>On Wed, 6 Jun 2012 11:24:34 +0800 majianpeng <majianpeng@xxxxxxxxx> wrote:
>
>> On Tue, 5 Jun 2012 18:28:13 neil wrote:
>> >On Tue, 5 Jun 2012 15:32:56 +0800 majianpeng <majianpeng@xxxxxxxxx> wrote:
>> >
>> >> In Commit 7bfec5f35c68121e7b1849f3f4166dd96c8da5b3:
>> >> "if there is a spare and a want_replacement device, start replacement."
>> >> But it did not consider the raid was degraded at the same time.
>> >> When we add spare disk in order to recovery, unless raid was ok and then
>> >> started replacement or vice versa.
>> >>
>> >> Signed-off-by: majianpeng <majianpeng@xxxxxxxxx>
>> >> ---
>> >> drivers/md/raid5.c | 48 +++++++++++++++++++++++++++++-------------------
>> >> 1 files changed, 29 insertions(+), 19 deletions(-)
>> >>
>> >> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
>> >> index d267672..f74c9a5 100644
>> >> --- a/drivers/md/raid5.c
>> >> +++ b/drivers/md/raid5.c
>> >
>> >Good point, but the code feels a little ... clumsy.
>> >
>> >How about this?
>> >
>> >NeilBrown
>> >
>> >
>> >diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
>> >index d267672..4f0861e 100644
>> >--- a/drivers/md/raid5.c
>> >+++ b/drivers/md/raid5.c
>> >@@ -5465,10 +5465,9 @@ static int raid5_add_disk(struct mddev *mddev, struct md_rdev *rdev)
>> > if (rdev->saved_raid_disk >= 0 &&
>> > rdev->saved_raid_disk >= first &&
>> > conf->disks[rdev->saved_raid_disk].rdev == NULL)
>> >- disk = rdev->saved_raid_disk;
>> >- else
>> >- disk = first;
>> >- for ( ; disk <= last ; disk++) {
>> >+ first = rdev->saved_raid_disk;
>> >+
>> >+ for (disk = first; disk <= last; disk++) {
>> > p = conf->disks + disk;
>> > if (p->rdev == NULL) {
>> > clear_bit(In_sync, &rdev->flags);
>> >@@ -5477,8 +5476,10 @@ static int raid5_add_disk(struct mddev *mddev, struct md_rdev *rdev)
>> > if (rdev->saved_raid_disk != disk)
>> > conf->fullsync = 1;
>> > rcu_assign_pointer(p->rdev, rdev);
>> >- break;
>> >+ goto out;
>> > }
>> >+ }
>> >+ for (disk = first; disk <= last; disk++) {
>> > if (test_bit(WantReplacement, &p->rdev->flags) &&
>> > p->replacement == NULL) {
>> > clear_bit(In_sync, &rdev->flags);
>> >@@ -5490,6 +5491,7 @@ static int raid5_add_disk(struct mddev *mddev, struct md_rdev *rdev)
>> > break;
>> > }
>> > }
>> >+out:
>> > print_raid5_conf(conf);
>> > return err;
>> > }
>> >
>> >
>> I tested and found a bug.I corrected it like this.
>
>You've added a test for 'p->rdev != NULL' - is that all?
>
No, I also add
>> + for (disk = first; disk <= last; disk++) {
+ p = conf->disks + disk;
>> + if (p->rdev != NULL &&
>> + test_bit(WantReplacement, &p->rdev->flags) &&
>> + p->replacement == NULL) {
You lost :
p = conf->disks + disk;
in next loop.
Thanks!
>That isn't necessary. If any p->rdev were NULL then the first loop would
>find it and the second loop would never be entered.
>
>
>> But I had a question:why p->rdev not protect by rcu_read_lock?
>> I think it should be.
>
>rcu is not necessary here. We hold mddev->mutex as does the code which
>removes devices, so we cannot race with it. We only need rcu when not
>holding the mutex, and when not performing resync/recovery/etc as that
>prevents ->rdev from being removed too.
>
>Thanks,
>NeilBrown
>
>
>
>>
>> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
>> index d267672..24162c1 100644
>> --- a/drivers/md/raid5.c
>> +++ b/drivers/md/raid5.c
>> @@ -5465,10 +5465,9 @@ static int raid5_add_disk(struct mddev *mddev, struct md_rdev *rdev)
>> if (rdev->saved_raid_disk >= 0 &&
>> rdev->saved_raid_disk >= first &&
>> conf->disks[rdev->saved_raid_disk].rdev == NULL)
>> - disk = rdev->saved_raid_disk;
>> - else
>> - disk = first;
>> - for ( ; disk <= last ; disk++) {
>> + first = rdev->saved_raid_disk;
>> +
>> + for (disk = first; disk <= last; disk++) {
>> p = conf->disks + disk;
>> if (p->rdev == NULL) {
>> clear_bit(In_sync, &rdev->flags);
>> @@ -5477,10 +5476,15 @@ static int raid5_add_disk(struct mddev *mddev, struct md_rdev *rdev)
>> if (rdev->saved_raid_disk != disk)
>> conf->fullsync = 1;
>> rcu_assign_pointer(p->rdev, rdev);
>> - break;
>> + goto out;
>> }
>> - if (test_bit(WantReplacement, &p->rdev->flags) &&
>> - p->replacement == NULL) {
>> + }
>> +
>> + for (disk = first; disk <= last; disk++) {
>> + p = conf->disks + disk;
>> + if (p->rdev != NULL &&
>> + test_bit(WantReplacement, &p->rdev->flags) &&
>> + p->replacement == NULL) {
>> clear_bit(In_sync, &rdev->flags);
>> set_bit(Replacement, &rdev->flags);
>> rdev->raid_disk = disk;
>> @@ -5490,6 +5494,7 @@ static int raid5_add_disk(struct mddev *mddev, struct md_rdev *rdev)
>> break;
>> }
>> }
>> +out:
>> print_raid5_conf(conf);
>> return err;
>> }
>>
>
>
--------------
majianpeng
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