Re: [RFC PATCH 0/5] md/raid1: introduce a new sync action to repair badblocks

[Zheng Qixing]

在 2026/1/6 23:36, Pascal Hambourg 写道:
> On 06/01/2026 at 03:44, Zheng Qixing wrote:
> > 在 2025/12/31 19:11, Roman Mamedov 写道:
> > > On Wed, 31 Dec 2025 15:09:47 +0800
> > >
> > > Could you also check here that it reads back successfully, and only 
> > > then clear?
> > >
> > > Otherwise there are cases when the block won't read even after 
> > > rewriting it.
>
> I confirm. The rewrite is reported successful but SMART reallocation 
> attributes did not change and a further read still fails.
>
> > I'm a bit worried that reading the data again before clearing the bad 
> > blocks might affect the performance of the bad block repair process.
>
> Isn't it more worrying to clear bad blocks while they may still be bad ?
> Bad blocks should be rare anyway, so performance impact should be low.
>
> > > Side note, on some hardware it might be necessary to rewrite a 
> > > larger area
> > > around the problematic block, to finally trigger a remap. Not 512B, 
> > > but at
> > > least the native sector size, which is often 4K.
> >
> > Are you referring to the case where we have logical 512B sectors but 
> > physical 4K sectors?
>
> Yes. Writing a single logical sector implies a read-modify-write of 
> the whole underlying physical sector and will not complete if the read 
> fails.

That makes sense. I will change it in the next version.

> > Can a physical 4K block have partial recovery (e.g., one 512B sector 
> > succeeds while the other 7 fail)?
>
> Not in my experience. There seems to be a single ECC for the whole 
> physical sector.

I will try to test with disks that have lbs=512 and pbs=4096.

If 512B IOs can be successfully issued, then the bad block repair logic 
does need to

consider the minimum repair length and alignment logic.


Thanks,

Qixing