Hi:

quoted

 However it seems to address multiple issues, and so should be multiple
patches.

quoted

Firstly, it allows fix_read_error to read from a disk that is being recovered.
It seems unlikely that this will ever be necessary, but it is theoretically
possible so I am happy with the patch.
I have applied a patch making just this change.

 This idea from the read_balance. 

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Secondly it records a bad block on every device if it cannot read from
anywhere.
I don't think this is necessary.  fix_read_error should only be addressing
the one read error.  It either fixes it or marks it as bad.
If there are other bad blocks on other disks they will be found and handled
eventually and adding extra code in here  just makes it more complex with
little gain.

In this situation
1:no channce to recover
2: performance,why judge more read?
3:like the action  in function fix_sync_read_error().

quoted

So unless you can convince me that it is actually behaving wrongly, I won't
be applying the rest of the patch.