issue as Linux with Direct I/O reads.

This commit updates the following:
1. Propogates checksum failures for reads all the way up to the
   top-level VDEV.
2. Reports errors through zpool status -d as DIO.
3. Has two zevents for checksum verify errors with Direct I/O. One for
   read and one for write.
4. Updates FreeBSD ABD code to also check for ABD_FLAG_FROM_PAGES and
   handle ABD buffer contents validation the same as Linux.
5. Updated manipulate_user_buffer.c to also manipulate a buffer while a
   Direct I/O read is taking place.
6. Adds a new ZTS test case dio_read_verify that stress tests the new
   code.
7. Updated man pages.
8. Added an IMPLY statement to zio_checksum_verify() to make sure that
   Direct I/O reads are not issued as speculative.
9. Removed self healing through mirror, raidz, and dRAID VDEVs for
   Direct I/O reads.

This issue was first observed when installing a Windows 11 VM on a ZFS
dataset with the dataset property direct set to always. The zpool
devices would report checksum failures, but running a subsequent zpool
scrub would not repair any data and report no errors.

Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Brian Atkinson <batkinson@lanl.gov>
Closes #16598
2024-10-09 12:28:08 -07:00
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2024-10-06 14:49:33 -07:00
2022-12-22 11:34:28 -08:00
2020-06-09 21:24:09 -07:00
2018-05-29 16:00:33 -07:00
2024-10-04 14:20:10 -07:00
2020-08-26 21:44:41 -07:00
2018-05-29 16:00:33 -07:00
2021-04-02 16:33:40 -07:00
2020-03-16 10:46:03 -07:00

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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.

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Official Resources

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 META file contains the officially recognized supported Linux kernel versions.
  • Supported FreeBSD versions are any supported branches and releases starting from 13.0-RELEASE.
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