Hi Song,
Thank you for your comments. I will address them. How do you want to
proceed? Do you want me to send a formal patch to the list (with
proper formatting this time)? As mentioned, I am not able to test this
fix on one of the latest kernels, but only on 4.14.99.
Thanks,
Alex.
On Thu, Nov 30, 2023 at 2:38 AM Song Liu <song@xxxxxxxxxx> wrote:
>
> Hi Alexander,
>
> Thanks for working on this.
>
> The patch looks good overall. A few comments below.
>
> On Wed, Nov 29, 2023 at 4:15 AM Alexander Lyakas <alex.bolshoy@xxxxxxxxx> wrote:
> >
> [...]
> >
> > Please kindly note the following:
> > - md has many features, which we don't use, such as: "non-persistent
> > arrays", "clustered arrays", "autostart", "journal devices",
> > "write-behind", "multipath arrays" and others. I cannot say how this
> > fix will interoperate with these features.
> > - I tested the fix only on superblock version 1.2. I don't know how
> > 0.9 superblocks work (because I never used them), so I did not change
> > anything in super_90_validate().
>
> I think we can leave 0.9 as-is.
>
> > - I tested the fix on our production kernel 4.14 LTS. I ported the
> > changes to the mainline kernel 6.7-rc3, but I do not have the ability
> > at the moment to test it on this kernel.
> [...]
> > drivers/md/md.c | 53 +++++++++++++++++++++++++++++++++++++++++++----------
> > 1 file changed, 43 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/md/md.c b/drivers/md/md.c
> > index c94373d..e490275 100644
> > --- a/drivers/md/md.c
> > +++ b/drivers/md/md.c
> > @@ -1195,6 +1195,7 @@ struct super_type {
> > struct md_rdev *refdev,
> > int minor_version);
> > int (*validate_super)(struct mddev *mddev,
> > + struct md_rdev *freshest,
> > struct md_rdev *rdev);
> > void (*sync_super)(struct mddev *mddev,
> > struct md_rdev *rdev);
> > @@ -1333,7 +1334,7 @@ static int super_90_load(struct md_rdev *rdev,
> > struct md_rdev *refdev, int minor
> > /*
> > * validate_super for 0.90.0
> > */
> > -static int super_90_validate(struct mddev *mddev, struct md_rdev *rdev)
> > +static int super_90_validate(struct mddev *mddev, struct md_rdev
> > *freshest, struct md_rdev *rdev)
> > {
> > mdp_disk_t *desc;
> > mdp_super_t *sb = page_address(rdev->sb_page);
> > @@ -1845,7 +1846,7 @@ static int super_1_load(struct md_rdev *rdev,
> > struct md_rdev *refdev, int minor_
> > return ret;
> > }
> >
> > -static int super_1_validate(struct mddev *mddev, struct md_rdev *rdev)
> > +static int super_1_validate(struct mddev *mddev, struct md_rdev
> > *freshest, struct md_rdev *rdev)
> > {
> > struct mdp_superblock_1 *sb = page_address(rdev->sb_page);
> > __u64 ev1 = le64_to_cpu(sb->events);
> > @@ -1941,13 +1942,15 @@ static int super_1_validate(struct mddev
> > *mddev, struct md_rdev *rdev)
> > }
> > } else if (mddev->pers == NULL) {
> > /* Insist of good event counter while assembling, except for
> > - * spares (which don't need an event count) */
> > - ++ev1;
> > + * spares (which don't need an event count).
> > + * Similar to mdadm, we allow event counter difference of 1
> > + * from the freshest device.
> > + */
> > if (rdev->desc_nr >= 0 &&
> > rdev->desc_nr < le32_to_cpu(sb->max_dev) &&
> > (le16_to_cpu(sb->dev_roles[rdev->desc_nr]) <
> > MD_DISK_ROLE_MAX ||
> > le16_to_cpu(sb->dev_roles[rdev->desc_nr]) ==
> > MD_DISK_ROLE_JOURNAL))
> > - if (ev1 < mddev->events)
> > + if (ev1 + 1 < mddev->events)
> > return -EINVAL;
> > } else if (mddev->bitmap) {
> > /* If adding to array with a bitmap, then we can accept an
> > @@ -1968,8 +1971,38 @@ static int super_1_validate(struct mddev
> > *mddev, struct md_rdev *rdev)
> > rdev->desc_nr >= le32_to_cpu(sb->max_dev)) {
> > role = MD_DISK_ROLE_SPARE;
> > rdev->desc_nr = -1;
> > - } else
> > + } else if (mddev->pers == NULL && freshest != NULL &&
> > ev1 < mddev->events) {
> > + /*
> > + * If we are assembling, and our event counter
> > is smaller than the
> > + * highest event counter, we cannot trust our
> > superblock about the role.
