From mboxrd@z Thu Jan  1 00:00:00 1970
From: NeilBrown <neilb@suse.de>
Subject: Re: RAD1 doesn't fail WRITE that was written only on a rebuilding
 drive
Date: Tue, 4 Jun 2013 09:52:35 +1000
Message-ID: <20130604095235.16261243@notabene.brown>
References: <CAGRgLy6tHN7ZPwxxRM4pzVbKP5fS0PLeXrhKoeZ0XJqVrb0pVQ@mail.gmail.com>
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To: Alexander Lyakas <alex.bolshoy@gmail.com>
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On Tue, 28 May 2013 15:46:33 +0300 Alexander Lyakas <alex.bolshoy@gmail.com>
wrote:

> Hello Neil,
> we continue testing last-drive RAID1 failure cases.
> We see the following issue:
>=20
> # RAID1 with drives A and B; drive B was freshly-added and is rebuilding
> # Drive A fails
> # WRITE request arrives to the array. It is failed by drive A, so
> r1_bio is marked as R1BIO_WriteError, but the rebuilding drive B
> succeeds in writing it, so the same r1_bio is marked as
> R1BIO_Uptodate.
> # r1_bio arrives to handle_write_finished, badblocks are disabled,
> md_error()->error() does nothing because we don't fail the last drive
> of raid1
> # raid_end_bio_io()  calls call_bio_endio()
> # As a result, in call_bio_endio():
> 	if (!test_bit(R1BIO_Uptodate, &r1_bio->state))
> 		clear_bit(BIO_UPTODATE, &bio->bi_flags);
> this code doesn't clear the BIO_UPTODATE flag, and the whole master
> WRITE succeeds, back to the upper layer.
>=20
> # This keeps happening until rebuild aborts, and drive B is ejected
> from the array[1]. After that, there is only one drive (A), so after
> it fails a WRITE, the master WRITE also fails.
>=20
> It should be noted, that I test a WRITE that is way ahead of
> recovery_offset of drive B. So after such WRITE fails, subsequent READ
> to the same place would fail, because drive A will fail it, and drive
> B cannot be attempted to READ from there (rebuild has not reached
> there yet).
>=20
> My concrete suggestion is that this behavior is not reasonable, and we
> should only count a successful WRITE to a drive that is marked as
> InSync. Please let me know what do you think?

Sounds reasonable.  Could you make and test a patch?  Then I'll apply it.

Thanks,
NeilBrown

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