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md: fix two problems with setting the "re-add" device state.

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commit 011abdc9df559ec75779bb7c53a744c69b2a94c6 upstream.

If "re-add" is written to the "state" file for a device
which is faulty, this has an effect similar to removing
and re-adding the device.  It should take up the
same slot in the array that it previously had, and
an accelerated (e.g. bitmap-based) rebuild should happen.

The slot that "it previously had" is determined by
rdev->saved_raid_disk.
However this is not set when a device fails (only when a device
is added), and it is cleared when resync completes.
This means that "re-add" will normally work once, but may not work a
second time.

This patch includes two fixes.
1/ when a device fails, record the ->raid_disk value in
    ->saved_raid_disk before clearing ->raid_disk
2/ when "re-add" is written to a device for which
    ->saved_raid_disk is not set, fail.

I think this is suitable for stable as it can
cause re-adding a device to be forced to do a full
resync which takes a lot longer and so puts data at
more risk.

Cc: <stable@vger.kernel.org> (v4.1)
Fixes: 97f6cd39da22 ("md-cluster: re-add capabilities")
Signed-off-by: NeilBrown <neilb@suse.com>
Reviewed-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
NeilBrown 2018-04-26 14:46:29 +10:00 committed by Greg Kroah-Hartman
parent 37e875042f
commit 4028e39598
1 changed files with 3 additions and 1 deletions
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4
drivers/md/md.c
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@ -2690,7 +2690,8 @@ state_store(struct md_rdev *rdev, const char *buf, size_t len)
err = 0;
}
} else if (cmd_match(buf, "re-add")) {
if (test_bit(Faulty, &rdev->flags) && (rdev->raid_disk == -1)) {
if (test_bit(Faulty, &rdev->flags) && (rdev->raid_disk == -1) &&
rdev->saved_raid_disk >= 0) {
/* clear_bit is performed _after_ all the devices
* have their local Faulty bit cleared. If any writes
* happen in the meantime in the local node, they
@ -8153,6 +8154,7 @@ static int remove_and_add_spares(struct mddev *mddev,
if (mddev->pers->hot_remove_disk(
mddev, rdev) == 0) {
sysfs_unlink_rdev(mddev, rdev);
rdev->saved_raid_disk = rdev->raid_disk;
rdev->raid_disk = -1;
removed++;
}