> > + * It could happen that our rdev was marked as
> > Faulty, and all other
> > + * superblocks were updated with +1 event counter.
> > + * Then, before the next superblock update,
> > which typically happens when
> > + * remove_and_add_spares() removes the device
> > from the array, there was
> > + * a crash or reboot.
> > + * If we allow current rdev without consulting
> > the freshest superblock,
> > + * we could cause data corruption.
> > + * Note that in this case our event counter is
> > smaller by 1 than the
> > + * highest, otherwise, this rdev would not be
> > allowed into array;
> > + * both kernel and mdadm allow event counter
> > difference of 1.
> > + */
> > + struct mdp_superblock_1 *freshest_sb =
> > page_address(freshest->sb_page);
> > + u32 freshest_max_dev =
> > le32_to_cpu(freshest_sb->max_dev);
> > +
> > + if (rdev->desc_nr >= freshest_max_dev) {
> > + /* this is unexpected, better not proceed */
> > + pr_warn("md: %s: rdev[%pg]:
> > desc_nr(%d) >= freshest(%pg)->sb->max_dev(%u)\n",
> > + mdname(mddev),
> > rdev->bdev, rdev->desc_nr, freshest->bdev,
> > + freshest_max_dev);
> > + return -EUCLEAN;
> > + }
> > +
> > + role =
> > le16_to_cpu(freshest_sb->dev_roles[rdev->desc_nr]);
> > + pr_warn("md: %s: rdev[%pg]: role=%d(0x%x)
> > according to freshest %pg\n",
> > + mdname(mddev), rdev->bdev, role,
> > role, freshest->bdev);
>
> I think this should be a pr_debug(). Or maybe only warn when
> freshest and current rdev disagree.
>
> > + } else {
> > role = le16_to_cpu(sb->dev_roles[rdev->desc_nr]);
> > + }
> > switch(role) {
> > case MD_DISK_ROLE_SPARE: /* spare */
> > break;
> > @@ -2876,7 +2909,7 @@ static int add_bound_rdev(struct md_rdev *rdev)
> > * and should be added immediately.
> > */
> > super_types[mddev->major_version].
> > - validate_super(mddev, rdev);
> > + validate_super(mddev, NULL/*freshest*/, rdev);
> > err = mddev->pers->hot_add_disk(mddev, rdev);
> > if (err) {
> > md_kick_rdev_from_array(rdev);
> > @@ -3813,7 +3846,7 @@ static int analyze_sbs(struct mddev *mddev)
> > }
> >
> > super_types[mddev->major_version].
> > - validate_super(mddev, freshest);
> > + validate_super(mddev, NULL/*freshest*/, freshest);
> >
> > i = 0;
> > rdev_for_each_safe(rdev, tmp, mddev) {
> > @@ -3828,7 +3861,7 @@ static int analyze_sbs(struct mddev *mddev)
> > }
> > if (rdev != freshest) {
> > if (super_types[mddev->major_version].
> > - validate_super(mddev, rdev)) {
> > + validate_super(mddev, freshest, rdev)) {
> > pr_warn("md: kicking non-fresh %pg
> > from array!\n",
> > rdev->bdev);
> > md_kick_rdev_from_array(rdev);
> > @@ -6836,7 +6869,7 @@ int md_add_new_disk(struct mddev *mddev, struct
> > mdu_disk_info_s *info)
> > rdev->saved_raid_disk = rdev->raid_disk;
> > } else
> > super_types[mddev->major_version].
> > - validate_super(mddev, rdev);
> > + validate_super(mddev, NULL/*freshest*/, rdev);
> > if ((info->state & (1<<MD_DISK_SYNC)) &&
> > rdev->raid_disk != info->raid_disk) {
> > /* This was a hot-add request, but events doesn't
> > --
> > 1.9.1
