mirror_zfs/module/zcommon
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
..
cityhash.c zcommon: add specialized versions of cityhash4 2024-09-19 15:18:59 -07:00
simd_stat.c Add missing guard defines for simd_stat 2024-09-24 09:07:26 -07:00
zfeature_common.c feature: large_microzap 2024-10-02 20:47:11 -07:00
zfs_comutil.c nvpair: Constify string functions 2023-03-14 15:25:50 -07:00
zfs_deleg.c nvpair: Constify string functions 2023-03-14 15:25:50 -07:00
zfs_fletcher_aarch64_neon.c Drop lying to the compiler in the fletcher4 code 2023-03-24 10:29:19 -07:00
zfs_fletcher_avx512.c Drop lying to the compiler in the fletcher4 code 2023-03-24 10:29:19 -07:00
zfs_fletcher_intel.c Drop lying to the compiler in the fletcher4 code 2023-03-24 10:29:19 -07:00
zfs_fletcher_sse.c Drop lying to the compiler in the fletcher4 code 2023-03-24 10:29:19 -07:00
zfs_fletcher_superscalar4.c Drop lying to the compiler in the fletcher4 code 2023-03-24 10:29:19 -07:00
zfs_fletcher_superscalar.c Drop lying to the compiler in the fletcher4 code 2023-03-24 10:29:19 -07:00
zfs_fletcher.c Replace P2ALIGN with P2ALIGN_TYPED and delete P2ALIGN. 2024-05-10 08:47:21 -07:00
zfs_namecheck.c Replace dead opensolaris.org license link 2022-07-11 14:16:13 -07:00
zfs_prop.c snapdir: add 'disabled' value to make .zfs inaccessible 2024-10-02 09:12:02 -07:00
zfs_valstr.c Always validate checksums for Direct I/O reads 2024-10-09 12:28:08 -07:00
zpool_prop.c Avoid computing strlen() inside loops 2024-10-02 09:10:06 -07:00
zprop_common.c Replace dead opensolaris.org license link 2022-07-11 14:16:13 -07:00