[dm-devel] [PATCH] md/raid0: Fail BIOs if their underlying block device is gone

[Roman Mamedov]

On Mon, 29 Jul 2019 16:33:59 -0300
"Guilherme G. Piccoli" <gpiccoli at canonical.com> wrote:

> Currently md/raid0 is not provided with any mechanism to validate if
> an array member got removed or failed. The driver keeps sending BIOs
> regardless of the state of array members. This leads to the following
> situation: if a raid0 array member is removed and the array is mounted,
> some user writing to this array won't realize that errors are happening
> unless they check kernel log or perform one fsync per written file.
> 
> In other words, no -EIO is returned and writes (except direct ones) appear
> normal. Meaning the user might think the wrote data is correctly stored in
> the array, but instead garbage was written given that raid0 does stripping
> (and so, it requires all its members to be working in order to not corrupt
> data).

If that's correct, then this seems to be a critical weak point in cases when
we have a RAID0 as a member device in RAID1/5/6/10 arrays.

-- 
With respect,
Roman