Re: [PATCH] BTRFS: Runs the xor function if a Block has failed

[Sanidhya Solanki]

On Wed, 30 Dec 2015 18:18:26 +0100
David Sterba <dsterba@xxxxxxx> wrote:

> That's just the comment copied, the changelog does not explain why
> it's ok to do just the run_xor there. It does not seem trivial to me.
> Please describe that the end result after the code change is expected.

In the RAID 6 case after a failure, we discover that the failure
affected the entire P stripe, without any bad data occurring. Hence, we
xor the previously stored parity data to return the data that was lost
in the P stripe failure.

The xor-red data is from the parity blocks. Hence, we are left with 
recovered data belonging to the P stripe.

If there is an error during the completion of the xor (provided by the
patch ), we got to the cleanup function.

Hope that is satisfactory.
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