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    Subject[PATCH AUTOSEL 5.4 154/350] md: no longer compare spare disk superblock events in super_load
    Date
    From: Yufen Yu <yuyufen@huawei.com>

    [ Upstream commit 6a5cb53aaa4ef515ddeffa04ce18b771121127b4 ]

    We have a test case as follow:

    mdadm -CR /dev/md1 -l 1 -n 4 /dev/sd[a-d] \
    --assume-clean --bitmap=internal
    mdadm -S /dev/md1
    mdadm -A /dev/md1 /dev/sd[b-c] --run --force

    mdadm --zero /dev/sda
    mdadm /dev/md1 -a /dev/sda

    echo offline > /sys/block/sdc/device/state
    echo offline > /sys/block/sdb/device/state
    sleep 5
    mdadm -S /dev/md1

    echo running > /sys/block/sdb/device/state
    echo running > /sys/block/sdc/device/state
    mdadm -A /dev/md1 /dev/sd[a-c] --run --force

    When we readd /dev/sda to the array, it started to do recovery.
    After offline the other two disks in md1, the recovery have
    been interrupted and superblock update info cannot be written
    to the offline disks. While the spare disk (/dev/sda) can continue
    to update superblock info.

    After stopping the array and assemble it, we found the array
    run fail, with the follow kernel message:

    [ 172.986064] md: kicking non-fresh sdb from array!
    [ 173.004210] md: kicking non-fresh sdc from array!
    [ 173.022383] md/raid1:md1: active with 0 out of 4 mirrors
    [ 173.022406] md1: failed to create bitmap (-5)
    [ 173.023466] md: md1 stopped.

    Since both sdb and sdc have the value of 'sb->events' smaller than
    that in sda, they have been kicked from the array. However, the only
    remained disk sda is in 'spare' state before stop and it cannot be
    added to conf->mirrors[] array. In the end, raid array assemble
    and run fail.

    In fact, we can use the older disk sdb or sdc to assemble the array.
    That means we should not choose the 'spare' disk as the fresh disk in
    analyze_sbs().

    To fix the problem, we do not compare superblock events when it is
    a spare disk, as same as validate_super.

    Signed-off-by: Yufen Yu <yuyufen@huawei.com>
    Signed-off-by: Song Liu <songliubraving@fb.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/md/md.c | 57 +++++++++++++++++++++++++++++++++++++++++++------
    1 file changed, 51 insertions(+), 6 deletions(-)

    diff --git a/drivers/md/md.c b/drivers/md/md.c
    index 1be7abeb24fdc..fc6ae8276a92f 100644
    --- a/drivers/md/md.c
    +++ b/drivers/md/md.c
    @@ -1149,7 +1149,15 @@ static int super_90_load(struct md_rdev *rdev, struct md_rdev *refdev, int minor
    rdev->desc_nr = sb->this_disk.number;

    if (!refdev) {
    - ret = 1;
    + /*
    + * Insist on good event counter while assembling, except
    + * for spares (which don't need an event count)
    + */
    + if (sb->disks[rdev->desc_nr].state & (
    + (1<<MD_DISK_SYNC) | (1 << MD_DISK_ACTIVE)))
    + ret = 1;
    + else
    + ret = 0;
    } else {
    __u64 ev1, ev2;
    mdp_super_t *refsb = page_address(refdev->sb_page);
    @@ -1165,7 +1173,14 @@ static int super_90_load(struct md_rdev *rdev, struct md_rdev *refdev, int minor
    }
    ev1 = md_event(sb);
    ev2 = md_event(refsb);
    - if (ev1 > ev2)
    +
    + /*
    + * Insist on good event counter while assembling, except
    + * for spares (which don't need an event count)
    + */
    + if (sb->disks[rdev->desc_nr].state & (
    + (1<<MD_DISK_SYNC) | (1 << MD_DISK_ACTIVE)) &&
    + (ev1 > ev2))
    ret = 1;
    else
    ret = 0;
    @@ -1525,6 +1540,7 @@ static int super_1_load(struct md_rdev *rdev, struct md_rdev *refdev, int minor_
    sector_t sectors;
    char b[BDEVNAME_SIZE], b2[BDEVNAME_SIZE];
    int bmask;
    + __u64 role;

    /*
    * Calculate the position of the superblock in 512byte sectors.
    @@ -1658,8 +1674,20 @@ static int super_1_load(struct md_rdev *rdev, struct md_rdev *refdev, int minor_
    sb->level != 0)
    return -EINVAL;

    + role = le16_to_cpu(sb->dev_roles[rdev->desc_nr]);
    +
    if (!refdev) {
    - ret = 1;
    + /*
    + * Insist of good event counter while assembling, except for
    + * spares (which don't need an event count)
    + */
    + if (rdev->desc_nr >= 0 &&
    + rdev->desc_nr < le32_to_cpu(sb->max_dev) &&
    + (role < MD_DISK_ROLE_MAX ||
    + role == MD_DISK_ROLE_JOURNAL))
    + ret = 1;
    + else
    + ret = 0;
    } else {
    __u64 ev1, ev2;
    struct mdp_superblock_1 *refsb = page_address(refdev->sb_page);
    @@ -1676,7 +1704,14 @@ static int super_1_load(struct md_rdev *rdev, struct md_rdev *refdev, int minor_
    ev1 = le64_to_cpu(sb->events);
    ev2 = le64_to_cpu(refsb->events);

    - if (ev1 > ev2)
    + /*
    + * Insist of good event counter while assembling, except for
    + * spares (which don't need an event count)
    + */
    + if (rdev->desc_nr >= 0 &&
    + rdev->desc_nr < le32_to_cpu(sb->max_dev) &&
    + (role < MD_DISK_ROLE_MAX ||
    + role == MD_DISK_ROLE_JOURNAL) && ev1 > ev2)
    ret = 1;
    else
    ret = 0;
    @@ -3597,7 +3632,7 @@ static struct md_rdev *md_import_device(dev_t newdev, int super_format, int supe
    * Check a full RAID array for plausibility
    */

    -static void analyze_sbs(struct mddev *mddev)
    +static int analyze_sbs(struct mddev *mddev)
    {
    int i;
    struct md_rdev *rdev, *freshest, *tmp;
    @@ -3618,6 +3653,12 @@ static void analyze_sbs(struct mddev *mddev)
    md_kick_rdev_from_array(rdev);
    }

    + /* Cannot find a valid fresh disk */
    + if (!freshest) {
    + pr_warn("md: cannot find a valid disk\n");
    + return -EINVAL;
    + }
    +
    super_types[mddev->major_version].
    validate_super(mddev, freshest);

    @@ -3652,6 +3693,8 @@ static void analyze_sbs(struct mddev *mddev)
    clear_bit(In_sync, &rdev->flags);
    }
    }
    +
    + return 0;
    }

    /* Read a fixed-point number.
    @@ -5570,7 +5613,9 @@ int md_run(struct mddev *mddev)
    if (!mddev->raid_disks) {
    if (!mddev->persistent)
    return -EINVAL;
    - analyze_sbs(mddev);
    + err = analyze_sbs(mddev);
    + if (err)
    + return -EINVAL;
    }

    if (mddev->level != LEVEL_NONE)
    --
    2.20.1
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