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panic in removal_remap test on 4K devices

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If the zfs_remove_max_segment tunable is changed to be not a multiple of
the sector size, then the device removal code will malfunction and try
to create mappings that are smaller than one sector, leading to a panic.

On debug bits this assertion will fail in spa_vdev_copy_segment():
    ASSERT3U(DVA_GET_ASIZE(&dst), ==, size);

On nondebug, the system panics with a stack like:
    metaslab_free_concrete()
    metaslab_free_impl()
    metaslab_free_impl_cb()
    vdev_indirect_remap()
    free_from_removing_vdev()
    metaslab_free_impl()
    metaslab_free_dva()
    metaslab_free()

Fortunately, the default for zfs_remove_max_segment is 1MB, so this
can't occur by default.  We hit it during this test because
removal_remap.ksh changes zfs_remove_max_segment to 1KB. When testing on
4KB-sector disks, we hit the bug.

This change makes the zfs_remove_max_segment tunable more robust,
automatically rounding it up to a multiple of the sector size. We also
turn some key assertions into VERIFY's so that similar bugs would be
caught before they are encoded on disk (and thus avoid a
panic-reboot-loop).

Reviewed-by: Sean Eric Fagan <sef@ixsystems.com>
Reviewed-by: Pavel Zakharov <pavel.zakharov@delphix.com>
Reviewed-by: Serapheim Dimitropoulos <serapheim@delphix.com>
Reviewed-by: Sebastien Roy <sebastien.roy@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Matthew Ahrens <mahrens@delphix.com>
External-issue: DLPX-61342
Closes #8893
This commit is contained in:
Matthew Ahrens
2019-06-13 13:12:39 -07:00
committed by Tony Hutter
parent 592ee2e6dd
commit 6083f40387
4 changed files with 59 additions and 14 deletions
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man/man5/zfs-module-parameters.5
+27
View File
@@ -2194,6 +2194,33 @@ pool cannot be returned to a healthy state prior to removing the device.
Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
\fBzfs_removal_suspend_progress\fR (int)
.ad
.RS 12n
.sp
This is used by the test suite so that it can ensure that certain actions
happen while in the middle of a removal.
.sp
Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
\fBzfs_remove_max_segment\fR (int)
.ad
.RS 12n
.sp
The largest contiguous segment that we will attempt to allocate when removing
a device. This can be no larger than 16MB. If there is a performance
problem with attempting to allocate large blocks, consider decreasing this.
.sp
Default value: \fB16,777,216\fR (16MB).
.RE
.sp
.ne 2
.na