Messages in this thread | | | Subject | Re: [PATCH v5 05/14] md: don't suspend the array for interrupted reshape | From | Yu Kuai <> | Date | Thu, 29 Feb 2024 10:14:14 +0800 |
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Hi,
在 2024/02/29 10:10, Xiao Ni 写道: > > 在 2024/2/1 下午5:25, Yu Kuai 写道: >> From: Yu Kuai <yukuai3@huawei.com> >> >> md_start_sync() will suspend the array if there are spares that can be >> added or removed from conf, however, if reshape is still in progress, > > > Hi Kuai > > Why md_start_sync can run when reshape is still in progress? > md_check_recovery should return without queue sync_work, right? > >> this won't happen at all or data will be corrupted(remove_and_add_spares >> won't be called from md_choose_sync_action for reshape), hence there is >> no need to suspend the array if reshape is not done yet. >> >> Meanwhile, there is a potential deadlock for raid456: >> >> 1) reshape is interrupted; >> >> 2) set one of the disk WantReplacement, and add a new disk to the array, >> however, recovery won't start until the reshape is finished; >> >> 3) then issue an IO across reshpae position, this IO will wait for >> reshape to make progress; >> >> 4) continue to reshape, then md_start_sync() found there is a spare disk >> that can be added to conf, mddev_suspend() is called; > > > I c. The answer for my above question is reshape is interrupted and then > it continues the reshape, right? >
Yes, reshape is interrupted and sync_thread is unregister, then sync_thread can be registered again to continue reshape.
Thanks, Kuai
> > Best Regards > > Xiao > >> >> Step 4 and step 3 is waiting for each other, deadlock triggered. Noted >> this problem is found by code review, and it's not reporduced yet. >> >> Fix this porblem by don't suspend the array for interrupted reshape, >> this is safe because conf won't be changed until reshape is done. >> >> Fixes: bc08041b32ab ("md: suspend array in md_start_sync() if array >> need reconfiguration") >> Signed-off-by: Yu Kuai <yukuai3@huawei.com> >> --- >> drivers/md/md.c | 13 +++++++++---- >> 1 file changed, 9 insertions(+), 4 deletions(-) >> >> diff --git a/drivers/md/md.c b/drivers/md/md.c >> index 6c5d0a372927..85fde05c37dd 100644 >> --- a/drivers/md/md.c >> +++ b/drivers/md/md.c >> @@ -9374,12 +9374,17 @@ static void md_start_sync(struct work_struct *ws) >> bool suspend = false; >> char *name; >> - if (md_spares_need_change(mddev)) >> + /* >> + * If reshape is still in progress, spares won't be added or removed >> + * from conf until reshape is done. >> + */ >> + if (mddev->reshape_position == MaxSector && >> + md_spares_need_change(mddev)) { >> suspend = true; >> + mddev_suspend(mddev, false); >> + } >> - suspend ? mddev_suspend_and_lock_nointr(mddev) : >> - mddev_lock_nointr(mddev); >> - >> + mddev_lock_nointr(mddev); >> if (!md_is_rdwr(mddev)) { >> /* >> * On a read-only array we can: > > . >
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