137 lines
4.7 KiB
Diff
137 lines
4.7 KiB
Diff
From 97b51a2c2d00b79a59f2a8e37134031b0c9e0223 Mon Sep 17 00:00:00 2001
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From: NeilBrown <neilb@suse.de>
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Date: Wed, 14 Oct 2020 13:12:48 +1100
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Subject: [PATCH 096/108] Super1: allow RAID0 layout setting to be removed.
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Once the RAID0 layout has been set, the RAID0 array cannot be assembled
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on an older kernel which doesn't understand layouts.
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This is an intentional safety feature, but sometimes people need the
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ability to roll-back to a previously working configuration.
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So add "--update=layout-unspecified" to remove RAID0 layout information
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from the superblock.
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Running "--assemble --update=layout-unspecified" will cause the assembly
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the fail when run on a newer kernel, but will allow it to work on
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an older kernel.
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Signed-off-by: NeilBrown <neilb@suse.de>
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Signed-off-by: Jes Sorensen <jsorensen@fb.com>
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---
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md.4 | 13 +++++++++++++
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mdadm.8.in | 15 +++++++++++++--
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mdadm.c | 5 +++--
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super1.c | 6 +++++-
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4 files changed, 34 insertions(+), 5 deletions(-)
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diff --git a/md.4 b/md.4
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index aecff38..60fdd27 100644
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--- a/md.4
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+++ b/md.4
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@@ -215,6 +215,19 @@ option or the
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.B "--update=layout-alternate"
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option.
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+Once you have updated the layout you will not be able to mount the array
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+on an older kernel. If you need to revert to an older kernel, the
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+layout information can be erased with the
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+.B "--update=layout-unspecificed"
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+option. If you use this option to
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+.B --assemble
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+while running a newer kernel, the array will NOT assemble, but the
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+metadata will be update so that it can be assembled on an older kernel.
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+
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+No that setting the layout to "unspecified" removes protections against
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+this bug, and you must be sure that the kernel you use matches the
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+layout of the array.
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+
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.SS RAID1
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A RAID1 array is also known as a mirrored set (though mirrors tend to
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diff --git a/mdadm.8.in b/mdadm.8.in
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index ab832e8..34a93a8 100644
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--- a/mdadm.8.in
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+++ b/mdadm.8.in
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@@ -1213,6 +1213,7 @@ argument given to this flag can be one of
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.BR no\-ppl ,
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.BR layout\-original ,
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.BR layout\-alternate ,
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+.BR layout\-unspecified ,
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.BR metadata ,
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or
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.BR super\-minor .
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@@ -1368,8 +1369,9 @@ The
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.B layout\-original
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and
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.B layout\-alternate
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-options are for RAID0 arrays in use before Linux 5.4. If the array was being
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-used with Linux 3.13 or earlier, then to assemble the array on a new kernel,
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+options are for RAID0 arrays with non-uniform devices size that were in
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+use before Linux 5.4. If the array was being used with Linux 3.13 or
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+earlier, then to assemble the array on a new kernel,
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.B \-\-update=layout\-original
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must be given. If the array was created and used with a kernel from Linux 3.14 to
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Linux 5.3, then
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@@ -1379,6 +1381,15 @@ will happen normally.
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For more information, see
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.IR md (4).
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+The
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+.B layout\-unspecified
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+option reverts the effect of
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+.B layout\-orignal
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+or
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+.B layout\-alternate
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+and allows the array to be again used on a kernel prior to Linux 5.3.
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+This option should be used with great caution.
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+
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.TP
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.BR \-\-freeze\-reshape
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Option is intended to be used in start-up scripts during initrd boot phase.
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diff --git a/mdadm.c b/mdadm.c
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index 1b3467f..493d70e 100644
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--- a/mdadm.c
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+++ b/mdadm.c
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@@ -796,7 +796,8 @@ int main(int argc, char *argv[])
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if (strcmp(c.update, "revert-reshape") == 0)
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continue;
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if (strcmp(c.update, "layout-original") == 0 ||
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- strcmp(c.update, "layout-alternate") == 0)
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+ strcmp(c.update, "layout-alternate") == 0 ||
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+ strcmp(c.update, "layout-unspecified") == 0)
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continue;
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if (strcmp(c.update, "byteorder") == 0) {
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if (ss) {
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@@ -828,7 +829,7 @@ int main(int argc, char *argv[])
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" 'summaries', 'homehost', 'home-cluster', 'byteorder', 'devicesize',\n"
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" 'no-bitmap', 'metadata', 'revert-reshape'\n"
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" 'bbl', 'no-bbl', 'force-no-bbl', 'ppl', 'no-ppl'\n"
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- " 'layout-original', 'layout-alternate'\n"
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+ " 'layout-original', 'layout-alternate', 'layout-unspecified'\n"
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);
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exit(outf == stdout ? 0 : 2);
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diff --git a/super1.c b/super1.c
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index 7664883..8b0d6ff 100644
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--- a/super1.c
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+++ b/super1.c
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@@ -1551,11 +1551,15 @@ static int update_super1(struct supertype *st, struct mdinfo *info,
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else if (strcmp(update, "nofailfast") == 0)
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sb->devflags &= ~FailFast1;
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else if (strcmp(update, "layout-original") == 0 ||
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- strcmp(update, "layout-alternate") == 0) {
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+ strcmp(update, "layout-alternate") == 0 ||
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+ strcmp(update, "layout-unspecified") == 0) {
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if (__le32_to_cpu(sb->level) != 0) {
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pr_err("%s: %s only supported for RAID0\n",
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devname?:"", update);
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rv = -1;
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+ } else if (strcmp(update, "layout-unspecified") == 0) {
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+ sb->feature_map &= ~__cpu_to_le32(MD_FEATURE_RAID0_LAYOUT);
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+ sb->layout = 0;
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} else {
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sb->feature_map |= __cpu_to_le32(MD_FEATURE_RAID0_LAYOUT);
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sb->layout = __cpu_to_le32(update[7] == 'o' ? 1 : 2);
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--
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2.7.5
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