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    Subject[39/93] md: fix degraded calculation when starting a reshape.
    2.6.32-stable review patch.  If anyone has any objections, please let us know.


    From: NeilBrown <>

    commit 9eb07c259207d048e3ee8be2a77b2a4680b1edd4 upstream.

    This code was written long ago when it was not possible to
    reshape a degraded array. Now it is so the current level of
    degraded-ness needs to be taken in to account. Also newly addded
    devices should only reduce degradedness if they are deemed to be

    In particular, if you convert a RAID5 to a RAID6, and increase the
    number of devices at the same time, then the 5->6 conversion will
    make the array degraded so the current code will produce a wrong
    value for 'degraded' - "-1" to be precise.

    If the reshape runs to completion end_reshape will calculate a correct
    new value for 'degraded', but if a device fails during the reshape an
    incorrect decision might be made based on the incorrect value of

    This patch is suitable for 2.6.32-stable and if they are still open,
    2.6.31-stable and 2.6.30-stable as well.

    Reported-by: Michael Evans <>
    Signed-off-by: NeilBrown <>
    Signed-off-by: Greg Kroah-Hartman <>

    drivers/md/raid5.c | 11 +++++++----
    1 file changed, 7 insertions(+), 4 deletions(-)

    --- a/drivers/md/raid5.c
    +++ b/drivers/md/raid5.c
    @@ -5432,11 +5432,11 @@ static int raid5_start_reshape(mddev_t *
    !test_bit(Faulty, &rdev->flags)) {
    if (raid5_add_disk(mddev, rdev) == 0) {
    char nm[20];
    - if (rdev->raid_disk >= conf->previous_raid_disks)
    + if (rdev->raid_disk >= conf->previous_raid_disks) {
    set_bit(In_sync, &rdev->flags);
    - else
    + added_devices++;
    + } else
    rdev->recovery_offset = 0;
    - added_devices++;
    sprintf(nm, "rd%d", rdev->raid_disk);
    if (sysfs_create_link(&mddev->kobj,
    &rdev->kobj, nm))
    @@ -5448,9 +5448,12 @@ static int raid5_start_reshape(mddev_t *

    + /* When a reshape changes the number of devices, ->degraded
    + * is measured against the large of the pre and post number of
    + * devices.*/
    if (mddev->delta_disks > 0) {
    spin_lock_irqsave(&conf->device_lock, flags);
    - mddev->degraded = (conf->raid_disks - conf->previous_raid_disks)
    + mddev->degraded += (conf->raid_disks - conf->previous_raid_disks)
    - added_devices;
    spin_unlock_irqrestore(&conf->device_lock, flags);

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      Last update: 2010-02-19 18:03    [W:0.022 / U:69.200 seconds]
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