On Mon, Jul 29 2019, Guilherme G. Piccoli wrote:
> Currently if a md/raid0 array gets one or more members removed while
> being mounted, kernel keeps showing state 'clean' in the 'array_state'
> sysfs attribute. Despite udev signaling the member device is gone, 'mdadm'
> cannot issue the STOP_ARRAY ioctl successfully, given the array is mounted.
>
> Nothing else hints that something is wrong (except that the removed devices
> don't show properly in the output of 'mdadm detail' command). There is no
> other property to be checked, and if user is not performing reads/writes
> to the array, even kernel log is quiet and doesn't give a clue about the
> missing member.
>
> This patch changes this behavior; when 'array_state' is read we introduce
> a non-expensive check (only for raid0) that relies in the comparison of
> the total number of disks when array was assembled with gendisk flags of
> those devices to validate if all members are available and functional.
> A new array state 'broken' was added: it mimics the state 'clean' in every
> aspect, being useful only to distinguish if such array has some member
> missing. Also, we show a rate-limited warning in kernel log in such case.
>
> This patch has no proper functional change other than adding a 'clean'-like
> state; it was tested with ext4 and xfs filesystems. It requires a 'mdadm'
> counterpart to handle the 'broken' state.
>
> Cc: NeilBrown <ne...@suse.com>
> Cc: Song Liu <songliubrav...@fb.com>
> Signed-off-by: Guilherme G. Piccoli <gpicc...@canonical.com>
> ---
> drivers/md/md.c | 23 +++++++++++++++++++----
> drivers/md/md.h | 2 ++
> drivers/md/raid0.c | 26 ++++++++++++++++++++++++++
> 3 files changed, 47 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index fba49918d591..b80f36084ec1 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -4160,12 +4160,18 @@ __ATTR_PREALLOC(resync_start, S_IRUGO|S_IWUSR,
> * active-idle
> * like active, but no writes have been seen for a while (100msec).
> *
> + * broken
> + * RAID0-only: same as clean, but array is missing a member.
> + * It's useful because RAID0 mounted-arrays aren't stopped
> + * when a member is gone, so this state will at least alert
> + * the user that something is wrong.
> + *
> */
> enum array_state { clear, inactive, suspended, readonly, read_auto, clean,
> active,
> - write_pending, active_idle, bad_word};
> + write_pending, active_idle, broken, bad_word};
> static char *array_states[] = {
> "clear", "inactive", "suspended", "readonly", "read-auto", "clean",
> "active",
> - "write-pending", "active-idle", NULL };
> + "write-pending", "active-idle", "broken", NULL };
>
> static int match_word(const char *word, char **list)
> {
> @@ -4181,7 +4187,7 @@ array_state_show(struct mddev *mddev, char *page)
> {
> enum array_state st = inactive;
>
> - if (mddev->pers)
> + if (mddev->pers) {
> switch(mddev->ro) {
> case 1:
> st = readonly;
> @@ -4201,7 +4207,15 @@ array_state_show(struct mddev *mddev, char *page)
> st = active;
> spin_unlock(&mddev->lock);
> }
> - else {
> +
> + if ((mddev->pers->level == 0) &&
Don't test if ->level is 0. Instead, test if ->is_missing_dev is not
NULL.
NeilBrown
> + ((st == clean) || (st == broken))) {
> + if (mddev->pers->is_missing_dev(mddev))
> + st = broken;
> + else
> + st = clean;
> + }
> + } else {
> if (list_empty(&mddev->disks) &&
> mddev->raid_disks == 0 &&
> mddev->dev_sectors == 0)
> @@ -4315,6 +4329,7 @@ array_state_store(struct mddev *mddev, const char *buf,
> size_t len)
> break;
> case write_pending:
> case active_idle:
> + case broken:
> /* these cannot be set */
> break;
> }
> diff --git a/drivers/md/md.h b/drivers/md/md.h
> index 41552e615c4c..e7b42b75701a 100644
> --- a/drivers/md/md.h
> +++ b/drivers/md/md.h
> @@ -590,6 +590,8 @@ struct md_personality
> int (*congested)(struct mddev *mddev, int bits);
> /* Changes the consistency policy of an active array. */
> int (*change_consistency_policy)(struct mddev *mddev, const char *buf);
> + /* Check if there is any missing/failed members - RAID0 only for now. */
> + bool (*is_missing_dev)(struct mddev *mddev);
> };
>
> struct md_sysfs_entry {
> diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
> index 58a9cc5193bf..79618a6ae31a 100644
> --- a/drivers/md/raid0.c
> +++ b/drivers/md/raid0.c
> @@ -455,6 +455,31 @@ static inline int is_io_in_chunk_boundary(struct mddev
> *mddev,
> }
> }
>
> +bool raid0_is_missing_dev(struct mddev *mddev)
> +{
> + struct md_rdev *rdev;
> + static int already_missing;
> + int def_disks, work_disks = 0;
> + struct r0conf *conf = mddev->private;
> +
> + def_disks = conf->strip_zone[0].nb_dev;
> + rdev_for_each(rdev, mddev)
> + if (rdev->bdev->bd_disk->flags & GENHD_FL_UP)
> + work_disks++;
> +
> + if (unlikely(def_disks - work_disks)) {
> + if (!already_missing) {
> + already_missing = 1;
> + pr_warn("md: %s: raid0 array has %d missing/failed
> members\n",
> + mdname(mddev), (def_disks - work_disks));
> + }
> + return true;
> + }
> +
> + already_missing = 0;
> + return false;
> +}
> +
> static void raid0_handle_discard(struct mddev *mddev, struct bio *bio)
> {
> struct r0conf *conf = mddev->private;
> @@ -789,6 +814,7 @@ static struct md_personality raid0_personality=
> .takeover = raid0_takeover,
> .quiesce = raid0_quiesce,
> .congested = raid0_congested,
> + .is_missing_dev = raid0_is_missing_dev,
> };
>
> static int __init raid0_init (void)
> --
> 2.22.0
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