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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spl	FreeBSD: Sync taskq_cancel_id() returns with Linux	2024-09-24 16:29:18 -07:00
zfs	Always validate checksums for Direct I/O reads	2024-10-09 12:28:08 -07:00