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    Subject[PATCH 4.14 107/157] md: fix two problems with setting the "re-add" device state.
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: NeilBrown <neilb@suse.com>

    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>

    ---
    drivers/md/md.c | 4 +++-
    1 file changed, 3 insertions(+), 1 deletion(-)

    --- a/drivers/md/md.c
    +++ b/drivers/md/md.c
    @@ -2823,7 +2823,8 @@ state_store(struct md_rdev *rdev, const
    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
    @@ -8594,6 +8595,7 @@ static int remove_and_add_spares(struct
    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++;
    }

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