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

module/zfs/vdev_mirror.c

@@ -764,6 +764,27 @@ vdev_mirror_io_done(zio_t *zio)
 
 	ASSERT(zio->io_type == ZIO_TYPE_READ);
 
+	/*
+	 * Any Direct I/O read that has a checksum error must be treated as
+	 * suspicious as the contents of the buffer could be getting
+	 * manipulated while the I/O is taking place. The checksum verify error
+	 * will be reported to the top-level Mirror VDEV.
+	 *
+	 * There will be no attampt at reading any additional data copies. If
+	 * the buffer is still being manipulated while attempting to read from
+	 * another child, there exists a possibly that the checksum could be
+	 * verified as valid. However, the buffer contents could again get
+	 * manipulated after verifying the checksum. This would lead to bad data
+	 * being written out during self healing.
+	 */
+	if ((zio->io_flags & ZIO_FLAG_DIO_READ) &&
+	    (zio->io_flags & ZIO_FLAG_DIO_CHKSUM_ERR)) {
+		zio_dio_chksum_verify_error_report(zio);
+		zio->io_error = vdev_mirror_worst_error(mm);
+		ASSERT3U(zio->io_error, ==, ECKSUM);
+		return;
+	}
+
 	/*
 	 * If we don't have a good copy yet, keep trying other children.
 	 */