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

man/man4/zfs.4

@@ -436,7 +436,7 @@ write.
 It can also help to identify if reported checksum errors are tied to Direct I/O
 writes.
 Each verify error causes a
-.Sy dio_verify
+.Sy dio_verify_wr
 zevent.
 Direct Write I/O checkum verify errors can be seen with
 .Nm zpool Cm status Fl d .

man/man8/zpool-events.8

@@ -98,7 +98,10 @@ This can be an indicator of problems with the underlying storage device.
 The number of delay events is ratelimited by the
 .Sy zfs_slow_io_events_per_second
 module parameter.
-.It Sy dio_verify
+.It Sy dio_verify_rd
+Issued when there was a checksum verify error after a Direct I/O read has been
+issued.
+.It Sy dio_verify_wr
 Issued when there was a checksum verify error after a Direct I/O write has been
 issued.
 This event can only take place if the module parameter

man/man8/zpool-status.8

@@ -82,14 +82,18 @@ Specify
 .Sy --json-pool-key-guid
 to set pool GUID as key for pool objects instead of pool names.
 .It Fl d
-Display the number of Direct I/O write checksum verify errors that have occured
-on a top-level VDEV.
+Display the number of Direct I/O read/write checksum verify errors that have
+occured on a top-level VDEV.
 See
 .Sx zfs_vdev_direct_write_verify
 in
 .Xr zfs 4
 for details about the conditions that can cause Direct I/O write checksum
 verify failures to occur.
+Direct I/O reads checksum verify errors can also occur if the contents of the
+buffer are being manipulated after the I/O has been issued and is in flight.
+In the case of Direct I/O read checksum verify errors, the I/O will be reissued
+through the ARC.
 .It Fl D
 Display a histogram of deduplication statistics, showing the allocated
 .Pq physically present on disk